Microbiology Part 2 Flashcards
The incorrect match between organism and characteristic is:
A. Chilomastix mesnili—Shepherd’s crook and lemon shape
B. Plasmodium malariae—“band troph”
C. Hymenolepis nana—striated shell
D. Wuchereria bancrofti—sheathed microfilariae
C
The incorrect match between method and method objective is:
A. Direct wet examination—detection of organism motility
B. Knott’s concentration—the recovery of operculated helminth eggs
C. Baermann’s concentration—the recovery of Strongyloides
D. Permanent stained fecal smear—confirmation of protozoa
B. Knotts concentration for detection of microfilaria
The incorrect match between organism and characteristic is:
A. Dientamoeba fragilis—tetrad karyosome in the nucleus
B. Toxoplasma gondii—diagnostic serology
C. Echinococcus granulosus—daughter cysts
D. Schistosoma mansoni—egg with terminal spine
D
There are few procedures considered STAT in parasitology. The most obvious situation would be:
A. Ova and parasite examination for giardiasis
B. Baermann’s concentration for strongyloidiasis
C. Blood films for malaria
D. Culture of amoebic keratitis
C
An immunosuppressed man has several episodes of pneumonia, intestinal pain, sepsis with gram-negative rods, and a history of military service in Southeast Asia 20 years earlier. The most likely cause is infection with:
A. Trypanosoma cruzi
B. Strongyloides stercoralis
C. Naegleria fowleri
D. Paragonimus westermani
B
A latent infection of S. stercoralis can occur after many years due to its capacity to cause autoinfection.
In a pediatric patient, the recommended clinical specimen for recovery of Enterobius vermicularis is the:
A. Stool specimen
B. Sigmoidoscopy scrapings
C. Duodenal aspirates
D. Series of Scotch tape preparations
D
Which parasite causes eosinophilic meningoencephalitis, a form of larva migrans causing fever, headache, stiff neck, and increased cells in the spinal fluid?
A. Necator americanus
B. Angiostrongylus cantonensis
C. Ancylostoma braziliense
D. Strongyloides stercoralis
B
“Cultures of parasites are different from bacterial cultures; no quality control is needed.” This statement is:
A. True, if two tubes of media are set up for each patient
B. True, if the media are checked every 24 hours
C. False, unless two different types of media are used
D. False, and organism and media controls need to be set up
D
Protozoan cysts were seen in a concentration sediment and tentatively identified as Entamoeba coli. However, the organisms were barely visible on the permanent stained smear because:
A. The organisms were actually not present in the concentrate sediment
B. There were too few cysts to allow identification on the stained smear
C. E. coli cysts were present but poorly fixed
D. The concentrate and permanent stained smear were not from the same patient
C
When humans have hydatid disease, the causative agent and host classification are:
A. Echinococcus granulosus—accidental intermediate host
B. Echinococcus granulosus—definitive host
C. Taenia solium—accidental intermediate host
D. Taenia solium—definitive host
A
A 45-year-old hunter developed fever, myalgia, and periorbital edema. He has a history of bear meat consumption. The most likely causative agent is:
A. Toxoplasma gondii
B. Taenia solium
C. Hymenolepis nana
D. Trichinella spiralis
D
In a condition resulting from the accidental ingestion of eggs, the human becomes the intermediate rather than the definitive host. The correct answer is:
A. Trichinosis
B. Cysticercosis
C. Ascariasis
D. Strongyloidiasis
B
A transplant patient on immunosuppressive drugs developed increasing diarrhea. The most likely combination of disease and diagnostic procedure is:
A. Trichinosis and trichrome stain
B. Microsporidiosis and modified trichrome stain
C. Toxoplasmosis and Gram stain
D. Paragonimiasis and wet preparation
B
After returning from a 2-year stay in India, a patient has eosinophilia, an enlarged left spermatic cord, and bilateral inguinal lymphadenopathy. The most likely clinical specimen and organism match is:
A. Thin blood films—Leishmania
B. Urine—concentration for Trichomonas vaginalis
C. Thin blood films—Babesia
D. Thick blood films—microfilariae
D
Patients with severe diarrhea should use “enteric precautions” to prevent nosocomial infections with:
A. Giardia lamblia
B. Ascaris lumbricoides
C. Cryptosporidium spp.
D. Cystoisospora belli
C
A 60-year-old Brazilian patient with cardiac irregularities and congestive heart failure suddenly dies. Examination of the myocardium revealed numerous amastigotes, an indication that the cause of death was most likely:
A. Leishmaniasis with Leishmania donovani
B. Leishmaniasis with Leishmania braziliense
C. Trypanosomiasis with Trypanosoma gambiense
D. Trypanosomiasis with Trypanosoma cruzi
D
When malaria smears are requested, what patient information should be obtained?
A. Diet, age, sex
B. Age, antimalarial medication, sex
C. Travel history, antimalarial medication, date of return to United States
D. Fever patterns, travel history, diet
C
In an outbreak of diarrheal disease traced to a municipal water supply, the most likely causative agent is:
A. Cryptosporidium spp.
B. Cystoisospora belli
C. Entamoeba histolytica
D. Dientamoeba fragilis
A
Within the United States, sporadic mini-outbreaks of diarrheal disease have been associated with the ingestion of strawberries, raspberries, fresh basil, mesclun (baby lettuce leaves), and snow peas. The most likely causative agent is:
A. Dientamoeba fragilis
B. Cyclospora cayetanensis
C. Schistosoma mansoni
D. Cystoisospora belli
B
Which of the following statements is true regarding onchocerciasis?
A. The adult worm is present in the blood
B. The microfilariae are in the blood during the late evening hours
C. The diagnostic test of choice is the skin snip
D. The parasite resides in the deep lymphatics
C
The most prevalent helminth to infect humans is:
A. Enterobius vermicularis, the pinworm
B. Ascaris lumbricoides, the large intestinal roundworm
C. Taenia saginata, the beef tapeworm
D. Schistosoma mansoni, one of the blood flukes
A
A helminth egg is described as having terminal polar plugs. The most likely helminth is:
A. Hookworm
B. Trichuris trichiura
C. Fasciola hepatica
D. Diphyllobothrium latum
B
Ingestion of which of the following eggs will result in infection?
A. Strongyloides stercoralis
B. Schistosoma japonicum
C. Toxocara canis
D. Opisthorchis sinensis
C
Plasmodium vivax and Plasmodium ovale are similar because they:
A. Exhibit Schüffner’s dots and have a true relapse in the life cycle
B. Have no malarial pigment and multiple rings
C. Commonly have appliqué forms in the red cells
D. Have true stippling, do not have a relapse stage, and infect old red cells
A
The term internal autoinfection can be associated with the following parasites:
A. Cryptosporidium spp. and Giardia lamblia
B. Cystoisospora belli and Strongyloides stercoralis
C. Cryptosporidium spp. and Strongyloides stercoralis
D. Giardia lamblia and Cystoisospora belli
C
Microsporidia have been identified as causing severe diarrhea, disseminated disease in other body sites, and ocular infections. Routes of infection have been identified as:
A. Ingestion
B. Inhalation
C. Direct contamination from the environment
D. Ingestion, inhalation, and direct contamination
D
An immunocompromised patient continues to have diarrhea after repeated ova and parasites (O&P) examinations (sedimentation concentration, trichrome permanent stained smear) were reported as negative; organisms that might be responsible for the diarrhea include:
A. Cryptosporidium spp., Giardia lamblia, and Cystoisospora belli
B. Giardia lamblia, microsporidia, and Endolimax nana
C. Taenia solium and Endolimax nana
D. Cryptosporidium spp. and microsporidia
D
Confirmation of an infection with microsporidia can be achieved by seeing:
A. The oocyst wall
B. Sporozoites within the spore
C. Evidence of the polar tubule
D. Organisms stained with modified acid-fast stain
C
Early ring stages of the fifth human malaria, Plasmodium knowlesi, resemble those of:
A. Plasmodium malariae
B. Plasmodium ovale
C. Plasmodium falciparum
D. Plasmodium vivax
C
Parasite stages that are immediately infective for humans on passage from the gastrointestinal tract include:
A. Schistosoma spp. eggs
B. Toxoplasma gondii bradyzoites
C. Giardia lamblia trophozoites
D. Cryptosporidium spp. oocysts
D
Older developing stages (trophs, schizonts) of the fifth human malaria, Plasmodium knowlesi, resemble those of:
A. Plasmodium malariae
B. Plasmodium ovale
C. Plasmodium falciparum
D. Plasmodium vivax
A
Autofluorescence requires no stain and is recommended for the identification of:
A. Entamoeba histolytica cysts
B. Toxoplasma gondii tachyzoites
C. Dientamoeba fragilis trophozoites
D. Cyclospora cayetanensis oocysts
D
Key characteristics of infection with Plasmodium knowlesi include:
A. Rapid erythrocytic cycle (24 hr), will infect all ages of RBCs, and can cause serious disease
B. Erythrocytic cycle limited to young RBCs and causes a relatively benign disease
C. The possibility of a true relapse from the liver, infection in older RBCs, and causes serious disease
D. Extended life cycle (72 hr), will infect all ages of RBCs, and disease is similar to that caused by P. ovale
A
Microsporidial infections can be confirmed using:
A. Light microscopy and modified trichrome stains
B. Phase contrast microscopy and routine trichrome stains
C. Electron microscopy and modified acid-fast stains
D. Fluorescence microscopy and hematoxylin stains
A
Although the pathogenicity of Blastocystis hominis remains controversial, newer information suggests that:
A. Most organisms are misdiagnosed as artifacts
B. Numerous strains/species are included in the name, some of which are pathogenic and some are nonpathogenic
C. The immune status of the host is solely responsible for symptomatic infections
D. The number of organisms present determines pathogenicity
B
Potential problems using EDTA anticoagulant and holding the blood too long prior to preparation of thick and thin blood films include:
A. Changes in parasite morphology, loss of organisms within several hours, and poor staining
B. Loss of Schüffner’s dots, poor adherence of the blood to the glass slide, and parasites beginning the vector cycle within the tube of blood
C. Neither A nor B
D. All of these options
D
Which of the following is a key characteristic of the thick blood film?
A. The ability to see the parasite within the RBCs
B. The ability to identify the parasites to the species level
C. The examination of less blood than the thin blood film
D. The necessity to lake the RBCs during or prior to staining
D
An emergency department physician ordered a culture and sensitivity test on a catheterized urine specimen obtained from a 24-year-old female patient. A colony count was done and gave the following results after 24 hours:
Blood agar plate = >100,000 col/mL of gram-positive cocci resembling staphylococci
MacConkey agar = No growth
Hemolysis = Neg Novobiocin = Resistant
CNA plate = Inhibited growth
Catalase = Positive
This isolate is:
A. Staphylococcus saprophyticus
B. Micrococcus luteus
C. Staphylococcus aureus
D. Streptococcus pyogenes
A
An outbreak of Staphylococcus aureus in the nursery department prompted the Infection Control Committee to proceed with an environmental screening procedure. The best screening media to use for this purpose would be:
A. CNA agar
B. THIO broth
C. Mannitol salt agar
D. PEA agar
C
A listless 12-month-old boy with a fever of 103°F was taken to the emergency department. He had been diagnosed with an ear infection 3 days earlier. A spinal tap was performed, but only one tube of CSF was obtained from the lumbar puncture. The single tube of CSF should be submitted first to which department?
A. Chemistry
B. Microbiology
C. Hematology
D. Cytology/Histology
B
A 65-year-old female outpatient was requested by her physician to submit a 24-hour urine specimen for protein and creatinine tests. He also requested testing for mycobacteria in the urine. Should the microbiology laboratory accept this 24-hour specimen for culture?
A. Yes, if the specimen is kept on ice
B. Yes, if the specimen is for aerobic culture only
C. No, the specimen must be kept at room temperature
D. No, the specimen is unsuitable for the recovery of mycobacteria
D
A lymph node biopsy obtained from a 30-year-old male patient was submitted to the microbiology laboratory for a culture and AFB smear for mycobacteria. The specimen was fixed in formalin. This specimen should be:
A. Accepted for AFB smear and cultured
B. Rejected
C. Held at room temperature for 24 hours and then cultured
D. Cultured for anaerobes only
B
A 49-year-old man who traveled to Mexico City returned with a bad case of dysentery. His symptoms were fever; abdominal cramping; and bloody, mucoidal, frequent stools. In addition to this, many WBCs were seen on the Gram stain smear. Stool culture gave the following results:
Gram stain: Gram-negative rods Indole = +
Urease = Neg
Lactose = +
Lysine decarboxylase
= Neg
Motility = Neg
What is the most likely organism?
A. Salmonella spp.
B. Proteus mirabilis
C. Escherichia coli
D. Enteroinvasive E. coli (EIEC)
D
An immunocompromised 58-year-old female chemotherapy patient received 2 units of packed RBCs. The patient died 3 days later, and the report from the autopsyrevealed that her death was due to septic shock. The blood bags were cultured, and the following results were noted:
GROWTH OF AEROBIC GRAM NEGATIVE RODS ON BOTH MACCONKEY AND BLOOD AGARS
Lactose = Neg Indole = Neg Urease = +
Sucrose = +
VP = Neg Motility 22°C = +
Citrate = Neg
H2S = Neg
Motility 37°C = Neg
What is the most likely identification?
A. Escherichia coli
B. Yersinia enterocolitica
C. Enterobacter cloacae
D. Citrobacter freundii
B
An 80-year-old male patient was admitted to the hospital with a fever of 102°F. A sputum culture revealed many gram-negative rods on MacConkey agar and blood agar. The patient was diagnosed with pneumonia. The following biochemical results were obtained from the culture:
H2S = Neg Citrate = + Motility = Neg
Lactose = +
Indole = +
Resistance to ampicillin
and carbenicillin
Urease = + VP = +
What is the most likely identification?
A. Klebsiella oxytoca
B. Proteus mirabilis
C. Escherichia coli
D. Klebsiella pneumoniae
A
A pediatric patient with severe bloody diarrhea who had been camping with his parents was admitted to the hospital with complications of hemolytic uremic syndrome (HUS). Several stool specimens were cultured with the following results noted:
Gram stain smear = Many gram-negative rods with no WBCs seen
Blood agar = Normal flora MacConkey agar = Normal flora
MacConkey agar with sorbitol = Many clear colonies (sorbitol negative)
Hektoen agar = Normal flora
Campy agar = No growth
What is the most likely identification?
A. Yersinia spp.
B. E. coli O157:H7
C. Salmonella spp.
D. Shigella spp.
B
A sputum culture from a 13-year-old cystic fibrosis patient grew a predominance of short, gram-negative rods that tested oxidase negative. On MacConkey, chocolate, and blood agar plates, the organism appeared to have a lavender-green pigment. Further testing showed:
Motility = +
Glucose = + (oxidative) Lysine decarboxylase = +
DNase = +
Maltose = + (oxidative) Esculin hydrolysis = +
What is the most likely identification?
A. Stenotrophomonas maltophilia
B. Acinetobacter baumannii
C. Pseudomonas aeruginosa
D. Burkholderia (P.) cepacia
A
A 14-year-old emergency department patient had been to the doctor’s office 2 days previously with abdominal pain, diarrhea, and a low-grade fever. He was diagnosed with pseudoappendicular syndrome. Cultures from the stool containing blood and WBCs showed the following results:
AEROBIC GRAM NEGATIVE RODS ON MACCONKEY AGAR CLEAR COLONIES
Campy agar = No growth
Lactose = Neg Indole = Neg Motility 37°C =
Neg
Sucrose = +
VP = Neg Motility 22°C = +
Citrate = Neg
H2S = Neg Hektoen agar = NF
What is the most likely identification?
A. Yersinia enterocolitica
B. Salmonella spp.
C. Shigella spp.
D. Escherichia coli
A
A patient with a human bite wound on the right forearm arrived at the clinic for treatment. The wound was inflicted 36 hours earlier, and a culture was taken by the physician on duty. After 48 hours, the culture results were:
Gram-stain smear = Gram-negative straight, slender rods
Chocolate agar plate = “Pitting” of the agar by small, yellow, opaque colonies
Oxidase = + Motility = Neg Glucose = +
Growth in increased CO2 = +
Catalase = Neg
Growth at 42°C = Neg
What is the most likely identification of this facultative anaerobe?
A. Pseudomonas aeruginosa
B. Acinetobacter baumannii
C. Kingella kingae
D. Eikenella corrodens
D
When testing for coagulase properties, staphylococci isolates from a 67-year-old male diabetic patient showed a positive tube test (free coagulase). The organism should be identified as:
A. Staphylococcus aureus
B. Staphylococcus haemolyticus
C. Staphylococcus saprophyticus
D. Micrococcus luteus
A
An isolate of Staphylococcus aureus was cultured from an ulcer obtained from the leg of a diabetic 79-year-old female patient. The organism showed resistance to methicillin. Additionally, this isolate should be tested for resistance or susceptibility to:
A. Erythromycin
B. Gentamicin
C. Vancomycin
D. Kanamycin
C
A dog bite wound to the thumb of a 20-year-old male patient became infected. The culture grew a gram-negative, slender rod, which was a facultative anaerobe.
The following results were noted:
Oxidase = + Motility = Neg Catalase = + Capnophilic = +
“Gliding” on the agar was noted. What is the most likely identification?
A. Pseudomonas aeruginosa
B. Capnocytophaga canimorsus
C. Acinetobacter baumannii
D. Proteus mirabilis
B
A patient exhibits fever, chills, abdominal cramps, diarrhea, vomiting, and bloody stools 10 to
12 hours after eating. Which organisms will
most likely grow from this patient’s stool
culture?
A. Salmonella or Yersinia spp.
B. E. coli O157:H7 or Shigella spp.
C. Staphylococcus aureus or Clostridium
D. Salmonella or enterococcus
B
An isolate recovered from a vaginal culture obtained from a 25-year-old female patient who is 8 months pregnant is shown to be a gram-positive cocci, catalase negative, and β-hemolytic on blood agar. Which tests are needed for further identification?
A. Optochin, bile solubility, PYR
B. Bacitracin, CAMP, PYR
C. Methicillin, PYR, trehalose
D. Coagulase, glucose, PYR
B
Which organism is the most often recovered gram- positive cocci (catalase negative) from a series of blood cultures obtained from individuals with endocarditis?
A. Streptococcus agalactiae
B. Clostridium perfringens
C. Enterococcus faecalis
D. Pediococcus spp.
C
A presumptive diagnosis of gonorrhea can be made from an exudate from a 20-year-old emergency department patient if which of the following criteria are present?
A. Smear of urethral exudate (male only) shows typical gram-negative, intracellular diplococci; growth of oxidase-positive, gram-negative diplococci on selective agar (modified Thayer–Martin)
B. Smear from vaginal area shows gram-negative diplococci; growth of typical colonies on blood agar
C. Smear from rectum shows typical gram-negative diplococci; no growth on chocolate agar
D. Growth of gram-negative cocci on MacConkey agar and blood agar
A
“Clue cells” are seen on a smear of vaginal discharge obtained from an 18-year-old female emergency department patient. This finding, along with a fishy odor (amine) after the addition of 10% KOH, suggests bacterial vaginosis caused by which organism?
A. Staphylococcus epidermidis
B. Streptococcus agalactiae
C. Gardnerella vaginalis
D. E. coli
C
A 1-month-old infant underwent a spinal tap to rule out bacterial meningitis. The CSF was cloudy, and the smear showed many pus cells and short gram-positive rods. After 18 hours, many colonies appeared on blood agar that resembled Streptococcus spp. or L. monocytogenes. Which of the following preliminary tests should be performed on the colonies to best differentiate L. monocytogenes from Streptococcus spp.?
A. Hanging-drop motility (25°C) and catalase
B. PYR and bacitracin
C. Oxidase and glucose
D. Coagulase and catalase
A
Which biochemical tests should be performed in order to identify colorless colonies growing on MacConkey agar (swarming colonies on blood agar) from a catheterized urine specimen?
A. Indole, phenylalanine deaminase, and urease
B. Glucose, oxidase, and lactose utilization
C. Phenylalanine deaminase and bile solubility
D. H2S and catalase
A
A gram-negative nonfermenter was isolated from a culture taken from a burn patient. Which of the following is the best choice of tests to differentiate Pseudomonas aeruginosa from Acinetobacter spp.?
A. Growth on MacConkey agar, catalase, growth at 37°C
B. Oxidase, motility, growth at 42°C
C. Growth on blood agar, oxidase, growth at 35°C
D. String test and coagulase test
B
A Haemophilus spp., recovered from a throat culture obtained from a 59-year-old male patient undergoing chemotherapy, required hemin (X factor) and NAD (V factor) for growth. This species also hemolyzed horse erythrocytes on blood agar. What is the most likely species?
A. H. ducreyi
B. H. parahaemolyticus
C. H. haemolyticus
D. H. aegyptius
C
Anaerobic gram-negative rods were recovered from the blood of a patient after gallbladder surgery. The bacteria grew well on agar containing 20% bile, but were resistant to kanamycin and vancomycin. What is the most likely identification?
A. Clostridium perfringens
B. Bacteroides fragilis group
C. Prevotella spp.
D. Porphyromonas spp.
A
In Breakpoint Antimicrobial Drug Testing, interpretation of susceptible (S), intermediate (I), and resistant (R) refers to testing antibiotics
by using:
A. The amount needed to cause bacteriostasis
B. Only the specific concentrations necessary to report S, I, or R
C. An MIC of 64 μg/mL
D. A dilution of drug that is one tube less than the toxic level
B
A CSF sample obtained from a 2-week old
infant with suspected bacterial meningitis grew gram-negative rods on blood and chocolate agars. The following results were noted:
MacConkey agar = No growth Glucose (open) OF = + Glucose (closed) OF = Neg Indole = +
Motility = Neg
42° C growth = Neg
ONPG = +
Urease = Neg Catalase = + Oxidase = + Pigment = Yellow
What is the correct identification?
A. Pseudomonas aeruginosa
B. Chryseobacterium meningosepticum
C. Acinetobacter baumannii
D. E. coli
B
During the summer break, several middle-aged elementary school teachers from the same school district attended a 3-day seminar in Chicago. Upon returning home, three female teachers from the group were hospitalized with pneumonia, flulike symptoms, and a nonproductive cough. Routine testing of sputum samples revealed normal flora. Further testing using buffered
CYE agar with L-cysteine and α-ketoglutarate in 5% CO2 produced growth of opaque colonies that stained faintly, showing thin gram-negative rods. What is the most likely identification?
A. Legionella pneumophila
B. Haemophilus influenzae
C. Eikenella corrodens
D. Streptococcus pneumoniae
A
A vancomycin-resistant gram-positive coccobacillus resembling the Streptococcus viridans group was isolated from the blood of a 42-year-old female patient undergoing a bone marrow transplant. The PYR and leucine aminopeptidase (LAP) tests were negative. The following results were noted:
Catalase = Neg
Esculin hydrolysis = Neg Hippurate hydrolysis = Neg
CAMP = Neg
Gas from glucose = + 6.5% salt broth = Neg
What is the correct identification?
A. Leuconostoc spp.
B. Enterococcus spp.
C. Staphylococcus spp.
D. Micrococcus spp.
A
A catalase-positive, gram-positive coccus (clusters on Gram stain smear) grew pale yellow, creamy colonies on 5% sheep blood agar. The specimen was recovered from pustules on the face of a 5-year-old girl with impetigo. The following
test reactions indicate which organism?
PYR = Neg
Esculin hydrolysis = Neg Vancomycin = Sensitive
LAP = Neg (V)
6.5% Salt broth = Neg CAMP test = Neg
What is the correct identification?
A. Leuconostoc spp.
B. Gemella spp.
C. Enterococcus spp.
D. Micrococcus spp.
B
A catalase-negative, gram-positive coccus resembling staphylococci (clusters on the Gram- stained smear) was recovered from three different blood cultures obtained from a 60-year-old patient diagnosed with endocarditis. The following test results were noted:
Glucose = + (Fermentation) PYR = Neg
Lysostaphin = Sensitive
Oxidase = Neg Bacitracin = Sensitive
A. Micrococcus spp.
B. Streptococcus spp.
C. Enterococcus spp.
D. Staphylococcus aureus
D
An immunocompromised patient with prior antibiotic treatment grew aerobic gram-positive cocci from several clinical specimens that were cultured. The organism was vancomycin resistant and catalase negative. Additional testing proved negative for enterococci. What other groups of organisms might be responsible?
A. Leuconostoc spp. and Pediococcus spp.
B. Streptococcus pyogenes and Streptococcus agalactiae
C. Micrococcus spp. and Gemella spp.
D. Clostridium spp. and Streptococcus bovis
A
A wound (skin lesion) specimen obtained from a newborn grew predominantly β-hemolytic colonies of gram-positive cocci on 5% sheep blood agar. The newborn infant was covered with small skin eruptions that gave the appearance of a “scalding of the skin.” The gram-positive cocci proved to be catalase positive. Which tests should follow for the appropriate identification?
A. Optochin, bile solubility, PYR
B. Coagulase, glucose fermentation, DNase
C. Bacitracin, PYR, 6.5% salt broth
D. CAMP, bile-esculin, 6.5% salt broth
B
A 20-year-old female patient entered the emergency clinic complaining of abdominal pain, fever, and a burning sensation during urination. An above-normal WBC count along with pus cells and bacteria in the urine specimen prompted the emergency physician to order a urine culture. The colony count reported for this patient revealed >100,000 col/mL of a nonhemolytic, catalase- negative, gram-positive organism on 5% sheep blood agar. The following test results indicate which organism?
PYR = +
6.5% Salt broth = + growth Bacitracin = Neg
Bile Esculin = + Optochin = Neg
A. Enterococcus faecalis
B. Streptococcus pyogenes
C. Streptococcus agalactiae
D. Streptococcus bovis
A
A tissue biopsy specimen of the stomach was obtained from a 38-year-old male patient diagnosed with gastric ulcers. The specimen was transported immediately and processed for culture and histology. At 5 days, the culture produced colonies of gram-negative (curved) bacilli on chocolate and Brucella agar with 5% sheep blood. The cultures were held at 35°C–37°C in a microaerophilic atmosphere. The colonies tested positive for urease. The most likely identification is:
A. E. coli
B. Helicobacter pylori
C. Enterococcus faecalis
D. Streptococcus bovis
B
A sputum specimen from an 89-year-old male patient with suspected bacterial pneumonia grew a predominance of gram-positive cocci displaying alpha-hemolysis on 5% sheep blood agar. The colonies appeared donut shaped and mucoidy and tested negative for catalase. The most appropriate tests for a final identification are:
A. Coagulase, glucose fermentation, lysostaphin
B. Penicillin, bacitracin, CAMP
C. Optochin, bile solubility, PYR
D. Bile esculin, hippurate hydrolysis
C
A catalase-positive, gram-positive short rod was recovered from the blood of a prenatal patient. The organism appeared on 5% sheep blood as white colonies surrounded by a small zone of beta-hemolysis. The following tests were performed, indicating the patient was infected with which organism?
Motility = + (tumbling on wet prep) room temperature
Motility = + (umbrella-shape on semisolid agar) room temperature
Glucose = + (fermentation) Esculin = + Voges–Proskauer = +
A. Listeria monocytogenes
B. Streptococcus agalactiae
C. Streptococcus pyogenes
D. Lactobacillus spp.
A
An emergency department physician suspected Corynebacterium diphtheriae when examining the sore throat of an exchange student from South America. What is the appropriate media for the culture of the nasopharyngeal swab obtained from the patient?
A. Chocolate agar
B. Thayer–Martin agar
C. Tinsdale medium
D. MacConkey agar
C
A 25-year-old pregnant patient complained of vaginal irritation. Cultures taken for STDs proved negative. A Gram-stained vaginal smear revealed many epithelial cells with gram-variable short rods (coccobacilli) covering the margins. What is the most likely cause of the vaginosis?
A. Group B streptococci spp.
B. Gardnerella vaginalis
C. Staphylococcus aureus
D. Staphylococcus saprophyticus
B
A 50-year-old male transplant patient was experiencing neurological difficulties after a pulmonary infection. A spinal tap revealed a cloudy CSF with a Gram-stained smear revealing gram-positive long-beaded bacilli. An acid-fast smear showed filamentous partially acid-fast bacilli. What is the most likely identification of the organism?
A. Nocardia asteroides
B. Mycobacterium avium
C. Mycobacterium bovis
D. Legionella spp.
A
Anaerobic gram-positive, spore-forming bacilli were recovered from the feces of a chemotherapy patient with severe diarrhea. The patient had undergone antibiotic therapy 1 week prior. The fecal culture produced growth only on the CCFA plate. No aerobic growth of normal flora was seen after 48 hours. The following results were noted:
Kanamycin = Sensitive Colistin = Resistant Lipase = Neg
Indole = Neg
Vancomycin = Sensitive Lecithinase = Neg Nitrate = Neg
Urease = Neg
Spores = + that fluoresce chartreuse (yellow-green)
What is the correct identification?
A. Clostridium perfringens
B. Clostridium tetani
C. Clostridium sordellii
D. Clostridium difficile
D
Anaerobic gram-positive diphtheroids (nonspore formers) were cultured from two separate blood culture bottles (at 5 days) obtained from a 25-year-old patient admitted to the hospital with dehydration, diarrhea, and other flulike symptoms. Four other blood culture bottles did not grow
any organisms at 7 days and were discarded. The following results were obtained from the recovered anaerobe:
Indole = +
Kanamycin = Sensitive Colistin = Resistant
Nitrate = + Catalase = + Vancomycin = Sensitive Major acid from PYG broth
by GLC = Propionic acid
What is the correct identification?
A. Eubacterium lentum
B. Propionibacterium acnes
C. Actinomyces spp.
D. Peptostreptococcus spp.
B
Anaerobic, nonpigmented, gram-negative rods were recovered from an anaerobic blood agar plate after 48 hours of incubation. The Gram-stained smear showed thin bacilli with pointed ends. The colonies on blood agar had the appearance of dry, irregular, white breadcrumb-like morphology with greening of the agar. The following reactions were noted:
Kanamycin = Sensitive Colistin = Sensitive Indole = +
Lipase = Neg
Growth on 20% bile agar = Neg
Vancomycin = Resistant
Nitrate = Neg
Catalase = Neg
Urease = Neg
What is the correct identification?
A. Fusobacterium nucleatum
B. Bacteroides fragilis
C. Clostridium perfringens
D. Peptostreptococcus spp.
A
Anaerobic gram-positive bacilli with subterminal spores were recovered from several blood cultures obtained from a patient diagnosed with a malignancy of the colon. The following results were recorded:
Indole = Neg Urease = Neg Lipase = Neg Catalase = Neg Lecithinase = Neg
Growth on blood agar = Swarming colonies
What is the correct identification?
A. Clostridium septicum
B. Clostridium perfringens
C. Clostridium sordellii
D. Propionibacterium acnes
A
Anaerobic gram-negative bacilli were recovered from fluid obtained from drainage of a postsurgical abdominal wound. The following test results were recorded:
Kanamycin = Resistant Colistin = Resistant
Growth on 20% bile plate = + Indole = V (Neg)
Urease = Neg
Vancomycin = Resistant
Pigment = Neg Nitrate = Neg Lipase = Neg
What is the correct identification?
A. Prevotella spp.
B. Bacteroides fragilis group
C. Porphyromonas spp.
D. Clostridium spp.
B
A 2-month-old infant in good health was scheduled for a checkup at the pediatrician’s office. After arriving for the appointment, the mother noted white patches on the baby’s tongue and in his mouth. The baby constantly used a pacifier. What is the most likely organism causing the white patches?
A. Cryptococcus neoformans
B. Candida albicans
C. Aspergillus fumigatus
D. None of these options
B
A 69-year-old male patient who was a cigarette smoker visited the doctor’s office complaining
of a cough and congestion of the lungs. Routine cultures of early morning sputum (× 3) for bacteria as well as for AFB revealed no pathogens. A fungal culture was also ordered that grew the following on Sabouraud dextrose agar after 3 days:
Hyphae = Septate with dichotomous branching Spores = Produced by conidial heads with
numerous conidia. Colonies = Velvety or powdery, white at first, then turning dark greenish to gray (reverse = white to tan) Vesicle = Holding phialides usually on upper two-thirds only
What is the most likely identification?
A. Aspergillus niger
B. Absidia spp.
C. Mucor spp.
D. Aspergillus fumigatus
D
A dehydrated 25-year-old male patient was admitted to the hospital with symptoms similar to those of chronic fatigue syndrome. Serological testing proved negative for recent streptococcal infection, Epstein–Barr virus, and hepatitis. Which of the following viral serological tests should help with a possible diagnosis?
A. CMV
B. Echovirus
C. Respiratory syncytial virus
D. Measles virus
A
A nursing student working in the emergency department accidentally stuck herself with a needle after removing it from an intravenous set taken from a suspected drug user. The best course of action, after reporting the incident to her supervisor, is to:
A. Test the student for HIV virus if flulike symptoms develop in 2–4 weeks
B. Immediately test the patient and the student for HIV using an EIA or ELISA test
C. Perform a Western blot assay on the student’s serum
D. Draw blood from the student only and freeze it for further testing
B
A 30-year-old female patient complained of vaginal irritation and symptoms (fever, dysuria, and inguinal lymphadenopathy) associated with sexually transmitted disease (STD). Examination showed extensive lesions in the genital area. Chlamydia spp. testing, Neisseria gonorrhoeae, and Gardnerella vaginalis cultures were negative. Rapid plasma reagin (RPR) testing was also negative. What is the next line of testing?
A. Darkfield examination
B. Herpes simplex testing
C. Trichomonas spp. testing
D. Group B streptococcal testing
B
A patient is being seen in the emergency department for a low-grade fever, headache, and general malaise after returning from Africa on a photographic safari. The physician has requested blood for malaria; the laboratory would like to have patient information regarding:
A. Specific travel history and body temperature every 4 hours
B. Liver function tests and prophylactic medication history
C. Transfusion history and body temperature every 4 hours
D. Prophylactic medication history and specific travel history
D
Examination of a modified acid-fast stained fecal smear reveals round structures measuring approximately 8–10 μm, some of which are stained and some of which are not. They do not appear to show any internal morphology. The patient is symptomatic with diarrhea, and the cause may be:
A. Blastocystis hominis
B. Polymorphonuclear leukocytes
C. Cyclospora cayetanensis
D. Large yeast cells
C
A patient has been diagnosed as having amebiasis but continues to be asymptomatic. The physician has asked for an explanation and recommendations regarding follow-up. Suggestions should include:
A. Consideration of Entamoeba histolytica versus Entamoeba dispar
B. A request for an additional three stools for culture
C. Initiating therapy, regardless of the patient’s asymptomatic status
D. Performance of barium x-ray studies
A
Although a patient is strongly suspected of having giardiasis and is still symptomatic, three routine stool examinations (O&P exam) have been performed correctly and reported as negative. Biopsy confirmed the patient had giardiasis. Reasons for these findings may include:
A. The patient was coinfected with several bacterial species
B. Giardia lamblia tends to adhere to the mucosal surface and more than three stool examinations may be required to confirm a suspected infection
C. The organisms present did not stain with trichrome stain and therefore the morphology is very atypical
D. Special diagnostic procedures such as the Knott concentration and nutrient-free agar cultures should have been used
B
A transplant patient is currently receiving steroids. The patient is now complaining of abdominal pain and has symptoms of pneumonia and positive blood cultures with gram-negative rods. The individual has been living in the United States for 20 years but grew up in Central America. The most likely parasite causing these symptoms is:
A. Trypanosoma brucei rhodesiense
B. Giardia lamblia
C. Strongyloides stercoralis
D. Schistosoma japonicum
C
Spores are found in select groups of bacteria. Whichof the following statements describes the major advan- tage to the bacteria that possess these structures?
a. Spores are resistant to heat, cold, drying, most chemicals, and boiling
b. Spores allow an organism to better control its local environment
c. Spores allow bacteria to attach or adhere to host tissues
d. Organisms with spores have a more efficient exchange of genetic material
A
Choose the binomial name that is correctly written.
a. Staphylococcus Aureus
b. Staphylococcus species aureus
c. Staphylococcus aureus
d. Staphylococcus aureus
Fermentation end-products are often used to aid in the identification of bacteria. Fermentation results in which of the following?
a. Conversion of glucose to pyruvate
b. Lactic acid, mixed acids, alcohols, CO2 production
c. CO2 and water
d. Specific teichoic acids
B
The exchange of cellular DNA between two living
bacterial cells that involves an intercellular bridge is which of the following processes?
a. Transformation
b. Transduction
c. Plasmidization
d. Conjugation
D
Transduction is defined as which of the following?
a. The change of the bacterial genotypes through the exchange of DNA from one cell to another
b. An internal change in the original nucleotide sequence of a gene or genes within an organism’s genome
c. The process by which genetic elements such aplasmids and transposons excise from one genomic location and insert into another
d. A mechanism that is mediated by viruses, by which DNA from two bacteria may come together in on cell, thus allowing for recombination
D
A mordant that is applied after the primary stain to chemically bond the alkaline dye to the bacterial cell wall is which of the following?
a. Safranin
b. Crystal violet
c. Gram’s iodine
d. Gram’s decolorizer
C
Which of the following bacteria should be considered important pathogens when reading gram-stained smears of soft tissue abscess?
a. Streptococcus pneumoniae
b. Neisseria gonorrhoeae
c. Pseudomonas aeruginosa
d. Staphylococcus aureus
D
85% N2, 10% H2, 5% CO2 is the environmental condition that best suits which type of organism?
a. Aerobes
b. Anaerobes
c. Capnophiles
d. Microaerophiles
B
Which medium can be described as containing bile salts and dyes (bromothymol blue and acid fuchsin) to selectively slow the growth of most nonpathogenic gram- negative bacilli found in the gastrointestinal tract and allow Salmonella spp. and Shigella spp. to grow?
a. Thayer-Martin
b. MacConkey
c. PEA (phenylethyl alcohol)
d. Hektoen
D
Choose the group of bacteria that is described as catalase-positive, gram-positive cocci that grow fac- ultatively anaerobic and that form grapelike clusters.
a. Neisseria spp.
b. Rothia (Stomatococcus) spp.
c. Staphylococcus spp.
d. Micrococcus spp.
C
The slide coagulase test is a rapid screening test for the production of which of the following?
a. Clumping factor
b. Free coagulase
c. Extracellular coagulase
d. Catalase
A
The first identification test performed on a clinical isolate of gram-positive, catalase-positive cocci should be which of the following?
a. Penicillin test
b. Gram stain
c. Oxidase test
d. Coagulase test
D
The toxic shock syndrome toxin-1 is an important vir- ulence factor in staphylococcal disease. This toxin is classified into which of the following groups of toxins?
a. Cytolytic toxin
b. Leukocidin
c. Phospholipase
d. Enterotoxin
D
Mannitol salt agar is selective and differential for which group of organisms?
a. Staphylococcus spp.
b. Enterococcus spp.
c. Gram-positive cocci
d. Streptococcus spp.
A
Within 5 hours of returning home from lunch at your most favorite fast food restaurant you feel very sick and are vomiting. Which of the following is the most likely causative organism?
a. Staphylococcus aureus
b. Vibrio parahaemolyticus
c. Shigella sonnei
d. Escherichia coli
A
The bacterial species that can be described as suscep- tible to bile and optochin, a-hemolytic, a major cause of bacterial meningitis, and often carrying an anti- phagocytic capsule is which of the following?
a. Enterococcus faecalis
b. Streptococcus pneumoniae
c. Streptococcus pyogenes
d. Streptococcus agalactiae
B
The bacterial species that can be described as suscep- tible to penicillin and bacitracin, b-hemolytic, a major cause of bacterial pharyngitis, and often carrying an antiphagocytic M protein is which of the following?
a. Enterococcus faecalis
b. Streptococcus pyogenes
c. Streptococcus agalactiae
d. Viridans streptococci
B
The bacterial species that can be described as able to hydrolyze hippurate, b-hemolytic, a major cause of neonatal meningitis and sepsis, and producer of the CAMP factor is which of the following?
a. Streptococcus pneumoniae
b. Streptococcus pyogenes
c. Streptococcus agalactiae
d. Viridans streptococci
C
The rapid antigen detection methods for throat swabs used for screening patients for streptococcal pharyngitis can be best described by which of the fol- lowing statements?
a. They can be useful in quickly identifying most cases of streptococcal pharyngitis
b. They are a quick way to rule out streptococcal pharyngitis and avoid giving antibiotics when not needed
c. They are always very sensitive and specific for streptococcal pharyngitis
d. They are a quick and accurate way to diagnose bacterial and viral pharyngitis
A
Enterococcus spp. can be differentiated from most Streptococcus spp. by which of the following tests?
a. Growth in presence of 6.5% salt
b. Production of catalase
c. Production of coagulase
d. Growth on PEA medium
A
A pure culture of a b-hemolytic Streptococcus sp. recovered from a leg ulcer gave the following reactions:
CAMP test =Negative
Bile esculin slant= No growth
PYR =Negative
Optochin= Resistant
Hippurate hydrolysis= Negative 6.5% Salt= No growth
Bacitracin =Resistant
SXT= Sensitive
Which of the following is the most likely identifica- tion of this organism?
a. Streptococcus pyogenes
b. Streptococcus agalactiae
c. Enterococcus faecalis
d. Streptococcus sp., not groups A, B, or D
D
The ability to grow well at refrigerator temperatures is a characteristic of which of the following organisms?
a. Mycobacterium gordonae
b. Listeria monocytogenes
c. Erysipelothrix
d. Bacillus cereus
B
A catalase-positive, gram-positive bacillus that is not acid-fast, does not branch, and does not form spores could possibly belong to which group of bacteria?
a. Corynebacterium
b. Bacillus
c. Nocardia
d. Mycobacterium
A
A throat culture was taken from a 6-year-old boy with a gray pseudomembrane covering his oro- pharynx. A catalase-positive organism was isolated on cysteine-tellurite medium and subcultured to Tinsdale medium, where it grew as black colonies with brown halos. A Gram stain was performed on these colonies. Which of the following cellular mor- phologies was most likely seen?
a. Gram-positive branching bacilli
b. Gram-positive cocci in short chains
c. Gram-positive bacilli in irregular clublike shape
d. Gram-positive cocci in grapelike clusters
C
A blood culture is positive for gram-positive bacilli that gave the following growth characteristics and
biochemical reactions:
MacConkeyagar:Nogrowth Catalase:Positive
H2S on TSI: negative Growth of blood agar, nonhemolytic Nonmotile No spores
These reactions are consistent with which of the following organisms?
a. Listeria spp.
b. Group B
b Streptococcus
c. Erysipelothrix spp.
d. Corynebacterium spp.
D
A skin lesion was opened and drained in surgery. The culture was positive for a gram-positive bacillus, which gave the following growth characteristics and biochemical reactions:
MacConkeyagar:Nogrowth Catalase:Negative H2S on TSI: Positive Growth of blood agar, nonhemolytic Nonmotile No spores. These reactions are consistent with which of the following organisms?
a. Listeria spp.
b. Group B b Streptococcus
c. Erysipelothrix spp.
d. Corynebacterium spp.
C
Which of the following sets of tests provide the best differentiation of Erysipelothrix from Listeria monocytogenes?
a. Gram-stained smear, oxidase, and optochin
b. Gram-stained smear, catalase, and motility
c. CAMP test, hydrogen sulfide production, esculin hydrolysis
d. Reverse CAMP, gram-stained smear, b-hemolysis
C
Neonatal meningitis is an uncommon but significant disease. Two important causes of this disease may be somewhat difficult to diff- erentiate on preliminary observation. Which of the following sets of tests provide the best differen- tiation of Streptococcus agalactiae from Listeria
monocytogenes?
a. Gram-stained smear, oxidase, and optochin
b. Gram-stained smear, catalase, and motility
c. CAMP test, hydrogen sulfide production, b-hemolysis
d. Reverse CAMP, gram-stained smear, b-hemolysis
B
Which of the following tests is important as a part of the genus identification or as part of a preliminary identification but is not used as a confirmatory iden- tification of Bacillus anthracis?
a. Demonstration of a capsule
b. Demonstration of spore formation
c. Positive PCR test
d. Lysis of the strain by specific bacteriophages
B
Bacillus anthracis and Bacillus cereus can be differ- entiated in the laboratory by a variety of different test results. Which of the following sets of tests best dif- ferentiate these two species?
a. Catalase and glucose fermentation
b. Motility and lecithinase production
c. Oxidaseandb-hemolysison5%sheepbloodagar
d. Motilityandb-hemolysison5%sheepbloodagar
D
Which of the following specimens would be best for identifying Bacillus cereus as the cause of an out-
break of food poisoning?
a. Blood
b. Rectal swabs
c. Stool samples
d. Food
A first morning sputum sample is received for acid- fast culture. The specimen is centrifuged, and the sed- iment is inoculated on two Lowenstein-Jensen slants that are incubated at 35 C with 5% to 10% CO2. After 1 week, the slants show abundant growth over the entire surface. Stains reveal gram-negative bacilli. Which of the following should be done to avoid this problem?
a. Use a medium specifically designed for the growth of AFB
b. Dilute out the sediment before inoculation with saline
c. Decontaminate the specimen with NALC– sodium hydroxide mixture
d. Incubate the tubes at room temperature to retard bacterial growth
C
A patient recently arrived in the United States from Africa presents with a long-standing cutaneous lesion, which is cultured for bacteria, fungi, and AFB. An AFB smear is made and is reported as pos- itive for AFB. After 8 weeks of culture on both non- selective and selective AFB media, no colonies appear. Which of the following organisms should be suspected?
a. M. kansasii
b. M. tuberculosis
c. M. leprae
d. M. avium-intracellulare complex
C
The mycobacterial species that occur in humans and belong to the M. tuberculosis complex include which of the following?
a. M. tuberculosis, nontuberculous Mycobacteria, M. bovis, and M. africanum
b. M. tuberculosis, M. gordonae, M. bovis BCG, and M. africanum
c. M. tuberculosis, M. bovis, M. avium, and M. intracellulare
d. M. tuberculosis, M. bovis, M. bovis BCG, and M. africanum
D
The Runyon system of classification is based on which of the following?
a. Colony and microscopic morphology
b. Biochemical characteristics
c. Growth rate and colonial pigmentation
d. All of the above are correct
C
In identification of mycobacterial isolates, the Tween 80 test involves which of the following?
a. An enzyme that is able to produce Tween 80 from certain ingredients found in the medium
b. Lipase that is able to hydrolyze polyoxyethylene sorbitan monooleate into oleic acid and polyoxyethylated sorbitol
c. The metabolism of niacin to nicotinic acid by enzymatic action
d. Testing the isolate for susceptibility to Tween 80
B
The gram-negative bacillus that can be described as oxidase-negative, nitrate-positive, indole-negative, citrate-positive, methyl red–positive, urease- negative, and H2S-positive is most likely which of the following?
a. Klebsiella pneumoniae
b. Salmonella enteritidis
c. Escherichia coli
d. Shigella sonnei
B
The swarming gram-negative bacillus that can be described as oxidase-negative, nitrate-positive, indole-negative, and H2S-positive is mostly likely which of the following?
a. Proteus aerogenes
b. Proteus vulgaris
c. Proteus mirabilis
d. Escherichia coli
c
Profuse watery diarrhea (“rice water stools”), lead- ing to dramatic fluid loss, severe dehydration, and hypotension that frequently leads to death, is the hallmark of which toxin activity?
a. Cholera toxin
b. Enteric endotoxin
c. Shiga toxin
d. Toxin A
A
The selective medium thiosulfate citrate bile salts sucrose (TCBS) agar is especially formu- lated for isolating which pathogen from stool cultures?
a. Vibrio spp.
b. Salmonella spp.
c. Shigella spp.
d. Plesiomonas spp.
A
The majority of human infections with Campylobacter spp. are caused by which of the following?
a. Direct contact with carriers of the bacterium
b. Contamination of food, milk, or water with animal feces
c. Multiplication of the organism in food products
d. Direct contact with persons infected with the bacterium
B
In the test for urease production, the presence of the enzyme hydrolyzes urea to which of the following?
a. Ammonia and CO2
b. Putrescine
c. Amines and CO2
d. Amines and water
A
The bacterial isolate on XLD agar shown in the image was isolated from a routine stool culture. Which of the following genera and species is the most likely identification for this organism?
a. Klebsiella pneumoniae
b. Salmonella enteritidis
c. Shigella sonnei
d. Serratia marcescens
B
Decarboxylationoftheaminoacidslysine,ornithine, and arginine results in the formation of which of the following products?
a. Ammonia
b. Urea
c. CO2
d. Amines
D
An organism was inoculated into a TSI tube and gave the following reactions:
Alkaline slant/ Acid butt
H2S: Not produced Gas: Not produced
The organism is most likely which of the following?
a. Klebsiella sp.
b. Shigella sp.
c. Salmonella sp.
d. Escherichia coli
B
The best specimen for the isolation of Bordetella pertussis is which of the following?
a. Throat swabs
b. Sputum
c. Nasopharyngeal aspirates
d. Anterior nose swab
C
Organisms belonging to the genus Brucella are best
described by which of the following statements?
a. Gram-positive diplococci
b. Gram-positive diphtheroid bacilli
c. Gram-negative coccobacilli
d. Gram-negative bacilli
C
Serum samples collected on a patient with pneumonia demonstrate a rising antibody titer to Legionella. A bronchoalveolar lavage sample was collected and revealed a positive DFA test for Legionella, but no organisms were recovered from this specimen when it was cultured on the appropriate medium and incu- bated for 2 days at 35 C in CO2. Which of the following is the best explanation?
a. Culture was not incubated long enough
b. Antibody titer
c. Specimenwasincubatedatthewrongtemperature
d. Positive DFA test result is a false positive
A
Of the following media, which provides the NAD necessary for the growth of Haemophilus spp.?
a. 5% sheep blood agar
b. Brain heart infusion agar
c. Chocolate agar
d. Nutrient agar
C
Performing the factor requirement test for Haemo- philus involves which of the following processes?
a. Inoculationofunsupplementedmediawithalight suspension of the organism and placement of factors X and V disks on the agar surface
b. Inoculationofliquidmedia,unsupplementedand supplemented with factors X and V
c. Detectingthepresenceofenzymesthatconverta- aminolevulinic acid (ALA) into porphyrins
d. Growth of the organism in the presence of bacte- rial species that produce X and V factors as metabolic by-products
A
Of the asaccharolytic ,oxidase-positivebacillithatdo not grow on MacConkey agar, which one is among the HACEK group of bacteria known to cause sub- acute bacterial endocarditis?
a. Eikenella corrodens
b. Weeksella virosa
c. Pseudomonas maltophilia
d. Sphingomonas paucimobilis
A
Which of the following statements best completes the following thought: Presumptive identification of an oxidase-positive, gram-negative diplococcus on Thayer-Martin medium from genital sites of a 6- year-old female as Neisseria gonorrhoeae?
a. Provides the physician with quick and reliable results at minimal cost
b. May sometimes be incorrect, and a repeat culture should be collected
c. May sometimes be incorrect and should not be reported until confirmed
d. Should be done only when venereal disease is suspected
C
The bacterial species that can be described as oxidase- positive, glucose-positive, maltose-positive, sucrose- negative, lactose-negative, and a major cause of bac- terial meningitis is most likely which of the following?
a. Neisseria meningitidis
b. Neisseria gonorrhoeae
c. Streptococcus pneumoniae
d. Viridans group Streptococcus
A
The bacterial species that can be described as oxidase- positive, glucose-positive, maltose-negative, sucrose- negative, lactose-negative, and a major cause of venereal disease is most likely which of the following?
a. Neisseria meningitidis
b. Neisseria gonorrhoeae
c. Streptococcus pyogenes
d. Viridans group Streptococcus
B
The oxidase test is a critical test when attempting to identify nonfermenting gram-negative bacilli. This test is designed to determine the presence of which of the following?
a. b-Galactosidase
b. Cytochrome oxidase
c. Glucose oxidizing enzymes
d. Oxygen
B
Which organism is associated with the disease Melioidosis?
a. Burkholderia ralstonia
b. Burkholderia pseudomallei
c. Burkholderia mallei
d. Burkholderia cepacia
B
Differentiation of Stenotrophomonas maltophilia and Burkholderia cepacia is best accomplished by which of the following tests?
a. Oxidase test
b. Maltose and glucose medium
c. Tyrosine-enriched heart infusion agar
d. Growth at 42 C
A
The respiratory culture of a patient with cystic fibrosis yielded a gram-negative bacillus with the following reactions:
Oxidase= Negative Glucose oxidative- fermentative
open= Positive (weak) Catalase=Positive
Motility =Positive
Maltose oxidative-fermentative
open=Positive (strong) Esculin hydrolysis= Positive
Which of the following is the most likely identifica- tion of this organism?
a. Burkholderia cepacia
b. Pseudomonas aeruginosa
c. Acinetobacter baumannii
d. Stenotrophomonas xylosoxidans
B
Which test group best differentiates Acinetobacter baumannii from Pseudomonas aeruginosa?
a. Oxidase, motility, nitrate reduction
b. Growth on MacConkey agar, catalase, nitrate reduction
c. Growth on blood agar, oxidase, catalase
d. TSI, urea, motility
A
Which of the following sets of results represent the most common reactions for Moraxella catarrhalis when tested in CTA sugar tubes?
a. Glucose: Negative; Maltose: Negative; Lactose: Negative; Sucrose: Negative
b. Glucose: Positive; Maltose: Negative; Lactose: Negative; Sucrose: Negative
c. Glucose: Positive; Maltose: Positive; Lactose: Negative; Sucrose: Negative
d. Glucose: Positive; Maltose: Negative; Lactose: Positive; Sucrose: Negative
A
A soluble, bright green pigment can be produced by Pseudomonas aeruginosa. This pigment is known as which of the following?
a. Pyoverdin
b. Pyocyanin
c. Pyorubin
d. Pyophena
B
A small portion of a colony of a gram-negative bacilli was smeared onto a filter paper test system. One percent tetramethyl-p-phenylenediamine dihydrochlor- ide was added. At 10 seconds, a dark purple color developed where the colony was added to the paper. Which of the following statements best describes the test results?
a. Positive indole test
b. Positive oxidase test
c. Positive urea test
d. Positive esculin test
B
Characteristics of Mycoplasma and Ureaplasma include which of the following?
a. They exhibit the presence of a thin gram-positive– like cell wall with no cell membrane
b. They demonstrate rapid growth on MacConkey agar, slow growth on basic nutrient agar
c. The have only a cell membrane with no cell wall
d. They exhibit rapid growth on MacConkey medium and routine blood agar plates
C
Which of the following is a cause of nongonococcal urethritis?
a. Mycoplasma hominis
b. Mycoplasma pneumoniae
c. Ureaplasma urealyticum
d. Mycoplasma orale
C
Which of the following is the most sensitive method for the diagnosis of Chlamydia trachomatis?
a. Cytology
b. Culture
c. Nucleic acid amplification
d. Serologic testing
C
An 8-year-old boy from Oklahoma presents with a 3-day history of fever, headache, and muscle aches. A rash first noted this morning on his ankles and wrists has now spread to include his trunk. The medical team has identified a list of possible organisms. Which of the following is the most likely cause of this infection?
a. Q Fever
b. Ehrlichiosis
c. Rocky Mountain spotted fever
d. Cat scratch disease
C
Which of the following is a stage of venereal syphilis that is characterized by the appearance of a chancre?
a. Primary syphilis
b. Secondary syphilis
c. Late syphilis
d. Tertiary syphilis
A
Which of the following is a nontreponemal serologic test in which soluble antigen particles are coalesced to form larger particles that are visible as clumps when they are aggregated by antibody?
a. Nontreponemal flocculation (NTF)
b. Fluorescent treponemal antibody absorption (FTA-ABS) test
c. Venereal Disease Research Laboratory (VDRL) test
d. T. pallidum particle agglutination (TP-PA) test
C
A patient in a rural area of Massachusetts had a 5-cm red rash with an expanding margin on his back. The lesion was obvious for approximately a month and then resolved. Several weeks later, the patient experi- enced episodes of partial facial paralysis and painful joints. Which of the following is the most likely infec- tious agent in this case?
a. Borrelia hermsii
b. Borrelia burgdorferi
c. Leptospira interrogans
d. Spirillum minor
B
A 16-year-old, sexually active patient comes to his physician’s office because of a circular, 1-cm lesion in the groin area which is ulcerated but not painful. A rapid plasma reagin test is performed and is reactive with a titer of 1:16. Culture and gram-stain smear results from an exudate of the lesion are negative. Which of the following is the most likely cause of this lesion?
a. Chlamydia trachomatis
b. Neisseria gonorrhoeae
c. Treponema pallidum
d. Haemophilus ducreyi
C
The gram-stained smear shows an organism isolated from a blood culture after bowel surgery. Under anaerobic incubation conditions, it grew as smooth, white, nonhemolytic colonies. The organism was not inhibited by colistin, kanamycin, or vancomycin and hydrolyzed esculin. The most likely identification of this isolate is which of the following?
a. Fusobacterium nucleatum
b. Fusobacterium varium
c. Bacteroides fragilis
d. Prevotella melaninogenica
C
Pseudomembranous colitis caused by Clostridium difficile is best confirmed by which of the following laboratory findings?
a. Presence of the toxin in stool
b. Isolation of C. difficile from stool
c. Gas production in thioglycolate media
d. Gram stain of stool showing many gram-positive bacilli
A
Lecithinase production, double zone hemolysis on sheep blood agar, and gram-stained morphology are all useful criteria in the identification of which of the following?
a. Clostridium perfringens
b. Streptococcus agalactiae
c. Escherichia coli
d. Clostridium tetani
A
When activating a hydrogen and carbon dioxide gen- erator system used for creating an anaerobic atmo- sphere, which of the following is an indication that the catalyst and generator envelope are functioning properly?
a. A decrease in temperature of the jar
b. Bubble formation on the surface of the plates
c. A change in color of the methylene blue indicator
d. The formation of a visible cloud of gas
C
In a clinical specimen, the presence of sulfur granules strongly indicates the presence of which anaerobic bacterium?
a. Bacteroides fragilis
b. Actinomyces spp.
c. Fusobacterium nucleatum
d. Clostridium tetani
B
Which of the following are a common element between using the E test and agar disk diffusion (Kirby-Bauer) for antimicrobial susceptibility testing?
a. Both establish an antibiotic gradient in agar
b. Both create a circular zone of bacterial inhibition
c. Expression of results is by MIC for both
d. The cost of the test is similar per drug
A
Which of the following clinical indications would most benefit from having quantitative (MIC) testing rather than qualitative (Sensitive, Intermediate, Resistant catagories) data from the laboratory?
a. Urinary tract infection
b. Bacterial meningitis
c. Pneumonia caused by Mycoplasma
d. Streptococcal pharyngitis
B
When performing antimicrobial susceptibility test- ing, the following definition of the minimum inhibitory concentration (MIC) is correct:
a. The highest concentration of an antibiotic in a dilution series that inhibits growth
b. The lowest concentration of an antibiotic in a dilution series that inhibits growth
c. The lowest concentration of an antibiotic in a dilution series that kills the bacteria
d. The lowest concentration of the antibiotic obtain- able in the patient without toxicity
B
In comparing quantitative MIC dilution testing to qualitative agar disk diffusion testing, the higher the MIC of the drug for that organism:
a. The smaller is the zone of inhibition
b. The more susceptible the organism will appear on disk diffusion
c. The larger is the zone of inhibition
d. The more toxic is the drug to the patient
C
In a quality control (QC) procedure on a new batch of Mueller-Hinton plates using a standard QC stock strain of Staphylococcus aureus, the disk inhibition zone sizes for three of the drugs tested were too small and fell below the expected QC range. Which of the following is the most likely reason for
this observation?
a. These three antibiotic disks were outdated and had lost potency
b. These three disks were faulty in that the antibiotic content was too high
c. Bacterial suspension of Staphylococcus was probably contaminated with another organism
d. The plates received insufficient incubation time
A
Which of the following definitions best fit the term urethritis?
a. Infection and or inflammation of the terminal portion of the lower urinary tract
b. The isolation of a specified quantitative count of bacteria in an appropriately collected urine specimen obtained from a person without symptoms or signs of urinary infection
c. Dysuria, frequency, and urgency but yielding fewer organisms than 105 colony-forming units of bacteria per milliliter (CFU/mL) urine on culture
d. Inflammation of the kidney parenchyma, calices (cup-shaped division of the renal pelvis), and pelvis
A
The organism most commonly associated with otitis media infections is associated with which of the following positive test results?
a. Coagulase
b. VP
c. Optochin
d. Bacitracin
C
Which organism is most often responsible for impetigo?
a. Staphylococcus epidermidis
b. Streptococcus pyogenes
c. Enterococcus faecalis
d. Streptococcus agalactiae
B
How do staphylococci spread so easily when infect- ing the skin?
a. They produce hyaluronidase, which hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissue
b. They produce lipase, which melts the fat under the skin, making it easier to spread
c. The hemolysins kill the white and red blood cells; then the protease liquefies the skin protein, allowing easy penetration for the bacteria
d. All of the above
A
Routine culture media for use with a specimen of cerebrospinal fluid should include which of the following sets of media?
a. 5% sheep blood agar, Lowenstein Jensen agar, 7H9 agar
b. 5% sheep blood agar, thioglycolate broth
c. 5% sheep blood agar, MacConkey agar, Sabourad dextrose agar
d. 5% sheep blood agar, chocolate agar, thioglycolate broth
D
A college student is examined at the emergency department; he is disoriented with a fever, intense headache, stiff neck, vomiting, and sensitivity to light. His friends say that he has been sick for about 2 days and that his condition worsened over the last 3 hours. The physician does a complete blood count (CBC) and electrolytes. The electrolytes are normal, but the patient’s white blood count (WBC) is 12,000 cells/L. What test should the doctor order next?
a. Urine culture
b. Stool culture
c. Cerebrospinal fluid Gram stain and culture
d. Blood culture
C
What cells are found in bacterial vaginosis?
a. Clue cells
b. Lymphocytes
c. Macrophages
d. Squamous epithelial cells
A
Which of the following terms is used to describe an increase of lymphocytes and other mononuclear cells (pleocytosis) in the cerebrospinal fluid and negative bacterial and fungal cultures?
a. Meningoencephalitis
b. Aseptic meningitis
c. Encephalitis
d. Meningitis
B
The culture of which sample routinely uses quantita- tion or the counting of bacterial cells present to assist in the interpretation?
a. Blood
b. Sputum
c. Urine
d. Abscess
C
Gram staining and reading a glass slide with a mixed smear of Staphylococcus and Escherichia coli along with each Gram staining run of specimens examined within the microbiology laboratory that day is an example of which of the following?
a. Quality assurance (QA) activity
b. Quality control (QC) activity
c. National regulatory activity
d. Office ofSafetyandHealthAdministrationactivity
B
Tracking the rate of skin organism contamination among a laboratory’s blood culture results on a monthly basis and introducing specific training to phlebotomists when rates exceed the norm would be an example of which of the following?
a. Good laboratory practice
b. Quality control
c. Universal standards
d. Quality assurance
D
Which of the following statements best defines “infectious substances”?
a. Articles or substances capable of posing a risk to safety
b. Substances known or reasonably expected to contain pathogens
c. Patient samples containing bacteria
d. Samples with class 3 pathogens
B
Which of the following is an example of an inappro- priate specimen or condition that would warrant rejection for microbiology culture?
a. A nonsterile container for a stool culture
b. A swab of a skin and soft tissue infection
c. A tissue sample for anaerobic culture
d. A 24-hour urine sample for bacteriology culture
D
Which of the following terms is best described as the process of reproduction in yeast that begins with a weakening and outpouching of the yeast cell wall and then formation of a cell wall septum between the mother and daughter yeast cells?
a. Binary fission
b. Unisexual division
c. Budding
d. Outpouch germing
C
The loose intertwined network of basic structural units of the molds that penetrates the substrate from which it obtains the necessary nutrients for growth is called which of the following?
a. Hyphae
b. Germ tubes
c. Pseudohyphae
d. Mycelium
D
The term hyaline molds is used to describe which of the following?
a. Molds that have septate hyphae
b. Molds that have septate, nonpigmented hyphae
c. The presence of pigmentation within the hyphae or the spores
d. Molds with intercalated hyaline chlamydoconidia
C
Large, usually multiseptate and club-shaped or spindle-
shaped spores are called which of the following?
a. Microconidia
b. Macroconidia
c. Conidiophores
d. Phialides
B
A patient with a Wood’s lamp–positive, dermatophytic infection has a skin scraping taken for culture. The organism grows on SDA agar with a light-tan front and salmon-colored reverse. Microscopically the organism produces rare distorted macroconidia and rare microconidia. Additionally, there was no growth on sterile rice media. What is the most likely organism?
a. Microsporum canis
b. Microsporum gypseum
c. Microsporum audouinii
d. Epidermophyton floccosum
C
A KOH preparation of respiratory secretions of a 78- year-old man reveals large, spherical, thick-walled yeast cells 8 to 15 mm in diameter, usually with a single bud that is connected to the parent cell by a broad base. Which fungus will likely be isolated from the culture?
a. Coccidioides immitis
b. Blastomyces dermatitidis
c. Histoplasma capsulatum
d. Paracoccidioides brasiliensis
B
Which of the following is a key characteristic of Coccidioides immitis?
a. Has a higher dissemination rate in white females
b. Is endemic in the northeastern United States
c. Produces endosporulating spherules in tissue
d. Forms foot cells
C
A germ tube–negative yeast is isolated in the labora- tory. The isolate is found to be negative for urease and unable to assimilate dextrose, maltose, or sucrose. CMT agar morphology showed blastoconi- dia only. The organism is most likely:
a. Candida albicans
b. Candida parapsilosis
c. Torulopsis glabrata
d. Geotrichum candidum
C
Which of the following is a key characteristic by which an unknown Cryptococcus spp. can be identi- fied as Cryptococcus neoformans?
a. Appearance of yellow colonies
b. Positive urease test
c. Presence of a capsule
d. Positive niger seed agar test
D
Which of the following statements concerning the germ tube test is true?
a. Using a heavy inoculum enhances the rapid pro- duction of germ tubes
b. Germ tubes should be read after 2 hours of incu- bation at 25 C
c. Candida albicans and Candida tropicalis can be used as positive and negative controls, respectively
d. Serum will be stable for 1 year if stored at room temperature
C
A mold isolated in the laboratory displays a white cottony macroscopic morphology. On microscopic evaluation, hyaline, septate hyphae, and “tooth- brush”-like conidiophres are seen. The most likely organism is which of the following?
a. Aspergillus sp.
b. Acremonium sp.
c. Gliocladium sp.
d. Scopulariopsis sp.
B
A mold is isolated in the laboratory that displays a velvety, gray-green colony morphology. On microscopic evaluation, flask-shaped conidiophores arranged in a brushlike formation are seen. The most likely organism is which of the following?
a. Penicillium sp.
b. Acremonium sp.
c. Paecilomyces sp.
d. Scopulariopsis sp.
A
The protein coat that surrounds the nucleic acid of a virion is called which of the following?
a. Capsomere
b. Capsid
c. Capsule
d. Nucleocapsid
b
During viral assembly, how are viral envelopes acquired?
a. By production of envelope constituents by host cellular DNA
b. As the virion buds from a host cell membrane
c. Through replication of viral nucleic acid
d. As host cell lysis produces many membrane fragments
B
Prions are best described by which of the following?
a. Infectious viral RNA without capsid proteins
b. Infectious protein with no associated nucleic acid
c. Infectious viral DNA without capsid proteins
d. Nonenveloped virus highly resistant to heat and chemical inactivation
B
The viral nucleocapsid always contains which of the following?
a. Viral genome
b. Virus-encoded glycoprotein
c. Virus-encoded polymerase
d. Viral envelope
A
Which of the following viruses are thought to predominately cause gastroenteritis?
a. Hepadnaviruses
b. Filoviruses
c. Noroviruses
d. Arboviruses
C
Which of the following groups contains the SARS virus?
a. Calicivirus
b. Coronavirus
c. Flavivirus
d. Filovirus
B
Which of the following groups of virus is best described as: ssRNA, enveloped, Pleomorphic/spherical capsid. Large club-shaped spikes on surface gives “corona” effect. Causes approximately 15% of coldlike illness
a. Influenza A
b. Influenza B
c. Coronaviruses
d. Pneumovirus
C
Which of the following is the specimen of choice for detecting rotavirus?
a. Throat swab
b. Urine sample
c. Bronchoalveolar wash
d. Feces sample
D
The test of choice and most sensitive assay for use with CSF to diagnose aseptic meningitis caused by enterovirus is which of the following?
a. Cell culture
b. PCR
c. Antigenemia immunoassay
d. Shell vial assay
B
Trophozoite forms of amoebae are found in what type of stool specimen?
a. Formed
b. Loose
c. Soft
d. Watery
D
Which preservation method is most suitable and the most widely used for subsequent fixed smear preparation?
a. Formalin-ethyl acetate
b. PVA
c. Trichrome
d. MIF
B
If the ova of this parasite are ingested by humans, the oncosphere form can migrate through the body via the bloodstream, resulting in the condition known as cysticercosis. Which of the following is correct?
a. Taenia solium
b. Entamoeba histolytica
c. Hymenolepis nana
d. Clonorchis sinensis
A
Ova recovered from the stool are routinely used to diagnose infections caused by all of the following except?
a. Necator americanus
b. Ascaris lubricoides
c. Trichuris trichiura
d. Strongyloides stercoralis
D
An MLS finds an E.coli cyst on a wet mount of a fresh stool specimen. Which of the following should be done?
a. Request a second specimen
b. Look for additional E. coli cysts
c. Examinetheremainingareaofthewetpreparation
d. Generate a final report
C
Which of the following parasites have migration through the lungs as part of their lifecycle?
a. Necator americanus, Ancylostoma duodenale, Strongyloides stercoralis
b. Giardia lamblia, Wuchereria bancrofti, Brugia malayi
c. Enterobius vermicularis, Trichuris trichiura, Trichinella spiralis
d. Toxocara canis, Toxoplasma gondii, Blastocystis hominis
A
Necator americanus rhabditiform larvae can be differentiated from Strongyloides stercoralis rhabditiform larvae by:
a. Length of the notched tail
b. Length of the head region
c. Segmentation
d. Size of the genital primordium
D
The only known human tapeworm with an operculum
a. D. latum
b. H. nana
c. G. lamblia
d. S. haematobium
A
Organisms belonging to the genus Neisseria are described as which of the following?
a. Gram-positive diplococci
b. Gram-negative diplococci
c. Gram-negative coccobacilli
d. Gram-negative bacilli
B
