Micrology problem solving Flashcards
- 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
CNA plate =
Inhibited growth
Hemolysis = Neg
Catalase = Positive
Novobiocin = Resistant
This isolate is:
A. Staphylococcus saprophyticus
B. Micrococcus luteus
C. Staphylococcus aureus
D. Streptococcus pyogenes
A. Staphylococcus saprophyticus
- 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. Mannitol salt agar
- 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. Microbiology
- 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. No, the specimen is unsuitable for the recovery
of mycobacteria
- 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. Rejected
- 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
Lactose = +
Indole = +
Lysine decarboxylase
= Neg
Urease = Neg
Motility = Neg
What is the most likely organism?
A. Salmonella spp.
B. Proteus mirabilis
C. Escherichia coli
D. Enteroinvasive E. coli (EIEC)
D. Enteroinvasive E. coli (EIEC)
- 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
Lactose = +
Urease = +
Citrate = +
Indole = +
VP = +
Motility = Neg
Resistance to ampicillin
and carbenicillin
What is the most likely identification?
A. Klebsiella oxytoca
B. Proteus mirabilis
C. Escherichia coli
D. Klebsiella pneumoniae
A. Klebsiella oxytoca
- 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 autopsy revealed that her death was due
to septic shock. The blood bags were cultured, and
the following results were noted:
GROWTH OF AEROBIC GRAMNEGATIVE RODS ON
BOTH MACCONKEY AND BLOOD AGARS:
Lactose = Neg
Sucrose = +
Citrate = Neg
Indole = Neg
VP = Neg
H2S = Neg
Urease = +
Motility 22°C = +
Motility 37°C = Neg
What is the most likely identification?
A. Escherichia coli
B. Yersinia enterocolitica
C. Enterobacter cloacae
D. Citrobacter freundii
B. Yersinia enterocolitica
- 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 Campy agar = No growth
flora
What is the most likely identification?
A. Yersinia spp.
B. E. coli O157:H7
C. Salmonella spp.
D. Shigella spp.
B. E. coli O157:H7
- 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
Sucrose = +
Citrate = Neg
Indole = Neg
VP = Neg
H2S = Neg
Motility 37°C = Neg
Motility 22°C = +
Hektoen agar = NF
What is the most likely identification?
A. Yersinia enterocolitica
B. Salmonella spp.
C. Shigella spp.
D. Escherichia coli
A. Yersinia enterocolitica
- 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 = +
DNase = +
Glucose = + (oxidative) Maltose = + (oxidative)
Lysine decarboxylase = + Esculin hydrolysis = +
What is the most likely identification?
A. Stenotrophomonas maltophilia
B. Acinetobacter baumannii
C. Pseudomonas aeruginosa
D. Burkholderia (P.) cepacia
A. Stenotrophomonas maltophilia
- 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
Catalase = Neg
Glucose = +
Growth in increased CO2 = + 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. Eikenella corrodens
- 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. Capnocytophaga canimorsus
- 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 perfringens
D. Salmonella or Staphylococcus spp.
B. E. coli O157:H7 or Shigella spp.
- 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. Staphylococcus aureus
- 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. Vancomycin
- 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. Bacitracin, CAMP, PYR
- Which organism is the most often recovered grampositive 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. Enterococcus faecalis
- 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. 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)
- “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
Microbiol
C. Gardnerella vaginalis
- 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. Hanging-drop motility (25°C) and catalase
- Acid-fast positive bacilli were recovered from the
sputum of a 79-year-old man who had been
treated for pneumonia. Which of the following
test reactions after 3 weeks of incubation on
Löwenstein–Jensen agar are consistent with
Mycobacterium tuberculosis?
A. Niacin = + Nitrate Photochromogenic
reduction = + = Neg
B. Niacin= Neg Optochin = + Catalase = +
C. PYR = + Urease = + Bacitracin = +
D. Ampicillin = Penicillin =
Resistant Resistant
A. Niacin = + Nitrate Photochromogenic
reduction = + = Neg
- 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. Indole, phenylalanine deaminase, and urease
- 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. Oxidase, motility, growth at 42°C
- 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. H. haemolyticus
- Large gram-positive bacilli (boxcar shaped) were
recovered from a blood culture taken from a
70-year-old female diabetic patient. The following
results were recorded:
Aerobic growth = Neg Anaerobic growth = +
Spores = Neg Motility = Neg
Lecithinase = + Hemolysis = β (double zone)
GLC (volatile acids) = acetic acid and butyric acid
What is the most likely identification?
A. Clostridium perfringens
B. Fusobacterium spp.
C. Bacteroides spp.
D. Clostridium sporogenes
A. Clostridium perfringens
- 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.
B. Bacteroides fragilis group
- 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. Only the specific concentrations necessary to
report S, I, or R
- 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 ONPG = +
Glucose (open) OF = + Urease = Neg
Glucose (closed) OF = Neg Catalase = +
Indole = + Oxidase = +
Motility = Neg Pigment = Yellow
42° C growth = Neg
What is the correct identification?
A. Pseudomonas aeruginosa
B. Chryseobacterium meningosepticum
C. Acinetobacter baumannii
D. E. coli
B. Chryseobacterium meningosepticum
- 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. Legionella pneumophila
- 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
CAMP = Neg
Esculin hydrolysis = Neg
Gas from glucose = +
Hippurate hydrolysis = Neg 6.5% salt broth = Neg
What is the correct identification?
A. Leuconostoc spp.
B. Enterococcus spp.
C. Staphylococcus spp.
D. Micrococcus spp.
A. Leuconostoc spp.
- 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:
PYR = Neg
LAP = Neg (V)
Esculin hydrolysis = Neg 6.5% Salt broth = Neg
Vancomycin = Sensitive CAMP test = Neg
What is the correct identification?
A. Leuconostoc spp.
B. Gemella spp.
C. Enterococcus spp.
D. Micrococcus spp.
B. Gemella spp.
- 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. Leuconostoc spp. and Pediococcus spp.
- 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?
Glucose = + (Fermentation) Oxidase = Neg
PYR = Neg Bacitracin = Sensitive
Lysostaphin = Sensitive
A. Micrococcus spp.
B. Streptococcus spp.
C. Enterococcus spp.
D. Staphylococcus spp.
D. Staphylococcus spp.
- 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. Coagulase, glucose fermentation, DNase
- 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, catalasenegative, gram-positive organism on 5% sheep
blood agar. The following test results indicate
which organism?
PYR = +
Bile Esculin = +
6.5% Salt broth = + growth
Bacitracin = Neg
Optochin = Neg
A. Enterococcus faecalis
B. Streptococcus pyogenes
C. Streptococcus agalactiae
D. Streptococcus bovis
A. Enterococcus faecalis
- 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. Optochin, bile solubility, PYR
- 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. Helicobacter pylori
- 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. Listeria monocytogenes
- 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. Tinsdale medium
- 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. Gardnerella vaginalis
- 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. Nocardia asteroides
- A 22-year-old pregnant woman (third trimester)
entered the emergency department complaining
of diarrhea, fever, and other flulike symptoms.
Blood cultures were ordered along with a urine
culture. After 24 hours, the urine culture was
negative, but the blood cultures revealed a
gram-positive short rod that grew aerobically on
blood agar. The colonies were small and smooth,
resembling a Streptococcus spp. with a small
narrow zone of β-hemolysis. The following test
results indicate which organism?
Motility = + (Wet mount = Catalase = +
Tumbling)
Glucose = + (Acid) Esculin hydrolysis = +
A. Listeria monocytogenes
B. Streptococcus pneumoniae
C. Streptococcus agalactiae
D. Corynebacterium spp.
A. Listeria monocytogenes
- 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 Vancomycin = Sensitive
Colistin = Resistant Lecithinase = Neg
Lipase = Neg
Nitrate = Neg
Indole = Neg
Urease = Neg
Catalase = Neg
Spores = +
CCFA agar = Growth of yellow, “ground-glass” colonies
that fluoresce chartreuse (yellow-green)
What is the correct identification?
A. Clostridium perfringens
B. Clostridium tetani
C. Clostridium sordellii
D. Clostridium difficile
D. Clostridium difficile
- 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 = +
Nitrate = + Catalase = +
Kanamycin = Sensitive Vancomycin = Sensitive
Colistin = Resistant 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. Propionibacterium acnes
- 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. Clostridium septicum
- Anaerobic gram-negative bacilli were recovered
from fluid obtained from drainage of a
postsurgical abdominal wound. The following
test results were recorded:
Kanamycin = Resistant Vancomycin = Resistant
Colistin = Resistant
Growth on 20%
bile plate = +
Pigment = Neg
Indole = V (Neg)
Nitrate = Neg
Urease = Neg Lipase = Neg
What is the correct identification?
A. Prevotella spp.
B. Bacteroides fragilis group
C. Porphyromonas spp.
D. Clostridium spp
B. Bacteroides fragilis group
- 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 Vancomycin = Resistant
Colistin = Sensitive
Nitrate = Neg
Indole = +
Catalase = Neg
Lipase = Neg
Urease = Neg
Growth on 20% bile agar = Neg
What is the correct identification?
A. Fusobacterium nucleatum
B. Bacteroides fragilis
C. Clostridium perfringens
D. Peptostreptococcus spp.
A. Fusobacterium nucleatum
- 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. Candida albicans
- 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. Aspergillus fumigatus
- A young male patient with a fungus of the feet
visited the podiatrist for relief from the itching.
A culture was sent to the microbiology laboratory
that grew after 8 days on Sabouraud dextrose
agar. Colonies were powdery pink with concentric
and radial folds, with the reverse side showing
brownish-tan to red in color. Other observations
were:
Hyphae = Septate
Urease = +
Macroconidia = Cigar shaped, thin walled with 1–6 cells
Microconidia = Round and clustered on branched
conidiophores
Red pigment on cornmeal (1% dextrose) = Neg
In vitro hair perforation = +
The most likely identification is:
A. Trichophyton mentagrophytes
B. Trichophyton rubrum
C. Candida albicans
D. Aspergillus niger
C. Candida albicans
- A 79-year-old female nursing home patient was
admitted to the hospital with a fever and central
nervous system dysfunction. Routine blood work
and blood cultures were ordered. After 48 hours,
the blood cultures revealed a budding yeast. The
following tests performed from Sabouraud
dextrose agar (after 3 days of growth) showed:
Germ tube = Neg growth Birdseed agar = Brown
Urease = +
Pseudohyphae = Neg
Blastospores =+ Chlamydospores = Neg
Arthrospores = Neg
Assimilation agar = + (dextrose, sucrose, maltose)
What is the most likely identification?
A. Candida albicans
B. Cryptococcus laurentii
C. Cryptococcus neoformans
D. Candida tropicalis
C. Cryptococcus neoformans
- 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. CMV
- 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. Immediately test the patient and the student for
HIV using an EIA or ELISA test
- 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. Herpes simplex testing
- 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. Prophylactic medication history and specific
travel history
- 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. Cyclospora cayetanensis