Elsevier MICRO Flashcards
Spores are found in select groups of bacteria. Which of the following statements describes the major advantage 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. Spores are resistant to heat, cold, drying, most chemicals, and boiling
Choose the binomial name that is correctly written.
a. Staphylococcus Aureus
b. Staphylococcus species aureus
c. Staphylococcus aureus
d. Staphylococcus aureus
c. 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. Lactic acid, mixed acids, alcohols, CO2 production
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. Conjugation
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 as plasmids 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 one
cell, thus allowing for recombination
d. A mechanism that is mediated by viruses, by which DNA from two bacteria may come together in one cell, thus allowing for recombination
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. Gram’s iodine
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. Staphylococcus aureus
The most appropriate interpretation of a gram stained smear of a sputum specimen would be which of the following? (gram-stained smear, 400x.)
a. Few epithelial cells, many PMNs
b. Inadequate specimen, do not culture for anaerobes
c. Many cells, many gram-positive cocci in pairs and chains
d. More than 25 epithelial cells, probable oral contamination, suggest recollect
d. More than 25 epithelial cells, probable oral contamination, suggest recollect
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. Anaerobes
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. Hektoen
Choose the group of bacteria that is described as catalase-positive, gram-positive cocci that grow facultatively anaerobic and that form grapelike clusters.
a. Neisseria spp.
b. Rothia (Stomatococcus) spp.
c. Staphylococcus spp.
d. Micrococcus spp.
c. Staphylococcus spp.
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. Clumping factor
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. Coagulase test
The Staphylococcus sp. that is more likely to cause uncomplicated urinary tract infections in non hospitalized hosts, especially sexually active
young women, is which of the following?
a. Staphylococcus saprophyticus
b. Staphylococcus aureus
c. Staphylococcus epidermidis
d. Staphylococcus intermedius
a. Staphylococcus saprophyticus
The toxic shock syndrome toxin-1 is an important virulence 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. Enterotoxin
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. Staphylococcus spp.
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. Staphylococcus aureus
The bacterial species that can be described as susceptible to bile and optochin, a-hemolytic, a major cause
of bacterial meningitis, and often carrying an antiphagocytic capsule is which of the following?
a. Enterococcus faecalis
b. Streptococcus pneumoniae
c. Streptococcus pyogenes
d. Streptococcus agalactiae
b. Streptococcus pneumoniae
The bacterial species that can be described as susceptible 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. Streptococcus pyogenes
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. Streptococcus agalactiae
The rapid antigen detection methods for throat swabs used for screening patients for streptococcal pharyngitis can be best described by which of the following 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. They can be useful in quickly identifying most cases of streptococcal pharyngitis
The hemolysis of this Streptococcus spp. would best be described as which of the following?
a. b-Hemolysis
b. g-Hemolysis
c. a-Hemolysis
d. k-Hemolysis
c. a-Hemolysis
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. Growth in presence of 6.5% salt
A pure culture of a b-hemolytic Streptococcus sp. recovered from a leg ulcer gave the following reactions:
CAMP test = Negative
Hippurate hydrolysis = Negative
Bile esculin slant = No growth
6.5% Salt = No growth
PYR = Negative
Bacitracin = Resistant
Optochin = Resistant
SXT = Sensitive
Which of the following is the most likely identification of this organism?
a. Streptococcus pyogenes
b. Streptococcus agalactiae
c. Enterococcus faecalis
d. Streptococcus sp., not groups A, B, or D
d. Streptococcus sp., not groups A, B, or 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. Listeria monocytogenes
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. Corynebacterium
A throat culture was taken from a 6-year-old boy with a gray pseudomembrane covering his oropharynx. 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 morphologies 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. Gram-positive bacilli in irregular clublike shape
A blood culture is positive for gram-positive bacilli that gave the following growth characteristics and biochemical reactions:
MacConkey agar: No growth
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. Corynebacterium spp.
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:
MacConkey agar: No growth
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. Erysipelothrix spp.
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. CAMP test, hydrogen sulfide production, esculin hydrolysis
Neonatal meningitis is an uncommon but significant disease. Two important causes of this disease may be somewhat difficult to differentiate on preliminary observation. Which of
the following sets of tests provide the best differentiation 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. Gram-stained smear, catalase, and motility
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 identification 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. Demonstration of spore formation
Bacillus anthracis and Bacillus cereus can be differentiated in the laboratory by a variety of different test
results. Which of the following sets of tests best differentiate these two species?
a. Catalase and glucose fermentation
b. Motility and lecithinase production
c. Oxidase and b-hemolysis on 5% sheep blood agar
d. Motility and b-hemolysis on 5% sheep blood agar
d. Motility and b-hemolysis on 5% sheep blood agar
Which of the following specimens would be best for identifying Bacillus cereus as the cause of an outbreak of food poisoning?
a. Blood
b. Rectal swabs
c. Stool samples
d. Food
d. Food
A first morning sputum sample is received for acid fast culture. The specimen is centrifuged, and the sediment is inoculated on two Lowenstein-Jensen slants
that are incubated at 35C 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. Decontaminate the specimen with NALC– sodium hydroxide mixture
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 positive for AFB. After 8 weeks of culture on both nonselective 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. M. leprae
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. M. tuberculosis, M. bovis, M. bovis BCG, and M. africanum
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. Growth rate and colonial pigmentation
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. Lipase that is able to hydrolyze polyoxyethylene
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. Salmonella enteritidis
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. Proteus mirabilis
Profuse watery diarrhea (“rice water stools”), leading 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. Cholera toxin
The selective medium thiosulfate citrate bile salts sucrose (TCBS) agar is especially formulated for isolating which pathogen from stool
cultures?
a. Vibrio spp.
b. Salmonella spp.
c. Shigella spp.
d. Plesiomonas spp.
a. Vibrio spp.
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. Contamination of food, milk, or water with animal feces
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. Ammonia and CO2
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. Salmonella enteritidis
The bacterial isolate shown below on CIN agar was isolated from a routine stool culture. Which of the
following genera and species is the most likely identification for this organism?
a. Shigella flexneri
b. Salmonella enteritidis
c. Yersinia enterocolitica
d. Escherichia coli
c. Yersinia enterocolitica
Decarboxylation of the amino acids lysine, ornithine, and arginine results in the formation of which of the
following products?
a. Ammonia
b. Urea
c. CO2
d. Amines
d. Amines
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. Shigella sp.
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. Nasopharyngeal aspirates
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. Gram-negative coccobacilli
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 incubated for 2 days at 35C in CO2. Which of the following is the best explanation?
a. Culture was not incubated long enough
b. Antibody titer
c. Specimen was incubated at the wrong temperature
d. Positive DFA test result is a false positive
a. Culture was not incubated long enough
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. Chocolate agar
Performing the factor requirement test for Haemophilus involves which of the following processes?
a. Inoculation of unsupplemented media with a light suspension of the organism and placement of factors X and V disks on the agar surface
b. Inoculation of liquid media, unsupplemented and supplemented with factors X and V
c. Detecting the presence of enzymes that convert aaminolevulinic acid (ALA) into porphyrins
d. Growth of the organism in the presence of bacterial species that produce X and V factors as metabolic by-products
a. Inoculation of unsupplemented media with a light suspension of the organism and placement of factors X and V disks on the agar surface
Of the asaccharolytic, oxidase-positive bacilli that do not grow on MacConkey agar, which one is among the HACEK group of bacteria known to cause subacute bacterial endocarditis?
a. Eikenella corrodens
b. Weeksella virosa
c. Pseudomonas maltophilia
d. Sphingomonas paucimobilis
a. Eikenella corrodens
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. May sometimes be incorrect and should not be reported until confirmed
The bacterial species that can be described as oxidase positive, glucose-positive, maltose-positive, sucrose negative, lactose-negative, and a major cause of bacterial meningitis is most likely which of the following?
a. Neisseria meningitidis
b. Neisseria gonorrhoeae
c. Streptococcus pneumoniae
d. Viridans group Streptococcus
a. Neisseria meningitidis
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. Neisseria gonorrhoeae
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. Gram-negative diplococci
The following were observed when the Hugh-Leifson oxidative-fermentative test was performed on a bacterial isolate. Which of the options below best describes the organism’s reaction?
a. Oxidizer
b. Nonoxidizer
c. Fermenter
d. Nonviable
a. Oxidizer