Micro EE Review Flashcards
1
Q
The aseptic collection of blood cultures requires that the skin be cleansed with:
A
70% alcohol and then 2% iodine or an iodophor
2
Q
When cleansing the skin with alcohol and then iodine for the collection of a blood
culture, the iodine (or iodophor) should remain intact on the skin for at least:
A
60 seconds
3
Q
What is the purpose of adding 0.025% to 0.050% sodium polyanethol sulfonate (SPS) to
nutrient broth media for the collection of blood cultures?
A
It inhibits phagocytosis and complement
4
Q
A flexible calcium alginate nasopharyngeal swab is the collection device of choice for
recovery of which organism from the nasopharynx?
A
Corynebacterium diphtheriae
5
Q
Semisolid transport media, such as Amies, Stuart, or Cary-Blair, are suitable for the
transport of swabs for culture of most pathogens except:
A
Neisseria gonorrhoeae
6
Q
Select the method of choice for recovery of anaerobic bacteria from a deep abscess
A
Needle aspirate after surface decontamination
7
Q
Select the primary and differential media of choice for recovery of most fecal pathogens.
A
Hektoen, MacConkey, MacConkey-Sorbitol, Campy blood, colistin–nalidixic acid (CNA)
agars; Selenite-F broth (SEL)
8
Q
Select the media of choice for recovery of Vibrio cholerae from a stool specimen
A
Thiosulfate–citrate–bile–sucrose (TCBS) agar and alkaline peptone water (APW) broth
9
Q
CNA agar is used primarily for the recovery of:
A
Staphylococcus aureus
10
Q
In the United States, most blood agar plates are prepared with 5% or 10% red blood
cells (RBCs) obtained from:
A
Sheep
11
Q
All of the following are appropriate when attempting to isolate N. gonorrhoeae from a
genital specimen except:
A
Culture specimens in ambient oxygen at 37°C
12
Q
Chocolate agar and MTM agar are used for the recovery of:
A
Haemophilus spp. and N. gonorrhoeae, respectively
13
Q
Cycloserine–cefoxitin–fructose agar (CCFA) is used for the recovery of
A
Clostridium difficile
14
Q
Deoxycholate agar (DCA) is useful for the isolation of:
A
Enterobacteriaceae
15
Q
Xylose lysine deoxycholate (XLD) agar is a highly selective medium used for the
recovery of which bacteria?
A
Enterobacteriaceae from gastrointestinal specimens
16
Q
A sheep blood agar plate is used as a primary isolation medium when all of the
following organisms are to be recovered from a wound specimen except:
A
Haemophilus influenzae and Haemophilus parainfluenzae
17
Q
Prereduced and vitamin K1-supplemented blood agar plates are recommended isolation
media for
A
Bacteroides, Peptostreptococcus, and Clostridium spp.
18
Q
Which procedure(s) is (are) appropriate for the diagnosis of Chlamydia spp. infections
when using genital specimens?
A
Obtain urethral, cervical swabs and urine specimens placed in transport media for the
direct detection of antigen or nucleic acid and/or culture
19
Q
Specimens for virus culture should be Cerebrospinal fluid (CSF) should be cultured immediately, but if delayed, the specimen
should be: in media containing:
A
Antibiotics and protein nutrient
20
Q
Cerebrospinal fluid (CSF) should be cultured immediately, but if delayed, the specimen
should be:
A
Incubated at 37°C and cultured as soon as possible
21
Q
The most sensitive method for the detection of β-lactamase in bacteria is by the use of:
A
Chromogenic cephalosporin
22
Q
The breakpoint of an antimicrobial drug refers to
A
The optimal therapeutic level of drug that is achievable in serum
23
Q
Which of the following variables may change the results of an MIC?
A
All of these options
24
Q
According to the Kirby-Bauer standard antimicrobial susceptibility testing method,
what should be done when interpreting the zone size of a motile, swarming organism,
such as a Proteus species?
A
The swarming area should be ignored
25
Which class of antibiotics is used for the treatment of serious gram-negative infections
as well as infections with Mycobacterium tuberculosis?
Aminoglycosides
26
Select the medium best suited for the recovery of Y. enterocolitica from a patient with
gastroenteritis
Cefsulodin–irgasan–novobiocin (CIN) agar
27
A suspected case of plague requires which of the following procedures to confirm
Yersinia pestis?
All of these options
28
SITUATION: Abdominal pain, fever, vomiting, and nausea prompted an older male to
seek medical attention. A watery stool specimen producing no fecal leukocytes or
erythrocytes was cultured, and it grew a predominance of gram-negative fermentative
bacilli. The colonies were β-hemolytic on blood agar and cream colored on MacConkey
agar. The colonies were both oxidase and catalase positive. What is the most likely
identification?
Aeromonas hydrophilia
29
SITUATION: Several attendees of a medical conference in the Gulf coast area became
ill after frequenting a seafood restaurant. A presumptive identification of V. cholerae
was made after stool specimens from several subjects grew clear colonies on
MacConkey agar and yellow colonies on TCBS agar. Which key tests would help
eliminate Aeromonas and Plesiomonas spp.?
Mannitol fermentation, Na+ requirement
30
SITUATION: A group of elementary students became ill after eating undercooked
ground beef prepared in the school cafeteria. The suspected pathogen, E. coli serotype
0157:H7, is usually recovered using which of the following media?
MacConkey agar with sorbitol
31
Biochemically, Enterobacteriaceae species are gram-negative rods that:
Ferment glucose, reduce nitrate to nitrite, and are oxidase negative
32
The ortho-nitrophenyl-β-galactopyranoside (ONPG) test is most useful when
differentiating:
Shigella spp. from some strains of Escherichia coli
33
The Voges-Proskauer (VP) test detects which end product of glucose fermentation?
Acetoin
34
At which pH does the methyl red (MR) test become positive?
4.5
35
A positive Simmons citrate test is seen as a:
Blue color in the medium after 24 hours of incubation at 35°C
36
In the test for urease production, ammonia reacts to form which product?
Ammonium carbonate
37
Which of the following reagents is added to detect the production of indole?
p-Dimethylaminobenzaldehyde
38
Decarboxylation of the amino acids lysine, ornithine, and arginine results in the
formation of:
Amines
39
Lysine iron agar (LIA) showing a purple slant and a blackened butt indicates:
Salmonella spp
40
Putrescine is an alkaline amine product of which bacterial enzyme?
Ornithine decarboxylase
41
Which genera are positive for phenylalanine deaminase?
Morganella, Providencia, and Proteus
42
Kligler iron agar (KIA) differs from triple-sugar iron agar (TSI) in the:
Use of sucrose in the medium
43
The malonate test is most useful in differentiating which members of the
Enterobacteriaceae family?
Salmonella subgroups 2, 3 (the former Arizona)
44
Which genera of the Enterobacteriaceae family are known to cause diarrhea and are
considered enteric pathogens?
Escherichia, Salmonella, Shigella, and Yersinia
45
An isolate of E. coli recovered from the stool of a patient with severe bloody diarrhea
should be tested for which sugar before sending it to a reference laboratory for
serotyping?
Sorbitol (fermentation)
46
Care must be taken when identifying biochemical isolates of Shigella because
serological cross reactions occur with:
Escherichia coli
47
Which species of Shigella is most commonly associated with diarrheal disease in the
United States?
Shigella sonnei
48
Which of the following tests best differentiates Shigella species from E. coli?
Lactose, indole, ONPG, and motility
49
Which genera of Enterobacteriaceae are usually nonmotile at 36°C?
Shigella, Klebsiella, and Yersinia
50
Fever, abdominal cramping, watery stools, and fluid and electrolyte loss preceded bloody stools 2 to 3 days before is characteristic of shigellosis but may also result from
infection with:
Campylobacter spp.
51
Cold enrichment of feces (incubation at 4°C) in phosphate-buffered saline prior to
subculture onto enteric media enhances the recovery of:
Yersinia enterocolitica
52
Which group of tests, along with colonial morphology on primary media, aids most in
the rapid identification of Enterobacteriaceae?
Indole, oxidase, MacConkey, and blood agar plates
53
A routine, complete stool culture procedure should include media for the isolation of E.
coli O157:H7 as well as:
Salmonella, Shigella, Yersinia, Campylobacter, and Staphylococcus aureus
54
Which group of tests best identifies the Morganella and Proteus genera?
Motility, urease, and phenylalanine deaminase
55
Which group of tests best differentiates Enterobacter aerogenes from Edwardsiella
tarda?
H2S production, sucrose fermentation, indole, and VP
56
Cronobacter sakazakii (formerly Enterobacter sakazakii) can best be differentiated from
Enterobacter cloacae by which of the following characteristics?
Yellow pigmentation and negative sorbitol fermentation
57
Members of the genus Cedecea are best differentiated from Serratia spp. by which test
result?
Negative DNase
58
Which of the following organisms is often confused with the Salmonella species
biochemically and on plated media?
Citrobacter freundii
59
A gram-negative rod is recovered from a catheterized urine sample from a nursing
home patient. The lactose-negative isolate tested positive for indole, urease, ornithine
decarboxylase, and phenylalanine deaminase and negative for H2S. The most probable
identification is:
Morganella spp
60
Which single test best separates Klebsiella oxytoca from K. pneumoniae?
Indole
61
Which of the following organisms, found in normal fecal flora, may be mistaken
biochemically for the genus Yersinia?
Proteus spp.
62
Why might it be necessary for both pink (lactose-positive) and colorless (lactosenegative) colonies from an initial stool culture on MacConkey agar to be subcultured
and tested further for possible pathogens?
Pathogenic Escherichia coli can be lactose positive or lactose negative
63
Which agar that is used for routine stool cultures is the medium of choice for the
isolation of Yersinia strains from stool specimens?
MacConkey agar
64
Which organism is sometimes mistaken for Salmonella and will agglutinate in
Salmonella polyvalent antiserum?
Citrobacter freundii strains
65
A bloody stool cultured from a 26-year-old woman after 3 days of severe diarrhea
showed the following results at 48 hours after being plated on the following media: MacConkey agar: Little normal flora with many non–lactose-fermenting colonies
Hektoen enteric agar: Many blue-green colonies
Campylobacter blood agar and C. difficile agar: No growth
Clear colonies (from MacConkey agar): Negative for oxidase, indole, urease, motility, and
H2S
Shigella spp.
66
Which one of the following organisms (are) is generally positive for β-glycosidase
(utilizes lactose)?
Escherichia coli
67
In the Kauffmann-White schema, the combined antigens used for serological
identification of the Salmonella spp. are:
O, Vi, and H antigens
68
The drugs of choice for treatment of infections with Enterobacteriaceae are:
Aminoglycosides, sulfamethoxazole-trimethoprim, third-generation cephalosporins
69
The Shiga-like toxin (verotoxin) is produced mainly by which Enterobacteriaceae
species?
Escherichia coli
70
Infections caused by Y. pestis are rare in the United States. Those cases that do occur
are most frequently located in which region?
New Mexico, Arizona, and California
71
A leg culture from a nursing home patient grew gram-negative rods on MacConkey
agar as pink to dark pink oxidase-negative colonies. Given the following results, which is
the most likely organism?
Klebsiella pneumoniae
72
Four blood cultures were taken over a 24-hour period from a 20-year-old woman with
severe diarrhea. The cultures grew motile (room temperature), gram-negative rods. A
urine specimen obtained via catheterization also showed gram-negative rods (100,000
col/mL). Given the following results, which is the most likely organism?
TSI = A/A gas
Indole = +
VP = Neg
MR = +
H2S = Neg
Citrate = Neg
Urease = Neg
Lysine decarboxylase = +
(PD) Phenylalanine deaminase = Neg
Escherichia coli
73
A stool culture from a 30-year-old man suffering from bloody mucoid diarrhea gave the
following results on differential enteric media:
MacConkey agar = clear colonies
XLD agar = clear colonies
Hektoen agar = green colonies
Salmonella–Shigella agar = small, clear colonies
Which tests are most appropriate for identification of this enteric pathogen?
TSI, motility, indole, urease, Shigella typing with polyvalent sera
74
A leg-wound culture from a hospitalized 70-year-old man with diabetes grew motile,
lactose-negative colonies on MacConkey agar. Given the following biochemical reactions
at 24 hours, what is the most probable organism?
H2S (TSI) = Neg
Indole = Neg
MR = Neg
VP = +
DNase = +
Citrate = +
Urease = Neg
(PD) Phenylalanine deaminase = Neg
Ornithine and lysine decarboxylase = +
Arginine decarboxylase = Neg
Gelatin hydrolysis = +
Serratia marcescens
75
Three blood culture specimens taken from a 30-year-old patient with cancer receiving
chemotherapy and admitted with a urinary tract infection (UTI) grew lactose-negative,
motile, gram-negative rods prior to antibiotic therapy. Given the following biochemical
reactions, which is the most likely organism?
H2S (TSI) = +
Indole = +
MR = +
VP = Neg
Citrate = Neg
Urease = +
DNase = +
(PD) Phenylalanine deaminase = +
Gelatin hydrolysis = +
Ornithine decarboxylase = Neg
Proteus vulgaris
76
Three consecutive stool cultures from a 25-year-old male patient produced scant
normal fecal flora on MacConkey and Hektoen agars. However, colonies on CIN agar
displayed “bull’s eye” colonies after 48 hours of incubation. The patient had been
suffering from enterocolitis with fever, diarrhea, and abdominal pain for 2 days. What
is the most likely identification of this gram-negative rod?
Yersinia enterocolitica
77
A 6-year-old female patient was admitted to the hospital following 2 days of severe
diarrhea. Cultures from three consecutive stool samples contained blood and mucus.
Patient history revealed that she had eaten a hamburger at a fast-food restaurant 3
days earlier. Which pathogen is most likely responsible for the following results?
Growth on:
XLD agar = Yellow colonies
HE agar = Yellow colonies
Mac agar = Light pink and dark pink colonies
Mac with sorbitol agar = Few dark pink and many colorless colonies
Escherichia coli O157:H7
78
Following a 2-week camping trip to the southwest United States, a 65-year-old male
patient was hospitalized with a high fever and an inflammatory swelling of the axilla
and groin lymph nodes. Several blood cultures were obtained, and cultures showed
growth of gram-negative rods resembling “closed safety pins.” The organism grew on
MacConkey agar showing non–lactose-fermenting colonies. Testing demonstrated a
nonmotile rod that was biochemically inert. What is the most likely pathogen identified?
Yersinia pestis
79
The majority of clinical laboratories with a microbiology department should have the
capability of serotyping which pathogenic Enterobacteriaceae species?
Escherichia coli O157:H7, Salmonella spp., Shigella spp.
80
Direct spread of pneumonic plague disease occurs by which route?
Inhalation of contaminated airborne droplets
81
Which isolates of the Enterobacteriaceae family most commonly produce extendedspectrum β-lactamase (ESBL)?
Escherichia coli and Klebsiella pneumoniae
82
Additional methods of definitive identification for the Enterobacteriaceae family
include which of the following:
All of the above
83
Which of the following Shigella spp. serotypes is the most often isolated in the United
States?
Serotype D (Shigella sonnei)
84
Which organism is transmitted by ingesting undercooked ground beef or raw milk
resulting in inflammation and bleeding of the mucosa of the large intestine (i.e.,
hemorrhagic colitis) which can also lead to hemolytic uremic syndrome (HUS) ?
Escherichia coli (STEC)—Shiga toxin
85
This organism is transmitted by ingesting contaminated fresh water and/or shell fish,
resulting in watery, dysentery-like stools and chronic diarrhea. Culture on stool media
and initial testing show the following results:
MacConkey agar = Both lactose-fermenting and non–lactose-fermenting colonies
Sheep blood agar = Nonhemolytic, shiny, opaque, smooth, nonspreading
Oxidase = + DNase = Neg String test = Neg
The most likely preliminary identification is?
Plesiomonas shigelloides
86
What are the most appropriate screening tests to presumptively differentiate and
identify the nonfermentative gram-negative bacilli (NFB) from the Enterobacteriaceae
species?
Oxidase, TSI, nitrate reduction, growth on MacConkey agar
87
Presumptive tests used for identification of the Pseudomonas spp. are:
Oxidase, oxidation–fermentation (OF) glucose (open), OF glucose (sealed), motility,
pigment production
88
Which tests are most appropriate to differentiate between Pseudomonas aeruginosa and
Pseudomonas putida?
Mannitol, nitrate reduction, growth at 42°C
89
Which test group best differentiates Acinetobacter spp. from P. aeruginosa?
Oxidase, motility, nitrate reduction
90
In addition to motility, which test best differentiates Acinetobacter spp. and Alcaligenes
faecalis?
Oxidase
91
The most noted differences between P. aeruginosa and Stenotrophomonas maltophilia
are:
Oxidase, 42°C growth, and polar tuft of flagella
92
Which nonfermentative bacillus is usually associated with a lung infection related to
cystic fibrosis (CF)?
Pseudomonas aeruginosa
93
A nonfermenter recovered from an eye wound is oxidase positive, motile with polar
monotrichous flagella, and grows at 42°C. Colonies are dry, wrinkled or smooth, buff to
light brown, and are difficult to remove from the agar. In which DNA homology group
should this organism be placed?
Pseudomonas stutzeri
94
Which organism is associated with immunodeficiency syndromes and melioidosis (a
glanders-like disease prevalent in Southeast Asia and northern Australia)?
Burkholderia pseudomallei
95
Which characteristics/biochemical tests are used to differentiate Burkholderia cepacia from S. maltophilia?
Pigment on blood agar, oxidase, DNase
96
The following results were obtained from a pure culture of gram-negative rods
recovered from the pulmonary secretions of a 10-year-old cystic fibrosis patient with
pneumonia:
Oxidase = +
Motility = +
Glucose OF (open) = + Gelatin hydrolysis = +
Pigment = Red
Arginine dihydrolase = + (nonfluorescent)
Growth at 42°C = +
Flagella = + (polar, monotrichous)
Which is the most likely organism?
Pseudomonas aeruginosa
97
Alcaligenes faecalis (formerly A. odorans) is distinguished from Bordetella
bronchiseptica with which test?
Urease (rapid)
98
Chryseobacterium spp. are easily distinguished from Acinetobacter spp. by which of the
following two tests?
Oxidase, growth on MacConkey agar
99
A gram-negative coccobacillus was recovered on chocolate agar from the CSF of an
immunosuppressed patient. The organism was nonmotile and positive for indophenol
oxidase but failed to grow on MacConkey agar. The organism was highly susceptible to
penicillin. The most probable identification is
Moraxella lacunata
100
Cetrimide agar is used as a selective isolation agar for which organism?
Pseudomonas aeruginosa
101
A specimen from a 15-year-old female burn patient was cultured after débridement,
and the following results were obtained:
Oxidase = +
Lysine decarboxylase = Neg
Catalase = +
Motility = +
Ornithine decarboxylase = Neg
Glucose = + for oxidation (open tube)
Arginine dihydrolase = +
Maltose = Neg for oxidation (open tube)
Penicillin = Resistant
Aminoglycosides = Susceptible
Colistin (Polymixin B) = Susceptible
Pseudomonas aeruginosa
102
A yellow pigment–producing organism, growing on chocolate agar, testing oxidase
positive, nonmotile and does not grow on MacConkey agar was recovered from the
blood of a neonate. What is the most likely organism?
Elizabethkingia (formerly Chryseobacterium) meningosepticum
103
Which reagent(s) is (are) used to develop the red color indicative of a positive reaction
in the nitrate reduction test?
Sulfanilic acid and α-naphthylamine
104
A culture from an intra-abdominal abscess produced orange-tan colonies on blood
agar that gave the following results:
Oxidase = +
Nitrate reduction = +
KIA = Alk/Alk (H2S)+
Motility = + (single polar flagellum)
DNase = +
Ornithine decarboxylase = +
Growth at 42°C = Neg
MacConkey agar = NLF (non–lactose fermenter)
The most likely identification is:
Shewanella putrefaciens
105
Chryseobacterium spp. and B. cepacia are easily differentiated by which test?
Motility
106
A 15-year-old female complained of a severe eye irritation after removing her soft
contact lenses. A swab specimen of the infected right eye was obtained by an
ophthalmologist, who ordered culture and sensitivity testing. The culture was plated on
blood agar and MacConkey agar. At 24 hours, growth of a gram-negative rod that
tested positive for cytochrome oxidase was noted. The Mueller-Hinton sensitivity plate
showed a bluish-green “lawn” of growth that proved highly resistant to most of the
antibiotics tested except amikacin, tobramycin, and ciprofloxacin. What is the most
likely identification?
Pseudomonas aeruginosa
107
Which of the listed Pseudomonas spp. is associated with the following virulence factors:
exotoxin A, endotoxins, proteolytic enzymes, antimicrobial resistance, and production
of alginate?
Pseudomonas aeruginosa
108
A 20-year-old horse groomer exhibited a “glanders-like” infection. His history indicated
he had suffered several open wounds on his hands 2 weeks before the swelling of his
lymph nodes. A gram-negative rod was recovered from a blood culture that grew well
on blood and MacConkey agars. Most of the biochemical tests were negative, including
the cytochrome oxidase test. What is the most likely identification?
Burkholderia mallei
109
A Vietnam War veteran presented with a “glanders-like” infection (melioidosis).
Several blood cultures produced gram-negative rods that were positive for cytochrome
oxidase, oxidized glucose and xylose, and grew at 42°C. What is the most likely
organism?
Burkholderia pseudomallei
110
Cytochrome oxidase-positive, nonfermentative gram-negative bacilli were recovered
from the stool of a patient with CF. The isolates produced wet (mucoidy) light blue
colonies on tryptic soy agar. Which identification is most likely?
Pseudomonas aeruginosa
111
Several postoperative hospitalized patients were colonized with gram-negative
coccobacilli growing on MacConkey agar. Specimens were obtained from blood, urine,
and wound sites. Testing revealed oxidase negative, nonmotile organisms. Which of the
following is the most likely cause of the nosocomial infections?
Acinetobacter spp
112
A nosocomial infection involving an 80-year-old female patient, recovering from
pneumonia, produced many oxidase-negative colonies on MacConkey agar. Further
testing results are:
Motility = +
Maltose = +
Resistant to most beta-lactams
Glucose = +
Resistant to most aminoglycosides
The most likely identification is:
Stenotrophomonas maltophilia
