Certification Exam Microbiology
Terms in this set (200)
Children who have infections with beta hemolytic streptococci can develop
b. acute glomerulonephritis
Haemophilus influenzae becomes resistant to ampicillin when the organism produces a(n):
Thioglycollate broth is stored at room temperature and in the dark so that
d. there is a decreased absorption of oxygen by the medium
A liquid fecal specimen from a three-month-old infant is submitted for microbiologic examination. In addition to culture on routine media for Salmonella and Shigella, this specimen routinely should be
b. examined for the presence of Campylobacter sp
An unusual number of methicillin-resistant Staphylococcus aureus were isolated in the lab in the past month. Which of the following the most likely explanation?
b. deterioration of the methicillin disks
A gram stained sptum smear revealed 25-50 squamous epithelial cells and 10-25 polymorphonuclear leukocytes per 100x field, as well as many lanet-shaped, gram positive cocci; many gram-negative rods; and many gram positive cocci in pairs, clums, and long chains. The technologist's best course of action would be to
d. call the nursing station and request a new specimen
Which of the following specimens requests is acceptable?
d. urine for culture of acid-fast bacilli
A gram positive coccus isolated from a blood culture has the following characteristics:
Optochin susceptibility: NEG
Bacitracin (0.04 U) susceptibility: NEG
Bile esculin hydrolysis: NEG
Hippurate hydrolysis: POS
This organism is most likely
Streptococcus agalactiae (Group B)
A gram negative rod was isolated from a wound infection caused by a bite from a pet cat. The following characteristic reactions were seen:
Glucose OF: Fermentative
MacConkey agar: No Growth
Which of the following is the most likely organism?
A 10 year old boy was admitted to the ER with lower right quadrant pain and tenderness. the following lab results were obtained
Segs: 75% (16%-65%)
WBC: 200 x 10^3µL (13.0 x 10^3µL)
The admitting diagnosis was appendicitis. During surgery the appendix appeared normal; an enlarged node was removed and cultured Small gram negative rods were isolated from the room temperature plate. The organism most likely is:
Which of the following is most often used to prepare a slide from a plate culture of a dermatophyte for microscopic observation?
lactophenol cotton blue
Which of the following is the most useful orphological feature in identifying the mycelial phase of Histoplasma capsulatum?
tuberculate macroconidia, 8-14 µm
The function of N-acetyl-L-cysteine required in the NALC-NaOH reagent for acid-fast digestion-decontamination procedures is to
liquify the mucus
Middlebrook 7H10 and 7H11 media must be refrigerated in the dark and incubated in the dark as well. If these conditions are not met, the media may prove toxic for mycobacteria because:
formaldehyde may be produced
Ureaplasma urealyticum are difficult to grow in the lab on routine media becuase of their requirement for
The cyst stsage may be recovered from formed fecal specimens submitted for parasitic examination if the specimen
is stored at refrigerator temperature
The stock cultures needed for quality control testing of deoxyribonuclease (DNAse) production are
Serratia marcescens/Escherichia coli
The stock cultures needed for quality control testing of deamination activity are
Proteus mirabilis/Escherichia coli
The stock cultures needed for quality control testing of oxidase production are
Escherichia coli/Pseudomonas aeruginosa
The stock cultures needed for quality control testing of motility are
Klebsiella pneumoniae/Escherichia coli
An antibiotic that inhbits cell wall synthesis is
Group B, beta-hemolytic streptococci may be distinguished from other hemolytic streptococci by which of the following procedures?
A gram egative diplococcus that grows on modified Thayer Martin medium can be further confirmed as Neisseria gonorrhoeae if it is
oxidase positive and glucose positive, maltose negative
Organisms that may be mistaken for Neisseria gonorrhoeae in gram stained smears of uterine cervix exudates include:
Coagglutination is associated with
Chocolate agar base containing vancomycin, colistin, nystatin, and trimethoprim is also known as:
Modified Thayer-Martin agar
Sodium bicarbonate and sodium citrate are components of which of the following?
One advantage of the antimicrobial dilution tests is that
it can detect varying degrees of organism sensitivity and resistance
Clinical resistance to penicillin dosages appears to correlate with beta-lactamase production in
Which of the following organisms is, to date, considered universally susceptible to penicillin?
First-generation cephalosporins can be adequately represented by
Which of the following media is routinely used to culture Campylobacter jejuni?
Which one of the following results is typical of Campylobacter jejuni?
optimal growth at 42˚C
Which of the following organisms must be incubated in a microaerophilic environment for optimal recovery of the organism?
The recovery of some Cryptococcus species may be compromised if the isolation media contains
The one characteristic by which an unknown Cryptococcus species can be identified as Cryptococcus neoformans is
positive Niger seed agar test
A cell culture line commonly used for the recovery of Chlamydia trachomatis from clinical specimens is
Fluid from a cutaneous black lesion was submitted for routine bacteriological culture. After 18 hours of incubation at 35˚C there was no growth on Mac agar, but 3 growth on sheep blood agar. The colonies were nonhemolytic, 4-5 mm in diameter, and off-white with a ground-glass appearance. Each colony had an irregular edge with comma-shaped outgrowths that stood up like "beaten egg whites" when gently lifted with an inoculating needle. A gram stained smear of a typical colony showed large, gram positive, recctangular rods. The organism is most likely
An 8 year old girl was admitted to the hospital with a 3 day history of fever, abdominal pain, diarrhea, and vomiting. A stool culture grew many lactose-negative colonies that yielded the following test results
Ornithine decarboxylase: +
Motility at 22˚C: +
The most probable identification of this organism is
An autopsy performed on an 8 year old child revealed Waterhouse-Friderichsen syndrome. Blood and throat cultures taken just prior to death were positive for which organism?
An anaerobic gram negative bacillus isolated from a blood culture following bowel surgery grew smooth, white, non-hemolytic colonies. A gram stain showed a pale, bipolar-staining rod with rounded ends. Bile stimulated growth of the organism and catalase was produced. The isolate was not inhibited by colistin, kanamycin, or bancomycin; indole was not produced. The most likely identification of this isolate is
Relapsing fever in humans is caused by
A suspension of organisms suspected to be Shigella based on biochemical reactions did not agglutinate with Shigella antisera subgroups A, B, C, and D. The tech would conclude that
this particular Shigella possesses a capsular antigen that blocks agglutination in O antiserum and must first be destroyed by heating
Which of the following tests is used to monitor bactericidal activity during anti-microbic therapy in cases of endocarditis?
In a disk diffusion susceptibility test, which of the following can result if disks are placed on the inoculated media and left at room temperature for an hour before incubation?
zones of larger diameter would result
Which one of the following combinations of organisms would be appropriate as controls to test the functions listed?
indole - Escherichia coli and Proteus mirabilis
Which one of the following organisms could be used as the positive quality control test for lecithinase on egg yolk agar?
The porphyrin test was devised to detect strains of Haemophilus capable of
synthesis of porphobilinogen
Failure to obtain anaerobiosis in anaerobe jars is most often due to the
inactivation of the palladium-coated alumina catalyst pellets
A 1-2 mm translucent, nonpigmented colony, isolated from an anaerobc culture of a lung abscess after 72 hours, was found to fluorescee brick-red under ultraviolet light. A gram stained smear of the organisms reveaed a coccobacillus that had the following characteristics:
Growth in bile: inhibited
Esculin hydrolysis: =
Glucose, lactose, and sucrose: Acid produced
The most likely identification of this isolate is:
Prevotella (Bacteroide) melaninogenica
A thin anaerobic, gram negative bacillus with tapered ends isolated from an empyema was found to be indole positive, lipase negative, and inhibited by 20% bile. Colonies were described as "speckled" or resembling "ground glass" and fluoresced weakly when exposed to ultraviolet light. The most probable identification of this isolate would be
Which of the following anaerobes is inhibited by sodium polyanethol sulfonate (SPS)?
A beta-hemolytic, catalase positive, gram positive coccus is coagulase-negative by the slide coagulase test. Which of the following is the most appropriate action in identification of this organism?
do a tube coagulase test to confirm the slide test
Which of the following is the most reliable test to differentiate Neisseria lactamica from Neisseria meningitidis?
Which of the following sets of tests best differentiate Salmonella and Citrobacter species?
KCN, malonate, beta-galactosidase, lysine decarboxylase
Which characteristic best differentiates Acinetobacter species from Moraxella species?
production of indophenol oxidase
Recent evidence has shown that spcimens to be inoculated for the recovery of acid-fast bacilli should be centrifuged at approximately
The most important constituent of the tubercle bacillus for the activity of the various tuberculins is the
An antibiotic used to suppress or kill contaminating fungi in media is
Which of the following statements concerning the germ tube test is true?
Candida albicans and Candida tropicalis can be used as positive and negative controls, respectively
The term "internal autoinfection" is generally used in referring to infections with
When stool examination is negative, the preferred specimen for the diagnosis of paragonimiasis is
Protozoan cysts are found in a wet mount of sediment from ethyl-acetate concentrated material. The cysts are without peripheral chromatin on the nuclear membrane. Each cyst has four nuclei and each nucleus has a large karyosome that appears as a refractive dot. These oval-shaped cysts are most likely
A batch of trichrome-stained slides for ova and parasite examination contains numerous minute crystals that totally obscure the microscopic field. Which of the following measures is the most appropriate remedial action?
Change the iodine alcohol solution to obtain a strong tea-colored solution, restrain.
Which of the following would you LEAST expect to culture from a case of otitis medie?
Which one of the following species of Mycobacterium does NOT usually fluoresce on fluorochrome stain?
Which of the following organisms can grow in the small bowel and cause diarrhea in children, traveler's diarrhea, or a severe cholera-like syndrome through the production of enterotoxins?
When combined antimicrobial drugs are clearly less effective than the most active drug alone, the condition is described as
The smallest concentration of antimicrobial agent that prevents growth in subculture or results in 99.9% decrease of the initial inoculum is the definition of
minimum bactericidal concentration
If the effect of combined antimicrobials is greater than the sum of the effects observed with the two drugs independently, the condition is described as
The smalleset amount of test antimicrobial that will inhibit visible growth of a microbe is the definition of
minimal inhibitory concentration
Beta-hemolytic streptococci that are bacitracin-resistant and CAMP positive are
Beta-hemolytic streptococci that are bacitracin sensitive and CAMP negative are
A TSI tube inoculated with an organism gave the following reactions:
No gas produced
This organism is most likely
Which of the following reagents should be used as a mucolytic, alkaline reagent for digestion and decontamination of a sputum for mycobacterial culture?
N-acetyl-L-cystine and NaOH
An organism was inoculated to a TSI tube and gave the following reactions:
This organism is most likely
An organism was inoculated into a TSI tube and gave the following reactions:
This organism is most likely
An organism was inoculated into a TSI tube and gave the following reactions:
This organism most likely is
It is important to identify individual members of the group D streptococci because
enterococci often show more antibiotic resistance than other group D streptococci
When testing for oxidase activity, for which of the following organisms is it recommended that a 5% aqueous solution of tetramethylphenylenediamine dihydrochloride be used rather than commercially available strips?
Anaerobic infections differ from aerobic infections in which of the following?
They are usually polymicrobic
The presence of 20% bile in blood agar would probably enhance the growth of
Which of the following organisms may exhibit a brick red fluorescence?
Veillonella parvula and Prevotella (Bacteroides) melaninogenicus
When a Brucella species is suspected in a blood culture, the bottle should be held for a minimum of:
An organism ahs been identified as a member of the fluorescent group of Pseudomonas. Which of the following sets f tests should be used to determine the species of the organism?
growth at 42˚C, pyocyanin production, gelatinase production
The ONPG test allows organisms to be classified as a lactose fermenter by testing for which of the following?
Which of the following combinations of media provides an egg base, agar base, and a selective egg or agar base media?
Lowenstein-Jensen, Middlebrook 7H11, Lowenstein-Jensen (Gruft Modification)
Organisms that can be easily identified to the species level from the ova in fecal specimens include
Paragonimus westermani, Hymenolepis nana
A stool specimen for ova and parasite examination contained numerous rhabditiform larvae. Which factor does NOT aid in the identification of larvae?
endemic area traveled
Nonmetallic surfaces contaminated with blood should be disinfeccted with
5% bleach (sodium hypochlorite)
Tests for beta lactamase production in Hemophilus influenzae:
should be performed on all blood and CSF isolates
Definitive identification of Neisseria gonorrhoeae is made with the
hydrolysis of carbohydrates
Listeria can be confused with some streptococci because of its hemolysis and because it is
At the present time Clostridium difficile toxin can be detected by
Most of the automated microbiology equipment currently available has been designed to replace
repetitive manual methods that are performed daily on a large number or specimens
The most critical distinction between Staphylococcus aureus and other staphylococci is
One of the enterotoxins produced by enterotoxigenic E. coli in traveler's diarrhea is similar to toxin produced by
Optimum growth of Campylobacter jejuni is obtained on suitable media incubated at 42˚C in an atmosphere containing
6% O2, 10-15% CO2, 85-90% nitrogen
Vibrio parahaemolyticus can be isolated best from feces on
thiosulfate citrate bile salts (TCBS) agar
Of the following bacteria, the most frequent cause of prosthetic heart valve infections occuring within two or three months after surgery is
The bacterium most often responsible for acute epiglottitis is
Diagnosis of typhoid fever during the first 2 days of illness can be confirmed best by
Streptococcus pneumoniae can be differentiated best from the viridan group of streptococci by
A culture from an infected dog bite yields a gram negative, bipolar staining bacillus. The organism is cytochrome oxidase and indole test positive. The most likely identification of this isolate is
Biochemical reactions of an organism are consistent with Shigella. A suspension is tested in polyvalent antiserum without resulting agglutination. However, after 15 minutes of boiling, agglutination occurs in polyvalent and group D antisera. This indicates that the
organism possesses capsular antigens
Which of the following would best differentiate Streptococcus agalactiae (Group B) from Streptococcus pyogenes (Group A)?
hydrolysis of sodium hippurate
Staibs medium (Niger seed agar) is useful in the identification of which of the following?
A urine culture from a patient with a urinary tract infection yields a yeast with the following characteristics
-Failure to produce germ tubes
-Hyphae not formed on cornmeal agar
Candida (Torulopsis) glabrata
Which one of the following organisms does not require susceptibility testing when isolated from a clinically significant source?
group A streptococci
Psittacosis is transmissible to man via contact with
Shigella species characteristically are
Characteristically, group D enterococci are
relatively resistant to penicillin
The best medium for culture of Francisella tularensis is
cystine blood agar
The best medium for culture of Bordetella pertussis is
The best medium for culture of Mycobacterium tuberculosis is
Haemophilus influenzae is most likely considered normal indigenous flora in the
A nonphotochromogen that grows best at 42˚C and is highly resistant to antibiotics is Mycobacterium:
A positive niacin test is most characteristic of Mycobacterium
A 27-year old scuba diver has an abrasion on his left thigh. A culture of this would grew an acid fast organism at 30˚C. This isolate is most likely Mycobacterium
Encephalitis is most commonly associated with which of the following viruses?
Colds and other acute respiratory diseases are most often associated with:
If present, a characteristic that is helpful in separating Pseudomonas aeruginosa from other members of the Pseudomonas family is
production of pyocyanin pigment
An important cause of acute exudative pharyngitis is
The organism most commonly associated with neonatal purulent meningitis is
group B streptococci
Which of the following is a synergystic bacterial infection?
Which of the following is a dimorphic fungus
Chlamydial infections have been implicated in
urethritis and conjunctivitis
A catheterized urine specimen from an 82 year old woman with recurrent infections is submitted for culture. The gram stain reveals
-No epithelial cells
-Many gram negative rods
-Many gram positive cocci in chains
The physician requests that sensitivities be performed on all pathogens isolated. In addition to the sheep blood agar and EMB plates routinely used for urine cultures, the technologist might also process a(n)
CNA agar plate
CSF from a febrile 25-year old man with possible meningitis is rushed to the lab for a stat gram stain and culture. While performing the gram stain, the tech accidentally spills most of the specimen. The smear shows many neutrophils no microorganisms. Since there is only enough CSF to inoculate one plate, the tech should use a
chocolate agar plate
A small GNR isolated fro an eye culture has the following test results:
X factor requirement: yes
V factor requirement: yes
Hemolysis on rabbit blood agar: No
This organism is most probably Haemophilus
When processing throat swabs for a strep culture, the medium of choice is
sheep blood agar plates
When performing a Kovac's indole test, the substrate must contain:
A throat swab is submitted for anaerobic culture. This specimen should be
A vaginal smear is submitted for a Gram stain for Neisseria gonorrhoeae. The tech finds the following results on the gram stain:
- Many WBCs
- Few epis
- Many GPR
- Few GNDC
- Few GPC in chains
The tech should
not read or report a gram stain on a vaginal specimen
The causative agent of cysticercosis is
A liquid stool specimen is collected at 10:00 pm nd brought to the lab for culture, ova and parasites. It is refrigerated until 10:10 AM the next day when the doctor requests that the technologist look for amebic trophhozoites. The best course of action would be to
request a fresh specimen
The optimal wound specimen for culture of anaerobic organisms should be
a syringe filled with pus, obtained before administration of antibiotics
Lab workers should always work under a biological safety hood when working with cultures of
Trophozoites of the cyst shown are likely to:
have slow, undefined motility
Upon finding the depicted in a fecal concentrate, the tech should
review the fecal concentration carefully for the presence of other microorganisms which may be pathogenic
An inexperienced parasitology student may confuse the depicted organism with
This structure depicts a
cyst of a nonpathogenic ameba
Photochromogens produce pigment when
exposed to light for 1 hour
Media used to support growth of Legionella pneumophila should contain which of the following additives?
charcoal and yeast extract
The ability to detect methicillin-resistant Staphylococcus aureus may be enhanced by
using Mueller-Hinton agar with 4% NaCl
A request is received in the lab for assistance in selecting the appropriate test(s) for detecting Lyme disease. Which of the following would be suggested?
the organism is difficult to isolate, and antibody titers will provide the most help
A Campylobacter species has been isolated from a blood culture. The Organism is susceptible to nalidixic acid and resistant to cephalothin. Which of the following tests would aid in the differentiation between Campylobacter jejuni and Campylobacter coli?
A campylobacter species isolated from a stool cutlure gives the following biochemical reactions:
Nalidixic acid: Susceptible
Hippurate hydrolysis: Positive
This biochemical profile is consistent with Campylobacter
A catheterized urine is inoculated onto blood and Mac agar using a 0.01 mL loop. After 48 hours, 68 colonies of a small translucent nonhemolytic organism grew on blood agar but not Mac. Testing reveals small GPC catalase negative. The preliminary report and follow up testing would be
growth on 6800 CFU/ml of a Streptococcus species, esculin hydrolysiis and NaCl growth to follow
Which of the following GNB ferments carbohydrates?
A CSF has been inoculated onto sheep blood and chocolate plates and into a tube of trypticase soy broth. All media were incubated in an atmosphere of 5% CO2. Which of the following organisms would usually be isolated by this procedure?
The examination of human feces is no help in the detection of
The scolex of Taenia saginata has
Structures important in the microscopic identification of Coccidioides immitis are
irregular staining, barrel-shaped arthrospores
An aspirate of a deep wound was plated on blood agar plates aerobically and anaerobically. At 24 hours there was growth on the anaerobic plate only. The next step in the evaluation of this culture is to
begin organism identification
A medium that is used for primary isolation an enhances the growth of a particular organism is called
Upon review of a sputum Gram stain, the tech notes that the nuclei of all of the neutrophils present in the smear are staining dark blue. The best explanation for this finding is
the slide was inadequately decolorized with acetone/alcohol
Which of the following factors would make an organism appear to be more resistant on a disk diffusion susceptibility test?
too many organisms in the inoculum
The most rapid means of detecting herpes virus in clinical specimens is
SPS is used as an anticoagulant for blood cultures because it
inactivates neutrophils and components of serum complement
Darkfield microscopy is commonly used to visualize
A digested and decontaminated sputum is inoculated into a Bactec 12B bottle and incubated in air at 37˚C. On day 14 a positive growth index is obtained and the auramine-rhodamine stain is positive. Broth from the initial bottle is inoculated into one Bactec 12B bottle and one Bactec 12B bottle with NAP. After reincubation, the uninoculated growth bottle shows an increase in growth index, while the bottle containing NAP shows no increase. The organism cultured from the sputum is Mycobacterium
A fibrous skin nodule is removed from the back of a patient from Central America. A microfilaria seen upon microscopic exam of the nodule would be:
A patient with a nosocomial pneumonia has a sputum gram stain that shows many white blood cells and numerous small GNCB. The organism grew in 24 hours as a mucoid, hemolytic colony on blood agar, and a colorless colony on a Mac agar. The organism had the following characteristics
The organism is
Which organism commonly causes food poisoning from consumption of foods containing excessive populations of organisms or preformed enterotoxin?
Multifocal brain lesion in AIDS patients is commonly caused by
In the Kirby-Bauer disk diffusion susceptibility test, which variable is critical when testing Pseudomonas species for antibiotic susceptibility?
cation content of media
Patient specimens are being tested for Brucella antibody. Which course of action is most appropriate when the control serum displays a titer that is fourfold lower than expected?
the results should not be reported; the test should be repeated on the original specimen and a new control
The gram stain procedure in the procedure manual calls for acetone-alcohol decolorization for 2 minutes. The best course of action for a newly employed tech would be able to
ask the supervisor if this is indeed the timing to be followed
A GNR has been isolated from feces, and the confirmed biochemical reactions fit those of Shigella. The organism does not agglutinate in Shigella antisera. What should be done next?
boil the organism and retest with the antisera
The diagnosis of Neisseria gonorrhoeae in females is best made from
a cervical culture
The reverse CAMP test, lecithinase production, double zone of hemolysis, a gram stain morphology are all useful criteria in the identification of
Which disinfectant inactivates HIV and HBV?
Used needles from blood collection should be
placed in a puncture-proof container
A gram stain from a swab of a hand wound reveals
- Moderate GPC in chains
- Moderate large GNB
Select the appropriate media that will selectively isolate each organism
Columbia CNA, Mac
All species of the genus Neisseria have the enzyme to oxidize:
A media for selective isolation of Neisseria from a cervical exudate is
A sputum culture from an alcoholic seen in the ER grows gray, mucoid, stringy colonies on sheep blood. The isolate grows readily on Mac agar and forms mucoid, dark pink colonies. The colonies yield the following test results:
- ONPG: +
- Indole: =
- Glucose: +
- Oxidase: =
- Citrate: +
- VP: +
The organism is most likely:
An organism previously thought to be nonpathogenic, Moraxella (Branhamella) catarrhalis, is now known to be associated with infection and nosocomial transmission. Characteristic identification criteria include:
A control strain of Clostridium should be used in the GasPak anaerobic jar to ensure:
that anaerobic environment is achieved
Which of the following groups of specimens would be acceptable for anaerobic culture?
pleural fluid, brain abscess
Antibiotics tested for isolated of Pseudomonas species include:
Examine the MIC tray shown and determine the MIC for gentamicin.
≤ 2 g/mL
More than 100,000 CFU/mL of GNB were isolated on MAC from a urine specimen. Biochemical results are as follows:
- Glucose: Acid, gas produced
- Indole: =
The organism is most likely
A urine culture had the following culture results:
Sheep blood: Swarming
CNA: no growth
Mac: 1. > 100,000 CFU/ml nonlactose-fermenter
2. > 100,000 CFU/ml red, nonlactose-fermenter
The isolates from MAC had the following reactions
Glucose: 1. 2.
Urea: 1. 2. =
TDA: 1. 2. =
H2S: 1. 2. =
The organisms are most likely
Proteus mirabilis and Serratia marcescens
An isolate on chocolate agar from a patient with epiglottitis was suggestive of Haemophilus species. Additiona testing showed that the isolate required NAD for growth and was nonhemolytic. The organism is most likley Haemophilus:
Which of the following is the most appropriate organism and media combination?
Yersinia enterocolitica- cesulodin-irgasan-novobiocin (CIN)
Which of the following is the most appropriate specimen source and primary media battery?
endocervical - chocolate, Thayer-Martin
Gram stain examination of a CSF specimen indicates the presence of yeast-like cells with GP granular inclusions. Which of the following techniques should be used next to assist in the ID of this organism?
When performing a stool culture, a colony type typical of an enteric pathogen is subcultred on a blood agar plate. The resulting pure culture is screened with several tests to obtain the following results:
- TSI: acid butt, alkaline slant, no gas, no H2S
- Phenylalanine deaminase: =
- Serological typing: Shigella flexneri (Shigella subgroup B)
The serological typing is verified with new kit and controls. The best course of action would be to
verify reactivity of motility medium with positive and negative controls
A first morning sputum is received for culture of mycobacteria. It is digested and concentrated by the N-acetyl-L-cysteine alkali method. Two Lowenstein-Jensen slants are incubated in the dark at 35˚C with 5-10% CO2. The smears reveal acid-fast bacilli, and after 7 days no growth appears on the slants. The best explanation is
cultures held for insufficient length of time
A first morning sputum specimen is received for acid fast culture. The specimen is centrifuged, and the sediment is inoculated on 2 lowenstein-Jensen slants that are incubated at 35˚C in 5-10% CO2. After 1 week, the slants show abundant growth over the entire surface. Stains reveal GNB. To avoid this problem
decontaminate the specimen with NALC-sodium hydroxide mixture
The characteristic most commonly associated with the presence of strict anaerobic bacteria and that can be taken as presumptive evidence of their presence in a clinical specimen is the
presence of a foul, putrid odor from tissue specimens and cultures
A beta-hemolytic streptococcus that has been isolated from an ear culture grows up to the edge of a 0.04 unit bacitracin disk. Which of the following tests would determine if the organism is an enterococcus?
growth in 6.5% NaCl broth
Gram stain of a deep wound showed many GPR spore forming. The specimen was placed on brain-heart infusion blood agar and incubated aerobically at 35˚C for 3 days. At the end of that time, the plates showed no growth. The most likely explanation is that the culture should have been incubated.
Acinetobacter lwoffi differs from Neisseria gonorrhoeae in that the former:
will grow on MAC and EMB media
A GNR that does not grow on MAC or sheep blood agars but grows well on chocolate agar has been isolated from sputum. Which of the following tests should be done next to identify the organism?
detemination of X and V factor requirements
Mycobacteria that produce pigment only after exposure to light are classified as
In a suspected case of Hansesn's disease (leprsosy), a presumptive diagnosis is established by
detection of weakly acid-fast rods in infected tissues
On a culture suspected to be Mycobacterium tuberculosis, the MOST important test to perform is
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