MLT Microbiology BOC
All of the BOC questions excluding MLS student only questions.
Terms in this set (100)
Proper media for culture of a urethral discharge from a man include:
chocolate and modified Thayer-Martin agars
A sheep blood agar inoculate with a 0.001 mL loop of urine grows 70 colonies of S. aureas. How many colony forming units should be reported?
The lowest concentration of antibiotic that inhibits growth of a test organism is the:
minimum inhibitory concentration
Which of the following clean catch urine culture colony indicates the patient likely has a urinary tract infection?
The steam autoclave method of sterilization:
uses 15lbs of pressure for 15 minutes
The expected colony count in a suprapubic urine from a healthy individual is:
An aspirate of a deep wound was plated on blood agar plates and incubated aerobically and anaerobically for 24 hours. At 24 hours there was growth on both plates. This indicates that the organism is a(n)?
A penicillin-resistant Neisseria gonorrhea produces:
Which selective media is used for the isolation of gram-positive organisms?
columbia CNA with 5% sheeps blood agar
The most sensitive substrate for the detection of beta-lactamase is?
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should be:
screened for high level aminoglycoside resisitance
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing Pseudomonas species for antibiotic susceptibility to aminoglycosides?
cation content of media
The procedure that assures the most accurate detection of mecA-mediated oxacillin resistance in routine broth microdilution susceptibility testing against S. aureus is:
use of cefoxitin for testing
When performing a stool culture, a colony type typical of an enteric pathogen is subcultured on a blood agar plate. The resulting pure culture is screened with several tests to obtain the following resulst:
---TSI- acid butt,alkaline slant, no gas, no H2S
---Phenylalanine deaminase- negative
---Serological typing- Shigella flexneri(shigella subgroup B)
The serological typing is verified with new kits and controls. The best course of action would be to:
verify reactivity of motility medium with positive and negative controls
Susceptibility testing performed on quality control organisms using a new media lot number yielded zone sizes that were too large for all antibiotics tested. The testing was repeated using a media from a previously used lot number, and all zone sizes were acceptable. Which of the following explains the unacceptable zone sizes?
The depth of the media was too thin...
3 sets of blood cultures were obtained from a patient with fever and suspected endocarditis. The aerobic bottle of 1 set had growth of Staphylococcus epidermidis at 5 days of incubation. This indicates that?
The organism is most likely a contaminant.
In order to isolate Campylobacter coli/jejuni, the fecal specimen should be?
Inoculated onto sensitive plating media, and incubated in reduced oxygen with added CO2 in 42C
An expectorated sputum is sent to the lab for culture from a patient with respiratory distress. The gram stain from the specimen shows many squamous epithelial cells and rare neutrophils. The microscopic appearance of the organisms present
Moderate GPC in chains and diplococci
Moderate palisading GPB
Which type of microscope would be the most useful in examining viruses and the structure of microbial cells?
After satisfactory performance of daily disk diffusion susceptibility quality control is documented, the frequency of quality control can be reduced to?
In disk diffusion susceptibility testing, as an antimicrobial agent diffuses away from the disk, the concentration of the antibiotic is?
The most common cause for failure of a GasPak anaerobic jar to establish an adequate environment for anaerobic incubation is?
Catalysts that have become inactivated after repeated used.
Which of the following specimen requests is acceptable?
Urine for culture of acid-fast bacilli
Which of the following groups of specimens would be acceptable for anaerobic culture?
Pleural fluid, brain abscess
A liquid fecal specimen from a 3 month old infant is submitted for microbiological examination. In addition to culture on routine media for Salmonella and Shigella, this specimen should be routinely?
Examined for the presence of Campylobacter spp.
Cerebrospinal fluid from a febrile 25 year old man with possible meningitis is rushed to the laboratory for a STAT gram stain and culture. While performing the gram stain, the technologist accidentally spills most of the specimen. The smear shows many neutrophils and no microorganisms. Since there is only enough CSF to inoculate 1 plate, the technologist should use a?
A diabetic foot swab from an 82 year old woman with recurrent infection is submitted for culture. The gram stain reveals:
Many neutrophils, no squamous epithelial cells
Many GPC in chains
The physician requests that all pathogens be worked up. In addition to the sheep blood and MacConkey agar plates routinely used for wound cultures, the technologist might also process a(n)?
CNA agar plate
Which of the following is the most appropriate specimen source and primary media battery?
Which of the following is the most appropriate organism and media combination?
Yersinia entercolitica- cefsulodin-irgasan-novobiocin(CIN)
A gram stain from a swab of a hand wound reveals
No squamous epithelial cells
Moderate GPC in chains
Moderate large GNB
Select the appropriate media that will selectively isolate each organism?
Columbia CNA, MacConkey
Upon review of a sputum gram stain, the technician 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
While performing a Kovac Indole test, the substrate must contain?
The ONPG test allows organisms to be classified as a lactose fermenter by testing which of the following?
A medium that aids in the presumptive identification of organisms based on their appearance on the medium is called?
Which of the following methods is inadequate for the detection of Vancomycin-intermediate S. aureus?
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 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
First-generation cephalosporins can be adequately represented by?
An antibiotic that inhibits cell wall synthesis is?
Which of the following organisms does not require susceptibility testing to the antimicrobial indicated when isolated clinically significant source?
Which of the following antibiotics would be routinely tested and reported for isolates of Pseudomonas aeroginosa?
Which of the following must be incubated in a micro-aerophilic environment for optimal recovery?
Vibrio parahaemolyticus can be isolated best from feces on?
Which of the following can be used to isolate Campylobacter jejuni?
Tests for beta-lactamase production in Haemophilus influenza?
Should be performed on all blood and CSF isolates
Media used to support growth of Legionella pneumophila should contain which of the following additives?
Charcoal and Yeast extract
The best medium for growth of Bordatella pertussis is?
The best medium for culture of Francisella tularensis is?
Cystine Glucose Blood Agar
When processing throat swabs for Group A Streptococcus culture, the medium or choice is?
Sheep Blood Agar
The ability to detect Oxacillin resistant Staphylococcus aureus may be enhanced by?
using Mueller-Hinton broth with 2% NaCl
The optimal wound specimen for culture of anaerobic organisms should be?
A syringe filled with pus, obtained before the administration of antibiotics
A 21 year old patient presents with pharyngitis. A throat swab is collected and submitted for anaerobic culture. The specimen should then be?
rejected as unacceptable
An antibiotic used to suppress or kill contaminating fungi in the media is?
Production of beta-lactamase is inducible in which of the following?
When using a control strain of Staphylococcus aureus, the technologist notices that the zone around the Oxacillin disk is too small. Which of the following is the most likely explanation?
Use of outdated Oxacillin disks
Which of the following organisms may be mistaken for Neisseria gonorrheae in gram stained smears of uterine cervix exudates?
A 73 year old man diagnosed as having pneumococcoal meningitis is not responding to his peniciliin therapy. Which of the following tests should be performed on the isolate to best determine this organisms susceptibility to Penicillin?
Oxacillin disk diffusion
Which of the following antimicrobials would be inappropriate to report on an E. coli isolated from a wound culture?
The susceptibility results below are reported on an Enterococcus faecalis isolated from peritoneal fluid:
Ampicillin - S
Vancomycin - R
Clindamycin - S
Levofloxacin - R
Linezolid - S
The physician calls questioning the results. Which of the following should have been done before the report was released?
The Clindamycin result should have been removed from the report since it is inactive against Enterococcus
Which of the following combinations is useful for confirming the presence of Extended Spectrum Beta Lactamases in E. coli?
Ceftazidime + Clavalunic Acid
Which of the following is the most important variable in the recovery of organisms in patients with bacteremia?
The volume of blood cultured
A vaginal/rectal swab is collected from a pregnant patient to screen for group B Streptococcus colonization. What is the best medium to use for specimen inoculation?
Susceptibility testing is performed on a Staphylococcus aureus isolate from a blood culture with the following results:
What should the technologist do next?
the cefazolin result should be changed to resistant since the oxacillin result is resistant
To quality control the autoclave, a vial of Bacillus sterothermophilus is autoclaved and should then be
incubated at 56 C
In a quality control procedure on a new batch of Mueller-Hinton plates using a stock culture of Staphyloscoccus aureus (ATCC 25923), all the disk zone sizes are too small. The most likely reason for this is that the
bacterial suspension was not diluted to the proper concentration
Which one of the following combinations of organisms would be appropriate as controls to test the functions listed?
indole-negative Escherichia coli and Proteus mirabilis
A urine Gram stain shows gram-positive cocci in clusters. The organism tested catalase positive. To speciate this organism from culture, the technician should perform a coagulase test and a/an:
The Gram stain from a blood culture shows gram-positive cocci in chains. No growth occurs on blood agar plates incubated both aerobically and anaerobically. Additional testing should be done to detect the presence of
Viridans streptococci can be differentiated from Streptococcus pneumoniae by
A reliable test for distinguishing Staphyloscoccus aureus from other staphylococci is
The optochin (ethylhydrocupreine hydrochloride) disk is used for the identification of
In the optochin (ethylhydrocupreine hydrochloride) susceptibility test, if there is a zone of inhibition of 19-30mm surrounding the disk following overnight incubation at 37C, the colony most likely consists of
Which 2 diseases are usually preceded by infection with beta-hemolytic streptococci?
glomerulonephritis, rheumatic fever
The enterotoxin produced by certain strains of hemolytic, coagulase positive Staphylococcus aureus:
causes one type of bacterial food poisoning
A gamma-hemolytic Streptococcus that blackens bile esculin agar but does not grow in 6.5% NaCl broth is most likely
group D Streptococcus
Gram stain examination from a blood culture bottle shows dark blue, spherical organisms is clusters. Growth on sheep blood agar shows small, round, pale yellow colonies. Further tests should include
catalase production and coagulase test
Gram-positive cocci in chains are seen on a Gram stain from a blood culture. The organism grows as a beta-hemolytic colony. Further tests that could be performed include
bile esculin, PYR, bacitracin, and hippurate
"Nutritionally deficient" streptococci are
in the genera Granulicatella and Abiotrophia
After 24 hours a blood culture from a newborn grows catalase negative, GPC. The bacterial colonies are small translucent and beta-hemolytic on a blood agar plate. Biochemical test results of a pure culture:
Bacitracin - R
CAMP Reaction - Positive
Bile Esculin - Not Hydrolyzed
6.5% NaCl Broth - No Growth
Assuming that all colonies react properly and reactions are verified, the next step would be to?
Perfrom a Streptococcus group typing
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 help to determine if the organism is Enterococcus?
growth in 6.5% NaCL broth
The organism most commonly associated with neonatal purulent meningitis is?
Group B Streptococci
An important cause of acute exudative pharyngitis is?
Of the following bacteria, the most frequent cause of prosthetic heart valve infections occurring within 2-3 months after surgery is?
A catheterized urine is inoculated onto blood and MacConley agar using a 0.01 mL loop. After 48 hours, 68 colonies of a small translucent, non-hemolytic organism grew on blood agar but not on MacConkey. Testing reveals small gram positive, catalase negative cocci. The preliminary report and follow up testing would be?
growth of 6800 colonies/mL of a Streptococcus species, esculin hydrolysis and NaCl growth to follow.
Children who have infections with beta hemolytic streptococci cam develop?
A gram positive coccus isolated from a blood culture has the following characteristics:
Optochin susceptibility - Negative
Bacitracin Susceptibility - Negative
Bile Esculin Hydrolysis - Negative
Hippurate Hydrolysis - Positive
Catalase - Negative
This organism most likely is?
A beta hemolytic streptococci that is bacitracin sensitive and CAMP negative is?
A beta hemolytic streptococci that is bacitracin negative and CAMP positive is?
Group B beta hemolytic streptococci may be distinguished from other hemolytic streptococci by which of the following procedures?
growth in 6.5% NaCl
It is important to differentiate between Enterococcus and group D streptococci because?
Enterococci often show more antibiotic resistance than group D streptococci
Streptococcus pneumoniae can be differentiated best from the viridans group of streptococci by?
Characteristically, enterococci are?
relatively resistant to Peniciliin
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 coagulase test
Which of the following would best differentiate Streptococcus agalactiae from Streptococcus pyogenes?
hydrolysis of sodium hippurate
The most critical distinction between S. aureus and other staphylococcus is?
Which of the following organisms is, to date, considered universally resistant to Penicillin?
A beta hemolytic gram positive coccus was isolated from the CSF of a 2 day old infant with signs of meningitis. The isolate grew on sheep blood agar under aerobic conditions and was resistant to a bacitracin disk. Which of the following should be performed for the identification of the organism?
latex antigen typing
How many hours after eating contaminated food do initial symptoms of staphylococcal food poisoning typically occur?
During the past month Staphylococcus epidermidis has been isolated from cultures at 2-3 times the normal rate from the previous year. The mot logical explanation for the increase in the isolates is that?
there has been a break in proper skin preparation before drawing blood for culture.
A yellow colony from a wound culture tested catalase positive and coagulase negative. The organism stained as GPC in clusters. Which of the following tests would differentiate between a CNS and Micrococcus?
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