BacT Final Flashcards
A urine sample is received in the laboratory for culture. If the specimen can not be plated immediately, it should be held:
in refrigeration
Which of the following media are both selective and differential?
Mannitol salt agar
A TSI medium is inoculated on Monday. On Wednesday, the TSI tube is completely pink. The microbiologist should report the reaction:
Inoculate a fresh TSI tube and incubate for 18-24 hours
Which of the following sets of specimens would be acceptable for anaerobic culture?
pleural fluid, brain abscess
The pH indicators neutral red and phenol red indicate the acidity in the medium by showing the color change as:
Red and yellow respectively
When acetone-alcohol (decolorizer) is intentionally omitted from the gram-stain procedure, streptococci and Neisseriae will be stain respectively:
purple and purple
Slide coagulase test is positive for an organism because:
clumping factor found on the cell wall reacts with plasma fibrinogen
A LIA slant shows a burgundy-red slant over a yellow butt. This reaction indicated that the organism:
deaminated lysine
Decarboyxlation of amino acids lysine, arginine and ornithine results in the formation of which of the major compounds:
amines
The medium used to determine whether an organism is oxidative or fermentative with respect to its metabolic activities is:
O-F medium
Factors influencing recovery and detection of microbial pathogens from specimens include:
transit time, storage temperature and sampling technique
A swab is not the appropriate collection device to use when collecting body fluid for culture because:
the amount of sample volume that can be collected is limited
The Gram reaction of a microorganism is determined by the composition of its:
cell wall
You receive a sputum specimen. It should be inoculated onto:
blood agar, chocolate agar, and MacConkey agar
An unlabeled specimen is received in the laboratory. Your best course of action would be:
reject and request another specimen
What is the specimen of choice for pharyngitis or sore throat?
Swab of throat exudate
If an organism shows growth on phenylethyl alcohol agar (PEA) and no growth on MacConkey (MAC) the organism is most likely:
Gram-positive
Select the method of choice for recovery of anaerobic bacteria from a deep abscess
Needle aspirate after surface decontamination
A positive Simmons citrate test is seen as a
Blue color in the medium after 24 hours incubation at 35*C
Which of the following reagents is added to detect the production of indole?
p-Dimethylaminobenzaldehyde (Kovac’s reagent)
Shigella species characteristically are:
non-motile
Streptococcus pneumoniae can be differentiated best from viridans streptococci by:
bile solubility
A yellow colony from a wound culture tested catalase-positive and coagulase-negative. The organism stained as gram-positive cocci in clusters. Which of the tests would differentiate between a coagulase-negative Staphylococcus and Micrococcus?
Bacitracin susceptibility
While swimming in a lake, a young boy cut his foot, and an infection developed. The culture grew a nonfastidious, gram-negative, oxidase positive, beta-hemolytic, motile bacilli. The most likely identification is:
Aeromonas hydrophila
Explosive watery diarrhea with severe abdominal pain, after eating raw shellfish is most indicative of infection caused by:
Vibrio parahemolyticus
All members of Enterobacteriaceae family have the following characteristics except:
capable of fermenting lactose
Which of the following tests should be done first in order to differentiate Aeromonas species from members of Enterobacteriaceae
Oxidase
Hemolytic uremic syndrome (HUS) is complication after infection with:
E. coli O157:H7
Which statement is NOT correct for the bacteria that cause strep throat?
susceptible to SXT (Trimet/sulpha) disc
The etiologic agent commonly associated with septicemia and meningitis of newborns is:
Streptococcus agalactiae
Abiotrophia, also known as nutritionally variant streptococci, will not grow on routine blood or chocolate agar because they are deficient in
Sulflhydryl or pyriodoxal
Gram stain of a sputum sample from a case of lobar pneumonia reveals many white blood cells and Gram-positive cocci, which are primarily diplococci. Which of the following statements would be appropriate given these findings?
An optochin test should be performed on the culture isolate
Which of the following is not true of Shigella species:
Large number of organisms must be ingested to cause infection
Question text
A young woman seen by her physician for a dermatologic problem that developed 48 hrs after she used the whirlpool at her spa. She was afebrile with a macular, pustular skin rash on her abdomen and back. A Gram-negative, oxidase-positive, nonfermenter, motile organism was recovered from the lesion. This case is most consistent with which of the following infectious processes?
Pseudomonas dermatitis
A pustule exudate submitted for culture is plated onto primary media. After 18 hours incubation, beta-hemolytic and white to pale colonies appear on sheep blood agar plate. Gram stain shows gram-positive cocci. The colonies test catalase-positive. The most appropriate test for the identification of the isolate is:
Coagulase
A visitor to South America returns with severe diarrhea and is suspected to be infected with Vibrio cholerea. The best media for recovery and identification of the organism is:
TCBS
Question text
Biochemical reactions of an organism is consistent with Salmonella. A suspension of the isolate is tested in polyvalent antiserum ‘A’ through ‘G’ as well as ‘Vi’ antiserum. There is aggluntination seen only in the ‘Vi’ antiserum. What should be done next?
Boil suspension of organism for 10 minutes to inactivate Vi antigen
A small Gram negative bacillus is isolated from purulent discharge from eye. It grows only on chocolate agar and is oxidase-positive. The most likely organism is
Haemophilus spp
A gastroenterologist submits a gastric biopsy from a patient with peptic ulcer. To obtain presumptive evidence of Helicobacter pylori, a portion of the specimen should be added to which of the media?
Urea broth
Stool sample is routinely screened for Campylobacter using Campy-BAP incubated microaerobically at 42*C.
True
Brucella and Francisella are both Gram negative coccobacilli
True
Generally, Escherichia coli is H2S negative on TSI tube, whereas most of the Salmonella species are H2S positive.
True
Pseudomonas aeruginosa belongs to the non-fluorescent group of pseudomonads.
False
Bacillus anthraxis is
nonmotile, nonhemolytic
Which infections are categorized as a zoonosis?
Anthrax and listeriosis
A small gram-positive rod that causes neonatal meningitis is septicemia is:
Listeria monocytogenes
A specimen of choice for the isolation of Bordetella pertussis from a case of whooping cough is:
nasopharyngeal swab
A 43-year-old patient complains of a very sore throat. The throat swab for routine culture grows a variety of organisms including diphtheroids; alpha, beta and non-hemolytic streptococci; staphylococci and Neisseria. The next step is to:
identify the beta-hemolytic streptococcus species
A direct smear from a nasopharyngeal swab stained with methylene blue
stain showed various letter shapes in palisade arrangement and deep blue
metachromatic granules. The most likely identification is:
Corynebacterium species
On which medium will Corynebacterium diptheriae colonies be black, surrounded by brown halo?
Tinsdale medium
Production of H2S in TSI medium and “test tube brush” growth in soft gelatin agar is highly suggestive of:
Erysipelothrix rhusiopathiae
The best specimen for the recovery of the mycobacteria from a sputum sample is:
first morning sample
A bronchial aspirate is processed for the acid-fast bacilli. Which of the following precautions should be taken to prevent infection of laboratory personnel?
process the specimen in a biological safety hood
Digestion and decontamination of sputum samples for mycobacteria culture are performed to:
reduce or eliminate contaminating bacteria, concentrate mycobacteria for identification, release any mycobacteria that are trapped in the mucin
Mycobacteria stained with Ziehl-Neelsen or Kinyoun methods with methylene blue as counter stain are seen microscopically as:
bright red rods against a blue background
All of the following are appropriate when attempting to isolate Neisseria gonorrhoeae from a genital specimen except:
culture the specimen in ambient oxygen at 37*C
Species of the genus Neisseria can be identified and differentiated by
sugar utilization tests
A Gram stain smear of a urethral discharge from a man showing extracellular and intracellular gram-negative diplococci within segmented neutrophils is diagnostic for:
N. gonorrhoeae
Gram-negative diplococci recovered from MTM (modified Thayer Martin) plate and giving a positive oxidase test can be presumptively identified as:
N. gonorrhoeae
N. meningitidis
N. lactamica
“Clue cells” seen in a foul-smelling vaginal discharge are associated with a diagnosis of bacterial vaginosis, caused by:
Gardnerella vaginalis
Routine laboratory testing for Treponema pallidum involves:
Serological analysis
Transmission of syphilis can occur by:
congenital passage from mother to newborn, sexual intercourse and direct contact with chancre
A cell culture line commonly used for the recovery of Chlamydia trachomatis from clinical specimens is:
McCoy’s
Which compound, detected by Lugol’s iodine, is used in the non-immunologic detection of Chlamydia trachomatis in cell culture?
Glycogen
A common member of the normal flora of upper respiratory tract is:
Viridans streptococcus
Which of the following mycobacteria has an optimal growth temperature of 28-32*C?
M. ulcerans
Pneumococci usually appear as gram-positive, lancet-shaped diplococci in a Gram-stained smear.
True
VDRL and RPR are types of screening tests for syphilis.
True
All clinical presentations of gonorrhea involve the genital tract only.
False
A sputum sample showing more than 10 epithelial cells per low power field or 10X magnification is considered appropriate for culture.
False
