BOC Microbiology Gram Negative Bacilli
A 25 year old man who had recently worked as a steward on a transoceanic grain ship presented to the emergency room with high fever, diarrhea and prostration. Axillary lymph nodes were hemorrhagic and enlarged. A Wayson stain of the aspirate shoed bacilli that were bipolar, resembling safety pins. The most likely identification of this organism is:
Yersinia perstis
An isolate on chocolate agar from a patient with epiglottitis was suggestive of Haemophilus species. Additional testing showed that the isolate required NAD for growth and was nonhemolytic. The organism is most likely Haemophilus:
parainfluenzae
Members of the family Enterobacteriaceae share which one of the following characteristics?
reduce nitrate to nitrite.
Biochemical reactions of an organism are consistent with Shigella. A suspension is tested in antiserum without resulting agglutination. However, after 15 minutes of boiling, agglutination occurs in group D antisera. The Shigella species is:
sonnei
MacConkey media for screening suspected cases of hemorrhagic E coli 0157:H7 must contain:
sorbitol
The stock cultures needed for quality control testing of motility are:
Klebsiella pneumoniae/Escherichia coli
Which one of the following results is typical of Campylobacter jejuni:
Optimal growth at 42c.
Appropriate culture requirements for a specimen from a patient suspected of having tularemia include:
A media with cysteine such as buffered charcoal yeast extract agar.
A nonfermenting gram negative bacillus is isolated from a wound. The nitrate and oxidase are strongly positive. The growth on sheep blood agar has a grape like odor. The organisms is:
Pseudomonas aeruginosa
An organism isolated from the surface of a skin burn is found to produce a diffusible green pigment on a blood agar plate. Further studies of the organism would most likely show the organism to be:
Pseudomonas aeruginosa
A gram negative bacillus 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 optimal incubator temperature for isolation of the campylobacter jejuni/coli group is:
42c
Optimum growth of Campylobacter jejuni is obtained on suitable media incubated at 42c in an atmosphere containing:
6% O2, 10%CO2, 85-90% nitrogen
While swimming in a lake near his home, a young boy cut his foot, and an infection developed. The culture grew a nonfastidious gram negative, oxidase positive, beta-hemolytic, motile bacilli that produced deoxyribonuclease. Them sot likely identification is:
Aeromonas hydrophila
A TSI tube inoculated with an organism gave the following reactions: alkaline slant, acid butt, no H2S, no gas produced
Shigella dysenteriae
Haemophilus influenzae becomes resistant to ampicillin when the organism produces a:
Beta-lactamase enzyme
Serum samples collected from a patient with pneumonia demonstrate a rising antibody titer to Legionella. A bronchoalveolar lavage (BAL) specimen from this patient had a positive antigen test for Legionella but no organisms were recovered on buffered charcoal yeast extract medium after 2 days of incubation. The best explanation is that the:
Culture was not incubated long enough.
Infection of the urinary tract is most frequently associated with:
Escherichia coli
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?
Escherichia coli.
Quality control of the spot indole test requires the use of ATCC cultures of:
Escherichia coli/Enterobacter cloacae
The stock cultures needed for quality control testing of oxidase production are:
Escherichia coli/Pseudomonas aeruginosa
an organism has been identified as a member of the fluorescent group of Pseudomonas. Which of the following sets of tests should be used to determine the species of the organism?
Growth at 42c, pyocyanin production, gelatinase production.
If present, a characteristic that is helpful in separating Pseudomonas aeruginosa from other members of the pseudomonas family is:
Growth at 42c.
A 4 year old boy is admitted to the hospital with suspected meningitis. He has not had most of the childhood vaccines. The suspected pathogen is:
Haemophilus influenzae
A small, gram negative bacillus is isolated from an eye culture. It grows only on chocolate agar and is oxidase variable. The most likely organisms is:
Haemophilus influenzae
An organism that exhibits the satellite phenomenon around colonies of staphylococci is:
Haemophilus influenzae
A cerebrospinal fluid has been inoculated onto sheep blood and chocolate agar 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?
Haemophilus influenzae.
A gram stain of a touch prep from a gastric biopsy shows gram negative bacilli that are slender and curved. The most likely pathogen is:
Helicobacter pylori
Plesiomonas shigelloides is a relatively new member of the family Enterobacteriaceae. what characteristic separates it from other members of the Enterobacteriaceae?
It is oxidase positive.
Haemophilus influenzae is most likely considered normal indigenous flora in the:
Oropharynx
Which characteristic best differentiates Acinetobacter species from Moraxella species?
Production of indophenol oxidse
The stock cultures needed for quality control testing of deamination activity are:
Proteus mirabilis/Escherichia coli
An organism was inoculated to a TSI tube and gave the following reactions: alkaline slant/acid butt, H2S gas produced:
Salmonella typhimurium
The stock cultures needed for quality control testing of deoxyribonuclease (DNase) production are:
Serratia marcescens/Escherichia coli
Which one of the following genera is among the least biochemically reactive members of the Enterobacteriaceae?
Shigella
A community hospital microbiology laboratory is processing significant numbers of stool cultures because of an outbreak of diarrhea following heavy rains and flooding in the country. A media that should be incorporated in the plating protocol is:
Thiosulfate citrate bile salts sucrose for Vibrio species.
Which one of the following gram negative bacilli ferments glucose
Yersinia enterocolitica
A gastroenterologist submits a gastric biopsy from a patient with a peptic ulcer. To obtain presumptive evidence of Helicobacter pylori, a portion of the specimen should be added to which media?
Urea broth
Which of the following specimens is considered to be the most sensitive for the recovery of Brucella in cases of chronic infection?
bone marrow
A laboratory aid receives a bronochoscopy sample with the request for culture of Legionella. The assistant asks a microbiologist for direction on plating protocol. the correct response from the microbiologist is:
culture on buffered charcoal yeast extract agar with antibiotics.
Shigella species characteristically are:
nonmotile.
Differentiating tests that will separate Burkholderia from Stenotrophomonas include:
oxidase.
