Microbiology: Gram-Negative Bacilli
42C
The optimal incubator temperature for isolation of the Campylobacter jejuni/coli group is:
Sorbitol
MacConkey media for screening suspected cases of hemorrhagic E coli O157:H7 must contain:
6% O2, 10-15% CO2, 85-90% nitrogen
Optimum growth of Campylobacter jejuni is obtained on suitable media incubated at 42C in an atmosphere containing:
Proteus mirabilis
>100,000 CFU/mL of a gram-negative bacilli were isolated on MacConkey from a urine specimen. Biochemical results are as follows: The organism is most likely:
Edwardsiella tarda
A fecal specimen, inoculated to xylose lysine deoxycholate (XLD) and Hektoen enteric (HE) produced colonies with black centers. Additional testing results are as follows: Glucose + H2S + Lysine decarboxylase + Urea - ONPG - Indole + The most probable identification is:
Providencia
A 64-year-old male with lymphoma has a positive blood culture at 18 hours incubation. The organism is a nonlactose fermenting gram-negative bacillus on MacConkey agar. Further testing gives the following reactions. Oxidase: - TSI: K/A, no hydrogen sulfate motility: + indole: + citrate: + ornithine decarboxylase: - urea: + phenylalanine deaminase: + VP: - The genus is:
Haemophilus influenzae
A CSF 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?
Campylobacter jejuni
A Campylobacter species isolated from a stool culture gives the following biochemical reactions: nalidixic acid: S cephalothin: R hippurate hydrolysis: + oxidase: + catalase: + This biochemical profile is consistent with:
Helicobacter pylori
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:
Shigella dysenteriae
A TSI tube inoculated with an organism gave the following reactions: alkaline slant, acid butt, no H2S, no gas produced This organism is most likely:
subculture the bottle, and incubate in microaerophilic conditions
A blood culture bottle with macroscopic signs of growth is Gram stained and the technician notes small, curved gram-negative bacilli resembling "gull wings." It is subcultured to blood and chocolate agar, and incubated aerobically and anaerobically. After 24 hours, no growth is apparent. The next step should be to:
Eikenella corrodens
A child was bitten on the arm by her sibling and the resulting wound grew a slender gram-negative bacilli that has the following characteristics? growth on SBA: colonies that pit the agar colonies odor: like bleach catalase: - oxidase: + TSI: no growth
67,000 CFU/mL Enterobacter cloacae
A clean catch urine sample from a nursing home patient is cultured using a 0.001 mL loop. It grows 67 colonies of a lactose fermenter that has the following biochemical reactions. TSI: acid/acid oxidase: - motility: + indole: - citrate: + VP: positive lysine decarboxylase: - ornithine decarboxylase: + urea: - What should the microbiologist report?
Vibrio vulnificus
A college student attended a beach party where raw oysters and other shellfish were consumed. The next day, he had symptoms of septicemia. The blood cultures grew gram-negative bacilli with the following characteristics: oxidase: + MAC: pink colonies O/129 (150ug): S The most likely organism is:
thiosulfate citrate bile salts sucrose for Vibrio species
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 county. A media that should be incorporated in the plating protocol is:
Pseudomonas aeruginosa
A nonfermenting gram-negative bacilli is isolated from a wound. The nitrate and oxidase are strongly positive. The growth on sheep blood agar has a grape-like odor. The organism is:
Acinetobacter baumannii
A patient with a nosocomial pneumonia has a sputum Gram stain that shows many neutrophils and numerous small gram-negative coccobacilli. The organism grew in 24 hours as a mucoid, hemolytic colony on blood agar and a colorless colony on a MacConkey agar. The organism had the following characteristics: The organism 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 organism is:
Klebsiella pneumoniae
A sputum culture from an alcoholic seen in the ER grows gray, mucoid, stringy colonies on sheep blood agar. The isolate grows readily on MacConkey 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:
Proteus mirabilis and Serratia marcescens
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 nonlactose-fermenter with red pigment The organisms are most likely:
will grow on MacConkey and EMB media
Acinetobacter lwoffii differs from Neisseria gonorrhoeae in that the former:
Yersinia enterocolitica
An 8-year-old girl was admitted to the hospital with a three-day history of fever, abdominal pain, diarrhea and vomiting. A stool culture grew many lactose-negative colonies that yielded the following test results:
Bordetella parapertussis
An aerobic, gram-negative coccobacillus was isolated on Bordet-Gengou agar from a nasopharyngeal swab 48 hours after culture from a 6-month-old infant with suspected pertussis. This organism exhibited the following characteristics: MAC: no growth Urea: negative at 4 hours, positive at 24 hours oxidase: negative catalase: positive
Yersinia enterocolitica
An isolate from a stool culture gives the following growth characteristics and biochemical reactions: MacConkey agar: colorless colonies Hektoen agar: yellow-orange colonies TSI: acid slant/acid butt, no gas, no H2S Urea: positive These screening reactions are consistent with which of the following enteric pathogens?
a media with cysteine such as buffered charcoal yeast extract agar
Appropriate culture requirements for a specimen from a patient suspected of having tularemia include:
colonies are large and spreading after 2-4 days
Characterisitics of the genus Capnocytophaga include:
requirement of 5-10% CO2 for growth
Characteristics of the HACEK group of bacteria include:
oxidase
Differentiating tests that will serparate Burkholderia from Stenotrophomonas include:
beta-lactamase enzyme
Haemophilus influenzae becomes resistant to ampicillin when the organism produces a(n):
oropharynx
Haemophilus influenzae is most likely considered normal indigenous flora in the:
growth at 42C
If present, a characteristic that is helpful in separating Pseudomonas aeruginosa from other members of the Pseudomonas family is:
Escherichia coli
Infection of the urinary tract is most frequently associated with:
reduce nitrate to nitrite
Members of the family Enterobacteriaceae share which one of the following characteristics?
Haemophilus aphrophilus
Multiple blood cultures from a patient with endocarditis grew a facultatively anerobic, pleomorphic gram-negative bacilli with the following characteristics: hemolysis: negative MAC: no growth BAP: growth in 5-10% CO2 CHOC: growth in 5-10% CO2 Catalase: - V factor: not required X factor: not required oxidase: negative nitrate: + indole: - The most likely identification is:
Vibrio cholerae
One of the enterotoxins produced by enterotoxigenic Escherichia coli in traveler's diarrhea is similar to a toxin produced by:
it is oxidase positive
Plesiomonas shigelloides is a relatively new member of the family Enterobacteriaceae. What characteristic separates it from other members of the Enterobacteriaceae?
Escherichia coli/Enterobacter cloacae
Quality control of the spot indole test requires the use of ATCC cultures of:
culture was not incubated long enough
Serum samples collected from a patient with pneumonia demonstrate a rising antibody titer to Legionella. A bronchalveolar 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:
nonmotile
Shigella species characteristically are:
take extra safety precautions for possible Brucella
The laboratory receives a blood culture from a veterinarian who has been ill for many weeks with fevers in the afternoon and evenings, arthritis, and fatigue. The blood culture is positive after 5 days, and the organism has the following characteristics: Gram stain: small, gram-negative coccobacilli BAP: growth after 48 hours with small, smooth, raised colonies What should the microbiologist do next?
synthesis of hemin
The porphyrin test was devised to detect strains of Haemophilus capable of:
Proteus mirabilis/Escherichia coli
The stock cultures needed for quality control testing of deamination activity are:
Serratia marcescens/Escherichia coli
The stock cultures needed for quality control testing of deoxribonuclease (DNase) production are:
Klebsiella penumoniae/Escherichia coli
The stock cultures needed for quality control testing of motility are:
Escherichia coli/Pseudomonas aeruginosa
The stock cultures needed for quality control testing of oxidase production are:
production of indophenol oxidase
Which characteristic best differentiates Acinetobacter species from Moraxella species?
rapid hydrolysis of urea
Which of the following characteristics best differentiates Bordetella bronchiseptica from Alcaligenes species?
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?
growth at 37C
Which of the following results is typical of Campylobacter fetus subspecies fetus?
KCN, malonate, beta-galactosidase, lysine decarboxylase
Which of the following sets of tests best differentiates Salmonella and Citrobacter species?
bone marrow
Which of the following specimens is considered to be the most sensitive for the recovery of Brucella in cases of chronic infection?
Shigella
Which one of the following genera is among the least biochemically reactive members of the Enterobacteriaceae?
Yersinia entercolitica
Which one of the following gram-negative bacilli ferments glucose? Alcalingenes faecalis Pseudomonas cepacia Acinetobacter lwoffi Yersinia entercolitica
optimal growth at 42C
Which one of the following results is typical of Campylobacter jejuni: optimal growth of 42C oxidase negative catalase negative nonmotile
Aeromonas hydrophila
While swimming in a lake near his home, a young boy cut his food, and an infection developed. The culture grew a nonfastidious gram-negative, oxidase positive, beta-hemolytic, motile bacilli that produced deoxyribonuclease. The most likely identification is:
Yersinia enterocolitica
A 10-year-old boy was admitted to the emergency room with lower right quadrant pain and tenderness. The following laboratory results were obtained: %segmented neutrophils 75% (16-60%) WBC 200x10^3/ul (13x10^3/ul) The admitting diagnosis was appendicitis. During surgery the appendix appeared normal; an enlarged node was removed and cultured. Small gram-negative bacilli were isolated from the room temperature plate. The organism most likely is:
Burkholderia cepacia
A 17-year-old female with cystic fibrosis is diagnosed with pneumonia. A sputum sample grew gram-negative bacilli with yellow, smooth colonies that have the following biochemical reactions: The most likely organism is:
Yersinia pestis
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 showed bacilli that were bipolar, resembling safety pins. The most likely identification of this organism is:
Haemophilus influenzae
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:
X factor: no growth V factor: no growth XV factor: growth horse blood: no hemolysis
A 4-year-old is admitted with symptoms of meningitis, and a Gram stain of the CSF reveals small, pleomorphic, gram-negative coccobacilli. After 24 hours incubation at 35C, small, moist, gray colonies, which are oxidase variable, are found on the chocolate agar plate only. Which of the following biochemical data would be consistent with this isolate?
Bordetella bronchiseptica
A culture from an infected dog bite on a small boy's finger yielded a small, gram-negative coccobacillus that was smooth, raised and beta-hemolytic on blood agar. The isolate grew on MAC forming colorless colonies. The organism was motile, catalase positive, oxidase positive, reduced nitrate, and was urease positive within 4 hours. No carbohydrates were fermented. The most likely identification of this isolate is:
urea broth
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?
Chromobacterium
A genus that is found in soil and water and causes infections in immunocompromised patients has the following characteristics: sheep blood agar: violet pigment MAC: growth 42C incubation: growth oxidase: + OF glucose: fermenter indole: -
boil the organism and retest with the antisera
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?
Pasteurella multocida
A gram-negative bacillus with bipolar staining was isolated from a wound infection caused by a bite from a pet cat. The following characteristic reactions were seen: oxidase: + glucose OF: fermentative catalase: + motility: - MAC: no growth Which of the following is the most likely organism?
culture on buffered charcoal yeast extract agar with antibiotics
A laboratory aid receives a bronchoscopy 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:
parainfluenzae
An isolate on chocolate agar from a patient with epiglottis was suggestive of Haemophilus species. Additional testing showed that the isolate required NAD for growth and was nonhemolytic. The organism is most likely Haemophilus:
Escherichia coli
An organism gave the following reactions TSI: acid slant/acid butt, no H2S, gas produced Indole: positive motility: positive citrate: negative lysine decarboxylase: positive urea: negative VP: negative This organism is most likely is:
a growth at 42C, pyocyanin production, gelatinase production
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?
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:
Haemophilus influenzae
An organism that exhibits the satellite phenomenon around colonies of staphylococci is:
Salmonella typhimurium
An organism was inoculated to a TSI tube and gave the following reactions: alkaline slant/acid butt, H2S, gas produced This organism likely is:
a boil suspension of the organism for 10 minutes to inactivate the Vi antigen
Biochemical reactions of an organism are consistent with Salmonella. A suspension is tested in polyvalent antiserum A through G and Vi antiserum. There is agglutination in the Vi antiserum only. What should be done next?
sonnei
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:
