Pathogenic Microbiology Test 4

167) 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? a. urea broth b. tetrathionate c. selenite d. tryptophan

a (Helicobacter pylori produces large amounts of extracellular urease and is positive for urea within 2 hours.)

132) Which one of the following genera is among the least biochemically reactive members of the Enterobacteriaceae? a. Proteus b. Pseudomonas c. Citrobacter d. Shigella

d (Shigella is lactose negative, most species do not produce gas, are VP, urea, lysine decarboxylase and citrate negative, and they are nonmotile.)

142) 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? a. test the organism with a new lot of antisera b. test with Vi antigen c. repeat the biochemical test d. boil the organism and retest with the antisera

d (Some Shigella produce capsular antigen that mask the cell wall and boiling removes the capsule.)

148) A fecal specimen, inoculated to xylose lysine deoxycholate (XLD) and Hektoen enteric (HE) produced colonies with black centers. Additional testing results are as follows: Biochemical screen: - Glucose: positive - H2S: positive - Lysine decarboxylase: positive - Urea: negative - ONPG: negative - Indole: positive Serological test: - Polyvalent: no agglutination - Group A: no agglutination - Group Bl: no agglutination - Group C: no agglutination - Group D: no agglutination - Group Vi: no agglutination The most probable identification is:

B. Edwardsiella tarda

139) 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?

B. Escherichia coli

168) A 4 yr. old boy is admitted to the hospital with suspected meningitis. He has not had most of the childhood vaccines. The suspected pathogen is:

B. Haemophilus influenzae

A surgical wound specimen produces pink colonies on MacConkey agar. There is no growth on CNA and abundant flat, spreading gray mucoid colonies on blood agar. The next four questions are talking about this case study above. This specimen contains:

A gram negative bacillus that ferments lactose

176) Optimum growth of Campylobacter jejuni is obtained on suitable media incubated at 42 C in an atmosphere containing:

A. 6% O2, 10%-15% CO2, 85%-90% nitrogen

193) Appropriate culture requirements for a specimen from a patient suspected of having tularemia include:

A. A media with cysteine such as BYCA

151) 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?

A. Boil suspension of the organism for 10 minutes to inactivate the Vi antigen

192) 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?

A. Growth at 42 C, pyocyanin production, gelatinase production

Enterohemorrhagic E. coli (EHEC) is:

Also known as verocytoxic E. coli May be associated with hemolytic uremic syndrome May often serotype as 0157:H7

174) A campylobacter species isolated from a stool culture gives the following biochemical reactions: - Nalidixic acid: susceptible - Cephalothin: resistant - Hippurate hydrolysis: positive - Oxidase: positive - Catalase: positive This biochemical profile is consistent with:

B. Campylobacter jejuni

182) A genus that is found in soil and water and causes infections in immunocompromised patients has the following characteristics: - Sheep blood agar: violet pigment - MacConkey agar: growth - 42 degrees Celsius incubation: growth - Oxidase: positive - OF glucose: fermenter - Indole: negative The genus is:

B. Chromobacterium

195) Characteristics of the genus Capnocytophaga include:

B. Colonies are large and spreading after 2-4 days

194) 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: negative - Oxidase: positive - TSI: no growth The identification of this organism is:

B. Eikenella corrodens

________ media is used to isolate Yersinia enterocolitica.

CIN Cefsulodin-irgasin-novobiocin

152) A clean catch urine sample from a nursing home patient is cultured using a .001mL loop. It grows 67 colonies of a lactose fermenter that has the following biochemical reactions: TSI: Acid/Acid Oxidase: negative Motility: positive Indole: negative Citrate: positive VP: positive Lysine decarboxylase: negative Ornithine decarboxylase: positive Urea: negative What should the microbiologist report?

C. 67,000 CFU/mL Enterobacter cloacae

187) 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. The most likely identification is:

C. Aeromonas hydrophila

201) Characteristics of the HACEK group of bacteria include:

C. Requirement of 5%-10% CO2 for growth

On Hektoen Enteric agar, Shigella appears as:

Clear or colorless colonies.

165) The optimal incubator temperature for isolation of the Campylobacter jejuni/coli group is:

D. 42 degrees Celsius

179) Haemophilus influenzae becomes resistant to ampicillin when the organism produces a:

D. Beta-lactamase enzyme

The IMVC reactions are - - + + which would eliminate __________ as a possible organism.

E. coli

The TSI is yellow over yellow with cracks but no blackening. This would be interpreted as:

Ferments glucose with gas production, ferments lactose and/ or sucrose

The organism is nonmotile, LDC +, ODC -, ADH - which would most likely indicate that the isolate is:

Klebsiella pneumoniae

Is Proteus mirabilis indole positive or negative?

Negative

Do all enterobacteriaceace members ferment lactose?

No

Does Shigella produce H2S or gas?

No

Is the H antigen found in the cell wall?

No

Are members of the tripe Klebsielleae VP positive or negative?

Positive

Rapid urease activity is characteristic of the genus _________.

Proteus

Swarming colonies on sheep blood agar would lead one to suspect:

Proteus

The production of deaminase is found in which of the following groups of bacteria?

Proteus, Providencia, and Morganella

The most frequently implicated species of Shigella in the United States is:

S. sonnei

What organisms produce H2S or gas?

Salmonella Proteus Citrobacter

__________ ____________ produces DNAse, lipase, gelatinase and sometimes a red pigment.

Serratia marcescens

In the ____________ __________ pathway for glucose fermentation, acetoin is detected.

Voges Proskauer

___________ ___________ causes plague, which is transmitted through fleas and rodents.

Yersinia pestis

153) Plesiomonas shigelloides is a relatively new member of the family Enterobacteriaceae. What characteristic separates it from other members of the Enterbacteriaceae? a. it is oxidase positive b. it ferments glucose c. it produces pyocyanin d. it requires 10% CO2 for growth

a (Enterobacteriaceae ferment glucose and are oxidase negative. Plesiomonas was a member of the Vibrio family in part because it is oxidase positive. However, it was moved to the Enterobacteriaceae family despite its positive oxidase reaction.)

160) An organism that exhibits the satellite phenomenon around colonies of staphylococci is: a. Haemophilus influenzae b. Neisseria meningitidis c. Neisseria gonorrhoeae d. Klebsiella pneumoniae

a (Haemophilus influenzae requires X and V factors. Sheep blood agar supplies X factor, and the staphylococci produce V factor, so colonies grow around staph colonies.)

130) MacConkey media for screening suspected cases of hemorrhagic E coli O157:H7 must contain: a. indole b. citrate c. sorbitol d. lactose

c (Sorbitol replaces lactose in MacConkey. E coli 0157:H7 does not ferment sorbitol, whereas other species of E coli are positive for fermentation of sorbitol. This makes the media a good screen for 0157:H7.)

138) 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 most likely is: a. Klebsiella pneumoniae b. Shigella dysenteriae c. Escherichia coli d. Enterobacteria cloacae

c (These biochemicals are characteristic for E coli. Klebsiella pneumoniae is indole negative and nonmotile. Shigella dysenteriae is nonmotile and Enterobacter cloacae is indole negative.)

133) Which one of the following gram-negative bacilli ferments glucose? a. Alcaligenes faecalis b. Pseudomonas cepacia c. Acinetobacter lwoffii d. Yersinia enterocolitica

d (Alcaligenes, Pseudomonas and Acinetobacter are all nonfermenters; Yersinia is a member of the Enterobacteriaceae and, by definition, ferments glucose.)

143) Biochemical reactions of an organism are consistent with Shigella. A suspension is tested in antiserum without resulting agglutination. However, after 15 mins. of boiling, agglutination occurs in group D antisera. The Shigella species is: a. dysenteriae b. flexneri c. boydii d. sonnei

d (Boiling removed the capsule so that the antiserum could react with cell wall antigen. Group D Shigella is S sonnei.)

131) Members of the family Enterobacteriaceae share which one of the following characteristics? a. produce cytochrome oxidase b. ferment lactose c. produce beta-hemolysis d. reduce nitrate to nitrite

d (Members of Enterobacteriaceae are oxidase negative, ferment glucose, and reduce nitrate to nitrite.)

150) A 25 yr. old man who had recently worked as a steward on a transoceanic grain ship presented to the ER 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 ID of this organism is: a. Brucella melitensis b. Streptobacillus moniliformis c. Spirillum minus d. Yersinia pestis

d (Yersinia pestis is classically described as having a "safety pin" appearance on Wayson stain. This patient's presentation is classic for bubonic plague.)

169) Acinetobacter lwoffii differs from Neisseria gonorrhoeae in that the former:

B. Will grow on MacConkey and EMB media

170) A 4-year-old is admitted with symptoms of meningitis, and a Gram stain of the cerebrospinal fluid reveals small, pleomorphic, gram-negative coccobacilli. After 24 hours incubation at 35 C, 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?

C. X factor: no growth / V factor: no growth / XV factor: growth / horse blood: no hemolysis

196) A laboratory aid receives a bronchoscopy sample with the request to culture for Legionella. The assistant asks a microbiologist for direction of plating protocol. The correct response from the microbiologist is:

D. Culture on buffered charcoal yeast extract agar with antibiotics

What are some characteristics of the Enterobacteriaceae?

all members are gram negative bacilli or coccobacilli all members are cytochrome oxidase negative all members grow on MacConkey agar

129) Infection of the urinary tract is most frequently associated with: a. Staphylococcus aureus b. Escherichia coli c. Enterococcus faecalis d. Serratia marcescens

b (>80% of uncomplicated UTIs are caused by E coli.)

163) 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: a. Acinetobacter lwoffii b. Haemophilus influenzae c. Stenotrophomonas maltophilia d. Pseudomonas aeruginosa

b (Growth only on chocolate agar is typical for Haemophilus influenzae, which is a gram-negative coccobacillus that causes upper respiratory infections.)

156) The stock cultures needed for quality control testing of oxidase production are: a. Escherichia coli / Klebsiella pneumoniae b. Salmonella typhimurium / Escherichia coli c. Escherichia coli / Pseudomonas aeruginosa d. Proteus mirabilis / Escherichia coli

c (Of the organisms listed only Pseudomonas aeruginosa is oxidase positive.)

157) The stock cultures needed for quality control testing of phenylalanine deamination activity are: a. Escherichia coli / Klebsiella pneumoniae b. Salmonella typhimurium / Escherichia coli c. Escherichia coli / Pseudomonas aeruginosa d. Proteus mirabilis / Escherichia coli

d (Of the organisms listed only Proteus mirabilis is phenylalanine deaminase positive)

158) The stock cultures needed for quality control testing of deoxyribonuclease (DNase) production are: a. Salmonella typhimurium / Escherichia coli b. Escherichia coli / Pseudomonas aeruginosa c. Proteus mirabilis / Escherichia coli d. Serratia marcescens / Escherichia coli

d (Of the organisms listed only Serratia marcescens is DNase positive.)

199) Differentiating tests that will separate Burkholderia from Stenotrophomonas include:

D. Oxidase

200) 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: - Oxidase: positive - TSI: alk/alk - Glucose: oxidized - Fluorescence: negative - Lysine decarboxylase: positive The most likely organism is:

A. Burkholderia cepacia

147) Which of the following tests best differentiates Salmonella and Citrobacter species?

A. KCN, malonate, beta-galactosidase, lysine decarboxylase

175) Which one of the following results is typical of Campylobacter jejuni?

A. Optimal growth at 42 C

178) Haemophilus influenzae is most likely considered normal indigenous flora in the:

A. Oropharynx

191) Which characteristic best differentiates Acinetobacter species from Moraxella species?

A. Production of indophenol oxidase

164) 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:

A. Subculture the bottle, and incubate in microaerophilic conditions

140) One of the enterotoxins produced by enterotoxigenic Escherichia coli in traveler's diarrhea is similar to a toxin produced by:

C. Vibrio cholerae

171) 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:

C. Helicobacter pylori

154) 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: negative TSI: alkaline/acid, no hydrogen sulfide Motility: positive Indole: positive Citrate: positive Ornithine decarboxylase: negative Urea: positive Phenylalanine deaminase: positive VP: negative The genus is:

C. Providencia

177) The porphyrin test was devised to detect strains of Haemophilus capable of:

C. Synthesis of hemin

166) 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: Oxidase: negative Catalase: positive Nitrate: negative ONPG: negative Ornithine decarboxylase: negative Lysine decarboxylase: negative

D. Acinetobacter baumannii

186) 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 MacConkey agar, 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:

D. Bordetella bronchiseptica

188) 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. The organism exhibited the following characteristics: - MacConkey agar: no growth - Urea: negative at 4 hours, positive at 24 hours - Oxidase: negative - Catalase: positive The most probable identification of this isolate is:

D. Bordetella parapertussis

173) If present, a characteristic that is helpful in separating Pseudomonas aeruginosa from other members of the Pseudomonas family is:

D. Growth at 42 C

146) 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: Oxidase: negative TSI: acid slant/acid butt Indole: negative Urease: positive Ornithine decarboxylase: positive Sucrose: positive H2S: negative Motility at 25 degrees Celsius: positive The most probable identification of this organism is:

C. Yersinia enterocolitica

190) 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:

D. Culture was not incubated long enough

189) Which of the following characteristics best differentiates Bordetella bronchiseptica from Alcaligenes species?

D. Rapid hydrolysis of urea

202) The lab 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 - SBA: growth after 48 hrs. with small, smooth, raised colonies. What should the microbiologist do next?

D. Take extra safety precautions for possible Brucella

197) A community hospital microbiology lab 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:

D. Thiosulfate citrate bile salts sucrose for Vibrio species

198) 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: positive - MacConkey agar: pink colonies - O/129 (150 ug): susceptible The most likely organism is:

D. Vibrio vulnificus

149) A 10-year-old boy was admitted to the emergency room with lower right quadrant pain and tenderness. The following laboratory results were obtained: Patient value Normal range % segmented neutrophils 75% 16% - 60% WBC count 200 x 10^3/uL (200 x 10^9/L) 13.0 x 10^3/uL (13.0 x 10^9/L) 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:

D. Yersinia enterocolitica

180) 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:

D. parainfluenzae

134) A sputum culture from an alcoholic seen in the ER grows gray, mucoid, stringy colonies on SBA. The isolate grows readily on MacConkey agar and forms mucoid, dark pink colonies. The colonies yield the following test results: ONPG - positive indole - negative glucose - positive oxidase - negative citrate - positive VP - positive The organism is most likely: a. Edwardsiella tarda b. Klebsiella pneumoniae c. Escherichia coli d. Proteus vulgaris

b (Klebsiella is the only distractor that is VP positive, and the other biochemical reactions are typical for K pneumoniae.)

144) >100,000 CPU/mL of a gram-negative bacilli were isolated On MacConkey from a urine specimen. Biochemical results are as follows: Glucose: acid, gas produced Indole: negative Urea: positive TDA: positive H2S: positive The organism is most likely: a. Morganella morganii b. Proteus mirabilis c. Proteus vulgaris d. Providencia stuartii

b (Morganella and Providencia do not produce H2S; the indole reaction differentiates P mirabilis and P vulgaris.)

141) Shigella species characteristically are: a. urease positive b. nonmotile c. oxidase positive d. lactose fermenters

b (The biochemical characteristic that best fits Shigella is that it is nonmotile. Shigella are urease negative and oxidase negative. Shigella are lactose nonfermenters.)

172) 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?

B. Haemophilus influenzae

185) 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: positive - Glucose OF: fermentative - Catalase: positive - Motility: negative - MacConkey agar: no growth Which of the following is the most likely organism?

B. Pasteurella multocida

181) Which of the following specimens is considered to be the most sensitive for the recovery of Brucella in cases of chronic infection?

C. Bone marrow

183) Which one of the following results is typical of Campylobacter fetus subspecies fetus?

C. Growth at 37 degrees Celsius

184) Multiple blood cultures from a patient with endocarditis grew a facultatively anaerobic, pleomorphic gram-negative bacilli with the following characteristics: - Hemolysis: negative - MacConkey agar: no growth - Sheep blood agar: growth in 5%-10% CO2 - Chocolate agar: growth in 5%-10% CO2 - Catalase: negative - V factor: not required - X factor: not required - Oxidase: negative - Nitrate: positive, reduced to nitrites - Indole: negative The most likely identification is:

C. Haemophilus aphrophilus

136) 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. Yersinia enterocolitica b. Shigella sonnei c. Vibrio parahaemolyticus d. Campylobacter jejuni

a (Shigella has colorless colonies on both MacConkey and Hektoen agars. Yersinia is lactose negative, but Hektoen agar [has both lactose and sucrose] produces yellow colonies from the fermentation of sucrose. V parahaemolyticus needs at least 1% NaCl to grow and Campylobacter does not grow on MacConkey or Hektoen agars.)

145) A urine culture had the following culture results: Sheep blood: swarming Columbia CNA: no growth MacConkey: - 1. >100,000 CFU/mL nonlactose-fermenter - 2. >100,000 CFU/mL nonlactose-fermenter with red pigment The isolates from MacConkey agar had the following biochemical reactions: Test Isolate 1 Isolate 2 TSI Alk/acid Alk/acid Urea Positive Negative TDA Positive Negative H2S Positive Negative The organisms are most likely: a. Proteus vulgaris and Enterobacter cloacae b. Proteus mirabilis and Serratia marcescens c. Morganella morganii and Klebsiella pneumoniae d. Providencia stuartii and Serratia liquefaciens

b (Serratia can produce a red pigment; Proteus mirabilis swarms, is TDA positive and produces H2S.)

135) An organism was inoculated to a TSI tube and gave the following reactions: alkaline slant/acid butt, H2S, gas produced This organism most likely is: a. Klebsiella pneumoniae b. Shigella dysenteriae c. Salmonella typhimurium d. Escherichia coli

c (Salmonella is the only distractor that produces H2S. Also, Klebsiella and E coli produce acid/acid reactions in TSI.)

155) The stock cultures needed for quality control testing of motility are: a. Salmonella typhimurium / Escherichia coli b. Escherichia coli / Pseudomonas aeruginosa c. Serratia marcescens / Escherichia coli d. Klebsiella pneumoniae / Escherichia coli

d (Of the organisms listed only Klebsiella pneumoniae is nonmotile.)

162) A nonfermenting gram-negative bacillus is isolated from a wound. The nitrate and oxidase are strongly positive. The growth on SBA has a grape-like odor. The organism is: a. Burkholderia cepacia b. Moraxella lacunata c. Chryseobacterium (Flavobacterium) meningosepticum d. Pseudomonas aeruginosa

d (Pseudomonas aeruginosa often has a sweet odor that smells like grapes.)

161) An organism isolate 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: a. Staphylococcus aureus b. Serratia marcescens c. Flavobacterium meningosepticum d. Pseudomonas aeruginosa

d (Pseudomonas aeruginosa produces the blue-green pigment, pyocyanin.)

159) Quality control of the spot indole test requires the use of ATCC cultures of: a. Pseudomonas aeruginosa / Proteus mirabilis b. Salmonella typhi / Shigella sonnei c. Escherichia coli / Proteus vulgaris d. Escherichia coli / Enterobacter cloacae

d (Quality control of indole requires both a positive and a negative control. E coli and E cloacae respectively produce a positive and negative reaction with indole.)

137) 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: a. Yersinia enterocolitica b. Salmonella typhi c. Salmonella enteritidis d. Shigella dysenteriae

d (Salmonella produce H2S in TSI and Yersinia produces an acid slant and acid butt. Shigella fits this biochemical profile.)