BOC: GNB

143. 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

153. Plesiomonas shigelloides is a relatively new member to the family of the Enterobacteriaceae. What characteristic separates it from other member of the Enterobacteriaceae?

It is oxidase positive. Enterobacteriaceae ferment glucose and are oxidase negative.

193. Appropriate culture requirement for a specimen from a patient suspected of having tularemia include:

Media with cysteine such as buffered charcoal yeast extract agar.

141. Shigella species characteristically are:

Nonmotile; Shigella is also urease and oxidase negative and nonfermenters.

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

Optimal growth at 42C.

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

Oropharynx, the upper respiratory tract.

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

Oxidase; both are gram-negative and grow on MAC, neither ferment glucose. Stenotrophomonas is oxidase-positive while most nonfermenters are oxidase-positive.

185. Gram-negative bacillus with bipolar staining was isolated from a wound infection caused by a cat bite. The following characteristic reactions were seen: Oxidase-negative; glucose OF- fermentative, Catalase-positive, motility-negative, MAC- no growth. Which of the following is the most likely organism?

Pasteurella multocida.

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

Production of indophenol oxidase. Both display resistance to penicillin, and some grow on MAC. Acinetobacter are oxidase-negative and Moraxella are oxidase-positive.

145. A urine culture had the following culture results: Sheep blood swarming, Columbia CNA no growth, MAC 1. >100,000 CFU/mL nonlactose fermenter 2. >100,00 CFU/mL nonlactose-fermenter with red pigment. The isolates from MAC had the following biochemical reactions: TSI- 1 and 2 alk/acid, Urea- 1. Positive 2. Negative; TDA - 1. Positive 2. Negative; H2S- 1. Positive 2. Negative. The organisms most likely are:

Proteus mirabilis and Serratia marcescens. Serratia can produce a red pigment, P. mirabilis swarms, is TDA positive and produces H2S.

142. A gram-negative bacillus has been isolated from feces, and the confirmed biochemical reactions fit those of Shigella. The organism doesn't agglutinate in Shigella antisera. What should be done next?

Boil the organism and retest with the antisera; some Shigella produce capsular antigen that mask cell wall and boiling removed the capsule.

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

Bone marrow, considered the most sensitive specimen.

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

Culture on buffered charcoal yeast extract agar with antibiotics.

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:

Culture was not incubated long enough, Legionella requires at least 7 days at 37-37C

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?

Growth at 42C, procyanin production, gelatinase production.

173. If present, a characteristic in differentiating Pseudomonas aeruginosa from other members of the Pseudomonas family is:

Growth at 42C, this temp is inhibitory for other Pseudomonas.

168. A 4yr 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, previously most common cause of bacterial meningitis in young children. Now there is a type B vaccine that has greatly reduced the H. influenzae incidence of meningitis.

160. An organism that exhibits the satellite phenomenon around colonies of staphylococci is:

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

163. A small gram-negative bacillus is isolated from an eye culture. It grows only on chocolate agar and is oxidase- negative. The most likely organism is:

Haemophilus influenzae.

172. 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?

Haemophilus influenzae.

180. 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:

parainfluenzae, require NAD for growth but not Hemin, this distinguishes it from H. influenzae.

197. A community hospital micro 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:

Thiosulfate citrate bile salts sucrose for Vibrio species.

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

42C, at this temp other organism from colon are inhibited.

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

6% O2, 10-15% CO2, 85-90% Nitrogen

152. A clean catch urine specimen 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- negative; Motility- positive; indole- negative; citrate- positive; VP- positive; Lysine decarboxylase- negative; Ornithine decarboxylase- positive; urea- negative. What should the microbiologist report?

67,000 CFU/mL Enterobacter cloacae.

179. Haemophilus influenzae becomes resistant to ampicillin when the organism produces a(n)"

Beta-lactamase enzyme

129. Infection of the urinary tract is most frequently associated with:

Escherichia coli.

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:

Escherichia coli.

139. Which of the following organisms can grow in the small bowel and cause diarrhea in children, traveler's diarrhea, or severe cholera-like syndrome through the production of exotoxins?

Escherichia coli.

156. The stock cultures needed for QC testing of oxidase production are:

Escherichia coli/ Pseudomonas aeruginosa. Pseudomonas aeruginosa is the only listed oxidase- positive.

159. QC of the spot indole test requires the use of ATCC cultures of:

Escherichia coli/Enterobacter cloacae. E. coli is positive.

202. The lab receives a blood culture from a veterinarian who has been ill for many weeks with fevers in the afternoons 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; Sheep blood agar- growth after 48hrs with small, smooth, raised colonies. What should the microbiologist do next? Take extra safety precautions for possibility of Brucella.

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:

Helicobacter pylori.

155. The stock cultures needed for QC testing of motility are:

Klebsiella pneumoniae/Escherichia coli, Klebsiella is the only non motile.

134. 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 results: ONPG- negative, Indole- negative, Glucose- positive, oxidase- negative, citrate- positive, VP- positive. The organism is most likely:

Klebsiella.

144. >100,000 CFU/mL of a gram-negative bacilli were isolated on MAC 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:

Proteus mirabilis, indole reaction helps differentiate P. mirabilis (-) and P. vulgaris (+).

157. The stock cultures needed for QC testing of deaminination activity are:

Proteus mirabilis/Escherichia coli. P mirabilis is phenylalanine deaminase positive.

161. 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:

Pseduomonas aeruginosa, produce the blue-green pigment, pyocyanin.

162. A nonfermenting gram-negative bacillus is isolated from a wound. The nitrate and oxidase are strongly positive. The grown on sheep blood agar has a grape like odor. The organism is:

Pseudomonas aeruginosa, often has sweet odor that smells like grapes.

131. Member of the Enterobacteriaceae share which of the following characteristics?

Reduce nitrate to nitrite, also oxidase-negative and ferment glucose.

135. An organism was inoculated to a TSI tube and gave the following reactions: Alkaline slant/acid butt, H2S, gas produced. The most likely organism is:

Salmonella typhimurium.

158. The stock cultures need for QC of deoxyribonuclease (DNase) production are:

Serratia marcescens/Escherichia coli. Serratia is positive.

137. A TSI tube inoculated with and organism gave the following reactions: Alkaline slant, acid butt, no H2S, no gas produced. The organism is most likely:

Shigella dysenteriae.

132. Which of the following genera is among the least biochemically reactive members of the Enterobacteriaceae?

Shigella, lactose-negative, most do not produce gas, VP, urea, lysine decarboxylase and citrate- negative, and they are non motile.

130. MacConkey media for screening suspected cases of hemorrhagic E. coli 0157:H7 must contain:

Sorbitol, doesn't ferment sorbitol while other species of E. coli do.

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?

Urea broth, Helicobacter pylori produce large amounts of extracellular urease and is positive for urea within 2 hrs.

136. An isolate from stool culture gives the following growth characteristics and biochemical reactions: MAC- colorless colonies, HE- yellow-orange colonies, TSI- acid slant/acid butt no gas no H2S, Urea-positive. The screening reactions are consistent with which of the following enteric pathogens?

Yersinia enterocolitica, Shigella has colorless colonies on both MAC and HE. Yersinia is lactose negative but HE has both lactose and sucrose and produces yellow colonies from fermentation of sucrose.

133. Which of the following gram-negative bacilli ferments glucose?

Yersinia enterocolitica.

150. A 25 yr old man who had recently worked as a steward on a transoceanic grain ship presented to the ER with a 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:

Yersinia pestis, classic for bubonic plague.