BOC Microbiology Test Questions with All Correct Answers

BOC Microbiology Test Questions with All Correct Answers Alcaligenes faecalis (formerly A. odorans) is distinguished from Bordetella bronchiseptica with which test? - Answer-Urease (rapid). Both organisms are oxidase positive, grow on Mac agar, and are motile by peritrichous flagella. Alcaligenes faecalis is Urease negative. Chryseobacterium spp. are easily distinguished from Acinetobacter spp. by which of the following two tests? - Answer-Oxidase, growth on Mac agar. (Acinetobacter is oxidase negative, grow on MAC agar, and are occobadcillary on gram stain. Chryseobacterium spp. are oxidase positive, no growth on Mac agar and are typically rod shaped) A gram-negative coccobacillus was recovered on chocolate agar from the CSF of an immunosuppressed patient. The organism was nonmotile and positive for indophenol oxidase but failed to grow on MAC agar. The organism was highly susceptible to penicillin. The most probable identification is: - Answer-Moraxella lacunata (Moraxella spp. are oxidase positive and non-motile, as well as highly sensitive to penicillin and usually seen in immunosuppressed patients). Cetrimide agar is used as a selective isolation agar for which organism? - Answer-Pseudomonas aeruginosa (Cetrimide aka acetyl trimethyl ammonium bromide, is used for the identification/isolation of P. aeruginosa with the exception of P. fluorescens, other psudomonads are inhibited along with other non-fermentative bacteria.) A specimen from a 15 year old burn patient was cultured after debridement, and the following results were obtained: ========================================= Oxidase pos, Catalase pos, Ornithine neg, Arg pos, Penicillin res, Lysine neg, Motility pos, Glucose pos (open tube), Maltose neg (open tube), aminoglycosides susceptible, colistin(polymixin b) susceptible. - Answer-Pseudomonas aeruginosa ( Acinetobacter spp. is oxidase negative and Moraxella spp. are highly susceptible to penicillin) A yellow pigment-producing organism that is oxidase positive, nonmotile, and does not grow on MacConkey agar is? - Answer-Chryseobacterium meningosepticum (Oxidase positive, yellow pigment, and do not grow on Mac agar.) Which reagent(s) is (are) used to develop the red color indicative of a positive reaction in the nitrate reduction test? - Answer-Sulfanilic acid and Alpha-naphthylamine A culture from an intra-abdominal abscess produced orange-tan colonies on blood agar that gave the following results: ======================================== Oxidase pos, KIA= K/K(H2S pos), Nitrate reduction pos, Motility pos single polar flagellum, ornithine decarb pos, DNase pos, Growth at 42C neg. - Answer-Shewanellae putrefaciens (S. putrefaciens produces abundant H2S on KIA or TSI. Shewanellae are the only nonfermenters that produce H2S on these media Chryseobacterium spp. and B. cepacia are easily differentiated by which test? - Answer-Motility (B. cepacia(93%) are weakly oxidase positive and motile. chryseobacterium spp. are oxidase positive but are nonmotile) A 15-year old female complained of a severe eye irritation after removing her soft-contact lenses. A swab of the infected right eye was obtained by an opthamalmologist, who ordered a culture and sensitivity test. The culture was plated on blood agar and MacConkey agar. At 24 hours, growth of a gram-negative rod that tested positive for cytochrome oxidase was noted. The Mueller-Hinton sensitivity plate showed a bluish green "lawn" of growth that proved highly resistant to most of the antibiotics tested except amikacin, tobramycin, and ciprofloxacin. What is the most likely identification? - Answer-Pseudomonas aeruginosa Which of the listed Pseudomonas spp. is associated with the following virulence factors: exotoxin A, endotoxins, proteolytic enzymes, antimicrobial resistance, and production of alginate? - Answer-Pseudomonas aeruginosa A 20-year old horse groomer exhibited a "glanders-like" infection. His history indicated he had suffered several open wounds on his hands 2 weeks beforethe swelling of his lymph nodes. A gram-negative rod was recovered from a blood coulture that grew well on blood and Mac agars. Most of the biochemical tests were negative, including the cytochrome oxidase test. What is the most likely identification? - Answer-Burkholderia mallei (a causative agent in mules, donkeys and horses)