Microbiology BOC Questions & Answers Solved 100% Correct!!

100,000 CFU/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 Proteus mirabilis b Morganella and Providencia do not produce H2S; the indole reaction differentiates P mirabilis and P vulgaris. 13 An Enterococcus isolated from multiple blood cultures in a patient endocarditis should be: a screened for high level aminoglycoside resistance b checked for tolerance c assayed for serum antimicrobial activity d tested for beta-lactamase production - a screened for high level aminoglycoside resistance a Systemic enterococcal infections, such as endocarditis, are commonly treated with a cell-wall-active agent and an aminoglycoside. These agents act synergistically to kill the organism. If the organism is resistant to one or both, there is no synergy, and the combination will fail. It is important to detect aminoglycoside and beta-lactam resistance in these cases. Enterococci have intrinsic moderate level resistance to aminoglycosides. Acquired resistance corresponds to very high MICs (greater than 500 pg/mL) for gentamicin and is termed high level resistance.A 1-2 mm translucent, nonpigmented colony, isolated from an anaerobic culture of a lung abscess after 72 hours, was found to fluoresce brick-red under ultraviolet light. A Gram stain of the organism revealed a coccobacillus that had the following characteristics: growth in bile: inhibited vancomycin: resistant kanamycin: resistant colistin: susceptible catalase: negative esculin hydrolysis: negative indole: negative The identification of this isolate is: a Bacteroides ovatus b Prevotella oralis c Prevotella melaninogenica d Porphyromonas asaccharolytica - c Prevotella melaninogenica c Both Prevotella and Porphyromonas colonies fluoresce brick red. Porphyromonas is susceptible to vancomycin and can be catalase positive. A 10-year-old boy was admitted to the emergency room with lower right quadrant pain and tenderness. The following laboratory results were obtain . . Patient value Normal range % segmented neutrophils 75% 16%-60% WBC count 200 x 13^3/uL (200x10^9/L) 13.0 x 10^3/uL (13.0 x 10^9/L) The admitting diagnosis was appendicitis. During surgery the PP re isolated from the room enlarged node was removed and cultured. Small gram-negative bacilli were temperature plate. The organism most likely is. a Prevotella melaninogenicab Shigella sonnei c Listeria monocytogenes d Yersinia enterocolitica - d Yersinia enterocolitica