| Question | Answer | % Correct |
|---|---|---|
| Small, creamy, beta-hemolytic colonies grow on blood agar. The organism is catalase positive, coagulase positive, and Gram stain reveals Gram-positive cocci in clusters. | Staphylococcus aureus | 73%
|
| Lactose-fermenting pink colonies grow on MacConkey agar. The organism is indole positive, oxidase negative, and Gram-negative rods are seen on staining. | Escherichia coli | 55%
|
| Tiny gray colonies grow on chocolate agar but not on blood agar. Gram-negative coccobacilli are seen on Gram stain. The isolate requires both X and V factors. | Haemophilus influenzae | 52%
|
| Colonies have a mucoid appearance on MacConkey agar. The organism is urease positive, indole negative, oxidase negative. | Klebsiella pneumoniae | 48%
|
| Large, gray-white colonies with a double zone of beta-hemolysis on anaerobic blood agar. Gram stain reveals large, boxcar-shaped Gram-positive rods. | Clostridium perfringens | 45%
|
| Alpha-hemolytic colonies appear on blood agar. The isolate is catalase negative, optochin sensitive, and bile soluble. Gram-positive lancet-shaped diplococci are seen. | Streptococcus pneumoniae | 42%
|
| Beta-hemolytic colonies appear on blood agar. Catalase negative, bacitracin sensitive, Gram-positive cocci in chains. | Streptococcus pyogenes | 36%
|
| A sputum culture yields colonies with a “breadcrumb-like” appearance. The organism is weakly acid-fast and filamentous on Gram stain. | Nocardia spp. | 33%
|
| A patient with HIV presents with meningitis. India ink staining of CSF reveals encapsulated yeast. Colonies grow on Sabouraud Dextrose Agar (SDA) and are urease positive. | Cryptococcus neoformans | 30%
|
| A colony shows swarming motility on blood agar. The organism is oxidase negative and urease positive. It produces hydrogen sulfide on TSI agar. | Proteus vulgaris | 18%
|