Practice Exam Flashcards
Highly refractile spheres, usually with a dimpled center:
Starch granules
Which of the following is the most potent androgen?
Testosterone
Which assay using 24-hour urine is considered the best single screening test for pheochromocytoma?
Metanephrines
Measurement of 24-hour urinary metanephrine is about 95% sensitive for pheochromocytoma, and is the best single test.
Which of the following buffers is used in the IFCC recommended method for ALP?
2-Amino-2-methyl-1-propanol
AMP buffer chelates phosphorus, preventing product inhibition; Zn+2 and Mg+2 are added to the substrate to activate ALP.
The “gold standard” in the diagnosis of acute coronary syndrome (ACS):
Troponin
Gram stain of a smear taken from the periodontal pockets of a 30-year-old man with poor dental hygiene showed sulfur granules containing gram-positive rods (short diphtheroids and some unbranched filaments). Colonies on blood agar resembled “molar teeth” in formation. The most likely organism is:
*
Actinomyces israelii
Which mechanism is responsible for botulism in infants caused by Clostridium botulinum?
Ingestion of spores in food or liquid:
Epidemiological studies have demonstrated that infant botulism results from the ingestion of spores via breastfeeding or exposure to honey. Preformed toxin has not been detected in food or liquids taken by the infants. C. botulinum multiplies in the gut of the infant and produces the neurotoxin in situ.
The classic form of foodborne botulism is characterized by the ingestion of:
Preformed toxin in food:
Foodborne botulism in adults and children is caused by ingestion of the preformed toxin (botulinum toxins A, B, E, and F) in food.
The neurotoxins of C. botulinum are protoplastic proteins made during the growing phase and released during lysis of the organisms. Confirmation of botulism is made by demonstration of the toxin in serum, gastric, or stool specimens.
Which of the following organisms will display lipase activity on egg yolk agar?
Clostridium botulinum
Clostridium novyi (A)
Clostridium sporogenes
Egg yolk agar is used to detect which enzyme produced by Clostridium species?
Lecithinase:
Egg yolk agar (modified McClung’s or neomycin egg yolk agar) is used to determine the presence of lecithinase activity, which causes an insoluble, opaque, whitish precipitate within the agar.
A suspected Bacillus anthracis culture obtained from a wound specimen produced colonies that had many outgrowths (Medusa-head appearance),but were not β-hemolytic on sheep blood agar. Which test should be performed next?
Penicillin (10-unit) susceptibility test
The best differentiating test to perform on a suspected B. anthracis culture is the 10-unit penicillin disk test. B. anthracis is susceptible but other Bacillus spp. are not.
