A microbiologist is looking at a set of plates from a seriously ill patient.The sheep blood agar (SBA) plate shows small, nonhemolytic colonies that have a fried egg appearance.On MacConkey, these organisms grow as a small, nonlactose fermenter.On Gram stain, this organism is a bipolar staining, plump gram-negative rod.What is the most probable organism?
A)Brucella mallei
B)Bacillus anthracis
C)Yersinia pestis
D)Burkholderia cepacia

Question

Quizplus · Accepted Answer

Laboratory Response Network (LRN) protocols define a suspicious Yersinia pestis isolate as a bipolar staining gram-negative node that forms very small colonies after 24 hours of incubation at 37° C, although colonies grown at room temperature may be larger.Colonies of Y.pestis on SBA may grow slowly, and cultures may have to be held for up to 48 hours for good colony growth.Colonies are nonhemolytic and can have a fried egg appearance.On media selective for gram-negative bacilli, such as MacConkey agar, the organism will grow as small, nonlactose fermenting colonies.

A Microbiologist Is Looking at a Set of Plates from a Seriously