|Description:||Under the low-power magnification of 20X of a digital Keyence scope , this photograph depicts the colonial growth displayed by Gram-negative Yersinia pestis bacteria, which were cultured on a sheep blood agar (SBA) medium, for a 120 hour (5 day) time period, at a temperature of 37°C.|
The cause of human plague, Yersinia pestis may be identified microscopically by examination of Gram, Wright, Giemsa, or Wayson's stained smears of peripheral blood, sputum, or lymph node specimen. Visualization of bipolar-staining, ovoid, Gram-negative organisms with a "safety pin" appearance permits a rapid presumptive diagnosis of plague.
If cultures yield negative results, and plague is still suspected, serologic testing is possible to confirm the diagnosis. One serum specimen should be taken as early in the illness as possible, followed by a convalescent sample 4-6 weeks or more after disease onset. See the link below for addition information on plague.