As a closer view of PHIL 12265, this photograph depicts the colonial morphology displayed by Gram-negative Yersinia pestis bacteria, which was grown on a medium of sheep's blood agar (SBA), for a 72 hour time period, at room temperature. Y. pestis is the bacterium responsible for causing the infectious disease known as plague.
When bubonic plague is left untreated, Yersinia pestis bacteria invade the bloodstream. As the plague bacteria multiply in the bloodstream, they spread rapidly throughout the body and cause a severe, and often fatal condition. Infection of the lungs with the plague bacterium causes the pneumonic form of plague, a severe respiratory illness. The infected person may experience high fever, chills, cough, and breathing difficulty and may expel bloody sputum. If plague patients are not given specific antibiotic therapy, the disease can progress rapidly to death. About 14% (1 in 7) of all plague cases in the United States are fatal.