TULARAEMIAS CAUSED BY the intracellular pathogen Francisella tularensis, a small, pleomorphic, aerobic, Gram-negative coccobacillus which requires a complex cysteine-containing growth medium for laboratory cultures. Capsules may form in tissues. The pathogen is not highly heat resistant but will survive freezing and drying. It survives well in the environment – especially in the cold with no… Read more »
AETIOLOGY ROCKY MOUNTAIN SPOTTED FEVER (RMSF) is caused by the rickettsial pathogen Rickettsia rickettsii, an obligate, intracellular parasite. These microorganisms are very small (0.3m-0.5m). Extracellular R. rickettsii ceases metabolic activity and leak cellular components, losing infectivity within a short time. The organism possesses several virulence factors, including surface proteins, a lipopolysaccharide (LPS) cell wall, and… Read more »
AETIOLOGY PLAGUE IS CAUSED BY the bacterium Yersinia pestis, a small Gram-negative, non-motile coccobacillus, which has a characteristics bipolar “safety-pin” appearance when stained. Although this organism is non-sporing, it may remain viable for weeks in sputum at room temperature, for 2 to 30 days in water, for two weeks in moist grain, or for months… Read more »
AETIOLOGY BRU CELLOSIS IS CAUSED BY organisms of the genus Brucella; particularly B. melitensis, B. suis and B. abortus. These organisms are small Gram-negative, aerobic, coccobacilli and are facultative intracellular parasites which grow within monocytes and macrophages. EPIDEMIOLOGY Brucellosis is primarily a disease of domestic animals, but humans may be infected through ingestion of animal… Read more »
AETIOLOGY ANTHRAX IS CAUSED BY the microorganism Bacillus anthracis, a large Gram-positive rod-shaped bacterium which is commonly found singly or in pairs. The organism is capsulated in clinical specimens, but endospores are produced in vitro, in soil, and in decaying animal tissue. These endospores are relatively resistant to heat and chemical disinfectants (they can be… Read more »
