Facultative anaerobic fermenting encapsulated Gram-negative bacillus of the Enterobacterales order.
Naturally found in the environment (soil, water, sewage). 5-36% of healthy individuals may have colonization of the gastrointestinal tract, and less frequently of the nasopharynx. Increased colonization seen with healthcare exposure.
Global distribution. Transmission by person-to-person contact or contact with environment.