In humans, Acinetobacter baumannii, a gram-negative coccobacillus, is an important cause of nosocomial bacteremia mainly in patients with suppressed immune responses. Diseases that occur include pneumonia, meningitis, endocarditis, peritonitis and tracheobronchitis. A. baumannii is ranked fourth as the cause of pneumonia in hospitalized patients. Acinetobacter spp. are found in soil and water and are commensals on skin and in throats of healthy people and animals. It is not a pathogen in healthy animals and in this rat it was probably a secondary infection due to the illness caused by the primary pathogen Corynebacterium kutscheri.
Infections occur sporadically as abscesses of superficial tissues.
Lesions in epizootic rat infections develop from pulmonary embolism, whereas mouse infections more typically result in septic embolization of the joints, liver, and kidney. Although C. kutscheri can be encountered as a primary pathogen, the most common scenario is unmasking of a latent infection by experimental modulations that lower host resistance or impair immunocompetence. Latent infections may not be associated with tissue lesions and C. kutscheri can often be isolated from tissues without lesions. In latently infected animals, C. kutscherimost frequently colonizes the oral cavity, cecum, colon, and rectum and rarely colonizes the lung, liver and kidney. The infection can spread by hematogenous dissemination to cause microabscesses in various internal organs.