In addition, experimental manipulations have been reported to provoke or exacerbate clinical disease caused by C. piliforme. Natural infection of laboratory mice and rats could severely alter the findings of studies involving the gastrointestinal and cardiopulmonary systems. Pseudomonas aeruginosa is a gram-negative rod that normally inhabits the nasopharynx, oropharynx, and lower digestive tract of many vertebrate species. P. aeruginosa is commonly found in soil and organic waste and as a normal skin inhabitant, and it is frequently cultured from facility water systems. Active exclusion of the organism from the animal facility is achievable but costly.
Transmission is via contact with contaminated water, feed, bedding, and infected rodents and humans.
Clinical signs are generally not observed in immunocompetent hosts, although the host response to P. aeruginosa infection varies among inbred mouse strains. Some immunocompromised mice and rats may develop hunched posture, apathy, dullness, shortness of breath, ruffled coat, emaciation, circling movements around their longitudinal axis, and oblique head posture, and some of them will die. Clinical disease is due to invasion of deep tissues, resulting in hematogenous spread of the bacteria to multiple organs. Entry into the vascular system may be facilitated by pseudomonal proteases and bradykinin generated in infectious foci. Pathologic lesions are found in affected tissues and consist of multifocal necrosis, abscess formation, and suppuration.