Abstract
Guineapigs were rederived by hysterectomy and associated with a colonization-resistant enteric microflora (CRF) of mouse origin to establish a strict barrier-maintained breeding colony. Infections were suspected in 55 of 209 animals autopsied. From 65 of 67 tissue samples selected for bacteriological examination 167 isolates, belonging to 16 usually non-pathogenic bacterial species or groups, were isolated mostly from cases of mastitis, typhlitis, enteritis, otitis media and pneumonia. Faecal streptococci, Pseudomonas aeruginosa, Clostridium perfringens, Citrobacter spp., C. freundii, Escherichia coli, Klebsiella oxytoca and Enterobacter cloacae accounted for 86·8% of all isolates. Variations in the recovery rate of these 8 species during the study and a gradual decline in the incidence of infections were observed. Elimination by rederivation of the autochthonous bacterial flora seemed to have predisposed to opportunistic infections by aerobic and facultatively anaerobic bacteria. Enteric colonization resistance to the growth of these bacteria was presumably insufficiently provided by the CRF of mouse origin and might be remedied by using a flora of guineapig origin.