Polychlorinated biphenyl‐degrading pseudomonads: Survival in mouse intestines and competition with normal flora

Abstract

Although naturally occurring and mutant organisms, historically, have been released into the environment for various purposes, health concerns associated with the release of microorganisms have recently resurfaced. Federal agencies have been given the task of reassuring society that any released organisms are not likely to produce adverse health effects. Methods, therefore, for evaluating the potential health effects due to environmental release of mutant and genetically engineered microorganisms are under investigation. A mouse model was developed that examines morbidity, mortality, and more indirect effects such as colonization potential of the intestinal tract, as well as competition with and alteration of the intestinal microbiota populations. The Pseudomonas spp. used in this study were isolated from a commercial product and used for degrading polychlorinated biphenyls. Mice were dosed individually with 10³, 10⁶, and 10⁹ colony‐forming units of each microorganism. At specific time intervals the intestines were removed and examined for the presence of the dosed microorganism. At the two higher doses, 10⁶ and 10⁹ colony‐forming units, P. maltophilia strain BC6 and two P. aeruginosa strains, BC16 and BC18, were recoverable 48 h after dosing. The naturally occurring P. aeruginosa strain, PAMG, isolated from a mouse intestinal homogenate produced a similar response. Statistical analysis indicated that in some of the dosed animals, an alteration in the distribution of normal intestinal microflora occurred. Pseudomonas maltophilia strain BC6 and P. aeruginosa strains BC16 and BC17 caused a change in the obligately anaerobic predominantly gram‐negative rod counts, and P. aeruginosa strain BC17 produced a dose effect on the total anaerobic count at the 10% confidence level. The total aerobic count was unaffected by the presence of the dosed pseudomonads.