Acute colonization study of polychlorinated biphenyl‐degrading pseudomonads in the mouse intestinal tract: Comparison of single and multiple exposures

Abstract

The coprophagic behavior of rodents has been used in a model examining the potential health effects of environmentally released microorganisms. Mutant polychlorinated biphenyl (PCB) degrading pseudomonads, isolated from a commercial product for PCB elimination, were used to evaluate the method. The PCB‐degrading component of the product was composed of one Pseudomonas maltophilia and three Pseudomonas aeruginosa strains enhanced for PCB degradation through nitrosoguanidine mutagenesis. Multiple ingestions of the biodegraders were compared with a single exposure. The direct health effects monitored were changes in weight, appetite and overall appearance. The indirect health effects monitored included recovery of the organisms from intestinal contents as well as competition with and alteration of the normal intestinal flora. When animals received a single dose by gavage of 109 colony forming units of an individual Pseudomonas sp., none of the four dosed strains were detected 14 d after dosing when animals were housed in metabolism cages. The use of these metabolism cages, which had wire flooring, limited coprophagy. When animals were housed in conventional cages, which allowed coprophagy, two of the four PCB degraders tested were recovered (104/g intestine). The lactose‐fermenting and total aerobic counts were unaffected when animals received a single dose of the biodegrader. In the multiple exposure model, P. maltophilia altered the lactose‐fermenting population. The total aerobic counts differed significantly from values for control animals when the animals were exposed to P. aeruginosa strains BC16, BC17 and BC18. Obligately anaerobic gram‐negative rod populations were affected in P. aeruginosa strain BC17‐dosed animals. Strains BC16 and BC18 altered both the obligately anaerobic rod populations and total anaerobic counts.

A Toxicological Screen to Determine in Vitro Survival and Competition of Environmentally Applied Pseudomonads With Mouse Fecal Microbiota

“…2A, C, and D). It is interesting thiiit strain PAMG was the best survivor of the pseudomonads tested, as it was also the longest surviving pseudomonad in vivo [8]. This is not surprising in view of its intestinal source.…”

“…This is not surprising in view of its intestinal source. Although no effect on the intestinal flora was seen in vivo with strain PAMG 48 h after dosing [7], the lactose positive enterobacteria were affected 14 d after dosing [8]. With other strains, alterations in the resident microbiota were seen in vivo but not in vitro.…”

“…As part of an overall program to assess potential health effects of released organisms, George et al [7-91 examined Pseudomonas spp., marketed as PCB-degraders, for their ability to colonize the CD-I mouse intestinal tract and compete with the normal intestinal microbiota. All of the pseudomonads were present in mouse intestinal homogenate at 24 h after dosing [7], and Alterations in several populations of the resident some strains were recoverable 14 d after dosing [8], 597 microbiota were observed. Pretreatment of the mice with ampicillin enhanced the survival of some of the pseudomonads [9].…”

A toxicological screen to determine in vitro survival and competition of environmentally applied pseudomonads with mouse fecal microbiota

“…Examination of this particular case showr, that the differences are attributable to an unexplained decline in the control counts in serial transfer culture 5 , rather than an effect of strain BC18 on the normal flora ( Fig. It is interesting thiiit strain PAMG was the best survivor of the pseudomonads tested, as it was also the longest surviving pseudomonad in vivo [8]. Total aerobic counts were higher in cultures containing a competitor strain (except PAMG) than those in their corresponding controls at 0 h, culture 1 (Fig.…”

“…2A). Although no effect on the intestinal flora was seen in vivo with strain PAMG 48 h after dosing [7], the lactose positive enterobacteria were affected 14 d after dosing [8]. 2B).…”