Transfer of R Factors from Escherichia Coli to Salmonellas in the Rumen of Sheep

Abstract

S U B S T A N T I A Ltransfer of R factors was found to occur in vivo between strains of Escherichia coli inoculated into the rumen of sheep provided the animals were deprived of food for 2 4 4 8 h (Smith, 1975). No antibiotic treatment was necessary. Negligible transfer occurred without starvation even when large numbers of donor and recipient organisms (c. 1010 cells of each) were inoculated into the rumen. The present investigations were undertaken to determine whether R factors could be transferred under similar conditions from E. coli to pathogenic salmonellas. MATERIALS AND METHODS Bacteriological techniques.Strains of E. coli originally isolated from sheep and into which the same R factor (conferring resistance to streptomycin 25 pg per ml and sulphadimidine 500 pg per ml) had been transferred, were tested in vitro for their ability to transfer the R factor to a series of salmonella cultures. Two combinations were chosen, donor strain D1 of E. coli with a strain of Salmonella lomita and donor strain D2 of E. coli with a strain of S. typhimurium. When c. 106 cells each of the donor and prospective recipient strains were inoculated into nutrient broth (Oxoid) and incubated at 37°C for 24 h, 1-5% of the final number of cells were resistant salmonellas into which the R factor had been transferred.Coliform organisms were counted on MacConkey Agar (Oxoid). The donor strains of E. coli were counted on this medium to which streptomycin 25 pg per ml and sulphadimidine 500 pg per ml had been added. Brilliant Green Agar (Oxoid) containing sulphadiazine (May & Baker) 80 pg per ml was used to determine total salmonellas. Resistant salmonella colonies, containing the R factor, were counted on this medium without sulphadiazine but

Transfer of antibiotic resistance between commensal and pathogenic members of the Enterobacteriaceae under ileal conditions

“…However, whilst preferential selection of transconjugant bacteria was possible, the absence of an apparent preference for any of the respective donor or recipient strains made this unlikely. Smith (1975Smith ( , 1977 reported transfer efficiencies between E. coli strains and between E. coli and Salmonella within the rumen at levels comparable with this study, although only following a brief period of starvation. One effect of starvation on the rumen is a decrease in acidity and an increase in total E. coli populations (Duncan et al 2000).…”

“…The ileum normally exhibits a steady and fairly continuous flow of chyme, regulated by the stomach, in the hours following a meal (Vander et al 1994). The simulation adopted here was fed by three discrete 15-min meals per day and may have become comparable with a starvation-state ileum for brief periods between each meal, potentially enhancing conditions for conjugation (Smith 1975(Smith ,1977. However, previous comparison of the simulation with ileal bacterial and short chain fatty acid composition revealed no significant differences during validation (Hillman et al 1994) and the model pH was constantly controlled, suggesting a negligible influence of starvation conditions in vitro.…”

In vivotransfer of an R factor within the lower gastro-intestinal tract of sheep

“…This occurred when a short period of starvation (24-48 h) was imposed on the animals. The ruminal environment appeared to be altered to the extent that it no longer exerted an inhibitory effect on the growth of the organisms introduced and in vivo transfer was demonstrated between E. coli organisms (Smith, 1975) and from E. coli donors to salmonella recipients (Smith, 1977). During these experiments it was noticed that exconjugant organisms (recipient cells containing the R factor) were sometimes present in the faeces of an animal before such organisms were detected in the rumen.…”

“…Although the organisms introduced into the rumen of fasted sheep disappeared quickly from this site when the animals were again fed daily, they were sometimes excreted continuously in the faeces for long periods afterwards. This occurred both with a chromosomal mutant of E. coli resistant to nalidixic acid (Smith, 1975) and with Salmonella lomita organisms (Smith, 1977 No antibiotics were administered to any of the animals during the course of an actual experiment. Although sometimes nalidixic acid was given by mouth to assist in implanting the prospective recipient E. coli in the lower gastro-intestinal tract, none of the carrier animals were used for at least several weeks afterwards when there should have been no residual influence from this drug affecting transfer of the R factor in vivo.…”

Nontyphoidal Salmonellae in United Kingdom Badgers: Prevalence and Spatial Distribution

“…There was evidence of two different clones of S. enterica serovar Lomita by PFGE but not of spatial clustering. S. enterica serovar Lomita has been detected in poultry in India and, in experimental infection, was able to establish colonization in the rumen of a sheep (13,27). There is one case of human spondylodiscitis reported in the literature (5).…”