Isolation and identification of adherent epimural bacteria during succession in young lambs

Abstract

Successive changes in aerobic and anaerobic bacterial counts and changes in the generic composition of the epimural community in lambs from 1 to 10 weeks were determined. Bacterial culture counts revealed a predominantly anaerobic community, with the mean anaerobic count being 1.4 X 10(7) CFU/cm2 of tissue surface. The aerobic count was highest at 1 week of age and declined significantly thereafter to a mean of 1.8 X 10(4) CFU/cm2, thus representing only 0.13% of the mean anaerobic count after week 1. Of the 345 strains isolated anaerobically at 1, 2, 4, 6, 8, and 10 weeks of age, 47, 32, 12, 32, 2, and 5% were capable of growth in a partially reduced medium, indicating a reduction in the number of facultative anaerobes with time. The majority of isolated strains were identified as belonging to genera commonly isolated from rumen contents. In some instances, however, strains did not correspond to previously described species, and some genera were present in proportions different from those expected in rumen fluid. At three of the sampling times, one genus was dominant, constituting 45 to 55% of the isolates. These dominant isolates were Streptococcus bovis, Bacteroides sp., and an anaerobic Streptococcus sp. for weeks 1, 2, and 10, respectively. During the transition period (weeks 4 to 8), two or more groups were codominant.