Ampicillin resistance and bacterial diversity in colon content from grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina) at the coast of Northern Norway

Abstract

Very little is known on the gut microbial ecology in seals. Environmental populations of bacteria, like those found in the gut of wildlife presumably unexposed to human antibiotic use, may be a reservoir of clinically important resistance genes. The purpose of this study was to characterize the bacterial diversity in the colon of grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina) at the cost of northern Norway by comparative sequence analysis of cloned 16S rRNA genes, and to determine the prevalence and diversity of blaTEM genes. Colon contents was collected from one male harbour seal and one female grey seal (pregnant) outside Ringvassøy (69.91ºN, 19.02ºE) in April-May 2006. No aerobic ampicillin resistant isolates were detected in the colon content from neither the harbour seal nor the grey seal. However, blaTEM alleles were detected in total DNA from tree of the eight colon samples of the grey seal, but no amplifications of the blaTEM genes were obtained in total-DNA from the two colon samples of the harbour seal. This indicates that the prevalence of blaTEM genes in the colon content of the harbour seal and the grey seal was low. A total of 153 assembled 16S rRNA gene sequences (~1,5 kb) were analyzed from the colon of the two seal species. From the harbour seal, 77 16S rRNA gene sequences were analyzed, identifying representatives associated with Firmicutes (all belonging to Clostridiales 49.4%), Bacteroidetes (all belonging to Bacteroidales 49.4%) and Fusobacteria (all belonging to Fusobacteriales 1.3%). From the grey seal, 76 16S rRNA gene sequences were obtained, including representatives from two bacterial phyla: Firmicutes (most of these were Clostridiales 72.4%) and Bacteroidetes (all belonging to Bacteroidales, 23.7%). The bacterial population in the colon of harbour seal and grey seal included species considered to be a part of the normal flora in e.g. humans and chickens. Only one clone from the harbour seal library showed >97% sequence similarity to their nearest database entries (BLAST). For the grey seal library about half of the clones showed <97% sequence similarity to their nearest database entries (BLAST). This indicates that several of the 16S rDNA sequences obtained from the seal colon represents novel bacterial species not yet isolated or characterized.