Presence of DNA from Chlamydia-like organisms in the nasal cavities of grey seal pups (Halichoerus grypus) and three different substrates present in a breeding colony.

BACKGROUND: Chlamydia-like organisms (CLO) have been found to be present in many environmental niches, including human sewage and agricultural run-off, as well as in a number of aquatic species worldwide. Therefore, monitoring their presence in sentinel wildlife species may be useful in assessing the wider health of marine food webs in response to habitat loss, pollution and disease. We used nasal swabs from live (n = 42) and dead (n = 50) pre-weaned grey seal pups and samples of differing natal substrates (n = 8) from an off-shore island devoid of livestock and permanent human habitation to determine if CLO DNA is present in these mammals and to identify possible sources. RESULTS: We recovered CLO DNA from 32/92 (34.7%) nasal swabs from both live (n = 17) and dead (n = 15) seal pups that clustered most closely with currently recognised species belonging to three chlamydial families: Parachlamydiaceae (n = 22), Rhabdochlamydiaceae (n = 6), and Simkaniaceae (n = 3). All DNA positive sediment samples (n = 7) clustered with the Rhabdochlamydiaceae. No difference was found in rates of recovery of CLO DNA in live versus dead pups suggesting the organisms are commensal but their potential as opportunistic secondary pathogens could not be determined. CONCLUSION: This is the first report of CLO DNA being found in marine mammals. This identification warrants further investigation in other seal populations around the coast of the UK and in other areas of the world to determine if this finding is unique or more common than shown by this data. Further investigation would also be warranted to determine if they are present as purely commensal organisms or whether they could also be opportunistic pathogens in seals, as well as to investigate possible sources of origin, including whether they originated as a result of anthropogenic impacts, including human waste and agricultural run-off.

Identification of a novel prophage regulator in Escherichia coli controlling the expression of type III secretion.

This study has identified horizontally acquired genomic regions of enterohaemorrhagic Escherichia coli O157:H7 that regulate expression of the type III secretion (T3S) system encoded by the locus of enterocyte effacement (LEE). Deletion of O-island 51, a 14.93 kb cryptic prophage (CP-933C), resulted in a reduction in LEE expression and T3S. The deletion also had a reduced capacity to attach to epithelial cells and significantly reduced E. coli O157 excretion levels from sheep. Further characterization of O-island 51 identified a novel positive regulator of the LEE, encoded by ecs1581 in the E. coli O157:H7 strain Sakai genome and present but not annotated in the E. coli strain EDL933 sequence. Functionally important residues of ECs1581 were identified based on phenotypic variants present in sequenced E. coli strains and the regulator was termed RgdR based on a motif demonstrated to be important for stimulation of gene expression. While RgdR activated expression from the LEE1 promoter in the presence or absence of the LEE-encoded regulator (Ler), RgdR stimulation of T3S required ler and Ler autoregulation. RgdR also controlled the expression of other phenotypes, including motility, indicating that this new family of regulators may have a more global role in E. coli gene expression.

Mucosal antibody responses of colonized cattle to Escherichia coli O157-secreted proteins, flagellin, outer membrane proteins and lipopolysaccharide.

The aim of this work was to characterize adaptive mucosal immune responses to Escherichia coli O157:H7 at the principal site of colonization in the bovine species. Following experimental infection, extracts from terminal rectum mucosal samples were tested for IgA antibodies by immunoblotting against different bacterial antigens including: whole-cell E. coli O157:H7 with and without proteinase treatment, outer membrane and cytoplasmic preparations, secreted protein supernatants and purified E. coli O157 lipopolysaccharide and H7 flagellin. Lipopolysaccharide and H7 flagellin preparations were also used to coat enzyme-linked immunosorbent assay plates to determine mucosal IgG1 and IgA antibody titers. In this work, evidence is presented of strong local IgA immune responses induced following infection at the bovine terminal rectal mucosa directed against multiple antigens including type III secretion-dependent proteins, O157 lipopolysaccharide, H7 flagellin and OmpC.