Daira Melendez1, Marilyn C Roberts1, Alexander L Greninger2, Scott Weissman3, David No1, Peter Rabinowitz1, Samuel Wasser4. 1. Department of Environmental and Occupational Health Sciences, School of Public Health, Seattle, WA 98195, USA. 2. Department of Laboratory Medicine, School of Medicine, Seattle, WA 98195, USA. 3. Children's Hospital, Seattle, WA 98145, USA. 4. Department of Biology, University of Washington, Seattle, WA 98195, USA.
Abstract
BACKGROUND: Limited studies have investigated the microbial diversity of wild marine mammals. OBJECTIVES: This study characterized Escherichia coli isolates collected from fresh faecal samples of endangered southern resident killer whales (Orcinus orca) located by detection dogs. METHODS: WGS of each strain was done to determine ST (using MLST), clonotype (C:H), antimicrobial resistance and virulence profile. Conjugation experiments were done to determine the mobility of the tet(B) tetracycline resistance gene. RESULTS: All isolates belonged to extraintestinal pathogenic E. coli (ExPEC) clonal lineages ST73 (8/9) and ST127 (1/9), often associated with human community-acquired urinary tract disease. Clonotyping using fumC and fimH alleles showed divergence in clonal lineages, with ST73 isolates belonging to the C24:H10 clade and the ST127 isolate belonging to C14:H2. The eight ST73 isolates carried multiple acquired antibiotic resistance genes, including aadA1, sul1 and tet(B), encoding aminoglycoside, sulphonamide and tetracycline resistance, respectively. Conjugative transfer of the resistance gene tet(B) was observed for three of the eight isolates. ST127 did not carry any of these acquired resistance genes. Virulence-associated genes identified included those encoding adhesins (iha, papC, sfaS), toxins (sat, vat, pic, hlyA, cnf1), siderophores (iutA, fyuA, iroN, ireA), serum survival/protectins (iss, ompT), capsule (kpsM) and pathogenicity island marker (malX). CONCLUSIONS: Orca whales can carry antibiotic-resistant potentially pathogenic strains of E. coli. Possible sources include contamination of the whale's environment and/or food. It is unknown whether these isolates cause disease in southern resident killer whales, which could contribute to the ongoing decline of this critically endangered population.
BACKGROUND: Limited studies have investigated the microbial diversity of wild marine mammals. OBJECTIVES: This study characterized Escherichia coli isolates collected from fresh faecal samples of endangered southern resident killer whales (Orcinus orca) located by detection dogs. METHODS: WGS of each strain was done to determine ST (using MLST), clonotype (C:H), antimicrobial resistance and virulence profile. Conjugation experiments were done to determine the mobility of the tet(B) tetracycline resistance gene. RESULTS: All isolates belonged to extraintestinal pathogenic E. coli (ExPEC) clonal lineages ST73 (8/9) and ST127 (1/9), often associated with human community-acquired urinary tract disease. Clonotyping using fumC and fimH alleles showed divergence in clonal lineages, with ST73 isolates belonging to the C24:H10 clade and the ST127 isolate belonging to C14:H2. The eight ST73 isolates carried multiple acquired antibiotic resistance genes, including aadA1, sul1 and tet(B), encoding aminoglycoside, sulphonamide and tetracycline resistance, respectively. Conjugative transfer of the resistance gene tet(B) was observed for three of the eight isolates. ST127 did not carry any of these acquired resistance genes. Virulence-associated genes identified included those encoding adhesins (iha, papC, sfaS), toxins (sat, vat, pic, hlyA, cnf1), siderophores (iutA, fyuA, iroN, ireA), serum survival/protectins (iss, ompT), capsule (kpsM) and pathogenicity island marker (malX). CONCLUSIONS: Orca whales can carry antibiotic-resistant potentially pathogenic strains of E. coli. Possible sources include contamination of the whale's environment and/or food. It is unknown whether these isolates cause disease in southern resident killer whales, which could contribute to the ongoing decline of this critically endangered population.