Carriage of critically important antimicrobial (CIAs) resistant pathogenic bacteria by wild animals is of concern. High-level FQ and ESC-resistant and low frequency of carbapenem and colistin resistant E. coli carriage by Australian Silver Gulls was reported in our previous study. We hypothesise that carriage of CIA-resistant E. coli among Silver Gulls leads to transfer of resistant bacteria to other bird species sharing the same environment. Three bird species foraging from a central place (Penguin Island, Perth, WA) occupying different foraging niches were included in this study to characterize and assess the potential source and determine the possible pathways of transmission of CIA-resistant E. coli.
Methods: Cloacal swabs from three bird species were cultured on selective media and presumptive E. coli isolate were subjected to identification by MALDI-TOF MS, antimicrobial susceptibility testing and a subset to next generation sequencing (n=55) on Illumina NextSeq 500 platform.
Results: CIA resistant E. coli carriage were 53%, 10% and 11% among Silver Gulls,
feral pigeons and Little Penguins respectively. Predominant STs were ST131, ST 69, ST 10, ST450 and ST695 amongst E. coli from all three species. E. coli ST1598 and ST 95 were detected in Penguins. The resistance genes detected were blaCTX-M-15, blaCTX-M-27, blaCTX-M-14 in E. coli from all three species. The other resistance genes detected only amongst isolates from seagulls included blaCMY-2 (3%) and one isolate each carrying blaCTX-M-3 and blaCTX-M-45.
Conclusion: This study reports the carriage of CIA resistant E. coli by all three bird species. The presence of CIA resistant E. coli in the cloacal swabs and the sharing of identical human associated pathogenic E. coli clones like ST131, ST69, ST95 and ST10 between the bird species indicates inter-species transmission. Penguin Island is a popular tourist destination and has high visitor numbers up to 80 000 engaged in coastal recreational activities. Contamination of such an environment with clinically significant CIA resistant E. coli warrants further investigations to determine the source of faecal contamination.