SPREAD OF ANTIMICROBIAL-RESISTANT BACTERIA IN THE ENVIRONMENT
‘Superbugs’ including vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), extended spectrum β-lactamase (ESBL) producing Enterobacterales and carbapenem-resistant Entero- bacterales (CRE) have now been detected in a small number of wildlife species and through only a few studies.
Antibiotic-resistant bacteria are now found in the habitats of several free-ranging Australian mammal species, but in most cases the mechanisms by which these bacteria have spread to these locations remain poorly studied. Evolving molecular technologies and rapid detection methods offer solutions to addressing gaps in transmission dynamics and direction of transfer. Whole genome sequencing and phylogenetics of resistant E. coli and K. pneumoniae from grey-headed flying-foxes indicated transmission occurred from humans and/or domestic animals into free-range wildlife via the environment (McDougall et al. 2021a; McDougall et al. 2021b; McDougall et al. 2022).A critical factor in the emergence of MDR bacterial strains such as MRSA and VRE was a change in transmission dynamics. MRSA and VRE were initially hospital-acquired infections, but are now well established in the community (Conly and Johnston 2003). The emergence of MDR strains external to hospitals likely facilitated transmission to non-human hosts such as livestock and companion animals (Platell et al. 2011). Nosocomial infections in veterinary clinics are being reported with increasing frequency (Guardabassi 2012). Caution needs to be taken with wildlife admitted to hospitals (may potentially be carrying MDR bacteria or may acquire such strains while in care) and to prevent spread upon release after rehabilitation.
Other vertebrate species, such as birds, also have potential to spread resistant bacteria. Resistant E. coli were isolated from multiple bird species in managed care settings (Blyton et al. 2015). In their free-range habitat, silver gulls (Chroococephalus novaehollandiae) were found to be carrying E. coli with class 1 integrons and genes encoding ESBLs and carbapenemases (Dolejska et al. 2009; Dolejska et al. 2016). Two VRE isolates were also isolated from free- range silver gulls: Enterococcus faecium and E. dispar being vanB and vanA genotypes, respectively (Oravcova et al. 2017). Resistant enteric bacteria have been reported in the green turtle (Chelonia mydas) (Ahasan et al. 2017) and resistant Salmonella in several Australian reptiles (McWhorter et al. 2021). There are increasing reports of antibiotic resistant bacteria in Australia’s terrestrial and marine vertebrates indicating the extent to which ecosystems and keystone species are being polluted with resistant bacteria and their genes.
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