Emergence of fluoroquinolone resistant Campylobacter jejuni and Campylobacter coli among Australian chickens in the absence of fluoroquinolone use.


Antimicrobial Resistance and Infectious Diseases Laboratory, College of Science, Health, Engineering and Education, Murdoch University, Murdoch, Australia [Email]


In a structured survey of all major chicken-meat producers in Australia we investigated the AMR and genomic characteristics of C. jejuni (n=108) and C. coli (n=96) from caecal samples of chickens at slaughter (n=200). The majority of C. jejuni (63%) and C. coli (86.5%) were susceptible to all antimicrobials. Fluoroquinolone resistance (ciprofloxacin) was detected among both C. jejuni (14.8%) and C. coli (5.2%), although this only included three and one STs respectively. Multi-drug resistance among C. jejuni (0.9%) and C. coli (4.1%) was rare and fluoroquinolone resistance, when present, was never accompanied by resistance to any other agent. Comparative genome analysis demonstrated that Australian isolates were found dispersed on different branches/clusters within the international collection. The major FQ-resistant STs of C. jejuni (ST7323, ST2083, ST2343) and C. coli (ST860) present in Australian chickens were similar to internaional isolates and have been reported previously in humans and animals overseas.The detection of a sub-population of Campylobacter isolates exclusively resistant to fluoroquinolone was unexpected since most critically-important antimicrobials (CIAs) such as fluoroquinolones are excluded from use in Australian livestock. A number of factors including the low-level of resistance to other antimicrobials, the absence of fluoroquinolone use, adoption of measures for preventing spread of contagion between flocks, and particularly the genomic identity of isolates all point to either humans, pest-species or wild birds as being the most plausible source of organisms. This study also demonstrates the need for vigilance in the form of surveillance for AMR based on robust sampling to manage AMR risks in the food-chain.ImportanceCampylobacter is one of the most common causes of gastroenteritis in humans with infections frequently resulting from exposure to under-cooked poultry products. Although human illness is typically self-limiting, a minority of cases do require antimicrobial therapy. Ensuring that Campylobacter originating from meat-chickens do not acquire resistance to fluoroquinolones is therefore a valuable outcome for public-health. Australia has never legalised the use of fluoroquinolones in commercial chickens and until now fluoroquinolone-resistant Campylobacter have not been detected in the Australian poultry. This structured survey of meat-chickens derived from all major Australian producers describes the unexpected emergence of fluoroquinolone resistance in Campylobacter jejuni and C. coli Genetic characterisation suggests that these isolates may have evolved outside of the Australian poultry sector and were introduced into poultry by humans, pest-species or wild birds. The findings dramatically underline the critical role of biosecurity in the overall fight against antimicrobial resistance.

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