Antimicrobial resistance status of <i>Enterococcus</i> from Australian cattle populations at slaughter

<div><p>Antimicrobial agents are used in cattle production systems for the prevention and control of bacterial associated diseases. A consequence of their use is the potential development of antimicrobial resistance (AMR). <i>Enterococcus faecium</i> and <i>Enterococcus faecalis</i> that are resistant to antimicrobials are of increased concern to public health officials throughout the world as they may compromise the ability of various treatment regimens to control disease and infection in human medicine. Australia is a major exporter of beef; however it does not have an ongoing surveillance system for AMR in cattle or foods derived from these animals. This study examined 910 beef cattle, 290 dairy cattle and 300 veal calf faecal samples collected at slaughter for the presence of enterococci. <i>Enterococcus</i> were isolated from 805 (88.5%) beef cattle faeces, 244 (84.1%) dairy cattle faeces and 247 (82.3%) veal calf faeces with a total of 800 enterococci subsequently selected for AMR testing. The results of AMR testing identified high levels of resistance to antimicrobials that are not critically or highly important to human medicine with resistance to flavomycin (80.2%) and lincomycin (85.4–94.2%) routinely observed. Conversely, resistance to antibiotics considered critically or highly important to human medicine such as tigecycline, daptomycin, vancomycin and linezolid was not present in this study. There is minimal evidence that Australian cattle production practices are responsible for disproportionate contributions to AMR development and in general resistance to antimicrobials of critical and high importance in human medicine was low regardless of the isolate source. The low level of antimicrobial resistance in <i>Enterococcus</i> from Australian cattle is likely to result from comprehensive controls around the use of antimicrobials in food-production animals in Australia. Nevertheless, continued monitoring of the effects of all antimicrobial use is required to support Australia’s reputation as a supplier of safe and healthy food.</p></div

Revised MICs and occurrence of resistance among <i>Enterococcus</i> isolates following additional phenotypic and genotypic assessment.

<p>Revised MICs and occurrence of resistance among <i>Enterococcus</i> isolates following additional phenotypic and genotypic assessment.</p

Dilution ranges and breakpoints for antimicrobial susceptibility testing.

<p>Dilution ranges and breakpoints for antimicrobial susceptibility testing.</p

Distribution of MICs and occurrence of resistance among <i>Enterococcus</i> isolates using the Sensititre test system.

<p>Distribution of MICs and occurrence of resistance among <i>Enterococcus</i> isolates using the Sensititre test system.</p

Prevalence of AMR in <i>Enterococcus faecalis and faecium</i> isolates from beef cattle, dairy cattle and veal calf faecal samples.

<p>Prevalence of AMR in <i>Enterococcus faecalis and faecium</i> isolates from beef cattle, dairy cattle and veal calf faecal samples.</p

Antimicrobial resistance profiles of <i>Enterococcus faecium</i> and <i>faecalis</i> isolates from beef cattle, dairy cattle and veal calf faecal samples.

<p>Antimicrobial resistance profiles of <i>Enterococcus faecium</i> and <i>faecalis</i> isolates from beef cattle, dairy cattle and veal calf faecal samples.</p

Primers, cycling conditions and expected product sizes of <i>Enterococcus</i> AMR gene PCRs.

<p>Primers, cycling conditions and expected product sizes of <i>Enterococcus</i> AMR gene PCRs.</p