Australian Group on Antimicrobial Resistance (AGAR) Australian Enterococcal Sepsis Outcome Programme (AESOP) Annual Report 2018

Abstract

From 1 January to 31 December 2018, thirty-six institutions around Australia participated in the Australian Enterococcal Sepsis Outcome Programme (AESOP). The aim of AESOP 2018 was to determine the proportion of enterococcal bacteraemia isolates in Australia that were antimicrobial resistant, and to characterise the molecular epidemiology of the <i>E. faecium</i> isolates. Of the 1,248 unique episodes of bacteraemia investigated, 93.5% were caused by either <i>E. faecalis</i> (54.2%) or <i>E. faecium</i> (39.3%). Ampicillin resistance was not detected in <i>E. faecalis</i> but was detected in 89.4% of <i>E. faecium</i>. Vancomycin non-susceptibility was not detected in <i>E. faecalis</i> but was reported in 45.0% of <i>E. faecium</i>. Overall 49.3% of <i>E. faecium</i> isolates harboured vanA or vanB genes. Of the <i>vanA</i>/<i>vanB</i> positive <i>E. faecium</i> isolates, 52.9% harboured <i>vanA</i> genes and 46.2% <i>vanB</i> genes; 0.8% harboured both <i>vanA</i> and <i>vanB</i> genes. The percentage of <i>E. faecium</i> bacteraemia isolates resistant to vancomycin in Australia is substantially higher than that seen in most European countries. <i>E. faecium</i> consisted of 59 multilocus sequence types (STs) of which 74.4% of isolates were classified into six major STs containing ten or more isolates. All major STs belong to clonal cluster (CC) 17, a major hospital-adapted polyclonal <i>E. faecium</i> cluster. The predominant STs (ST17, ST1424, ST796, ST80, ST1421, and ST262) were found across most regions of Australia. The most predominant clone was ST17 which was identified in all regions except the Australian Capital Territory and the Northern Territory. Overall, 55.8% of isolates belonging to the six predominant STs harboured <i>vanA</i> or <i>vanB</i> genes. The AESOP 2018 study has shown that enterococcal bacteraemias in Australia are frequently caused by polyclonal ampicillin-resistant high-level gentamicin-resistant <i>vanA</i>- or <i>vanB</i>-harbouring <i>E. faecium</i> which have limited treatment options.