Dominance of IMP-4-Producing Enterobacter cloacae among Carbapenemase-Producing Enterobacteriaceae in Australia

<jats:title>ABSTRACT</jats:title> <jats:p> The prevalence of carbapenemase-producing <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Enterobacteriaceae</jats:named-content> (CPE) has been increasing worldwide. <jats:italic>bla</jats:italic> <jats:sub>IMP</jats:sub> has been reported to be the predominant carbapenemase-encoding gene within <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Enterobacteriaceae</jats:named-content> in Australia. However, there are limited data currently available on CPE from Queensland, Australia. A total of 58 CPE isolates were isolated between July 2009 and March 2014 from Queensland hospitals. The clonality of isolates was determined by Diversilab repetitive sequence-based PCR. The isolates were investigated for the resistance mechanisms carbapenemase, extended-spectrum β-lactamase, and AmpC β-lactamase and for aminoglycoside resistance and plasmid-mediated quinolone resistance genes by PCR. The plasmid types associated with carbapenemase-encoding genes were characterized. The majority of the CPE were <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Enterobacter cloacae</jats:named-content> ( <jats:italic>n</jats:italic> = 29). The majority of Queensland CPE isolates were IMP producers and comprised 11 species ( <jats:italic>n</jats:italic> = 48). Nine NDM-producing <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Enterobacteriaceae</jats:named-content> were identified. One NDM-producing <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Klebsiella pneumoniae</jats:named-content> isolate coproduced OXA-48. One <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">K. pneumoniae</jats:named-content> isolate was an OXA-181 producer. The incidence of IMP producers increased significantly in 2013. <jats:italic>bla</jats:italic> <jats:sub>IMP-4</jats:sub> was found in all IMP-producing isolates. <jats:italic>bla</jats:italic> <jats:sub>TEM</jats:sub> , <jats:italic>qnrB</jats:italic> , and <jats:italic>aacA4</jats:italic> were common among IMP-4 producers. The HI2 (67%) and L/M (21%) replicons were associated with <jats:italic>bla</jats:italic> <jats:sub>IMP-4</jats:sub> . All HI2 plasmids were of sequence type 1 (ST1). All but one of the NDM producers possessed <jats:italic>bla</jats:italic> <jats:sub>CTX-M-15</jats:sub> . The 16S rRNA methylase genes found among NDM producers were <jats:italic>armA</jats:italic> , <jats:italic>rmtB</jats:italic> , <jats:italic>rmtC</jats:italic> , and <jats:italic>rmtF</jats:italic> . The substantial increase in the prevalence of CPE in Queensland has been associated mainly with the emergence <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">E. cloacae</jats:named-content> strains possessing HI2 plasmids carrying <jats:italic>bla</jats:italic> <jats:sub>IMP-4</jats:sub> over the past 2 years. The importation of NDM producers and/or OXA-48-like producers in patients also contributed to the increased emergence of CPE. </jats:p>