Emergence of Vancomycin-Resistant Enterococci in Australia: Phenotypic and Genotypic Characteristics of Isolates

Enterococci with resistance to glycopeptides have recently emerged in Australia. We developed multiplex PCR assays for vanA, vanB, vanC1, and vanC2 or vanC3 in order to examine the genetic basis for vancomycin resistance in Australian isolates of vancomycin-resistant Enterococcus faecium and E. faecalis (VRE). The predominant genotype from human clinical E. faecium isolates was vanB. The PCR van genotype was consistent with the resistance phenotype in all but six cases. One vanA E. faecalis isolate had a VanB phenotype, one vanB E. faecium isolate had a VanA phenotype, and four E. faecalis isolates were consistently negative for vanA, vanB, vanC1, and vanC2 or vanC3, even though they exhibited a VanB phenotype. These four isolates were subsequently examined for the presence of vanD by published methods and were found to be negative. No vancomycin-susceptible strains produced a PCR product. On the basis of our findings the epidemiology of VRE in Australia appears to be different from that in either the United States or Europe. Our multiplex PCR assays gave a rapid and accurate method for determining the genotype and confirming the identification of glycopeptide-resistant enterococci. Rapid and accurate methods are essential, because laboratory-based surveillance is critical in programs for the detection, control, and prevention of the transmission of glycopeptide-resistant enterococci.

糖肽类耐药肠球菌近期在澳大利亚出现。本研究针对vanA、vanB、vanC1及vanC2/vanC3建立了多重聚合酶链反应（polymerase chain reaction, PCR）检测体系，用于分析澳大利亚万古霉素耐药屎肠球菌与粪肠球菌（以下简称VRE）分离株的万古霉素耐药遗传基础。临床分离的屎肠球菌株中，优势耐药基因型为vanB。除6株菌株外，其余所有分离株的PCR检测van基因型与耐药表型均保持一致。其中1株携带vanA的粪肠球菌分离株表现为VanB表型，1株携带vanB的屎肠球菌分离株表现为VanA表型；另有4株粪肠球菌分离株，尽管呈现VanB表型，但vanA、vanB、vanC1及vanC2/vanC3的PCR检测结果均为阴性。后续通过已发表的方法对这4株分离株开展vanD基因检测，结果均为阴性。所有万古霉素敏感菌株均未扩增出PCR产物。基于本研究结果，澳大利亚VRE的流行病学特征与美国或欧洲均存在差异。本研究建立的多重PCR检测体系可快速、准确地鉴定糖肽类耐药肠球菌的基因型并确认其菌种属性。快速准确的检测方法不可或缺，因为基于实验室的监测在糖肽类耐药肠球菌传播的检测、控制与预防工作中至关重要。