Antimicrobial Resistance and Infectious Diseases (AMRID) Research Laboratory, Murdoch University, Western Australia.
Antimicrobial Resistance and Infectious Diseases (AMRID) Research Laboratory, Murdoch University, Western Australia.
Int J Antimicrob Agents. 2019 Jun;53(6):814-819. doi: 10.1016/j.ijantimicag.2019.02.009. Epub 2019 Mar 7.
The first outbreak of vancomycin-resistant Enterococcus faecium (VREfm) in Western Australia was recorded in 2001. A state-wide infection control effort that oversaw patient screening and transfers successfully terminated the outbreak within six months; however, the outbreak re-emerged two years later. Over the two outbreaks, the vanB-positive multilocus sequence type (ST) 173 E. faecium strain was isolated from 201 patients. Our objective was to identify differences in genetic traits leading to successful transmission of ST173 VREfm compared with non-ST173 VREfm isolated during the same period. We also aimed to describe the changes observed in the ST173 VREfm genome collected during the two outbreaks. Virulence factors ecbA, fss3, psaA and scm identified in the non-ST173 isolates were largely absent in the ST173 isolates. The esp gene was not identified beyond 45% coverage for any isolate in this study. In terms of resistance genes, tet(U) was identified in 94.7% of ST173 VREfm isolated in the first outbreak but was largely absent in ST173 VREfm isolated in the second outbreak and in non-ST173 VREfm. Seven ST173 VREfm isolates (Clade A) carried dfrG but not tet(M) resistance genes. The average genome size of ST173 VREfm isolated in the first outbreak was significantly larger than the genome size of ST173 VREfm isolated in the second outbreak. The reduced number of virulence factors in ST173 isolates may explain the low infection and high colonization rates observed during the outbreak. In addition, isolates with larger genomes were found to be associated with outbreaks.
2001 年，西澳大利亚州记录了第一例万古霉素耐药粪肠球菌（VREfm）的爆发。一项全州范围的感染控制努力，监督了患者筛查和转院，成功地在六个月内结束了疫情；然而，两年后疫情再次爆发。在这两次爆发中，从 201 名患者中分离出了带有 vanB 阳性多基因座序列型（ST）173 的屎肠球菌。我们的目的是确定导致 ST173 VREfm 成功传播的遗传特征与同期分离的非 ST173 VREfm 之间的差异。我们还旨在描述在两次爆发期间收集的 ST173 VREfm 基因组中观察到的变化。在非 ST173 分离株中发现的 ecbA、fss3、psaA 和 scm 毒力因子在 ST173 分离株中基本上不存在。在这项研究中，没有任何分离株的 esp 基因覆盖率超过 45%。就耐药基因而言，在第一次爆发中分离的 94.7%的 ST173 VREfm 中鉴定出 tet(U)，但在第二次爆发中分离的 ST173 VREfm 和非 ST173 VREfm 中基本上不存在。7 株 ST173 VREfm（A 群）携带 dfrG 但不携带 tet(M)耐药基因。第一次爆发中分离的 ST173 VREfm 的平均基因组大小明显大于第二次爆发中分离的 ST173 VREfm 的基因组大小。ST173 分离株中较少的毒力因子可能解释了在疫情期间观察到的低感染率和高定植率。此外，还发现具有较大基因组的分离株与疫情有关。
