血液分离粪肠球菌毒力基因、MLST分型及生物膜形成能力研究

Characteristics of Virulence,MLST and Biofilm in Enterococcus Faecalis Isolated from Blood Stream Infection

目的对血液分离的粪肠球菌进行毒力基因、多位点序列分型(MLST)及生物膜形成能力研究。方法收集2011年7月至2018年2月从我院血培养阳性标本中分离的72株粪肠球菌,采用多重PCR法检测常见5种毒力基因(esp、gelE、asa1、cylA和hyl)。采用MLST技术分析菌株序列型(ST)从而进行同源性分析。采用结晶紫染色法检测生物膜的形成。结果72株粪肠球菌5种毒力基因的检出率分别为:esp(45/72,62.5%)、gelE(61/72,84.7%)、asa1(61/72,84.7%)、cylA(50/72,69.4%)和hyl(0/72,0.0%)。其中35株(48.6%)为4种毒力基因共存。MLST分型共检出26个ST型,包括16个已知型别和10个新型别,其中ST4占绝对优势(21/72,29.2%),其次为ST16(8/72,11.1%)、ST6(7/72,9.7%)和ST179(6/72,8.3%),其余ST型均不超过4株菌。72株粪肠球菌中,仅6株(6/72,8.3%)无生物膜形成,其余66株(66/72,91.7%)生物膜阳性株按照生物膜形成强度分为弱(+)、中等(++)、强(+++)和很强(++++),占比依次为20.8%(15/72)、43.1%(31/72)、15.3%(11/72)和12.5%(9/72)。结论我院血液标本分离的粪肠球菌具有较高的毒力基因携带率和生物膜形成能力,且以ST4型为优势型别。

Objective To investigate characteristics of virulence,MLST and biofilm in Enterococcus faecalis isolated from bloodstream infection.Methods 72 E.faecalis isolates were collected from blood culture of inpatients between July,2011 and February,2018.The occurrence of the esp,gelE,asa1,cylA and hyl were evaluated by a multiplex PCR method.MLST scheme was used to assess the clonality.The ability of biofilm formation assay was tested by crystal violet staining method.Results The prevalence of the five virulence genes among 72 strains were esp(45/72,62.5%),gelE(61/72,84.7%),asa1(61/72,84.7%),cylA(50/72,69.4%)and hyl(0/72,0.0%).Of these,35 strains(48.6%)harbored four virulence genes simultaneously.MLST analysis demonstrated 26 STs(sequence type)in 72 strains,including 16 known STs and 10 new STs.Among them,the most common ST was ST4(21/72,29.2%),followed by ST16(8/72,11.1%),ST6(7/72,9.7%)and ST179(6/72,8.3%),and the remaining STs were no more than 4 strains.Of 72 strains,only 6(6/72,8.3%)could not form biofilm,and the remaining 66(66/72,91.7%)biofilm positive strains were divided into four categories according to biofilm intensity:weak(+),medium(++),strong(+++)and very strong(++++),representing 20.8%(15/72),43.1%(31/72),15.3%(11/72)and 12.5%(9/72)individually.Conclusion E.faecalis isolated from bloodstream infection in our hospital shows both high prevalence of virulence genes and strong biofilm formation capacity and ST4 is the dominant sequence type.