侵袭性金黄色葡萄球菌感染患儿的感染株与定植株的分子病原学特征比较

Comparison of molecular characteristics between infective and colonizing strains in children with invasive Staphylococcus aureus infection

目的研究侵袭性金黄色葡萄球菌(SA)感染患儿的感染部位分离株与其鼻腔定植株的分子生物学特征,并对两类不同来源菌株的一致性进行分析。方法2019年1月至8月四川省妇幼保健院儿科病房收治的社区侵袭性SA感染患儿的无菌部位收集到45株SA侵袭株,并从患儿鼻前庭筛查出28株定植株。采用肉汤稀释法对菌株进行药敏试验测定;采用PCR法检测菌株中耐药基因mecA、blaZ及毒力基因杀白细胞素(pvl)的携带情况;采用脉冲场凝胶电泳(PFGE)分型技术检测感染株和定植株的同源性。结果62.2%(28/45例)的感染患儿鼻前庭存在SA定植。侵袭株40.0%(18/45株)是耐甲氧西林SA(MRSA)菌株,定植株32.1%(9/28株)为MRSA菌株,二者相比差异无统计学意义(P>0.05)。感染株对克林霉素、阿奇霉素、红霉素的抵抗力强于定植株,耐药率差异均有统计学意义(χ^2=7.114、7.820、5.359,均P<0.05)。感染株和定植株的耐药基因balZ和毒力基因pvl的携带率差异均无统计学意义(均P>0.05)。表型上显示,与MRSA感染相比,甲氧西林敏感SA(MSSA)感染更容易发生鼻腔一致性定植[16.7%(3/18例)比48.1%(13/27例),χ^2=4.671,P<0.05]。PFGE分型技术检测结果显示,感染MSSA菌株的患儿与感染MRSA菌株者相比,前者更易存在同源性的SA定植[59.3%(16/27株)比27.8%(5/18株),χ^2=4.301,P<0.05]。结论侵袭性SA感染患儿的感染株与定植株对某些抗生素的耐药情况存在差异,但其常见耐药和毒力基因的携带情况无差异性。MSSA菌株感染患儿较MRSA菌株感染患儿的鼻腔内更有可能出现一致性定植菌。在侵袭性SA感染患儿中筛查SA的定植状态可能有潜在的临床意义。

Objective To study the molecular biological characteristics of isolates from the infection site and isolates colonizing in anterior nares of children with invasive Staphylococcus aureus(SA)infection,and to analyze the concordance between the two types of strains from different sources.Methods A total of 45 strains were collected from children with invasive SA infection treated in the Pediatric Ward of Sichuan Provincial Maternal and Child Health Care Hospital from January 2019 to August 2019,and 28 colonization isolates were obtained from the anterior nares of these patients.The susceptibility test was carried out by broth dilution method.The drug resistance genes mecA and blaZ and the virulence gene panton-valentine leucocidin(pvl)were detected by PCR.The homology of infective and colonizing isolates was detected by pulsed-field gel electrophoresis(PFGE)typing technique.Results Colonization of SA was found in the nasal vestibule of 62.2%(28/45 cases)of patients with invasive SA infection.A total of 40.0%(18/45 strains)of the infective isolates and 32.1%(9/28 strains)of the colonizing isolates were Methicillin-resistant SA(MRSA),and the difference was not statistically significant(P>0.05).The resistance of infective isolates to Clindamycin,Azithromycin and Erythromycin was stronger than that of colonizing isolates,the difference of drug resistance rate was statistically significant(χ^2=7.114,7.820,5.359,all P<0.05).There were no differences in the carrying rates of the drug resistance gene blaZ and the virulence gene pvl between the infective and colonizing bacteria(P>0.05).Phenotypically,Methicillin-susceptible SA(MSSA)was more susceptible to concordant colonization than MRSA[16.7%(3/18 cases)vs.48.1%(13/27 cases),χ^2=4.671,P<0.05].PFGE indicated that patients with invasive MSSA infection were significantly more likely to have a concordant MSSA colonization isolate in their anterior nares,compared with patients with invasive MRSA infection[59.3%(16/27 strains)vs.27.8%(5/18 strains),χ^2=4.301,P<0.05].Conclusions The infective and colonizing strains of invasive SA show no difference in their resistance to some anti-biotics,but they carry almost the same number of drug resistance and virulence genes.Compared with those with MRSA infection,patients with MSSA infection are more likely to have concordant colonizing isolates.It is of potential clinical significance to screen the colonizing SA strains in patients with invasive SA infection.