北京市集贸市场生鲜猪肉肠球菌种水平鉴定及耐药特征

The species-level identification and antimicrobial susceptibility analysis of Enterococcus spp. of raw pork collected from a free trade market in Beijing

目的评价和比较不同肠球菌种水平鉴定方法的准确性,了解北京市集贸市场生鲜猪肉肠球菌的种水平分布及耐药特征。方法利用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)和VITEK 2 COMPACT两种方法对北京市集贸市场生鲜猪肉肠球菌开展种水平鉴定,两种方法鉴定结果不一致的菌株使用API 20 Strep、16S rRNA和23S rRNA序列分析再次鉴定。比较不同种肠球菌对10种临床常用抗生素的药物敏感性。结果在5种肠球菌种水平鉴定方法中,16S rRNA序列分析和最终结果的符合率最高,为100.0%;VITEK 2 COMPACT符合率最低,仅为4.0%(1/25)。在86株肠球菌中,粪肠球菌占82.6%(71/86),其次为希拉肠球菌占14.0%(12/86)。粪肠球菌对环丙沙星(CIP)的耐药率高于希拉肠球菌,差异有统计学意义(χ~2=10.751,P<0.01);对四环素(TET)、高浓度链霉素(HLSR)和高浓度庆大霉素(HLGR)的耐药率均高于希拉肠球菌,但差异无统计学意义(TET:χ~2=3.865,P>0.05;HLSR:χ~2=1.608,P>0.05;HLGR:χ~2=0.553,P>0.05),但对红霉素(ERY)和氯霉素(CHL)的耐药率明显低于希拉肠球菌,差异有统计学意义(ERY:χ~2=20.244,P<0.01;CHL:χ~2=14.139,P<0.01)。结论 16S rRNA和MALDI-TOF-MS序列分析技术在肠球菌种水平快速鉴定上有较高准确性,不同种属肠球菌呈现不同耐药特征,本研究为有效监测食源性耐药肠球菌的传播和流行提供了科学数据。

Objective This study was to compare and assess the accuracy of species-level identification methods for Enterococcus spp.,and to understand the species distribution and antimicrobial susceptibility characteristics of Enterococcus spp. collected of raw pork from a free trade market in Beijing. Methods By using matrix-assisted laser desorption/ionization time of flight mass spectrometry（ MALDI-TOF-MS） and 16 S rRNA gene analysis,the species of Enterococcus spp. were identified,and the inconsistent results were further identified by API 20 Strep,16 S rRNA and 23 S rRNA gene analysis. Moreover,the susceptibility of isolated Enterococcus spp. to 10 antibiotics was analyzed at species level. Results Among the five identification methods,16 S rRNA gene analysis showed 100. 0% consistence with the final species identification results,but the VITEK 2 COMPACT showed the lowest consistence of only 4. 0%（ 1/25）. The most prevalent species in Enterococcus spp. was Enterococcus faecalis,accounting for 82. 6%（ 71/86） followed by Enterococcus hirae 14. 0%（ 12/86）. Enterococcus faecalis strains showed higher antimicrobial susceptibility than Enterococcus hirae tociprofloxacin,tetracycline,high-level streptomycin and high-level gentamicin（ ciprofloxacin： χ~2= 10. 751,P 0. 01;tetracycline： χ~2= 3. 865,P 0. 05; high-level streptomycin： χ~2= 1. 608,P 0. 05; high-level gentamicin： χ~2= 0. 553,P 0. 05）,but showed apparently lower antimicrobial susceptibility on erythromycin and chloramphenicol than Enterococcus hirae（ erythromycin： χ~2= 20. 244,P 0. 01; chloramphenicol： χ~2= 14. 139,P 0. 01）. Conclusion The 16 S rRNA gene analysis and MALDI-TOF-MS have higher accuracy at species level identification for Enterococcus spp.. Different species of Enterococcus spp. showed various antimicrobial susceptibility characteristics. This study was important for the effective monitoring of drug-resistant enterococci spread and prevalence.