安徽省临床分离致泻性大肠埃希菌主要流行基因型及同源性分析

The main prevalent genotypes and homology of clinically isolated diarrheagenic Escherichia coli in Anhui Province

摘要:

目的 了解安徽地区临床分离致泻性大肠埃希菌（DEC）的耐药状况、基因同源性及主要基因型。 方法 采用微量肉汤稀释法进行药物敏感性试验，采用多位点序列分型（MLST）和脉冲场凝胶电泳（PFGE）分型进行基因型检测和同源性分析。 结果 268株DEC中，57.1%为多重耐药菌，其中肠聚集性大肠埃希菌（EAEC）118株，肠毒素性大肠埃希菌（ETEC）98株，肠致病性大肠埃希菌（EPEC）47株，3种病理类型菌株对常用抗菌药物的耐药率分别为：氨苄西林83.9%、73.5%、78.7%，萘啶酸65.3%、75.5%、34.0%，头孢唑林53.4%、35.7%、34.0%，四环素61.0%、31.6%、74.5%，复方磺胺甲唑63.6%、23.5%、46.8%，氨苄西林/舒巴坦28.0%、9.2%、29.8%，庆大霉素34.7%、7.1%、34.0%，氯霉素22.9%、5.1%、21.3%，环丙沙星18.6%、4.1%、14.9%；2株EAEC和1株ETEC对亚胺培南耐药。55株EAEC分为35个ST型，优势基因型是ST10（14.5%）；55株ETEC分为14个ST型，优势基因型是ST48（32.7%）和ST218（16.4%）；15株EPEC分为12个ST型，优势基因型是ST28（13.3%）、ST517（13.3%）和ST2088（13.3%）。微进化树分析结果显示：55株ETEC中，马鞍山市分别有5、3、2、2株菌100%同源，合肥市有5株菌100%同源；55株EAEC中，阜阳市、滁州市各有2株菌100%同源；15株EPEC中，有2组2株菌100%同源，分离自马鞍山市。50株EAEC PFGE同源性聚类分析结果为：100%同源有2株，分离自蚌埠市，其余菌株同源性均在90%以下；21株EPEC的基因同源性均在75%以下；30株ETEC、3株肠侵袭性大肠埃希菌（EIEC）和5株ETEC+aEAEC的基因同源性达97.6%、93.6%各2株，其余菌株同源性都在90%以下。 结论 本研究发现安徽省临床分离的DEC耐药情况较严重，其中EAEC的耐药率高于EPEC和ETEC，ETEC的耐药率在各致病型中最低。分子分型检测发现本地区临床分离的DEC基因型较分散，在各致病型中，ETEC的基因型相对集中。微进化树分析提示ETEC存在地区同源性感染。在分子分型技术上，MLST能区分出优势基因型和聚集性，优于PFGE分型。

Abstract:

Objective To investigate antimicrobial resistance, gene homology and main genotypes of clinically isolated diarrheagenic Escherichia coli (DEC) in Anhui Province. Methods Antimicrobial susceptibility testing was performed with microbroth dilution method, genotyping detection and homology analysis was conducted with multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Results Among 268 strains of DEC, 57.1% were multidrug-resistant organisms, including 118 strains of enteroaggregative Escherichia coli (EAEC), 98 strains of enterotoxigenic Escherichia coli (ETEC) and 47 strains of enteropathogenic Escherichia coli (EPEC), resistance rates of 3 types of pathological strains to commonly used antimicrobial agents were as follows: ampicillin 83.9%, 73.5%, 78.7%, nalidixic acid 65.3%, 75.5%, 34.0%, cefazolin 53.4%, 35.7%, 34.0%, tetracycline 61.0%, 31.6%, 74.5%, compound sulfamethoxazole 63.6%, 23.5%, 46.8%, ampicillin/sulbactam 28.0%, 9.2%, 29.8%, gentamicin 34.7%, 7.1%, 34.0%, chloramphenicol 22.9%, 5.1%, 21.3%, ciprofloxacin 18.6%, 4.1%, 14.9%; two EAEC strains and 1 ETEC strain were resistant to imipenem. 55 EAEC strains were divided into 35 ST, the dominant genotype was ST10 (14.5%); 55 ETEC strains were divided into 14 ST, the dominant genotypes were ST48 (32.7%) and ST218 (16.4%); 15 EPEC strains were divided into 12 ST, the do-minating genotypes were ST28 (13.3%), ST517 (13.3%) and ST2088 (13.3%). Minimum-evolution (ME) tree analysis showed that among 55 ETEC strains, 5, 3, 2 and 2 strains isolated from Ma'anshan City were 100% homologous respectively, 5 strains isolated from Hefei City were 100% homologous; among 55 EAEC strains, 2 strains isolated from Fuyang City and 2 strains isolated from Chuzhou City were 100% homologous respectively; among 15 EPEC strains isolated from Ma'anshan City, 2 strains in 2 groups were 100% homologous. PFGE homo-logy cluster analysis results of 50 EAEC strains were as follows: 2 strains isolated from Bengbu City were 100% homologous, homology of the other strains was less than 90%; gene homology of 21 EPEC strains were all less than 75%; homology of 30 ETEC strains, 3 enteroinvasive Escherichia coli (EIEC) strains, and 5 ETEC+aEAEC strains reached 97.6% with 2 strains and 93.6% with 2 strains respectively, and the homology of the remaining strains was below 90%. Conclusion Antimicrobial resistance of clinically isolated DEC in Anhui Province is se-rious, resistance rate of EAEC is higher than that of EPEC and ETEC, resistance rate of ETEC is the lowest among the pathogenic types. Molecular typing detection found that the genotypes of clinically isolated DEC in this area are relatively scattered, among the pathogenic types, genotype of ETEC is relatively concentrated. ME tree analysis suggests that ETEC may have a regional homologous infection. In molecular typing technology, MLST can distinguish dominant genotype and aggregation, which is better than PFGE typing.