尿源产超广谱β-内酰胺酶肠杆菌科细菌中16S rRNA甲基化酶基因及菌株克隆测定

目的 了解16S rRNA甲基化酶基因在尿源产超广谱β-内酰胺酶（ESBLs)肠杆菌科细菌中的分布及菌株序列型别，为临床用药提供依据。 方法 采用琼脂稀释法及PCR法对引起尿路感染的74株产ESBLs肠杆菌科细菌进行体外药敏、16S rRNA 甲基化酶基因检测与分型，MLST法进行溯源性序列分型研究。 结果 74株产ESBLs肠杆菌科细菌中93.4%耐庆大霉素、18.4%耐奈替米星、13.2%耐妥布霉素、仅5.3%耐阿米卡星与异帕米星。74株菌中22株（29.7%）检出16S rRNA甲基化酶基因，其中7株检出rmtB基因, 18株检出armA基因,3株同时检出rmtB和armA基因。22株16S rRNA甲基化酶基因阳性菌株对庆大霉素、奈替米星耐药率为100%，对妥布霉素者为59.1%，对阿米卡星及异帕米星者仅为18.2%。多位点序列分型显示19株甲基化酶基因阳性大肠埃希菌序列型为:12株为ST117，2株为ST2003，ST3843、ST915、ST844、ST2581、ST2922各1株；3株甲基化酶阳性肺炎克雷伯菌分为ST1184、ST490、ST337。 结论 大部分尿源性大肠埃希菌可能源于同一克隆。16S rRNA甲基化酶基因在尿源产ESBLs肠杆菌科细菌中分布广泛，与氨基糖苷类药物耐药有明显相关性。

Detection of 16S rRNA Methylase Genes and Genotypes in ESBLs-producing Enterobacteriaceae Isolates fromUrinary Tract Infections

Objective To study the prevalence of 16S rRNA methylase genes in extended-spectrum-lactamascs(ESBLs)-producing Enterobacteriacea, and the correlations of 16S rRNA methylase genes with anminoglycoside resistnace. Methods Seventy-four ESBLs-producing Enterobacteriacea stains were isolated from urinary tract infections. Minimal inhibitory concentrations (MICs) of 5 aminoglycosides against the ESBLs-producing Enterobacteriacea were detected by two-fold agar dilution method. PCR amplification and DNA sequencing were used for screening and identifying 16S rRNA methylase genes. The clonality of 16S rRNA methylase gene positive ESBLs-producing Enterobacteriaceae was assessed by multilocus sequence typing (MLST). Results The bacterial resistant rates to gentamycin, netilmicin, tobramycin,amikacin and isepamicin were 93.4%, 18.4%, 13.2%, 5.3% and 5.3%, respectively. Tweenty-two out of 74 clinical isolates were 16S rRNA methylase genes positive (29.7%), including 18 armA gene and 7 rmtB gene, and 3 strains with both genes. The resistant rates of those 22 strains to gentamycin , netilmicin, tobramycin, amikacin and isepamicin were 100%, 100%, 59.1%, 18.2% and 18.2%, respectively. Among 19 E.coli isolates, seven sequence types (STs) were identified，named as ST117 (12 strains), ST2003 (2 strains), ST3843 (1 strain), ST915 (1 strain), ST844 (1 strain), ST2581 (1 strain) and ST2922 (1 strain). MLST showed that 3 K.pneumoniae isolates were nonclonal. Conclusion 16S rRNA methylase genes were widely distributed in urinary ESBLs-producing Enterobacteriacea, showing obvious relationship with the resistance to aminoglycosides. The therapy of Amikacin or Isepamicin may be considered in UTIs with 16S rRNA gene positive ESBLs-producing Enterobacteriacea.