耐三代头孢菌素沙门菌的耐药基因分析

Analysis for drug resistance genes of Salmonella resistant to third-generation cephalosporins

目的了解耐三代头孢菌素沙门菌的耐药基因分布特征,为疾病的防控和治疗提供依据。方法选取对头孢噻肟(CTX)和(或)头孢他啶(CAZ)耐药的临床分离的沙门菌157株,进行血清学分型和超广谱β-内酰胺酶(ESBLs)确证试验,采用PCR方法检测7种β-内酰胺类耐药基因。结果157株沙门菌中,分布有20种血清型,以鼠伤寒沙门菌和肠炎沙门菌为主。共127株检出耐药基因,检出率为80.89%,包括bla_(TEM)103株、bla_(CTX-M)79株、bla_(OXA-10)9株和bla_(SHV)1株,未检出bla_(PER)、bla_(CMY)和bla_(ACC)。ESBLs阳性80株,占50.96%;其中23株(28.75%)检出1种耐药基因,50株(62.50%)检出2种耐药基因,7株(8.75%)检出3种耐药基因;携带的耐药基因模式以bla_(CTX-M-1G)+bla_(TEM)(35株)、bla_(CTX-M-9G)+bla_(TEM)(14株)和bla_(CTX-M-9G)(12株)多见。ESBLs阴性77株,占49.04%;其中46株(59.74%)检出1种耐药基因,1株(1.30%)检出2种耐药基因,30株(38.96%)未检出耐药基因;携带的耐药基因模式以bla_(TEM)(46株)为主。对CTX耐药的沙门菌和对CTX不耐药的沙门菌bla_(CTX-M)的检出率差异有统计学意义(χ^(2)=83.366,P=0.000)。对CAZ耐药的沙门菌和对CAZ不耐药的沙门菌bla_(TEM)检出率差异无统计学意义(χ^(2)=0.268,P=0.384)。鼠伤寒沙门菌和肠炎沙门菌bla_(CTX-M-1G)和bla_(CTX-M-9G)的携带率差异有统计学意义(χ^(2)=6.285,P=0.012;χ^(2)=8.735,P=0.003)。bla_(TEM)在表型为CAZ耐药、CTX敏感或中介组,CTX耐药、CAZ敏感或中介组及CAZ和CTX均耐药组中的携带率差异无统计学意义(χ^(2)=0.270,P=0.874)。结论耐三代头孢菌素沙门菌携带的耐药基因以bla_(TEM)和bla_(CTX-M)为主,同时伴有bla_(OXA-10)和bla_(SHV),呈多样性,需要持续监测和研究。

Objective To learn the distribution of drug resistance genes of the third-generation cephalosporin-resistant Salmonella to provide evidences for the prevention and treatment.Methods A total of 157 clinically isolated Salmonella strains resistant to cefotaxime(CTX)and/or ceftazidime(CAZ)were selected for serological typing and extended-spectrum β-lactamase(ESBLs)confirmation experiments,and then 7 genes resistant β-lactamase were detected by PCR.Results A total of 20 serotypes,mainly Salmonella typhimurium and Salmonella enteritidis,distributed among 157 strains of Salmonella.The resistance genes were detectable in 127 Salmonella strains with detection rate of 80.89%,including 103 strains of type bla_(TEM),79 of bla_(CTX-M),9 of bla_(OXA-10) and 1 of bla SHV,but no bla PER,bla CMY and bla ACC were detected.ESBLs were positive in 80 strains,accounting for 50.96%.One kind of resistance gene were detected in 23 strains(28.75%),2 kinds were detected in 50 strains(62.50%)and 3 kinds were detected in 7 strains(8.75%).The patterns of carried drug resistance gene were usually as bla_(CTX-M-1G)+bla_(TEM)(n=35),bla_(CTX-M-9G)+bla_(TEM)(n=14)and bla_(CTX-M-9G)(n=12).ESBLs negative was confirmed in 77 strains,accounting for 49.04%,among them 46 strains carried one resistance gene(59.74%),1 strain carried two resistance genes(1.30%)and 30 strains carried no resistance gene(38.96%).The mode of carried resistance gene was mainly bla_(TEM)(n=46).The difference of the detection rate of bla_(CTX-M) between the strains of Salmonella resistant to CTX and no resistant to CTX was statistically significant(χ^(2)=83.366,P=0.000).No statistically significant difference of the detection rate of bla_(TEM) between the stains of Salmonella resistant to CAZ and no resistant to CAZ was found(χ^(2)=0.268,P=0.384).The distribution of bla_(CTX-M-1G) and bla_(CTX-M-9G) between Salmonella typhimurium and Salmonella enteritidis was statistically different(χ^(2)=6.285,P=0.012;χ^(2)=8.735,P=0.003).There was no statistically significant difference for the carrying rate of bla_(TEM) among the phenotype of CAZ-resistant,CTX-sensitive or intermediary group,CTX-resistant,CAZ-sensitive or intermediary group and both CAZ and CTX-resistant groups(χ^(2)=0.270,P=0.874).Conclusion The third-generation cephalosporin-resistant Salmonella usually carried resistance genes bla_(TEM) and bla_(CTX-M),as well as bla_(OXA-10) and bla SHV,showing diversity,which deserved continuous monitoring and inverstigation.