上海市鸡源单增李斯特菌株分子流行病学调查

Prevalence,Serotype Diversity,Antimicrobial Resistance and Biofilm Formation Capacity of Listeria monocytogenes Isolated from Chickens in Shanghai

为了解上海市大型超市售卖鸡肉中单增李斯特菌的污染情况,本研究于2018年7月从上海市的多个超市中随机采集冷藏鸡翅样品270份,并对分离菌株的耐药性、血清型及生物被膜形成能力进行测定。通过常规细菌学和分子鉴定方法共确定38株单增李斯特菌,总分离率为14.07%;对分离株采用PCR法进行血清学分型,结果显示分离株以血清型1/2a(3a)型为主(63.16%,24/38),血清型1/2c(3c)次之(36.84%,14/38);K-B法药敏试验结果显示分离菌株对头孢曲松的耐药性最高(52.63%),对诺美沙星(18.42%)和四环素(15.79%)次之,对头孢噻吩、庆大霉素、氨苄西林和阿莫西林的耐药率较低,均为5.26%,对新霉素、大观霉素、卡那霉素和氯霉素的耐药率最低,均为2.63%;所有分离株对诺氟沙星、环丙沙星和链霉素这3种药物均敏感,13.16%分离株表现出多重耐药现象,最多可耐受6种抗生素;结晶紫染色法测定生物被膜形成能力,结果表明所有菌株均能形成生物被膜,且84.21%(32/38)的分离菌株能形成较强生物被膜,其中1/2a(3a)和1/2c(3c)血清型分别占59.37%和40.63%。本研究结果表明上海市鸡肉源食品中单增李斯特菌污染情况比较严重,主要流行1/2a(3a)血清型,耐药模式多样且日趋严重,大多菌株具有强生物被膜形成能力,提示应进一步加强对动物源性食品中单增李斯特菌的监控,以降低食品安全问题带来的风险。

The objective of the present study was to investigate the prevalence of Listeria monocytogenes isolates in retail chickens of large supermarkets in Shanghai.A total of 270 frozen chicken wing samples were randomly collected in July 2018 and subject to bacterial isolation.Thirty eight samples(14.07%)were tested positive for L.monocytogenes and confirmed by both bacteriological and molecular methods.Serotyping of these isolates was performed by PCR method.The results showed that 63.16%(24/38)L.monocytogenes isolates were serotype 1/2a(3a)and 36.84%(14/38)were serotype 1/2c(3c).Then the antibiotic susceptibility test was performed by disk method.The results showed that these isolates had the highest drug resistance to ceftriaxone(52.63%)following by norfloxacin(18.42%),tetracycline(15.79%).The drug resistance was lower to cephalothiophene,gentamicin,ampicillin and amoxicillin(5.26%)and even lower to neomycin,macroamycin,kanamycin and chloramphenicol(2.63%).All isolates were susceptible to norfloxacin,ciprofloxacin and streptomycin.In addition,a number of isolates(13.16%)showed multiple drug resistance rate up to 6 antimicrobial agents.The biofilm formation ability was determined by crystal violet staining,and the result showed that all of these isolate produces biofilms,among which 84.21%(32/38)isolates had strong biofilm formation ability belonging to the major serovar 1/2a(3a)(59.37%)and serovar 1/2c(3c)(40.63%).This study indicated that the contamination of L.monocytogenes in chicken samples was a severe condition in Shanghai as the isolates had multiple drug resistance and strong biofilm formation ability.The results suggested a necessity to inspect and survey theL.monocytogenes contamination in meat foods to reduce the incidence of foodborne infections in humans.