陕西杨凌区市售食品中单增李斯特菌污染状况的调查与分析

Survey of Listeria monocytogenes from retail food in Yangling,Shaanxi

【目的】了解陕西杨凌辖区生猪肉、生羊肉、生鸡肉、速冻饺子和即食食品等5类食品中单增李斯特菌的污染情况及其耐药性和血清型,为确保食品安全提供依据。【方法】随机采集杨陵2家超市及1家农贸市场的食品样本共计95个,其中包括生猪肉27份、生羊肉11份、生鸡肉38份、速冻饺子6份和即食食品13份,按照国标GB/T4789.30-2008进行单增李斯特菌的分离培养,用PCR方法进行单增李斯特菌的确证,并用多重PCR法对确证菌株进行血清型测定,采用琼脂稀释法进行药敏性试验。【结果】95个样本中,单增李斯特菌的分离率为13.7%(13/95),其中以即食食品分离率最高,为30.8%(4/13);其次是生鸡肉和生羊肉,分别为21.1%(8/38)和9.1%(1/11);而速冻饺子和生猪肉均未检出单增李斯特菌。超市采集样品中单增李斯特菌污染的检出率较高,为23.6%,农贸市场采集样品中未检出单增李斯特菌。不同温度贮存的样品中,4℃贮存样品单增李斯特菌污染的检出率最高,为31.6%,-18℃条件贮存样品的检出率为5.9%,而常温贮存样品中未检出单增李斯特菌。单增李斯特菌对头孢西丁、红霉素、甲氧苄啶/磺胺甲恶唑、四环素、氯霉素、头孢哌酮的耐药率分别为100%,11.1%,14.8%,26%,4%和3.7%,对庆大霉素、环丙沙星、阿米卡星100%敏感。单增李斯特菌分属5个血清型群体,其中17(63.0%)株为1/2b或3b型,6株(22.2%)为1/2a或3a型,1株(3.7%)为1/2c或3c型,1株(3.7%)为4b、4d或4c型,2(7.4%)株为4a或4c型。【结论】陕西杨凌辖区即食食品和生鸡肉是主要污染单增李斯特菌的食品品种,该单增李斯特菌菌株存在一定程度的多重耐药现象,主要为1/2b或3b及1/2a或3a血清型,对消费者的健康有一定的潜在的危险。

【Objective】The aim of the present study was to investigate the presence,serotyping and antimicrobial susceptibility of Listeria monocytogenes（L.monocytogenes）strains isolated from food samples.【Method】A total of 95 food samples,including 27 pork,11 lamb,38 chicken,6 dumpling and 13 ready-to-eat food samples,were collected from two supermarkets and one open market in Yangling,Shaanxi province of China during March to April 2009 and screened for the presence of L.monocytogenes.All L.monocytogenes isolates were subjected to serotypes identification using PCR and antimicrobial susceptibility.【Result】Of the total 95 samples,the positive rates of L.monocytogenes were 13.7%.The most L.monocytogenes polluted samples were ready-to-eat food（30.8%）,followed by chicken（21.1%）and lamb（9.1%）.However,none was isolated from pork and frozen dumplings.The overall L.monocytogenes prevalence of food samples collected from supermarkets and open markets was 23.6% and 0,respectively,but differences were significant（P〈0.01）.The highest prevalence of S.aureus was on chicken carcasses stored at chilled temperature（4 ℃）（27.5%）,then at frozen temperature（5.9%）,whereas the lowest was observed in ambient food samples（0）.Resistances were common cefoxitin（100%）,followed by tetracycline（26%）,trimethoprimsulfamethoxazole（14.8%）,erythromycin（11.1%）,chloramphenicol（7.4%）,and cefoperazone（3.7%）,but none was resistant to gentamicin,ciprofloxacin,and amikcin.The L.monocytogenes isolates belonged to five serogroups,with serotype 1/2b or 3b being dominant（63.0%）,followed by 1/2a or 3a（22.2%）,4a or 4c（7.4%）,1/2c or 3c and 4b,4d or 4c（each 3.7%）.【Conclusion】Our findings indicate that readytoeat foods and raw chicken were mainly contaminated with L.monocytogenes,and many L.monocytogenes isolates exhibited multiple antimicrobial resistance.In addition,our data also indicate the widespread distribution of epidemiologically important serotypes（1/2b or 3b and 1/2a or 3a）of L.monocytogenes poses a potential risk to public health.