我国部分地区即食食品和蔬菜中金黄色葡萄球菌污染分布及耐药和基因分型情况

【目的】系统调查了我国15个代表性城市在即食食品(卤肉、烤肉、凉拌菜和巴氏奶)和蔬菜样品中金黄色葡萄球菌(Staphylococcus aureus)的污染分布情况,并对分离株进行耐药性分析及多位点序列分型(Multilocus sequence typing,MLST)研究,为食源性金黄色葡萄球菌的风险识别和分子溯源提供基础数据。【方法】依据GB 4789.10-2010对540份即食食品和蔬菜样品进行定性和最大可能数(Most probable number,MPN)分析;采用K-B纸片扩散法检测金黄色葡萄球菌分离株的耐药特征并通过PCR检测mecA基因;应用MLST方法确证金黄色葡萄球菌的主要ST型。【结果】结果发现9.3%(50/540)的样品中检出金黄色葡萄球菌,其中卤肉污染率最高,为16.3%(30/184),其次为烤肉(9.2%,6/65),蔬菜(6/150,4.0%)污染率最低。定量分析发现62.0%的阳性样品污染水平处于0.3–1.0 MPN/g,其中3份阳性样品污染水平≥110 MPN/g。对50株分离株进行24种抗生素耐药性检测,发现82.0%的分离株对氨苄西林和青霉素耐药,64.0%的分离株为多重耐药株。对mecA阳性分离株进行SCCmec分型,发现均为SCCmecⅣa。所有分离株进行MLST分型,共检出14种型别,其中ST3595和ST3847为新ST型。【结论】普遍的多重耐药性表明我国食源性金黄色葡萄球菌的耐药状况已较为严重,对消费者的安全健康存在潜在威胁。ST型与耐药存在一定的关联性,这为进一步了解该菌在我国食品中的流行趋势和风险评估提供了科学的数据支撑。

Prevalence, antimicrobial susceptibility, and genetic characteristics of Staphylococcus aureus from retail ready-to-eat foods and vegetables in some regions of China

Objective] To investigate the prevalence, antimicrobial susceptibility, and genetic characteristics of Staphylococcus aureus from ready-to-eat foods (stewed meat, roast, salad and pasteurized milk) and vegetables from 15 representative cities of China and to provide baseline information for effective tracing S. aureus source and controlling food contamination.Methods] All samples were subjected to qualitative and most probable number (MPN) analysis for S. aureus according to the National Food Safety Standard-Food microbiological examination:S. aureus. Antimicrobial susceptibility of all isolates was evaluated using the Kirbye-Bauer disk diffusion and mecA-positive isolates was obtained by PCR. The sequence types of S. aureus were performed via multilocus sequence typing (MLST).Results] In total 540 food samples, 9.3% (50/540) were tested positive for S. aureus, of which the most polluted foods were stewed meat (16.3%, 30/184) followed by roast (9.2%, 6/65), and vegetable showed lowest prevalence (4.0%, 6/150). Most probable number (MPN) analysis showed that 62.0% samples were ranged from 0.3 to 1 MPN/g, and three samples exceeded 110 MPN/g. 82.0% isolates were resistant to ampicillin and penicillin G, and 64.0% isolates were multi-drug resistant. In addition, the mecA-positive isolates were both belonged to the SCCmecIVa subtype using staphylococcal cassette chromosome mec (SCCmec) typing. Furthermore, 14 sequence types (STs) were obtained by MLST, including two novel STs (ST3595 and ST3847).Conclusion] The general multi-drug resistance exhibited by S. aureus was still the most serious issue of common concern, which posing a health risk for consumers. In addition, the antimicrobial susceptibility of S. aureus was highly associated with STs. Therefore, it is necessary to provides scientific data for further analysis of epidemic trends and risk assessment of bacteria prevalent in foods.