College of Food Science and Engineering, Northwest A & F University, Yangling, Shaanxi 712100, China.
Int J Food Microbiol. 2012 Feb 1;153(1-2):142-7. doi: 10.1016/j.ijfoodmicro.2011.10.030. Epub 2011 Nov 10.
Dry infant foods are not sterile and could be contaminated with various bacteria including certain pathogens. The aim of this study was to investigate the prevalence of Staphylococcus aureus in infant foods and to characterize these strains. A total of 367 infant food samples, including 143 samples of powdered infant formula milk (PIF) and 224 samples of infant rice cereal (IRC), were collected in the Shaanxi Province of China during the period of July to August 2010 and screened for S. aureus. All S. aureus isolates were characterized by antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE), and detection of genes encoding enterotoxins, exfoliative toxins, Panton-Valentine leukocidin (PVL), and toxic shock syndrome toxin 1. Among all the samples examined, sixteen of 143 PIF samples (11.2%) and 14 of 224 IRC samples (6.3%) were positive for S. aureus. From these positive samples, 29 S. aureus strains were isolated from PIF and 25 from IRC. Of these S. aureus isolates, 83.3% were resistant to at least one antimicrobial, 35.2% to three or more antimicrobials. Resistance was most frequently observed to erythromycin (75.9%), followed by ciprofloxacin (51.9%) and trimethoprim/sulfamethoxazole (27.8%), while significantly fewer isolates were resistant to gentamicin (22.2%), tetracycline (18.5%), or cefoxitin (3.7%). In addition, 63.0% of isolates were positive for one or more toxin genes tested. The three most predominant toxin genes were pvl (40.7%), seg (38.9%), and sec (18.5%), followed by sea (7.4%), seb (7.4%), sed (5.6%), and see (5.6%). The ets, tsst-1, seh, sei, and sej genes were not detected. A total of 39 PFGE patterns were generated among 51 selected food isolates. Our findings indicate that PIF and IRC in the Shaanxi province were contaminated with S. aureus, and many S. aureus isolates harbored multiple toxin genes and exhibited multiple antimicrobial resistance. In addition, these S. aureus isolates were genetically diverse. The presence of S. aureus strains in these infant foods poses a potential threat to infant health.
干燥的婴儿食品并非无菌，可能会受到各种细菌的污染，包括某些病原体。本研究旨在调查婴儿食品中金黄色葡萄球菌的流行情况，并对这些菌株进行特征描述。2010 年 7 月至 8 月期间，在中国陕西省采集了 367 份婴儿食品样本，包括 143 份配方奶粉和 224 份婴儿米粉，并对这些样本进行了金黄色葡萄球菌筛查。所有金黄色葡萄球菌分离株均通过药敏试验、脉冲场凝胶电泳（PFGE）和肠毒素、表皮剥脱毒素、杀白细胞素 Panton-Valentine （PVL）和中毒性休克综合征毒素 1 基因的检测进行了特征描述。在所检查的所有样本中，143 份配方奶粉中有 16 份（11.2%）和 224 份婴儿米粉中有 14 份（6.3%）呈金黄色葡萄球菌阳性。从这些阳性样本中，从配方奶粉中分离出 29 株金黄色葡萄球菌，从婴儿米粉中分离出 25 株。这些金黄色葡萄球菌分离株中，83.3%至少对一种抗菌药物耐药，35.2%对三种或更多种抗菌药物耐药。最常见的耐药药物为红霉素（75.9%），其次是环丙沙星（51.9%）和甲氧苄啶-磺胺甲噁唑（27.8%），而庆大霉素（22.2%）、四环素（18.5%）和头孢西丁（3.7%）的耐药率明显较低。此外，63.0%的分离株携带一种或多种测试的毒素基因。三个最主要的毒素基因是 pvl（40.7%）、seg（38.9%）和 sec（18.5%），其次是 sea（7.4%）、seb（7.4%）、sed（5.6%）和 see（5.6%）。未检测到 ets、tsst-1、seh、sei 和 sej 基因。在 51 株选定的食品分离株中，共产生 39 种 PFGE 模式。我们的研究结果表明，陕西省的配方奶粉和婴儿米粉受到了金黄色葡萄球菌的污染，许多金黄色葡萄球菌分离株携带多种毒素基因，并表现出多种抗菌药物耐药性。此外，这些金黄色葡萄球菌分离株具有遗传多样性。这些婴儿食品中金黄色葡萄球菌的存在对婴儿健康构成了潜在威胁。
