Effects of citrox treatment on the survival of Methicillin-Resistant Staphylococcus aureus (MRSA) in chicken fillets packed under vacuum

Abstract Citrox has natural antibacterial effect against many foodborne pathogens and contaminated bacteria. It mainly contains citric acid, ascorbic acid, and malic acid. We studied the antimicrobial effects of citrox solution (1% and 2%) on the total viable count of methicillin-resistant Staphylococcus aureus (MRSA) on chicken meat fillet. The samples were treated with 106 CFU/g of meat, vacuum-packed (VP), and 4 °C for 3, 6, 9, 12, 15, 18, 21 days. We have also studied the effect of citrox on the total volatile basic nitrogen (TVBN) content and pH changes during the storage periods. The results revealed that citrox inhibited the growth of methicillin-resistant S. aureus (MRSA), in the chicken fillet. The total viable count of MRSA gradually decreased in all treated samples that were stored at 4 °C about 2 log cycle than Chicken-Staph groups after 3, 6, 9, and 12 days and about 1 log cycle than Chicken-Salt group after 3, 6, and 9 days of storage. Total volatile base nitrogen (TVB-N) were observed to be reduced in Chicken- Citrox-treated samples stored at 4 °C than Chicken-Staph, and Chicken-Salt treated samples. The results indicated that citrox is effective to reduce the total count of S. aureus (MRSA) in the first three days of storage by a reduction in the number of bacteria 1 log cycle.

摘要 Citrox对多种食源性致病菌及污染杂菌具有天然抗菌活性，其主要成分为柠檬酸、抗坏血酸与苹果酸。本研究探究了1%、2%浓度的Citrox溶液对鸡胸肉中耐甲氧西林金黄色葡萄球菌（methicillin-resistant Staphylococcus aureus, MRSA）总活菌数的抑菌效果。实验以每克肉样接种10^6菌落形成单位（CFU）的菌量处理样品，采用真空包装（vacuum-packed, VP），于4℃条件下分别贮藏3、6、9、12、15、18、21天。此外，本研究还考察了Citrox对贮藏期间总挥发性盐基氮（total volatile basic nitrogen, TVBN）含量及pH值变化的影响。结果表明，Citrox可有效抑制鸡胸肉中耐甲氧西林金黄色葡萄球菌（MRSA）的生长。在4℃贮藏条件下，经Citrox处理的所有样品中MRSA总活菌数均呈逐渐下降趋势；贮藏3、6、9、12天时，其活菌数较Chicken-Staph组低约2个对数级，贮藏3、6、9天时较Chicken-Salt组低约1个对数级。4℃贮藏条件下，经Citrox处理的鸡胸肉样品总挥发性盐基氮（TVB-N）含量低于仅接种MRSA组及盐水处理组。研究结果表明，Citrox可在贮藏前3天有效降低金黄色葡萄球菌（MRSA）的总菌数，细菌数量降幅可达1个对数级。