Food Science and Nutrition Department, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia.
Food Science and Nutrition Department, Faculty of Home Economics, Helwan University, Cairo, Egypt.
Biosci Rep. 2019 Nov 29;39(11). doi: 10.1042/BSR20191225.
Milk pasteurization eliminates vegetative pathogenic microorganisms and reduces microorganisms associated with spoilage. Camel milk is a well-accepted, traditionally consumed food in Arab countries. The present study aimed to investigate the microflora of pasteurized camel milk sold in Riyadh City, Saudi Arabia. The heat resistance of the microflora was tested in culture medium and lab-sterilized milk, and its composition was verified by multiplex polymerase chain reaction (PCR) using specific primers. Further verification was performed by using separate specific primers. The identified strain survived heat treatment at 65, 72, 80, 85, and 90°C for 30, 15, 10, 5, and 2 min, respectively. An unanticipated result was obtained when an enterotoxin producing strain of Staphylococcus aureus showed abnormal resistance to heat treatment. The enterotoxin gene within the PCR fragment was identified as enterotoxin C by DNA sequencing. During Basic Local Alignment Search Tool (BLAST) analysis, the isolated enterotoxin C genes showed >99% similarity to published database sequences of the Staphylococcus aureus strain SAI48 staphylococcal enterotoxin C variant v4 (sec) gene. The decimal reduction value (D-value) at 90°C (D90) was determined after 10 s. This is the first time to report this abnormally heat resistant and enterotoxin-producing strain of Staphylococcus aureus. The use of ultra-high temperatures (UHTs) is preferable for reducing or killing bacteria in camel milk, especially if this problem is encountered in many camel milk factories.
巴氏杀菌法可以消除营养体病原微生物，并减少与变质有关的微生物。骆驼奶是阿拉伯国家广泛接受的传统食品。本研究旨在调查沙特阿拉伯利雅得市销售的巴氏杀菌骆驼奶中的微生物菌群。在培养基和实验室消毒的牛奶中测试了微生物菌群的耐热性，并使用特定引物的多重聚合酶链反应（PCR）验证了其组成，进一步使用单独的特定引物进行了验证。鉴定出的菌株在 65、72、80、85 和 90°C 下分别经过 30、15、10、5 和 2 分钟的热处理后存活下来。金黄色葡萄球菌产肠毒素菌株对热处理表现出异常耐热性，这一结果出人意料。通过 DNA 测序鉴定 PCR 片段中的肠毒素基因是肠毒素 C。在基本局部比对搜索工具（BLAST）分析期间，分离的肠毒素 C 基因与金黄色葡萄球菌 SAI48 株金黄色葡萄球菌肠毒素 C 变体 v4（sec）基因的已发表数据库序列显示出>99%的相似性。在 90°C 下的十进制减少值（D90）在 10 秒后确定。这是首次报道这种异常耐热和产肠毒素的金黄色葡萄球菌菌株。超高温（UHT）更适合用于减少或杀死骆驼奶中的细菌，特别是如果在许多骆驼奶工厂中遇到这个问题。
