Elafify Mahmoud, Sadoma Noha M, Abd El Aal Salah F A, Bayoumi Mohamed A, Ahmed Ismail Tamer
Department of Food Hygiene and Control, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt.
Food Control Department, Faculty of Veterinary Medicine, Zagazig University, Zagazig 44519, Egypt.
Animals (Basel). 2022 Apr 4;12(7):922. doi: 10.3390/ani12070922.
The objectives of the current study were first to determine the prevalence of non O157:H7E. coli, especially Shiga toxin-producing Escherichia coli (STEC) in retailed milk and dairy products in Egypt. Second, the antimicrobial resistance profiling and virulence genes of the isolated E. coli strains were screened. Third, evaluation of the inhibitory effects of D-tryptophan against E. coli O26:H11 was further performed. The results revealed that 20% (30/150) of the samples were STEC positive, with 64 isolates harboring some virulent genes, such as Stx1, Stx2, eaeA, and hylA. Serological identification revealed four different pathotypes belonging to EPEC, ETEC, EHEC, and EIEC. Antimicrobial susceptibility testing revealed that 100%, 98.44%, 92.19%, 71.87%, 65.63% and 64.06% of the isolates had a resistance against tetracycline, oxacillin, erythromycin, nalidixic acid, sulphamethoxazol, and ampicillin, respectively. D-tryptophan addition (40 mM) to E. coli O26:H11-inoculated soft cheese and ice cream revealed a significant reduction (p < 0.05) in bacterial growth, especially when accompanied with other food stressors. D-Tryptophan is considered as an effective food preservative and as a promising alternative candidate in the dairy industry.
本研究的目的首先是确定埃及零售牛奶和乳制品中非O157:H7大肠杆菌，尤其是产志贺毒素大肠杆菌（STEC）的流行情况。其次，对分离出的大肠杆菌菌株进行抗菌药物耐药性分析和毒力基因筛查。第三，进一步评估D-色氨酸对大肠杆菌O26:H11的抑制作用。结果显示，20%（30/150）的样本为STEC阳性，有64株分离菌携带一些毒力基因，如Stx1、Stx2、eaeA和hylA。血清学鉴定显示有四种不同的致病型，分别属于肠致病性大肠杆菌（EPEC）、肠毒素性大肠杆菌（ETEC）、肠出血性大肠杆菌（EHEC）和肠侵袭性大肠杆菌（EIEC）。抗菌药物敏感性测试显示，分别有100%、98.44%、92.19%、71.87%、65.63%和64.06%的分离菌对四环素、苯唑西林、红霉素、萘啶酸、磺胺甲恶唑和氨苄青霉素耐药。在接种了大肠杆菌O26:H11的软奶酪和冰淇淋中添加D-色氨酸（40 mM）后，细菌生长显著减少（p < 0.05），尤其是在伴有其他食品应激因素时。D-色氨酸被认为是一种有效的食品防腐剂，也是乳制品行业中一个有前景的替代候选物。
