Drug Radiation Research Department, National Center for Radiation Research and Technology, Egyptian Atomic Energy Authority (EAEA), Cairo, 11787, Egypt.
Microbiology and Chemistry Department, Faculty of Science, Zagazig University, Zagazig, 44519, Egypt.
BMC Microbiol. 2023 May 12;23(1):127. doi: 10.1186/s12866-023-02873-2.
BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathogen, that is transmitted from a variety of animals, especially cattle to humans via contaminated food, water, feaces or contact with infected environment or animals. The ability of STEC strains to cause gastrointestinal complications in human is due to the production of Shiga toxins (sxt). However, the transmission of multidrug-resistance STEC strains are linked with a severity of disease outcomes and horizontal spread of resistance genes in other pathogens. The result of this has emerged as a significant threat to public health, animal health, food safety, and the environment. Therefore, the purpose of this study is to investigate the antibiogram profile of enteric E. coli O157 isolated from food products and cattle faeces samples in Zagazig City, Al-Sharkia, Egypt, and to reveal the presence of Shiga toxin genes stx1 and stx2 as virulence factors in multidrug-resistant isolates. In addition to this, the partial 16S rRNA sequencing was used for the identification and genetic recoding of the obtained STEC isolates. RESULTS: There was a total of sixty-five samples collected from different geographical regions at Zagazig City, Al-Sharkia-Egypt, which were divided into: 15 chicken meat (C), 10 luncheon (L), 10 hamburgers (H), and 30 cattle faeces (CF). From the sixty-five samples, only 10 samples (one from H, and 9 from CF) were identified as suspicious E. coli O157 with colourless colonies on sorbitol MacConkey agar media with Cefixime- Telurite supplement at the last step of most probable number (MPN) technique. Eight isolates (all from CF) were identified as multidrug-resistant (MDR) as they showed resistance to three antibiotics with multiple antibiotic resistance (MAR) index ≥ 0.23, which were assessed by standard Kirby-Bauer disc diffusion method. These eight isolates demonstrated complete resistance (100%) against amoxicillin/clavulanic acid, and high frequencies of resistance (90%, 70%, 60%,60%, and 40%) against cefoxitin, polymixin, erythromycin, ceftazidime, and piperacillin, respectively. Those eight MDR E. coli O157 underwent serological assay to confirm their serotype. Only two isolates (CF8, and CF13), both from CF, were showed strong agglutination with antisera O157 and H7, as well as resistance against 8 out of 13 of the used antibiotics with the highest MAR index (0.62). The presence of virulence genes Shiga toxins (stx1 and stx2) was assessed by PCR technique. CF8 was confirmed for carrying stx2, while CF13 was carrying both genes stx1, and stx2. Both isolates were identified by partial molecular 16S rRNA sequencing and have an accession number (Acc. No.) of LC666912, and LC666913 on gene bank. Phylogenetic analysis showed that CF8, and CF13 were highly homologous (98%) to E. coli H7 strain, and (100%) to E. coli DH7, respectively. CONCLUSION: The results of this study provides evidence for the occurrence of E. coli O157:H7 that carries Shiga toxins stx1 and/or stx2, with a high frequency of resistance to antibiotics commonly used in human and veterinary medicine, in Zagazig City, Al-Sharkia, Egypt. This has a high extent of public health risk posed by animal reservoirs and food products with respect to easy transmission causing outbreaks and transfer resistance genes to other pathogens in animal, human, and plants. Therefore, environmental, animal husbandry, and food product surveillance, as well as, clinical infection control, must be strengthened to avoid the extra spread of MDR pathogens, especially MDR STEC strains.
背景:产志贺毒素大肠杆菌(STEC)是一种人畜共患病病原体,通过受污染的食物、水、粪便或接触受感染的环境或动物,从各种动物(尤其是牛)传播给人类。STEC 菌株引起人类胃肠道并发症的能力归因于志贺毒素(stx)的产生。然而,多药耐药 STEC 菌株的传播与疾病结果的严重程度以及其他病原体中耐药基因的水平传播有关。这已成为对公共卫生、动物健康、食品安全和环境的重大威胁。因此,本研究的目的是调查埃及 Sharkia 省 Zagazig 市食品和牛粪便样本中分离的肠型大肠杆菌 O157 的抗生素谱,并揭示存在于多药耐药分离株中的志贺毒素基因 stx1 和 stx2 作为毒力因子。此外,还使用部分 16S rRNA 测序对获得的 STEC 分离株进行鉴定和遗传编码。
结果:从埃及 Sharkia 省 Zagazig 市的不同地理区域共采集了 65 个样本,分为:15 个鸡肉(C)、10 个午餐肉(L)、10 个汉堡(H)和 30 个牛粪便(CF)。在 65 个样本中,只有 10 个样本(一个来自 H,9 个来自 CF)被鉴定为可疑大肠杆菌 O157,在最可能数(MPN)技术的最后一步,在 Sorbitol MacConkey 琼脂培养基上具有无色菌落,添加头孢克肟- tellurite。8 个分离株(均来自 CF)被鉴定为多药耐药(MDR),因为它们对三种抗生素表现出耐药性,多重抗生素耐药性(MAR)指数≥0.23,这是通过标准 Kirby-Bauer 圆盘扩散法评估的。这 8 个分离株对阿莫西林/克拉维酸完全耐药(100%),对头孢西丁、多粘菌素、红霉素、头孢他啶和哌拉西林的耐药频率分别为 90%、70%、60%、60%和 40%。这 8 个 MDR 大肠杆菌 O157 进行血清学检测以确认其血清型。只有两个分离株(CF8 和 CF13),均来自 CF,与 O157 和 H7 抗血清强烈凝集,并且对 13 种抗生素中的 8 种具有最高 MAR 指数(0.62)的抗生素耐药。通过 PCR 技术评估了志贺毒素(stx1 和 stx2)毒力基因的存在。CF8 被证实携带 stx2,而 CF13 携带 stx1 和 stx2 两种基因。两个分离株均通过部分分子 16S rRNA 测序鉴定,在基因库中的登录号(Acc. No.)为 LC666912 和 LC666913。系统发育分析表明,CF8 和 CF13 与大肠杆菌 H7 株高度同源(98%),与大肠杆菌 DH7 株完全同源(100%)。
结论:本研究结果表明,在埃及 Sharkia 省 Zagazig 市,存在携带志贺毒素 stx1 和/或 stx2 的大肠杆菌 O157:H7,对人类和兽医常用的抗生素具有高频耐药性。这对动物和食品产品中的动物宿主构成了高度的公共卫生风险,容易引起暴发,并将耐药基因转移到动物、人类和植物中的其他病原体。因此,必须加强环境、畜牧业和食品产品监测以及临床感染控制,以避免多药耐药病原体,特别是多药耐药 STEC 菌株的进一步传播。
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