Department of Food Hygiene, Safety, and Technology, Faculty of Veterinary Medicine, Mansoura University, Mansoura, 35516, Egypt.
Faculty of Veterinary Medicine, Badr University in Cairo (BUC), Badr City, 11829, Cairo, Egypt.
Ann Clin Microbiol Antimicrob. 2024 Jul 4;23(1):61. doi: 10.1186/s12941-024-00713-3.
The emergence of multidrug-resistant (MDR) Salmonella strains, especially resistant ones toward critically important antimicrobial classes such as fluoroquinolones and third- and fourth-generation cephalosporins, is a growing public health concern. The current study, therefore, aimed to determine the prevalence, and existence of virulence genes (invA, stn, and spvC genes), antimicrobial resistance profiles, and the presence of β-lactamase resistance genes (bla, bla, bla, and bla) in Salmonella strains isolated from native chicken carcasses in Egypt marketed in Mansoura, Egypt, as well as spotlight the risk of isolated MDR, colistin-, cefepime-, and levofloxacin-resistant Salmonella enterica serovars to public health.
One hundred fifty freshly dressed native chicken carcasses were collected from different poultry shops in Mansoura City, Egypt between July 2022 and November 2022. Salmonella isolation was performed using standard bacteriological techniques, including pre-enrichment in buffered peptone water (BPW), selective enrichment in Rappaport Vassiliadis broth (RVS), and cultivating on the surface of xylose-lysine-desoxycholate (XLD) agar. All suspected Salmonella colonies were subjected to biochemical tests, serological identification using slide agglutination test, and Polymerase Chain Reaction (PCR) targeting the invasion A gene (invA; Salmonella marker gene). Afterward, all molecularly verified isolates were screened for the presence of virulence genes (stn and spvC). The antimicrobial susceptibility testing for isolated Salmonella strains towards the 16 antimicrobial agents tested was analyzed by Kirby-Bauer disc diffusion method, except for colistin, in which the minimum inhibition concentration (MIC) was determined by broth microdilution technique. Furthermore, 82 cefotaxime-resistant Salmonella isolates were tested using multiplex PCR targeting the β-lactamase resistance genes, including bla, bla, bla, and bla genes.
Salmonella enterica species were molecularly confirmed via the invA Salmonella marker gene in 18% (27/150) of the freshly dressed native chicken carcasses. Twelve Salmonella serotypes were identified among 129 confirmed Salmonella isolates with the most predominant serotypes were S. Kentucky, S. Enteritidis, S. Typhimurium, and S. Molade with an incidence of 19.4% (25/129), 17.1% (22/129), 17.1% (22/129), and 10.9% (14/129), respectively. All the identified Salmonella isolates (n = 129) were positive for both invA and stn genes, while only 31.8% (41/129) of isolates were positive for the spvC gene. One hundred twenty-one (93.8%) of the 129 Salmonella-verified isolates were resistant to at least three antibiotics. Interestingly, 3.9%, 14.7%, and 75.2% of isolates were categorized into pan-drug-resistant, extensively drug-resistant, and multidrug-resistant, respectively. The average MAR index for the 129 isolates tested was 0.505. Exactly, 82.2%, 82.2%, 63.6%, 51.9%, 50.4%, 48.8%, 11.6%, and 10.1% of isolated Salmonella strains were resistant to cefepime, colistin, cefotaxime, ceftazidime/clavulanic acid, levofloxacin, ciprofloxacin, azithromycin, and meropenem, respectively. Thirty-one out (37.8%) of the 82 cefotaxime-resistant Salmonella isolates were β-lactamase producers with the bla as the most predominant β-lactamase resistance gene, followed by bla and bla genes, which were detected in 21, 16, and 14 isolates respectively).
The high prevalence of MDR-, colistin-, cefepime-, and levofloxacin-resistant Salmonella serovars among Salmonella isolates from native chicken is alarming as these antimicrobials are critically important in treating severe salmonellosis cases and boost the urgent need for controlling antibiotic usage in veterinary and human medicine to protect public health.
多药耐药（MDR）沙门氏菌菌株的出现，尤其是对氟喹诺酮类和第三代和第四代头孢菌素等重要抗菌药物类别的耐药菌株，是一个日益严重的公共卫生问题。因此，本研究旨在确定从埃及曼苏拉市市场上销售的本地鸡胴体中分离出的沙门氏菌菌株的流行率和存在情况，以及毒力基因（invA、stn 和 spvC 基因）、抗微生物药物耐药谱和β-内酰胺酶耐药基因（bla、bla、bla 和 bla）的存在情况，并强调分离出的多药耐药、多粘菌素、头孢吡肟和左氧氟沙星耐药的沙门氏菌血清型对公共卫生的风险。
2022 年 7 月至 11 月期间，从埃及曼苏拉市的不同家禽店采集了 150 只新鲜处理的本地鸡胴体。使用包括预增菌在缓冲蛋白胨水中（BPW）、选择性增菌在瑞普斯维迪亚德肉汤（RVS）和在木糖-赖氨酸-去氧胆酸盐（XLD）琼脂表面培养在内的标准细菌学技术进行沙门氏菌分离。所有疑似沙门氏菌的菌落均进行生化试验、使用玻片凝集试验进行血清学鉴定和针对侵袭 A 基因（invA；沙门氏菌标记基因）的聚合酶链反应（PCR）。之后，所有分子验证的分离株均筛选毒力基因（stn 和 spvC）的存在情况。采用 Kirby-Bauer 纸片扩散法分析分离出的沙门氏菌菌株对 16 种抗菌药物的药敏试验，除多粘菌素外，最低抑菌浓度（MIC）采用肉汤微量稀释法测定。此外，用针对β-内酰胺酶耐药基因（bla、bla、bla 和 bla）的多重 PCR 检测 82 株头孢噻肟耐药的沙门氏菌分离株。
通过沙门氏菌标记基因 invA 分子确认 150 只新鲜处理的本地鸡胴体中有 18%（27/150）携带沙门氏菌。在 129 株确认的沙门氏菌分离株中鉴定出 12 种沙门氏菌血清型，其中最主要的血清型为肯塔基沙门氏菌、肠炎沙门氏菌、鼠伤寒沙门氏菌和莫拉德沙门氏菌，其发生率分别为 19.4%（25/129）、17.1%（22/129）、17.1%（22/129）和 10.9%（14/129）。所有鉴定的沙门氏菌分离株（n=129）均携带 invA 和 stn 基因，而只有 31.8%（41/129）的分离株携带 spvC 基因。129 株沙门氏菌验证分离株中有 121 株（93.8%）对至少三种抗生素耐药。有趣的是，3.9%、14.7%和 75.2%的分离株分别被归类为泛耐药、广泛耐药和多药耐药。129 株分离株的平均 MAR 指数为 0.505。确切地说，82.2%、82.2%、63.6%、51.9%、50.4%、48.8%、11.6%和 10.1%的分离沙门氏菌菌株分别对头孢吡肟、多粘菌素、头孢噻肟、头孢他啶/克拉维酸、左氧氟沙星、环丙沙星、阿奇霉素和美罗培南耐药。82 株头孢噻肟耐药的沙门氏菌分离株中，有 31 株（37.8%）为β-内酰胺酶产生菌，其中 bla 是最主要的β-内酰胺酶耐药基因，其次是 bla 和 bla 基因，分别在 21、16 和 14 株分离株中检测到。
从埃及曼苏拉市市场上销售的本地鸡胴体中分离出的沙门氏菌血清型中，多药耐药、多粘菌素、头孢吡肟和左氧氟沙星耐药的情况令人担忧，因为这些抗菌药物在治疗严重沙门氏菌病方面至关重要，这也迫切需要控制兽医和人类医学中抗生素的使用，以保护公众健康。
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