Division of Microbiology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, United States.
Pacific Regional Laboratory-Southwest, U.S. Food and Drug Administration, Irvine, CA 92612, United States.
Int J Food Microbiol. 2015 Dec 2;214:12-17. doi: 10.1016/j.ijfoodmicro.2015.07.017. Epub 2015 Jul 16.
Food contaminated with extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica has emerged as an important global issue due to the international food-product trade. Therefore, the purpose of this study was to investigate whether imported food products can serve as a reservoir for non-typhoidal Salmonella (NTS) that can transmit β-lactam-resistance to humans through ingestion of the contaminated food. NTS isolates (n=110) were collected from various imported food products (n=3480) from 2011 to 2013. The NTS isolates were analyzed by serotyping, antimicrobial susceptibility tests, and plasmid profiling. Salmonella ser. Weltevreden, Salmonella ser. Newport, Salmonella ser. Senftenberg, Salmonella ser. Virchow, Salmonella ser. Enteritidis, Salmonella ser. Typhimurium, and Salmonella ser. Bareilly were the most prevalent serovars. Nine NTS strains were resistant to ampicillin and/or one or more cephalosporins (MIC>32 μg/mL). Polymerase chain reaction (PCR) detection revealed that all nine isolates carried the bla(TEM-1) β-lactamase gene, with or without the bla(CTX-M-9) or bla(OXA-1) genes. Two isolates, PSS_913 and PSS_988, exhibited decreased susceptibility to extended-spectrum cephalosporins and ampicillin. Plasmids ranging in size from less than 8 to over 165 kbp, from all of the 9 resistant isolates, belonged to the IncHI1, IncI1, IncN, or IncX groups. Conjugation experiments and Southern hybridization, using bla(TEM-1), confirmed the plasmid-mediated transfer of ESBL genes, which resulted in increased MICs of β-lactams for Escherichia coli transconjugants. The contamination of imported food products by NTS with conjugative plasmid-borne ESBL genes may contribute to the spread of ESBL-producing NTS and compromise the therapeutic activity of extended-spectrum β-lactam antibiotics.
食源性产extended-spectrum β-lactamase (ESBL)-的沙门氏菌enterica 已经成为一个重要的全球性问题，由于国际食品产品贸易。因此，本研究的目的是调查进口食品是否可以作为非伤寒沙门氏菌（NTS）的储存库，通过摄入受污染的食物将β-内酰胺耐药性传播给人类。从 2011 年至 2013 年，从各种进口食品（n=3480）中收集了 110 株 NTS 分离株。通过血清分型、抗菌药物敏感性试验和质粒谱分析对 NTS 分离株进行分析。沙门氏菌血清型 Weltevreden、沙门氏菌血清型 Newport、沙门氏菌血清型 Senftenberg、沙门氏菌血清型 Virchow、沙门氏菌血清型 Enteritidis、沙门氏菌血清型 Typhimurium 和沙门氏菌血清型 Bareilly 是最常见的血清型。9 株 NTS 株对氨苄西林和/或一种或多种头孢菌素（MIC>32μg/ml）耐药。聚合酶链反应（PCR）检测显示，所有 9 株分离株均携带 bla(TEM-1)β-内酰胺酶基因，无论是否携带 bla(CTX-M-9)或 bla(OXA-1)基因。PSS_913 和 PSS_988 两种分离株对头孢菌素和氨苄西林的敏感性降低。来自所有 9 株耐药分离株的大小从小于 8 至超过 165 kbp 的质粒属于 IncHI1、IncI1、IncN 或 IncX 组。接合实验和 Southern 杂交，使用 bla(TEM-1)，证实了 ESBL 基因的质粒介导转移，导致大肠杆菌转导体的β-内酰胺 MIC 增加。NTS 携带可接合质粒的 ESBL 基因污染进口食品可能导致 ESBL 产生 NTS 的传播，并损害扩展谱β-内酰胺抗生素的治疗活性。
