Bacterial Epidemiology and Antimicrobial Resistance Research Unit, Agricultural Research Service, U.S. Department of Agriculture Athens, GA, USA.
Front Microbiol. 2013 May 23;4:135. doi: 10.3389/fmicb.2013.00135. eCollection 2013.
The prevalence of antimicrobial resistance (AR) in bacteria isolated from U.S. food animals has increased over the last several decades as have concerns of AR foodborne zoonotic human infections. Resistance mechanisms identified in U.S. animal isolates of Salmonella enterica included resistance to aminoglycosides (e.g., alleles of aacC, aadA, aadB, ant, aphA, and StrAB), β-lactams (e.g., bla CMY-2, TEM-1, PSE-1), chloramphenicol (e.g., floR, cmlA, cat1, cat2), folate pathway inhibitors (e.g., alleles of sul and dfr), and tetracycline [e.g., alleles of tet(A), (B), (C), (D), (G), and tetR]. In the U.S., multi-drug resistance (MDR) mechanisms in Salmonella animal isolates were associated with integrons, or mobile genetic elements (MGEs) such as IncA/C plasmids which can be transferred among bacteria. It is thought that AR Salmonella originates in food animals and is transmitted through food to humans. However, some AR Salmonella isolated from humans in the U.S. have different AR elements than those isolated from food animals, suggesting a different etiology for some AR human infections. The AR mechanisms identified in isolates from outside the U.S. are also predominantly different. For example the extended spectrum β-lactamases (ESBLs) are found in human and animal isolates globally; however, in the U.S., ESBLs thus far have only been found in human and not food animal isolates. Commensal bacteria in animals including Escherichia coli and Enterococcus spp. may be reservoirs for AR mechanisms. Many of the AR genes and MGEs found in E. coli isolated from U.S. animals are similar to those found in Salmonella. Enterococcus spp. isolated from animals frequently carry MGEs with AR genes, including resistances to aminoglycosides (e.g., alleles of aac, ant, and aph), macrolides [e.g., erm(A), erm(B), and msrC], and tetracyclines [e.g., tet(K), (L), (M), (O), (S)]. Continuing investigations are required to help understand and mitigate the impact of AR bacteria on human and animal health.
美国食品动物分离的细菌中抗菌药物耐药性（AR）的流行在过去几十年中有所增加，同时人们对 AR 食源性病原体感染的担忧也有所增加。在美国动物分离的沙门氏菌中鉴定出的耐药机制包括对氨基糖苷类药物的耐药性（例如，aacC、aadA、aadB、ant、aphA 和 StrAB 的等位基因）、β-内酰胺类药物（例如，bla CMY-2、TEM-1、PSE-1）、氯霉素（例如，floR、cmlA、cat1、cat2）、叶酸途径抑制剂（例如，sul 和 dfr 的等位基因）和四环素[例如，tet(A)、(B)、(C)、(D)、(G)和 tetR 的等位基因]。在美国，沙门氏菌动物分离株中的多药耐药（MDR）机制与整合子或移动遗传元件（MGEs）有关，例如可在细菌之间转移的 IncA/C 质粒。人们认为 AR 沙门氏菌起源于食品动物，并通过食物传播给人类。然而，从美国人类中分离出的一些 AR 沙门氏菌与从食品动物中分离出的 AR 沙门氏菌具有不同的 AR 元素，这表明一些 AR 人类感染的病因不同。在美国以外地区分离出的 AR 机制也主要不同。例如，扩展谱β-内酰胺酶（ESBLs）在全球范围内的人类和动物分离株中均有发现；然而，在美国，迄今为止仅在人类而非食品动物分离株中发现了 ESBLs。动物中的共生菌，如大肠杆菌和肠球菌属，可能是 AR 机制的储库。从美国动物分离的大肠杆菌中发现的许多 AR 基因和 MGEs与沙门氏菌中的基因相似。从动物中分离的肠球菌属经常携带 AR 基因的 MGEs，包括对氨基糖苷类药物（例如，aac、ant 和 aph 的等位基因）、大环内酯类[例如，erm(A)、erm(B)和 msrC]和四环素类[例如，tet(K)、(L)、(M)、(O)、(S)]的耐药性。需要进行持续的研究，以帮助了解和减轻 AR 细菌对人类和动物健康的影响。
