Bacterial Epidemiology and Antimicrobial Resistance Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Athens, Georgia 30605, USA.
Microb Drug Resist. 2011 Sep;17(3):407-18. doi: 10.1089/mdr.2010.0189. Epub 2011 Apr 3.
Multidrug-resistant (MDR) Salmonella enterica serovar Typhimurium is the most prevalent penta-resistant serovar isolated from animals by the U.S. National Antimicrobial Resistance Monitoring System. Penta-resistant isolates are often resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline. To investigate MDR in Salmonella Typhimurium (including variant 5-), one isolate each from cattle, poultry, and swine with at least the ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline phenotype were selected for each year from 1997 to 2007 (n = 33) for microarray analysis of antimicrobial resistance, incompatibility IncA/C, and HI1 plasmid genes. Cluster analysis based on these data separated 31 of the isolates into two groups A and B (15 and 16 isolates, respectively). Isolates in group A were phage type DT104 or U302 and were mostly swine isolates (7/15). Genes detected included intI1, bla(PSE-1), floR, aadA, sulI, tet(G), and tetR, which are often found in Salmonella Genomic Island I. Isolates in group B had numerous IncA/C plasmid genes detected and were mostly cattle isolates (9/16). Genes detected included bla(CMY-2), floR, aac(3), aadA, aphA1, strA, strB, sulI, sulII, dfrA, dhf, tet(A)(B)(C)(D), and tetR, which are often found on MDR-AmpC IncA/C plasmids. The IncA/C replicon was also detected in all group B isolates. The two remaining isolates did not cluster with any others and both had many HI1 plasmid genes detected. Linkage disequilibrium analysis detected significant associations between plasmid replicon type, phage type, and animal source. These data suggest that MDR in Salmonella Typhimurium is associated with DT104/Salmonella Genomic Island I or IncA/C MDR-AmpC encoding plasmids and these genetic elements have persisted throughout the study period.
多重耐药（MDR）鼠伤寒沙门氏菌血清型是美国国家抗菌药物耐药性监测系统从动物中分离出的最普遍的五重耐药血清型。五重耐药株通常对氨苄西林、氯霉素、链霉素、磺胺甲恶唑和四环素耐药。为了研究鼠伤寒沙门氏菌（包括 5-型变体）的 MDR，从 1997 年到 2007 年，每年从牛、禽和猪中各选择一个至少具有氨苄西林、氯霉素、链霉素、磺胺甲恶唑和四环素表型的分离株，用于抗菌药物耐药性、不相容性 IncA/C 和 HI1 质粒基因的微阵列分析。基于这些数据的聚类分析将 31 个分离株分为两组 A 和 B（分别为 15 和 16 个分离株）。组 A 中的分离株为噬菌体型 DT104 或 U302，主要为猪分离株（15 个分离株中的 7 个）。检测到的基因包括 intI1、bla(PSE-1)、floR、aadA、sulI、tet(G)和 tetR，这些基因通常存在于沙门氏菌基因组岛 I 中。组 B 中的分离株检测到许多 IncA/C 质粒基因，主要为牛分离株（16 个分离株中的 9 个）。检测到的基因包括 bla(CMY-2)、floR、aac(3)、aadA、aphA1、strA、strB、sulI、sulII、dfrA、dhf、tet(A)(B)(C)(D)和 tetR，这些基因通常存在于 MDR-AmpC IncA/C 质粒上。IncA/C 复制子也在所有组 B 分离株中检测到。其余两个分离株与其他分离株没有聚类，并且都检测到许多 HI1 质粒基因。连锁不平衡分析检测到质粒复制子类型、噬菌体型和动物来源之间存在显著关联。这些数据表明，鼠伤寒沙门氏菌的 MDR 与 DT104/沙门氏菌基因组岛 I 或 IncA/C MDR-AmpC 编码质粒有关，这些遗传元件在整个研究期间一直存在。
