Zhao S, Qaiyumi S, Friedman S, Singh R, Foley S L, White D G, McDermott P F, Donkar T, Bolin C, Munro S, Baron E J, Walker R D
Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, USA.
J Clin Microbiol. 2003 Dec;41(12):5366-71. doi: 10.1128/JCM.41.12.5366-5371.2003.
Salmonella enterica serotype Newport isolates resistant to at least nine antimicrobials (including extended-spectrum cephalosporins), known as serotype Newport MDR-AmpC isolates, have been rapidly emerging as pathogens in both animals and humans throughout the United States. Resistance to extended-spectrum cephalosporins is associated with clinical failures, including death, in patients with systemic infections. In this study, 87 Salmonella serotype Newport strains were characterized by pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility testing and examined for the presence of class 1 integrons and bla(CMY) genes. Thirty-five PFGE patterns were observed with XbaI, and three of these patterns were indistinguishable among isolates from humans and animals. Fifty-three (60%) Salmonella serotype Newport isolates were identified as serotype Newport MDR-AmpC, including 16 (53%) of 30 human isolates, 27 (93%) of 29 cattle isolates, 7 (70%) of 10 swine isolates, and 3 (30%) of 10 chicken isolates. However, 28 (32%) Salmonella serotype Newport isolates were susceptible to all 16 antimicrobials tested. The bla(CMY) gene was present in all serotype Newport MDR-AmpC isolates. Furthermore, the plasmid-mediated bla(CMY) gene was transferable via conjugation to an Escherichia coli strain. The transconjugant showed the MDR-AmpC resistance profile. Thirty-five (40%) of the isolates possessed class 1 integrons. Sequence analyses of the integrons showed that they contained aadA, which confers resistance to streptomycin, or aadA and dhfr, which confer resistance to trimethoprim-sulfamethoxazole. One integron from a swine isolate contained the sat-1 gene, which encodes resistance to streptothricin, an antimicrobial agent that has never been approved for use in the United States. In conclusion, Salmonella serotype Newport MDR-AmpC was commonly identified among Salmonella serotype Newport isolates recovered from humans and food animals. These findings support the possibility of transmission of this organism to humans through the food chain.
肠炎沙门氏菌新港血清型分离株对至少九种抗菌药物（包括超广谱头孢菌素）耐药，即所谓的新港血清型多重耐药AmpC分离株，在美国动物和人类中作为病原体迅速出现。对超广谱头孢菌素的耐药性与全身感染患者的临床治疗失败（包括死亡）有关。在本研究中，通过脉冲场凝胶电泳（PFGE）和药敏试验对87株沙门氏菌新港血清型菌株进行了特征分析，并检测了1类整合子和bla(CMY)基因的存在情况。用XbaI观察到35种PFGE图谱，其中3种图谱在人和动物分离株中无法区分。53株（60%）沙门氏菌新港血清型分离株被鉴定为新港血清型多重耐药AmpC，包括30株人源分离株中的16株（53%）、29株牛源分离株中的27株（93%）、10株猪源分离株中的7株（70%）和10株鸡源分离株中的3株（30%）。然而，28株（32%）沙门氏菌新港血清型分离株对所有16种测试抗菌药物敏感。bla(CMY)基因存在于所有新港血清型多重耐药AmpC分离株中。此外，质粒介导的bla(CMY)基因可通过接合转移至大肠杆菌菌株。接合子表现出多重耐药AmpC耐药谱。35株（40%）分离株含有1类整合子。整合子的序列分析表明，它们含有赋予链霉素耐药性的aadA，或赋予甲氧苄啶-磺胺甲恶唑耐药性的aadA和dhfr。一株猪源分离株的一个整合子含有sat-1基因，该基因编码对链丝菌素的耐药性，链丝菌素是一种从未在美国获批使用的抗菌药物。总之，在从人和食用动物中分离出的沙门氏菌新港血清型分离株中，常见新港血清型多重耐药AmpC。这些发现支持了这种生物体通过食物链传播给人类的可能性。
