title: Antimicrobial Resistance ofSalmonella entericaSerovar Typhimurium in Shanghai, China.
abstract: We aimed to analyze the antimicrobial resistance phenotypes and to elucidate the molecular mechanisms underlying resistance to cephalosporins, ciprofloxacin, and azithromycin inSalmonella entericaserovar Typhimurium isolates identified from patients with diarrhea in Shanghai. The isolates showed high rates of resistance to traditional antimicrobials, and 20.6, 12.7, and 5.5% of them exhibited decreased susceptibility to cephalosporins, ciprofloxacin, and azithromycin, respectively. Notably, 473 (84.6%) isolates exhibited multidrug resistance (MDR), including 161 (28.8%) isolates that showed an ACSSuT profile. Twenty-two MDR isolates concurrently exhibited decreased susceptibility to cephalosporins and ciprofloxacin, and six of them were co-resistant to azithromycin. Of all the 71 isolates with decreased susceptibility to ciprofloxacin, 65 showed at least one mutation (D87Y, D87N, or D87G) ingyrA, among which seven isolates simultaneously had mutations ofparC(S80R) (n= 6) orparC(T57S/S80R) (n= 1), while 49 isolates with either zero or one mutation ingyrAcontained plasmid-mediated quinolone resistance (PMQR) genes includingqnrB, qnrS, and aac(6')-Ib-cr. Among the 115 cephalosporin-resistant isolates, the most common ESBL gene wasblaCTX-M, followed byblaTEM-1,blaOXA-1, andblaSHV -12. Eight subtypes ofblaCTX-Mwere identified andblaCTX-M-14(n= 22) andblaCTX-M-55(n= 31) were found to be dominant. To the best of our knowledge, this is the first report of the presence ofblaCTX-M-123andblaCTX-M-125inS.Typhimurium. Besides,mphAgene was identified in 15 of the 31 azithromycin-resistant isolates. Among the 22 isolates with reduced susceptibility to cephalosporins and ciprofloxacin, 15 contained ESBL and PMQR genes. Coexistence of these genes lead to the emergence of MDR and the transmission of them will pose great difficulties inS.Typhimurium treatments. Therefore, surveillance for these MDR isolates should be enhanced.
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical SciencesBeijing, China; Western Theater CommandTianshui, China.
authors.forename: Jinyan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical SciencesBeijing, China; The Key laboratory of Pharmacology and Molecular Biology, Medical College, Henan University of Science and TechnologyLuoyang, China.
authors.forename: Yongrui
authors.initials: Y
authors.lastname: Li
authors.affiliation: Shanghai Municipal Center for Disease Control and Prevention Shanghai, China.
authors.forename: Xuebin
authors.initials: X
authors.lastname: Xu
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Beibei
authors.initials: B
authors.lastname: Liang
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Fuli
authors.initials: F
authors.lastname: Wu
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Yang
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Qiuxia
authors.initials: Q
authors.lastname: Ma
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Chaojie
authors.initials: C
authors.lastname: Yang
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Hu
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Liu
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Chunyu
authors.initials: C
authors.lastname: Sheng
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Xie
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Xinying
authors.initials: X
authors.lastname: Du
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Rongzhang
authors.initials: R
authors.lastname: Hao
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Shaofu
authors.initials: S
authors.lastname: Qiu
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Song
keywords: ESBL; PMQR; Salmonella; azithromycin; ciprofloxacin