Molecular characterization of antimicrobial susceptibility of Salmonella isolates: First identification of a plasmid carrying qnrD or oqxAB in Taiwan

Cheng-Yen Kao; Chun-An Chen; Yi-Fang Liu; Hsiu-Mei Wu; Chien-Shun Chiou; Jing-Jou Yan; Jiunn-Jong Wu

doi:10.1016/j.jmii.2015.03.004

Molecular characterization of antimicrobial susceptibility of Salmonella isolates: First identification of a plasmid carrying qnrD or oqxAB in Taiwan

J Microbiol Immunol Infect. 2017 Apr;50(2):214-223. doi: 10.1016/j.jmii.2015.03.004. Epub 2015 May 14.

Authors

Cheng-Yen Kao¹, Chun-An Chen¹, Yi-Fang Liu¹, Hsiu-Mei Wu¹, Chien-Shun Chiou², Jing-Jou Yan³, Jiunn-Jong Wu⁴

Affiliations

¹ Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
² Centers for Disease Control, Taichung, Taiwan.
³ Department of Pathology, National Cheng Kung University Hospital, Tainan, Taiwan.
⁴ Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan; Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan. Electronic address: jjwu@mail.ncku.edu.tw.

PMID: 26055690
DOI: 10.1016/j.jmii.2015.03.004

Abstract

Background/purpose: The aim of this study is to characterize antibiotic-nonsusceptible Salmonella isolates in Taiwan.

Methods: A total of 76 Salmonella isolates showing lower susceptibility to cephalosporins or quinolones were identified from 1416 clinical isolates from 1999 to 2008. Minimal inhibitory concentrations for selected antimicrobial agents were tested by the agar dilution method. Antibiotic resistance-related genes were determined by polymerase chain reaction (PCR) combined with sequencing. Southern blotting, conjugation tests, and transformation tests were used to characterize plasmid-mediated quinolone resistance (PMQR) determinants.

Results: The observed nonsusceptible phenotypes of 76 isolates were against cefoxitin (57.9%), cefotaxime (43.4%), ceftazidime (40.8%), ceftriaxone (42.1%), cefepime (5.3%), ciprofloxacin (80.3%), and levofloxacin (81.6%). Among 44 cephalosporin-resistant isolates, TEM-1, CMY-2, CMY-14, CTX-M-3-like and CTX-M-15-like determinants were present in 31 (70.5%), 32 (72.7%), 1 (2.3%), 1 (2.3%), and 1 (2.3%) of isolates, respectively. PCR screening for PMQR genes of 62 quinolone-nonsusceptible isolates revealed the presence of qnrS, qnrD, aac(6')-Ib-cr, and oqxAB in 3 (4.8%), 2 (3.2%), 1 (1.6%), and 10 (16.1%) isolates, respectively. Among 36 isolates showing high resistance to quinolones, S83F/D87N and S83F/D87G amino acid substitutions of GyrA were found in 29 (80.6%) and 6 (16.7%) isolates, respectively. Moreover, among quinolone highly resistant isolates, eight (22.2%) of isolates showed over-expression of the PAβN-sensitive efflux pump. Transformants and transconjugants harboring qnrD- or oqxAB-plasmids showed decreased susceptibility to quinolones.

Conclusion: GyrA mutations are the major mechanisms associated with quinolone-resistant Salmonella isolates in Taiwan. Overproduction of efflux pump genes and the presence of qnr and oqxAB play additional roles in reduced susceptibility to quinolones.

Keywords: Salmonella; cephalosporin; oqxAB; plasmid-mediated quinolone resistance; qnrD.

MeSH terms

Anti-Bacterial Agents / pharmacology
Anti-Infective Agents / pharmacology*
Bacterial Proteins / genetics
Base Sequence
Cephalosporins / pharmacology*
DNA Gyrase / genetics
Drug Resistance, Multiple, Bacterial
Escherichia coli / genetics
Genes, Bacterial
Genotype
Humans
Microbial Sensitivity Tests / methods
Plasmids / genetics
Polymerase Chain Reaction
Quinolones / pharmacology*
Salmonella / drug effects*
Salmonella / genetics*
Salmonella / isolation & purification
Taiwan
beta-Lactamases / genetics

Substances

Anti-Bacterial Agents
Anti-Infective Agents
Bacterial Proteins
Cephalosporins
Quinolones
beta-Lactamases
DNA Gyrase