title: Decreased Susceptibility to Azithromycin Among Clinical Shigella Isolates from China.
abstract: The aim of this study was to detect the decreased susceptibility to azithromycin (DSA) and associated mechanisms in Shigella from China. Three hundred and ninety-two Shigella isolates, including 134 Shigella flexneri and 258 Shigella sonnei isolates, were examined for minimum inhibitory concentrations (MICs) and zone sizes to azithromycin by broth microdilution and disk diffusion methods, respectively. The MICs were compared with corresponding zone diameters to find whether there was uniformity between both tests. Twelve macrolide-resistant genes located on mobile elements were determined for the DSA isolates by PCR, and chromosomal efflux pump activity was analyzed using Phe-Arg-β-naphthylamide inhibition test and quantitative real-time PCR. Shigella isolates displayed MICs of 0.125-512 μg/ml and zone sizes of 6-26 mm against azithromycin. There were 80 (20.4%) isolates to be DSA. No significant difference was found between the DSA rates of S. flexneri and S. sonnei isolates (p = 0.052). There was an intimate relativity between MICs and zone diameters (p < 0.001). Only the plasmid-borne mphA conferring high-level DSA was detected in 55.0% (44/80) DSA-Shigella isolates. This study highlighted the prevalence of DSA-Shigella and mphA in the region studied. Clinical laboratories and clinicians should pay attention to the elevated azithromycin MICs in Shigella spp.
authors.affiliation: 1 Department of Clinical Laboratory, Zhejiang Xiaoshan Hospital , Hangzhou, China .
authors.forename: Chuanling
authors.initials: C
authors.lastname: Zhang
authors.affiliation: 2 Department of Clinical Laboratory, Shanghai General Hospital, School of Medicine, Shanghai Jiaotong University , Shanghai, China .
authors.forename: Rulin
authors.initials: R
authors.lastname: Zhang
authors.affiliation: 2 Department of Clinical Laboratory, Shanghai General Hospital, School of Medicine, Shanghai Jiaotong University , Shanghai, China .
authors.forename: Qi
authors.initials: Q
authors.lastname: Yu
authors.affiliation: 1 Department of Clinical Laboratory, Zhejiang Xiaoshan Hospital , Hangzhou, China .
authors.forename: Xu
authors.initials: X
authors.lastname: Chu
authors.affiliation: 3 Department of Clinical Microbiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine , Shanghai, China .
authors.forename: Jingyong
authors.initials: J
authors.lastname: Sun
authors.affiliation: 2 Department of Clinical Laboratory, Shanghai General Hospital, School of Medicine, Shanghai Jiaotong University , Shanghai, China .
authors.forename: Qingzhong
authors.initials: Q
authors.lastname: Liu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism; D017963:Azithromycin / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D002681:China / Q000453:epidemiology; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004405:Dysentery, Bacillary / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D015870:Gene Expression; D006801:Humans; D008826:Microbial Sensitivity Tests; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D012763:Shigella flexneri / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D012764:Shigella sonnei / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C029772:arginine beta-naphthylamide; D017963:Azithromycin; D001120:Arginine; D017853:Phosphotransferases (Alcohol Group Acceptor)
keywords: Enterobacteriaceae; antimicrobial; microbial drug resistance; minimum inhibitory concentrations (MICs); polymerase chain reaction (PCR)