Centers for Disease Control and Prevention, Atlanta, Georgia 30329, USA.
Microb Drug Resist. 2010 Dec;16(4):245-8. doi: 10.1089/mdr.2010.0028. Epub 2010 Jul 12.
To investigate azithromycin susceptibility in Shigella sonnei in the United States, we examined the azithromycin minimum inhibitory concentrations (MICs) of outbreak and routine human S. sonnei isolates. Isolate susceptibility clustered at 8 mg/L, but three isolates displayed higher MICs (>64 mg/L) to azithromycin. All three isolates contained a plasmid-encoded mphA gene, known to encode a macrolide-2'-phosphotransferase enzyme. Transformation of the mphA gene into Escherichia coli DH10B allowed the transfer of decreased susceptibility to azithromycin. Although these isolates might traditionally be defined as resistant, there are no established breakpoints for resistance to confirm that treatment of these isolates with azithromycin would fail, which complicates susceptibility screening.
为了研究美国宋内志贺菌对阿奇霉素的敏感性，我们检测了暴发和常规人类宋内志贺菌分离株的阿奇霉素最低抑菌浓度（MIC）。分离株的敏感性聚集在 8mg/L，但有 3 株对阿奇霉素的 MIC 值较高（>64mg/L）。这 3 株分离株均含有一个质粒编码的 mphA 基因，该基因编码一种大环内酯-2'-磷酸转移酶。mphA 基因转化为大肠杆菌 DH10B 可使阿奇霉素的敏感性降低。虽然这些分离株传统上可能被定义为耐药，但目前尚无耐药性的确定临界点来证实这些分离株用阿奇霉素治疗会失败，这使得药敏筛查变得复杂。
