Salmonella Typhimurium與Salmonella Choleraesuis喹諾酮抗藥性決定區位突變型別與抗藥性能力之比較研究

Abstract

Fluoroquinolones are one of the alternative treatments for Salmonella infections with multi-drug resistance. However, the recent fluoroquinolone resistance results in more therapeutic failures and mortality. A total of 360 non-typhoidal Salmonella isolates were collected from humans and animals to compare quinolone resistance determine region (QRDR) mutations in S. Typhimurium and S. Choleraesuis with different MIC levels of quinolone resistance. The minimum inhibitory concentrations of nalidixic acid and ciprofloxacin were determined by broth microdilution method. Mutations of the QRDR regions (including gyrA, gyrB, parC and parE gene) were identified through sequencing after PCR. The results indicated that comparing to S. Typhimurium, more mutation patterns of QRDR regions were identified in S. Choleraesuis. In S. Typhimurium, the mutation Val87Gly of ParC but without any mutations of GyrA can mediate resistance to nalidixic acid and low level resistance to ciprofloxacin. However, the mutation Thr57Ser of ParC has to be accompanied by the mutations of GyrA to increase the MICs to resistant level of nalidixic acid and to reduce susceptibility for ciprofloxacin. The concurrence of the GyrA mutations (Ser83Phe and Asp87Gly) and the ParC mutation (Ser80Leu) led to the highest MICs of nalidixic acid and ciprofloxacin. The mutation of GyrA at position 83 led to resistance of nalidixic acid and low level resistance of ciprofloxacin. In S. Choleraesuis, The concurrent mutations of GyrA (Ser83Phe and Asp87Gly) and ParC (Thr57Ser and Ser80Arg) led to the highest MIC levels of nalidixic acid and ciprofloxacin. Although previous studies have shown that the mutation of GyrA at position 87 was associated with fluoroquinolone resistance, one isolate of S. Typhimurium and 14 isolates of S. Choleraesuis with the mutation Asp87Gly but no mutation at position 83 of GyrA was not associated with fluoroquinolone resistance. The results of this study show the difference of antimicrobial-resistant profiles and mutations of QRDR between S. Typhimurium and S. Choleraesuis. According to the similar observations in S. Typhimurium and S. Choleraesuis, this is the first study to show that mutation Asp87Gly but no mutation at position 83 of GyrA was not associated with fluoroquinolone resistance.