Evaluation of the contribution of gyrA mutation and efflux pumps to fluoroquinolone and multidrug resistance in pathogenic Escherichia coli isolates from dogs and cats.
Evaluation of the contribution of gyrA mutation and efflux pumps to fluoroquinolone and multidrug resistance in pathogenic Escherichia coli isolates from dogs and cats.
复制标题
评估 gyrA 突变和外排泵对狗和猫致病性大肠杆菌分离株中氟喹诺酮和多药耐药性的贡献。
DOI：
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发表时间：
2011
影响因子：
1
通讯作者：
Calvin M. Johnson
中科院分区：
文献类型：
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作者：
B. Shaheen;D. Boothe;O. Oyarzabal;Chengming Wang;Calvin M. Johnson
目标
目的 研究 gyrA 突变和外排泵对狗和猫大肠杆菌分离株中氟喹诺酮类药物耐药性和多药耐药性的影响。
样本人群
536 株大肠杆菌临床分离株。
程序
通过肉汤微量稀释技术测定恩诺沙星和其他 6 种药物的最低抑菌浓度 (MIC)。采用实时PCR检测gyrA突变情况； Phe-Arg-β-萘酰胺（一种外排泵抑制剂）用于检查外排泵过度表达的贡献。
结果
氟喹诺酮类药物的 MIC 逐步增加，在没有突变的情况下最低，在单点突变的情况下较高，在 2 个点突变的情况下最高。后一类的阻力水平很高（断点的 8 倍），但这与 AcrAB 外排泵的表达有关。无论是否存在突变，外排泵的抑制都会导致 MIC 降低至 MIC ≤ 4 mg/L 的分离株的敏感断点以下。具有单一突变的分离株的 MIC 降低幅度最大（MIC 降低了 67 倍以上），但具有 2 个突变的分离株的 MIC 绝对降低幅度最大 (124 mg/L)。在具有多重耐药性的分离株中抑制 AcrAB 外排泵会降低结构上与氟喹诺酮无关的药物的 MIC。
结论和临床相关性
大肠杆菌对氟喹诺酮类药物的耐药性似乎是一种逐步现象，MIC随着gyrA点突变数量的增加而增加，但与氟喹诺酮类耐药相关的高水平耐药性和多药耐药性反映了AcrAB外排泵的过度表达。
OBJECTIVE
To investigate the contribution of gyrA mutation and efflux pumps to fluoroquinolone resistance and multidrug resistance among Escherichia coli isolates from dogs and cats.
SAMPLE POPULATION
536 clinical isolates of E coli.
PROCEDURES
Minimum inhibitory concentrations (MICs) were determined for enrofloxacin and 6 other drug classes by use of broth microdilution techniques. Real-time PCR assay was used to determine the mutation in gyrA; Phe-Arg-β-naphthylamide, an efflux pump inhibitor, was used to examine the contribution of efflux pump overexpression.
RESULTS
The MIC for fluoroquinolones increased in a stepwise fashion and was lowest in the absence of mutations, higher with a single point mutation, and highest with 2 point mutations. Level of resistance in the latter category was high (8 times the breakpoint), but this was associated with expression of the AcrAB efflux pump. Inhibition of the efflux pump resulted in a reduction in the MIC to less than the susceptible breakpoint for isolates with an MIC ≤ 4 mg/L, regardless of the presence of a mutation. The greatest magnitude in MIC decrease (MIC was decreased by a factor of > 67 fold) was for isolates with a single mutation but the greatest absolute decrease in MIC (124 mg/L) was for isolates with 2 mutations. Inhibition of the AcrAB efflux pump in isolates characterized by multidrug resistance decreased the MIC of drugs structurally unrelated to fluoroquinolone.
CONCLUSIONS AND CLINICAL RELEVANCE
Fluoroquinolone resistance in E coli appeared to be a stepwise phenomenon, with MIC increasing as the number of point mutations in gyrA increased, but high-level resistance and multidrug resistance associated with fluoroquinolone resistance reflected overexpression of the AcrAB efflux pump.