耐氟喹诺酮类鸡源性沙门氏菌DNA旋转酶gyrA基因序列分析

Nucleotide sequence of DNA gyrase gyrA gene of fluoroquinolones-resistant salmonella isolated from chickens

取临床分离的对5种氟喹诺酮类药物(环丙沙星、氧氟沙星、恩诺沙星、单诺沙星和沙拉沙星)均耐药的9株鸡源性沙门氏菌耐药株,提取其染色体DNA。设计引物gyrAF和gyrAR扩增其DNA旋转酶gyrA基因的氟喹诺酮类耐药决定区(QRDR),对PCR扩增产物进行测序及序列分析。与质控菌株相比,9株临床分离耐药株中只有菌株38和60的gyrA基因发生单碱基突变,菌株38的gyrA基因第371位碱基发生C→T突变,菌株60的gyrA基因第350位碱基发生A→C突变,两处突变均位于QRDR内,其余菌株的核苷酸未发生任何突变。菌株38的碱基突变导致gyrA基因第121位氨基酸发生R→C取代,即Arg→Cys;菌株60的碱基突变导致gyrA基因第114位氨基酸发生M→L取代,即Met→Leu。上述结果提示,gyrA基因QRDR突变并非沙门氏菌耐药性产生的主要原因。

Nine strains resistant to five fluoroquinolones （Ciprofloxacin, Ofloxacin, Enrofloxacin, Danofloxacin, Sarafloxacin） were isolated from clinical samples and extracted the chromosomal DNA of these strains. Designed primers to amplify the QRDR of gyrA, then the PCR products were sequenced and analyzed. In comparision with NCTC5776, a single mutation was found at base 371 in gyrA of strain 38 which changed from C to T, and a single mutation was found at base 350 in gyrA of strain 60 which changed from A to C. No mutation was found in gyrA of the rest. The mutation of strain 38 led to an amino acid substitution of Arg121Cys and the mutation of 60 led to an amino acid substitution of Met9114Leu. These results indicated that the mutation in QRDR of gyrA was not the major reason for fluoroquinolone resistance in salmonella.