Investigation of Plasmid-mediated Quinolone Resistance in Escherichia coli

• Main Authors: Chih-Chun Hsu, 許智珺
• Other Authors: Hung-Chih Kuo
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/24933103083969730878

碩士 === 國立嘉義大學 === 獸醫學系研究所 === 103 === Escherichia coli (E. coli) can cause serious disease in human and animals. In economic animal, E. coli infection may cause of diarrhea, respiratory disease and arthritis. Fluoroquinolones have been used effectively against E. coli infections. The mechanisms of quinolone resistance were initially identified to be mediated by mutations located in the quinolone resistance-determining region (QRDR) of the gyrA and parC genes. To date, three types of plasmid-mediated quinolone resistance (PMQR) determinants, including a Qnr-mediated inhibition of quinolone binding to DNA, a QepA encoded efflux pump, and the AAC(6’)-Ib-cr mediated fluoroquinolones (FQ) acetylation, have been identified in clinical isolates. In this study, E. coli were isolated from clinical case which were sent to the College of Agriculture Animal Disease Diagnostic Center and Veterinary Teaching Hospital of 國立嘉義大學 in 2011-2014. The results showed that 1,291 isolates of E. coli from animal. E. coli were chosen according to Clinical and Laboratory Standards Institute (CLSI) guidelines, minimal inhibitory concentration test (MIC) was used for antimicrobial susceptibility testing. The percentage of susceptibility of swine, canine, chicken, turkey, duck and goose isolates for FLU were 28.82 %, 62.86 %, 21.17 %, 30.95 %, 36.00 % and 26.79 %, respectively. The percentage of susceptibility of these isolates for ENR were 52.49 %, 84.29 %, 44.85 %, 54.76 %, 56.00 % and 51.79 %, respectively. All isolates were screened for the presence of PMQR determinants. Of the 1,291 E. coli isolates, 14.10 % (182/1,291) harbored at least one PMQR gene. The most common PMQR gene was qnrS (9.68 %), followed by aac(6’)-ib-cr (4.34 %) and qnrB (0.31 %). None of these isolates were positive for qnrA, qnrC, qnrD or qepA. PCR amplifications in QRDR of the gyrA and parC genes among PMQR-positive isolates were carried out using specific primers, and all PCR products were sequenced and analysed. E. coli isolates susceptibility to all tested fluoroquinolones can’t find QRDR mutation. GyrA Serine83Leucine/Alanine or Aspartic acid87Glycine was detected in isolates resistant to NAL. Two QRDR mutations were detected in isolates possessed high level resistance to NAL and FLU, whereas isolates with further resistance to other fluoroquinolones had in addition 1 or 2 QRDR mutation. These results indicated that fluoroquinolone resistance of E. coli isolates with PMQR and QRDR mutation was serious. The number of mutations in QRDR correlated significantly with the quinolone MICs (p＜0.01). According to the statistical analysis results, economic animal E. coli isolates susceptibility to all tested fluoroquinolones are significantly lower than canine E. coli isolates (p＜0.05). Based on our study results, conservative use of antimicrobial agents in animal farms in Taiwan is strongly recommended.