Antimicrobial Resistance and Resistance Gene Determinants in Clinical Escherichia coli from a Captive Population of Amur Tiger in China

Antimicrobial resistance has emerged in the past few years as a major problem and many programs have been set up for its surveillance in human and veterinary medicine. The purpose of this study was to investigate the abundance and diversity of extended-spectrum P-lactamase genes and fluoroquinolone resistance genes from a captive population of Amur tiger in China. Most isolates were susceptible to amoxicillin/clavulanic acid, aztreonam, polymyxin B, and also exhibited high incidence rates of resistance to ampicillin, doxycycline, chloramphenicol, tetracycline and trimethoprim sulfur. Two gene cassette arrangements (dfrA12-aadA2 and dfrA15) were identified. The most prevalent extended-spectrum p-lactamase (ESBL) genes identified were TEM which was detected in 80% (24/30) isolates. The prevalence of quinolone resistance-determining region (QRDR) determinants (gyrA, gyrB, parC and parE) were investigated in a collection of 30 ESBL producing enterobacterial isolates with reduced susceptibility to fluoroquinolones. DNA sequencing revealed point mutations in gyrA (Ser83-Leu, Asp87-Asn, Glu 214-Gly), gyrB (Ser195-->Asn), and parE (Ser85-->ALa). No mutations were observed in parC. The epidemiological relationship between positive isolates was studied by pulsed-field gel electrophoresis (PFGE). PFGE analysis revealed these isolates were grouped into eleven clusters at 95% similarity level. We have demonstrated the distribution of the class I integrons and found gene cassettes not previously reported in integrons among Escherichia coli strains isolated from a captive population of Amur tiger.