Dissemination and Characterization of Plasmids Carrying oqxAB-blaCTX-M Genes in Escherichia coli Isolates from Food-Producing Animals

• Published in: PloS one Vol. 8; no. 9; p. e73947
• Main Authors: Liu, Bao-Tao, Yang, Qiu-E, Li, Liang, Sun, Jian, Liao, Xiao-Ping, Fang, Liang-Xing, Yang, Shou-Shen, Deng, Hui, Liu, Ya-Hong
• Format: Journal Article
• Language: English
• Published: San Francisco Public Library of Science 09.09.2013
• Subjects: Acids; Animals; Antibiotics; Antimicrobial agents; Bacteria; Bacterial infections; Conjugation; Digestion; Drug resistance; E coli; Escherichia coli; Food; Gel electrophoresis; Genes; Gram-negative bacteria; Health care; Laboratories; Mutation; Nuclease; Plasmids; Pulsed-field gel electrophoresis; Southern blotting; Veterinarians; Veterinary colleges; Veterinary medicine; China
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0073947

Background The association of PMQR and ESBLs in negative-bacteria isolates has been of great concern. The present study was performed to investigate the prevalence of co-transferability of oqxAB and blaCTX-M genes among the 696 Escherichia coli (E. coli) isolates from food-producing animals in South China, and to characterize these plasmids. Methods The ESBL-encoding genes (blaCTX-M, blaTEM and blaSHV), and PMQR (qnrA, qnrB, qnrS, qnrC, qnrD, aac(6’)-Ib-cr, qepA, and oqxAB) of these 696 isolates were determined by PCR and sequenced directionally. Conjugation, S1 nuclease pulsed-field gel electrophoresis (PFGE) and Southern blotting experiments were performed to investigate the co-transferability and location of oqxAB and blaCTX-M. The EcoRI digestion profiles of the plasmids with oqxAB-blaCTX-M were also analyzed. The clonal relatedness was investigated by PFGE. Results Of the 696 isolates, 429 harbored at least one PMQR gene, with oqxAB (328) being the most common type; 191 carried blaCTX-M, with blaCTX-M-14 the most common. We observed a significant higher prevalence of blaCTX-M among the oqxAB-positive isolates (38.7%) than that (17.4%) in the oqxAB-negative isolates. Co-transferability of oqxAB and blaCTX-M was found in 18 of the 127 isolates carrying oqxAB-blaCTX-M. These two genes were located on the same plasmid in all the 18 isolates, with floR being on these plasmids in 13 isolates. The co-dissemination of these genes was mainly mediated by F33:A-: B- and HI2 plasmids with highly similar EcoRI digestion profiles. Diverse PFGE patterns indicated the high prevalence of oqxAB was not caused by clonal dissemination. Conclusion blaCTX-M was highly prevalent among the oqxAB-positive isolates. The co-dissemination of oqxAB-blaCTX-M genes in E. coli isolates from food-producing animals is mediated mainly by similar F33:A-: B- and HI2 plasmids. This is the first report of the co-existence of oqxAB, blaCTX-M, and floR on the same plasmids in E. coli.