Genetic Determinants of Resistance to Extended-Spectrum Cephalosporin and Fluoroquinolone in Escherichia coli Isolated from Diseased Pigs in the United States
Investigation published in mSphere
October 28th, 2020
Fluoroquinolones and cephalosporins are critically important antimicrobial classes for both human and veterinary medicine. We previously found a drastic increase in enrofloxacin resistance in clinical Escherichia coli isolates collected from diseased pigs from the United States over 10 years (2006 to 2016). However, the genetic determinants responsible for this increase have yet to be determined. The aim of the present study was to identify and characterize the genetic basis of resistance against fluoroquinolones (enrofloxacin) and extended-spectrum cephalosporins (ceftiofur) in swine E. coli isolates using whole-genome sequencing (WGS). blaCMY-2 (carried by IncA/C2, IncI1, and IncI2 plasmids), blaCTX-M (carried by IncF, IncHI2, and IncN plasmids), and blaSHV-12 (carried by IncHI2 plasmids) genes were present in 87 (82.1%), 19 (17.9%), and 3 (2.83%) of the 106 ceftiofur-resistant isolates, respectively. Of the 110 enrofloxacin-resistant isolates, 90 (81.8%) had chromosomal mutations in gyrA, gyrB, parA, and parC genes. Plasmid-mediated quinolone resistance genes [qnrB77, qnrB2, qnrS1, qnrS2, and aac-(6)-lb′-cr] borne on ColE, IncQ2, IncN, IncF, and IncHI2 plasmids were present in 24 (21.8%) of the enrofloxacin-resistant isolates. Virulent IncF plasmids present in swine E. coli isolates were highly similar to epidemic plasmids identified globally. High-risk E. coli clones, such as ST744, ST457, ST131, ST69, ST10, ST73, ST410, ST12, ST127, ST167, ST58, ST88, ST617, ST23, etc., were also found in the U.S. swine population. Additionally, the colistin resistance gene (mcr-9) was present in several isolates. This study adds valuable information regarding resistance to critical antimicrobials with implications for both animal and human health
Singh SH., Lim S., Hong S., Elnekave E., Johnson T., Rovira A., Vannucci F., Clayton JB., Perez AM. and Alvarez J..
 | Department of Veterinary Population Medicine. College of Veterinary Medicine. University of Minnesota (UMM). |
| Department of Biology. University of Nebraska at Omaha. | |
| Bioinformatics and Computational Biology Program. University of Minnesota (UMM). |
| Department of Microbiology and Immunology. Rega Institute. KU Leuven—University of Leuven. | |
| Department of Veterinary and Biomedical Sciences. Veterinary Diagnostic Laboratory. College of Veterinary Medicine. University of Minnesota (UMM). |
| Nebraska Food for Health Center. University of Nebraska. | |
 | Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM). |
| Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM). |
