Identification of risk factors associated with antimicrobial resistance in equine fecal Escherichia coli isolates.

Antimicrobial resistance is a growing global problem that will need a multinational collaborative effort to overcome this serious challenge. The aim of the study is to investigate the potential risk factors associated with the prevalence and distribution of antimicrobial-resistance genes (ARGs) of Escherichia coli isolates obtained from equine fecal samples. One hundred and eighteen horses from different geographical locations and management systems were enrolled in the study and a questionnaire containing information about each individual horse was designed and filled. The enrolled horses belonged to 2 main categories (Hospitalized horses (n = 31), and Non hospitalized horses (n = 87)). In total, 103 E. coli isolates were collected from the 118 horse fecal samples. Genes that are responsible for resistance to β-lactams, tetracyclines, aminoglycosides, and trimethoprim were detected using uniplex and multiplex polymerase chain reaction (PCR). The prevalence of antimicrobial resistance was significantly higher in hospitalized horses compared to non-hospitalized ones (p ≤ .05), particularly against (trimethoprim, doxycycline, oxytetracycline, and amoxicillin-clavulanic acid). The most prevalent antimicrobial-resistant genes were aminoglycoside resistant genes (strA, strB, and aadA) in percentages; 89%, 85%, and 84%, respectively. Statistical analysis revealed a significant association between risk factors and occurrence of ARGs (p ≤ .05). Significant risk factors include the last treatment and history of antimicrobial administration, breed of horses, use of horses, type of diet fed for horses, practice management and history of last illness. Tetracycline-resistance gene (tetA) was 23 times more likely to be found in the Arabian and local breeds of horses compared to English and warmblood breed. TetA is also 8 times more likely to be found in horses that were fed a natural diet compared to other horses that were fed manufactured/ processed feed. In conclusion, E. coli bacterium can harbor high resistance to different classes of antimicrobials which increases the risk of potential uncontrolled transmission of the multi-drug resistant E. coli bacterium to veterinarians and horse handlers, as well as to the equine population itself.