Antimicrobial resistance among commensal enteric bacteria isolated from healthy cattle in Libya

Abstract

Introduction: Enterococcus and E. coli are important commensals bacteria widely used as bio-indicators to monitor the occurrence and distribution of antimicrobial resistance. Methods: rectal faecal samples were collected from healthy cattle from the suburban and farming areas in Tripoli within the period 2017-2018. Samples were subjected to standard and presumptive laboratory methods to isolate E. coli isolates and enterococci species then further subjected to Kirby-Bauer disk diffusion antimicrobial susceptibility test. A selection of multidrug resistant isolates of Enterococci and E. coli isolates were further investigated and analysed using the phoenix automated microbiology identification and susceptibility system. PCRs protocols were further applied to screen for blaTEM, blaSHV, bla CTX-M, class 1 and 2 integrons and the qacEΔ1-sul1 region of class 1 integrons. Results: a total of 103 healthy cattle were included in the study yielding 206 Enterococcus species and 162 E. coli antimicrobial resistant isolates. Of these, 73% and 61% were respectively characterized as multidrug-resistant strains. The MDR enterococci strains (n=27) expressed various susceptibility patterns distributed over four different enterococci species including E. faecium, E. faecalis, E. hirae, and VanC type enterococci. Eight enterococci isolates expressed low level susceptibility to vancomycin of which three isolates were VanC intrinsic type and five were vancomycin intermediate susceptibility represented by VanC/type (n=2), E. faecium (n=1), E. hirae (n=1) and E. faecalis (n=1). The investigated MDR E. coli strains (n=61) revealed high-level resistance to ampicillin (100%), trimethoprim/sulfamethoxazole (81%), gentamicin (30%) and ciprofloxacin (7%) but no resistance was identified to other important critical antimicrobial classes. PCRs revealed that only seventeen MDR E. coli isolates (n=17/25) were positive for blaTEM, and sixteen isolates (n=16/25) positive for the class 1 integrons. Conclusion: this is the first surveillance report on antimicrobial resistance among commensal bacterial organisms isolated from cattle in Libya. Healthy cattle can carry important bacterial strains expressing different and important antimicrobial resistance phenotypes that require continuous monitoring and antimicrobial stewardship in veterinary medicine.