Antimicrobial resistance of Escherichia coli isolates from cattle in Eastern Algeria.

Background and Aim: Lack of information about the antibiotic resistance in commensal Escherichia coli from Algerian livestock prompted us to do this study to determine the different levels of antimicrobial susceptibility, antibiotic multidrug resistance (MDR) rates, and phenotypical patterns of E. coli strains isolated from healthy cattle to control the spread of animal-resistant strains to humans and the environment.

Materials and Methods: A total of 198 cattle were sampled (swabbed in the rectum), reared in the farms of Souk Ahras, Tebessa, and Oum el Bouaghi governorates of Eastern Algeria. Isolation of E. coli strains was performed on MacConkey agar and then the different strains were identified to the species level using an API 20E identification kit. Antimicrobial susceptibility was determined using a panel of 13 antibiotic disks by disk diffusion method on Mueller-Hinton agar. The double-disk synergy test with cefotaxime and amoxicillin-clavulanate disks was used for the screening of extended-spectrum beta-lactamase phenotypes. For colistin susceptibility, the minimum inhibitory concentration was examined using broth microdilutions technique.

Results: The results showed that among the 198 E. coli isolates, elevated resistance rates were observed for ampicillin (59.09%) and tetracycline (43.43%), and moderate resistance rates for cephalothin (16.16%), trimethoprim/sulfamethoxazole (15.15%), and amoxicillin/clavulanate (11.62%); however, low resistance rates were found for nalidixic acid (8.08%), ciprofloxacin (7.07%), kanamycin (6.56%), cefotaxime (4.54%), chloramphenicol (4.04%), nitrofurantoin (2.52%), cefoxitin (2.02%), gentamycin (1.01%), and no resistance to colistin. However, nine extended-spectrum ß-lactamases producing E. coli strains were identified. Forty-four different patterns were determined, indicating a wide variety of resistance, ranging from one antimicrobial to a combination of 10. Analysis of coresistances revealed that 63 isolates (31.82%) were susceptible to all antibiotics used in the study, 42 isolates (21.21%) were resistant to one antibiotic, 43 isolates (21.72%) were resistant to two antibiotics, 24 isolates (12.12%) resistant to three antibiotics, 26 isolates (13.13%) were resistant for more than three agents, and 45 isolates (22.73%) were MDR (which means resistant to three or more families of antibiotics).

Conclusion: This study demonstrates that commensal E. coli remains a potential source of antibiotic resistance in view of the high prevalence of antimicrobial resistance. The vast range of MDR phenotypes, especially extended-spectrum ß-lactamases producing strains, emphasizes the urgent requirement to adopt measures to control the use of antimicrobials, in particular, by private veterinarians, as well as the strengthening of veterinary surveillance networks for antimicrobial resistance to control the spread of MDR bacteria from animals to humans and the environment.