Phenotypic and Genotypic Antimicrobial Resistance Profiles of Escherichia coli O157 Isolates from Cattle in Cameroon

Background: Escherichia coli O157, a Shiga toxin-producing serotype of E. coli implicated in severe foodborne diseases, is a major public health concern worldwide. Most human infections are attributed to the consumption of infected beef and contaminated bovine products. The burden of E. coli O157 disease is compounded by the extensive use of antibiotics in the animal production line which might lead to the selection for antibiotic resistance. The aim of this study was to describe the antibiotic resistance patterns of E. coli O157 isolates from cattle in Cameroon.

Methods: Fifty-six E. coli O157 isolates previously obtained were subjected to antibiotic susceptibility testing using the Kirby-Bauer disc diffusion technique. Polymerase chain reaction was used to screen the isolates for the presence of eight antibiotic resistance genes.

Results: Antibiotics susceptibility profiling of the 56 isolates showed ofloxacin was the most active drug (55; 98.2%), followed by gentamicin (51; 91.1%). Ampicillin was the least active drug with only 7 (12.5%) isolates susceptible. Multidrug resistance was a common phenomenon exhibited by 33 isolates comprising 17 phenotypic profiles (A8-A24). The most frequent phenotypic profile was TETRSTRRAMPRTRIRERYR (tetracycline, streptomycin, ampicillin, trimethoprim, and erythromycin resistance) which accounted for 17.0% of the resistant strains. All the 8 resistance genes investigated were observed in one or more isolates and genotypic resistance was generally consistent with the resistant phenotypes observed. The most commonly observed resistance genes were tetA (73.2%) and aac(3)-IV (57.1%). Five isolates had none of the resistance genes investigated while 25 carried at least three different resistance determinants.

Conclusions: Cattle in Cameroon are infected with multidrug-resistant E. coli O157 and are a potential risk to consumers. Hence adequate animal food production measures should be prescribed and implemented to minimize the development and spread of antibiotic resistant E. coli O157.