Evaluation of efflux activity in multi drug resistant commensal Escherichia coli isolated from poultry

Abstract

In the present study, 40 MDR Escherichia coli isolates from poultry faeces were evaluated for their multiple antibiotic resistance index and mechanism of resistance. All the isolates were found resistant to nine or more different classes of antibiotics and had an MAR index of more than 0.2. Efflux mechanism of resistance was detected using Ethidium bromide agar (Et-br) cartwheel method where exclusion of the Et-br by the bacterial isolates leads to no florescence and vice-versa. To distinguish whether the MDR phenotype is because of over expressed efflux or decrease in number of porins, percent decrease in the cfu/ml of an isolate in presence of CCCP (efflux inhibitor) and antibiotic as compared to the antibiotic alone was calculated. There was observed a reduced growth of all the isolates in presence of CCCP for all the four antibiotics used in the study i.e. Ceftazidime, Tetracycline, Chloramphenicol and Streptomycin but no absolute efflux i.e. 100% reduction was observed. Therefore, it was concluded that active efflux pumps play a role in antibiotic resistance mechanism along with some other mechanism that prevents the entry of antibiotics in the bacterial cell milieu might be reduction in the number of porins could be responsible for this multidrug phenotype. It was also noticed that antibiotic abuse in the poultry environments was present to the extent that E. coli colonizing the chick at initial stage were MDR and such isolates persist in the poultry environment.