Laboratory Dilutions of Thioridaxine with Potential to Enhance Antibiotic Sensitivity in a Multidrug Resistant Escherichia Coli Uropathogen

Abstract

This research effort seeks to use doses of thioridaxine to enhance antibiotic sensitivity in a MDR Escherichia coli strain. Five axenic (pure) strains of Escherichia coli coded EC1 to EC5 were obtained from five infected midstream urine samples among several other urine samples inoculated on sterile Cystine Lactose Electrolyte Deficient (CLED) agar with appropriate labeling in the Microbiology and Biotechnology Laboratory of Western Delta University, Oghara, Nigeria and stocked on sterile Nutrient agar slants at 4oC in a refrigerator. Slant cultures were sub-cultured aseptically on fresh sterile CLED agar plates and incubated aerobically at 37oC for 24hrs to confirm Escherichia coli strains. Gram staining, indole production, methyl red test, voges praskaeur and citrate utilization tests were done on the resulting colonies to further confirm the strains as E.coli. Antibiotic susceptibility test was done by agar disc diffusion method on all confirmed strains on sterile Mueller- Hinton agar plates before and after treatment with laboratory dilutions of thioridaxine. Only E.coli strain 2 (EC2) was multidrug resistant as it resisted 4(44.4%) of the antibiotics used which were cefuroxime, nalidixic acid, augmentin and tetracycline. Other strains resisted 1-2 antibiotics. The highest (15.6±20.6mm) and least (2.0±8.1mm) zones of inhibition by all five strains were recorded for ofloxacin and cefuroxime respectively. Whereas all five uropathogen strains resisted augmentin, they were sensitive to ciprofloxacin, ofloxacin (both being fluoroquinolones), gentamicin, chloramphenicol and nitrofurantoin. After treatment with 2000-2240ug/ml laboratory dilutions of thioridaxine, ≤50.0% loss of resistance was recorded for 2040ug/ml, 2160ug/ml and 2240ug/ml dilutions. Thioridaxine dilution of 2040ug/ml induced 250% and 90% resistance losses of EC2 to ciprofloxacin and nitrofurantoin respectively with an overall mean±S.E loss of 68.0±24.4%. Resistance losses of 112.5%, 130.0% and 100.0% to ciprofloxacin, nitrofurantoin and chloramphenicol respectively were recorded after 2160ug/ml treatment and 68.5±16.3% overall loss of resistance. Thioridaxine dilutions of 2240ug/ml induced 55.6±25.0% overall loss of resistance with a corresponding 50.0%, 50.0%, 58.1%, 70.0% and 50.0% resistance losses with gentamicin, ciprofloxacin, ofloxacin, nitrofurantoin and chloramphenicol respectively. Less than 50% resistance losses were recorded for 2000, 2080, 2120 and 2200ug/ml dilutions. Minimum inhibitory concentration of chloramphenicol was lowered by 2080ug/ml, 2160ug/ml and 2240ug/ml dilutions by two-fold (15ug), two-fold (15ug) and four-fold (7.5ug) respectively. The medical/ chemotherapeutic implications of these findings are discussed.