In vitro dilutions of thioridaxine with potential to enhance antibiotic sensitivity in a multidrug resistant <i>Staphylococcus aureus</i> uropathogen

Abstract

This research effort seeks to use doses of thioridaxine to enhance antibiotic sensitivity in a multidrug resistant (MDR) Staphylococcus aureus strain. Five axenic (pure) strains of S. aureus coded SA₁ to SA₅ were obtained from five infected midstream urine samples, inoculated on sterile cystine lactose electrolyte deficient (CLED) agar and stocked on sterile nutrient agar slants at 4°C in a refrigerator. Bacteria strains were sub-cultured on fresh sterile CLED agar and mannitol salt agar plates to confirm S. aureus strains. Gram staining, catalase test and coagulase test were done on the resulting colonies to further confirm the strains as S. aureus. Antibiotic susceptibility test was done by agar disc diffusion method using sterile Mueller- Hinton agar plates before and after treatment with laboratory dilutions of thioridaxine. S. aureus strains 1, 3 and 5 were multidrug resistant as they resisted 3 (37.5%), 3 (37.5%) and 4 (50.0%) of the antibiotics used. The highest (11.8±1.4 mm) and least (0.8±10.0 mm) zones of inhibition by all five strains were recorded for streptomycin and augmentin, respectively whereas, all five uropathogen strains resisted cloxacillin, they were sensitive to gentamycin, cotrimoxazole, chloramphenicol and streptomycin. After treatment with 2000 to 2240 ug/ml laboratory dilutions of thioridaxine, ≤50.0% loss of resistance was recorded for each of all seven dilutions but only 2240 ug/ml dilution recorded mean±S.E. loss of 56.2±17.8% for gentamycin, cotrimoxazole and streptomycin after treatment of SA₅ uropathogen. This was followed by resistance losses of 41.4±10.8 and 42.7±8.3% induced by 2080 and 2200 ug/ml dilutions, respectively. Cumulative effect of all dilutions resulted in 40.0±8.2 and 40.5±17.1% borderline resistance losses to cotrimoxazole and chloramphenicol, respectively. Minimum inhibitory concentration of chloramphenicol was lowered by 2080, 2160 and 2240 ug/ml dilutions of thioridazine by four-fold (7.5 ug), four-fold (7.5 ug) and two-fold (15 ug), respectively. Upon this, the medical/chemotherapeutic implications of these findings are discussed.
 
Key words: In vitro, dilutions, thioridaxine, enhance, antibiotic, sensitivity, multidrug resistant Staphylococcus aureus.