Antibacterial activity and time kill kinetics of Amlodipine, Thioridazine and Promethazine against pathogenic clinical bacterial isolates .

Background: The emergence of multi-drug resistant bacterial strains worldwide has necessitated the scientific search for novel, potent, and affordable antimicrobial agents including medicinal plants and non-antibiotic drugs for therapy of infectious diseases. The objective of this study is to assess in vitro antibacterial activities and time kill kinetics of some non-antibiotic drugs against pathogenic clinical bacterial isolates. Methodology: In vitro antibacterial activities including minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time kill kinetics of Amlodipine (AML), Thioridazine (THI) and Promethazine (PRO) against Staphylococcus aureus, coagulase negative staphylococci (CoNS), Streptococcus spp, Escherichia coli, Enterobacter spp, Klebsiella pneumoniae and Pseudomonas aeruginosa clinical isolates were determined using disc diffusion, broth microdilution and plate count techniques. Results: The mean growth inhibition zones by the disc diffusion assay of AML, THI and PRO against the isolates were ≤15.1±1.0 mm with MIC and MBC values ranging from 12.5 to 50μg/ml and 25 to 100μg/ml respectively. The time-kill assay revealed bactericidal effect of AML, THI and PRO on Gram positive bacteria evidenced by mean log reductions in viable bacterial cell counts ranging from 0.13 Log10 to 2.41 Log10 CFU/ml for S. aureus, 0.88 Log10 to 2.08 Log10 CFU/ml for Streptococcus spp, and 0.26 Log10 to 2.34 Log10 CFU/ml for CoNS after ≤30hrs post inoculation at 1xMIC. The range of log reduction in viable cell counts of Gram-negative bacteria exposed to AML, THI and PRO were E. coli (0.11 to 3.23 Log10 CFU/ml), P. aeruginosa (0.52 to 2.56 Log10 CFU/ml), K. pneumoniae (0.85 to 3.0 Log10 CFU/ml) and Enterobacter spp (0.38 to 2.08 Log10 CFU/ml) after ≤30 hrs post inoculation at 1x MIC. Conclusion: These findings demonstrate in vitro antibacterial efficacies and time kill kinetics of AML, THI and PRO against pathogenic clinical bacterial isolates, which indicate that these non-antibiotic drugs may be useful therapeutic alternatives in the bid to reduce the burden of infectious diseases associated with antibiotic resistant pathogens. [ABSTRACT FROM AUTHOR]