Synergistic Effect of Combination Antibiotics against Salmonella Typhi after Co-Culture with Resistant Shigella Flexneri

Abstract

Some bacteria have gone evolutionary change and become resistant to several antibiotics. For that reason, the selection of effective antibiotics has become more difficult. In prospect of Bangladesh no standard combination antibiotics are available against resistant pathogens. So, we tried to find out the combination of antibiotics against resistant pathogen. In our present study, the anti-microbial activity with combination antibiotics was determined after co-culture of resistant pathogen with the sensitive strain. Disc diffusion technique was used for this study. This method is essentially a qualitative or semi-quantitative test indicating the sensitivity or resistance of microorganisms. Co-culture was performed with sensitive strain Salmonella typhi and registance strain Shigella flexneri. In this study, Salmonella typhi showed sensitivity against ciprofloxacin, vancomycin and imipenem with different concentration (20, 40, 60 and 80 μg/ml). This sensitive strain showed zone of inhibition of 20-27, 19-23 and 21-27 mm against ciprofloxacin, vancomycin and imipenem respectively. But Shigella flexneri did not give any zone of inhibition against these antibiotics at same concentration. After treatment with antibiotics ciprofloxacin, vancomycin and imipenem co-cultured newly resistant Salmonella typhi did not give optimum zone of inhibition. The resistance Salmonella typhi exhibited optimum zone of inhibition against combination antibiotics. Combination of ciprofloxacin and imipenem was exhibited optimum ZOI. Vancomycin and imipenem combined antibiotics was also exhibited optimum ZOI. The values of ZOI obtained individually were 0-4, 0-5, 4-9 mm for vancomycin, ciprofloxacin and imipenem against resistant S.typhi. The higher values of ZOI for the combination of vancomycin and imipenem were obtained which was 18-29 mm. For the combination of ciprofloxacin and imipenem 19-32 mm ZOI was obtained. The result of the study showed that co-cultured resistant Salmonella typhi was 10% more inhibited by combination antibiotics in comparison to single antibiotic. The present study indicates the synergistic effects of the antibiotics combination. These combinations therapy can be used as beneficial treatment approach in multi-drug resistant Salmonella typhi infections