Abstract

Objective: Screening antibacterial susceptibility of gentamicin, vancomycin, azithromycin, chloramphenicol and cefotaxime against selected gram positive and gram negative bacteria. Experimental approach: The goals of the assay are to detect possible antibiotic sensitivity against Bacillus subtillis, Staphyllococcus aureus, Pseudomonas aeruginosa, Echerichia coli. Growth pattern of bacterial strains without any compound stimulation were studied through time dependent measurement of bacterial OD at 600nm at every 6 hrs interval. Antimicrobial susceptibility was screened through determination of minimum inhibitory concentration (MIC) by broth micro dilution method against all these organisms where compounds showed differential inhibition. Followed by this zone of inhibition were evaluated with respect to MIC. Finding: Azithromycin showed minimum concentration as MIC against all organisms followed by vancomycin and cefotaxime. Amount of inhibition were visualised through study of zone diameter at MIC level. Inhibited zone diameter reflect the MIC level of compound and antibacterial susceptibility of selected two gram positive and two gram negative organism. Discussion: Current testing methods provide assessment of antibiotic activity using the categories susceptible, intermediate, or resistant. Lowest MIC of Azithromycin is supported by inhibited zone diameter. Gentamicin also showed high zone of inhibition which suggest that the compound exert significant bactericidal effect at MIC. Whereas other compounds irrespective of their MIC, they did not show significant zone of inhibition. Conclusion: Thus azithromycin can be selected as most susceptible antibiotic against these selected organisms followed by gentamicin in higher concentration. However, newer or emerging mechanisms of resistance require constant vigilance regarding the ability of each test method to accurately detect resistance.

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