isolation and characterization of isolates of bacillus cereus group and their comparative antibiotic susceptibility testing against oxytetracycline

Background: bacillus cereus is a very important organism widely used for microbiological assays of pharmaceutical products especially in antibiotic susceptibility testing. the increasing emergence of antibiotic-resistant bacterial strains has emphasized the need for effective antibiotic susceptibility testing of pathogens for the management of patient's health.methods: the present study isolated of 5 strains of b. cereus  (r-01, r-02, c-01, c-03 & ss-01) from different samples collected from ghaziabad, uttar pradesh, india. pure cultures were then characterized based on microscopy, cultural and biochemical characteristics and also compared with standard reference strain b. cereus  mtcc 430. further, all the 5 isolates were subjected to maldi-tof analysis to confirm their identity. finally, antimicrobial susceptibility of all the indigenous strains was tested in comparison with b. cereus  mtcc 430 using the agar well diffusion method at various concentrations of oxytetracycline (1.6, 2.0, 2.5, 3.12, 3.91, 4.0, 8.0, 12.0, & 16.0 µg/ml).results: morphological, cultural and biochemical characteristics confirmed the identity of all the bacterial isolates as b. cereus which was further authenticated by maldi-tof analysis. the antibiotic susceptibility tests revealed that out of 5 indigenous isolates, r-01 and r-02 were found to be susceptible at all tested concentrations of oxytetracycline; whereas c-01, c-03 and ss-01 were found to be resistant at a concentration 2.5 µg/ml and below.conclusion: the antibiotics susceptibility test results displayed sensitivity profile of all 05 indigenous isolates of b. cereus  against the oxytetracycline and revealed that 02 isolates (r-01 and r-02) were more sensitive to oxytetracycline compared to others.