Tehran University of Medical Sciences Journal of Medical Bacteriology 2251-8649 14 1 2026 02 11 11 23 EN Kirti Saini Institute of Applied Medicine and Research, Duhai, 9th Km. Stone, Delhi-Meerut Road, Ghaziabad-201206, UP, India. Anil Teotia Indian Pharmacopoeia Commission, Ministry of Health & Family Welfare, Government of India, Sector-23, Raj Nagar, Ghaziabad, Uttar Pradesh, India-201002 Prasad Thota Indian Pharmacopoeia Commission, Ministry of Health & Family Welfare, Government of India, Sector-23, Raj Nagar, Ghaziabad, Uttar Pradesh, India-201002 Ajay Lagashetti Microbiology Division, Indian Pharmacopoeia Commission Min. of Health & Family Welfare, Govt. of India, Sector-23, Raj Nagar, Ghaziabad, Uttar Pradesh, India Manoj Pandey Indian Pharmacopoeia Commission, Ministry of Health & Family Welfare, Government of India, Sector-23, Raj Nagar, Ghaziabad, Uttar Pradesh, India-201002 Ajayendra Keshari Indian Pharmacopoeia Commission, Ministry of Health & Family Welfare, Government of India, Sector-23, Raj Nagar, Ghaziabad, Uttar Pradesh, India-201002 Sanjay Mendiratta Indian Pharmacopoeia Commission, Ministry of Health & Family Welfare, Government of India, Sector-23, Raj Nagar, Ghaziabad, Uttar Pradesh, India-201002 Meenakshi Dahiya Indian Pharmacopoeia Commission, Ministry of Health & Family Welfare, Government of India, Sector-23, Raj Nagar, Ghaziabad, Uttar Pradesh, India-201002 Vivekanandan Kalaiselvan Indian Pharmacopoeia Commission, Ministry of Health & Family Welfare, Government of India, Sector-23, Raj Nagar, Ghaziabad, Uttar Pradesh, India-201002 2025 08 13 2025 08 28 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. https://jmb.tums.ac.ir/index.php/jmb/article/view/600