Evaluation of antibiotic resistance in emerging strains of Bacillus cereus and antibiotic potency estimations of Oxytetracycline.

Background: Antimicrobial resistance (AMR) is the greatest threat to the global clinical and healthcare sectors due to the emergence of mutagenic and multidrug-resistant (MDR) strains in the environmental contaminants. Thus, it is essential to regularly monitor these novel microbial strains for its genomic variations and antibiotic susceptibility assessments. The quality of the antibiotic produced is also a concern for national and international drug approval regulatory bodies, which assess the antibiotic potency of medications. In this study, we are estimating simultaneously the antibiotic sensitivity of emerging Bacillus cereus isolates as well as potency of manufactured antibiotics against these emerging indigenous strains. The standard test drug used for analysis is Oxytetracycline along with reference strain Bacillus cereus (ATCC 11778) for determining the antibiotic potency of test drug against new strains of B. cereus.

Methods and results: Bacterial identification will be performed using series of biochemical tests followed by 16 s rRNA gene sequencing. According to the pharmacological test procedures of antibiotic assay, their antimicrobial sensitivity against oxytetracycline was estimated using the Cup-plate antibiotic assay. Simultaneously, the test antibiotics potency was calculated using two-level factorial antibiotic assay method of to determine the drug's effectiveness against two test strains of B. cereus. The observed ZOI at high and low dilutions (16 µg/ml-4 µg/ml) of the Oxytetracycline (IPRS reference standard origin) was found to be (30.2-25.0 mm) for ATCC 11778, (29.0-25 mm) for AIR-01 and (17 mm-13 mm) for EW-01, respectively. The calculated potency of for Bacillus cereus (ATCC 11778) was 95.32%, whereas the potency for the indigenous B. cereus AIR-01 was 86.84% due to its low sensitivity towards oxytetracycline.

Conclusions: The calculated antibiotic potency of oxytetracycline against Bacillus cereus (ATCC 11778) was reported to be 95.32%, while the antibiotic potency against native B. cereus (AIR-01) was found to be 86.84%, which cannot be calculated for (EW-01) due to the presence of a moderate to complete antimicrobial resistance against the test drug sample.