Antimicrobial Resistance of Bacillus cereus Local Isolates by Phenotypic and Genotypic Screening Analysis

Abstract

Foodborne outbreaks, notably caused by Bacillus cereus, have become a growing concern due to globalization and increased international trade. The bacterium is capable of producing spores which are resilitent and can survive common food processing. Additionally, B. cereus has the ability to produce cereulide toxins in foods that can cause emetic illnesses as well as enterotoxins in human intestine leading to diarrhea. B. cereus has been implicated in significant foodborne illness cases worldwide, including in Indonesia. The rise of antibiotic resistance in bacteria has raised concerns in public health. In B. cereus, resistance to ß-lactam antibiotics posseses a serious challenge, as the bacterium can transfer resistance genes across the food chain. This study aimed to evaluate the antimicrobial resistance properties of several B. cereus isolates, focusing on their phenotypic resistance and the presence of resistance genes, to better understand and manage this threat in public health and food safety contexts. This study was conducted in three stages, the first step was culture preparation which includes confirmation tests by Gram and spore staining, catalase test, the second step involved antibiotic resistance screening of B. cereus using Kirby-Bauer method, while the third step included detection of antibiotic resistance genes using PCR analysis for phenotypically resistant isolates. Of the twenty-one (21) local isolates analyzed, all (100%; 21/21) were susceptible to chloramphenicol and ciprofloxacin but resistant to ampicillin, cefoxitin, cephalothin, and penicillin G. Ninety five percent (20/21) isolates showed intermediate traits with regard to erythromycin resistance while 28.6% (6/21) had intermediate resistance tetracycline. The detection of resistance-encoding genes showed that 100% (21/21) of the isolates possessed the bla1 gene. None of the tetracyline resistance and sensitive isolates (0%; 0/21) own tetB and tetL genes suggesting that other tet genes may need to be tested.