Chromium and Antibiotic Resistance in Bacteria Isolated from Chicken Waste

BACKGROUND: Hexavalent chromium (Cr(VI)), a known carcinogenic element, is predominantly found in industrial waste and is increasingly utilized as a feed additive in poultry, both directly and indirectly. The accumulation of excess chromium and antibiotics in poultry feed contributes to the development of antimicrobial resistance (AMR) within associated microbial communities. This situation raises significant public health concerns regarding environmental contamination and the emergence of multidrug-resistant (MDR) pathogens. METHODS: This study aimed to isolate and characterize chromium-resistant bacteria from poultry waste and evaluate their antibiotic susceptibility patterns. Samples were collected from two urban areas of Dhaka: Siddheswari and Malibagh. A total of 11 bacterial isolates capable of tolerating Cr(VI) were identified. Among these, isolates showing the highest chromium tolerance were selected for further analysis. RESULTS: Three isolates exhibited Cr(VI) resistance up to approximately 1400 mg/L. Based on their highest chromium tolerance levels, four isolates were chosen for detailed characterization. All four isolates were identified as Staphylococcus aureus . Among them, strain PL07 demonstrated the highest minimum bactericidal concentration (~1467 mg/L) and one of the highest minimum inhibitory concentration values (~867 mg/L), indicating significant chromium resistance. Isolate PL03 showed the highest resistance to seven tested antibiotics, suggesting a potential link between chromium tolerance and multidrug resistance. CONCLUSION: These findings underscore the growing concern about AMR in chromium-resistant bacteria from poultry waste. Our study provides critical evidence for developing targeted preventive strategies in public health, including stricter regulation of feed additives, improved waste management protocols, and enhanced surveillance systems. By addressing carcinogenic chromium contamination in the poultry industry, we can mitigate the emergence and proliferation of MDR pathogens, ultimately protecting both environmental integrity and human health across the food chain.