Study on antibiotic resistance of culturable resistant bacteria during pig manure composting

Abstract:

Pig manure often carries antibiotics resistance bacteria (ARB) because antibiotics are usually added in feed. Composting is an effective way to reduce the environmental risk of pig manure returning to the field, but the characteristics of ARB in pig manure composting products are still unclear. The purpose of this study was to reveal the species, number, and distribution of ARB in pig manure composting products. In this study, the number, resistance, and species of resistant bacteria contained in the composting of pig manure and pig manure with additional chlortetracycline (CTC) were investigated through measures such as plate counting, minimum inhibitory concentration (MIC) of antibiotic, and 16S rRNA sequencing. Results show that the number of culturable bacteria in composting process first increased and then decreased, and the number of culturable bacteria in compost was far less than that in fresh manure samples. Antibiotics residues such as CTC, enrofloxacin (ENR), erythromycin (ERY), and sulfamerazine (SMZ) were detected in pig manure samples. At the end of composting, ENR resistant bacteria in the compost increased slightly, while SMZ, ERY, and CTC resistant bacteria were effectively reduced. A total of 25 strains of ARB were screened out, and the detection rate for multi-ARB was 20%. Aerobic composting is effective to reduce the number and types of ARB, but there are still a small number of multi-ARB, which poses a potential threat to the environment.