Spatial and seasonal variations of chloramphenicol resistance genes and their co-occurring analysis with bacteria in a typical mangrove area of Hainan island, China

Abstract Antibiotic residues and antibiotic resistance genes (ARGs) have been found worldwide. Chloramphenicol, one of antibiotics, had been banned for its use in breeding industry in many countries. The status about chloramphenicol resistance genes (CRGs) in mangrove ecosystems is still unknown. In the present study, quantitative PCR was employed to investigate the abundance of CRGs. The residual determination of chloramphenicols was performed via ultra-high pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Although the concentrations of chloramphenicol residues were at undetectable or relatively low levels, the abundance of CRGs was still alarming. The CRG abundance was dynamically different with the season change, and was highest in the surface layer and gradually decreased with the sampling sites away from the mangrove. The 16S rRNA high-throughput gene sequencing results revealed that cyanobacteria, fusobacteria and planctomycetes were the most dominant phyla co-occurring with CRGs. The results indicated that antibiotic residues could make a long term impacts on the environment eventhough after their degradation.