Objective To determine the distribution of various antibiotic resistance genes (ARGs) in raw water from drinking water source, and to explore the correlation between the ARGs and common carbapenem-resistant and multidrug-resistant bacteria isolated from drinking water source, so as to provide scientific evidence for improving the safety of urban drinking water.
Methods A total of 30 raw water samples were collected from a major drinking water source in Shanghai in 2020. Bacterial strains were selectively cultured on Columbia blood agar medium containing 1 μg·μL-1 meropenem, and then identified by MALDI-TOF-MS mass spectrometry system. Minimum inhibitory concentration (MIC) of the strains was detected by broth microdilution method. The water samples were filtered through a 0.45 μm filter membrane and diversity of ARGs was determined by using high-throughput metagenomic sequencing.
Results A total of 64 strains of carbapenem-resistant bacteria were isolated from the water samples, including Stenotrophomonas maltophilia, Enterococcus faecium, Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae, which were resistant to a variety of common antibiotics. Using metagenomic sequencing, 1 244 ARGs were identified. The relative average abundance of the top 100 ARGs accounted for 96.1%, and that of the multidrug-resistant ARGs accounted for 63.41%. Furthermore, the multidrug-resistant ARGs were mainly adeJ, mexT, adeC, oprM, mexF, mdfA, mexB, mdtK, adeK, etc. Using Spearman's correlation, five multidrug-resistant bacteria isolated from the drinking water source were significantly associated with the ARGs.
Conclusion Relative abundance of multidrug-resistant ARGs is high in raw water from main drinking water source. The five isolated carbapenem-resistant and multidrug-resistant bacteria are significantly correlated with the ARGs. It warrants strengthening the rational and standardized application of antibiotics to protect water resources and ensure the safety of drinking water.