Positive antibiotic and resistance genes in source water of three regions and correlation analysis

Background China is a big country in the production and use of antibiotics. The abuse of antibiotics enables bacteria in water environment to acquire resistance, and promotes the generation and spread of antibiotics resistance genes (ARGs). The problem of antibiotic-resistant bacteria is increasingly serious and has become a public security issue of global concern. Water environment is a huge reservoir of antibiotics and ARGs. It is of great significance to study the pollution of antibiotics and ARGs in water to protect water sources and optimize the biosecurity of drinking water.

Objective To evaluate the detection of antibiotics and ARGs in typical water sources, and to explore the relationship between antibiotics and ARGs.

Methods Water samples were collected in Heilongjiang, Liaoning, and Hubei provinces during the wet season (from August to October) in 2020. Ten water samples were collected from each of the three places, and a total of 30 water samples were collected in this study. Five kinds of antibiotics, including macrolides, quinolones, sulfonamides, tetracycline, and β-lactam, were detected by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The integron (Intl1), 16S rRNA, and 6 kinds of ARGs were detected by quantitative real-time PCR (qPCR). The ARGs include one macrolide ARGs (ermB), one β-lactam ARGs (bla_TEM), two tetracycline ARGs (tetC, tetQ), and two sulfonamide ARGs (sul1, sul2).

Results The types of detected antibiotics varied by the three regions, and the concentration ranges of the same antibiotics varied by the three regions (P<0.05). The concentration ranges of selected five kinds of antibiotics were 0.11-418.80 ng·L⁻¹ in region A, 0.12-23.23 ng·L⁻¹ in region B, and 4.69-285.75 ng·L⁻¹ in region C, respectively. The detection rates of all six ARGs were 100%. The absolute abundance of ARGs in region A ranged from 22.56 to 94355.91 copies·mL⁻¹, that in region B ranged from 27.99 to 80584.32 copies·mL⁻¹, and that in region C ranged from 41.99 to 111068.19 copies·mL⁻¹. The absolute abundance of bla_TEM was higher among the ARGs, followed by sul1 and sul2. In addition, the absolute abundance of Intl1 was also at a high level. The results of correlation analysis showed that the abundance of ARGs was positively correlated with each other. There was no correlation between specific antibiotics and corresponding ARGs. There was a positive correlation between Intl1 and sul1 or sul2 (P<0.05).

Conclusion The types and concentrations of antibiotics and the abundance of ARGs in source water vary greatly in the study areas. The association between antibiotics and ARGs is uncertain. Intl1 may play an important role in the horizontal transfer of sulfonamide resistance genes.