[Investigation of Antibiotic Resistance of Indigenous Bacteria and Abundance of Class I Integron in Matrix of Constructed Wetlands of Different Configurations].

Environmental indigenous bacteria (Staphylococcus and Pseudomonas) were isolated from 9 different constructed wetlands (CWs) in summer and winter. The antibiotic resistance analysis of the isolated bacteria was conducted by Kirby-Bauer disc agar diffusion method. And the quantitative PCR assay was used to quantify the abundance of class I integron (int1) in the matrix of CWs. The results indicated that over 84% of isolates among the 522 Staphylococcus strains and 543 Pseudomonas strains had antibiotic resistance and above 68% of isolates had multi-antibiotic resistance, the average of MRI index was 0.22. Antibiotic resistance of indigenous bacteria in CWs was at the same resistance level of human or animal bacteria in certain environment, indicating that indigenous bacteria from constructed wetlands had relatively high level of resistance. Staphylococcus and Pseudomonas strains had higher resistances to Ampicillin (AMP) and Sulfamethoxazole (SXT), and extremely low resistance rates of lower than 3% to Tetracycline (TE), Gentamicin (CN) and Ciprofloxacin (CIP). To Ceftazidime (CAZ) and Chloramphenicol (C), the two kinds of indigenous bacteria showed distinctly different resistances. Quantitative PCR revealed that the abundance of intl in CWs was 1.14 x 10(5)-5.66 x 10(5) copies · g(-1), and its relative abundance was 0.54%-3.68%. Both of season and wetland type had important impact on antibiotic resistance and abundance of int1. The antibiotic resistance rate and the multiple resistance index (MRI) for the indigenous bacteria and the abundance of int1 in summer were higher than those in winter. Among three types of CWs, the antibiotic resistance rate and the MRI value were the highest in the downward vertical flow, while the int1 abundance was the highest in the sub-surface flow. The research indicated that indigenous bacteria acquired antibiotic resistance due to long term exposure to antibiotics of certain concentrations and antibiotic-resistant intestinal bacteria in sewage environment. The environmental risks of antibiotic resistant bacteria and resistant genes in CWs should not be ignored.