潍坊市典型生活污水抗生素抗性基因与可移动遗传元件的分布特征OA

[Background]Sewage environments serve as crucial reservoirs for the enrichment,diffusion,and transmission of antibiotic resistance genes(ARGs).Mobile genetic elements(MGEs)can me-diate horizontal transfer of ARGs.Exploring their relationships under selective pressure in waste-water environments is of significant public health importance. [Objective]To investigate the distribution profiles of ARGs and MGEs among antibiotic resistant bacteria isolated from three municipal wastewater treatment plants(WWTPs)in Weifang City,thereby providing a scientific basis for mitigating ARGs dissemination in sewage environments. [Methods]Influent samples were collected from three WWTPs(Chengbei,Chengxi,and Shawo)in Weifang City.Antibiotic-resistant bacteria were isolated and cultured using selective media supplemented with eight individual antibiotics(amoxicillin,cefradine,erythromycin,streptomycin,vancomycin,ofloxacin,sulfadiazine,and tetracycline).Bacterial identification was performed using Sanger 16s rDNA gene sequencing.Antimicrobial susceptibility to six antibiotics was evaluated using the Kirby-Bauer(K-B)disk diffusion method,with resistance phenotypes determined according to the Clinical and Laboratory Standards Institute(CLSI)guidelines.The relative abundances of seven ARGs[e.g.,β-lactam blaTEM,and aminoglycoside aac(6')-Ib-cr]and two MGEs(integron intI 1 and transposon tnpA-IS4)were quantified via real-time quantitative PCR(qPCR)using the 16s rRNA as an internal reference.Correlations between ARGs and MGEs were evaluated using Pearson correlation analysis. [Results]A total of 15 drug-resistant bacterial species were detected,with Aeromonas media(detection rate:24.39%)and Aeromonas rivipollensis(detection rate:19.51%)identified as the co-dominant species.Ofloxacin and erythromycin demonstrated potent antibacterial efficacy(part inhibition zone diameters of 32-41 mm),whereas amoxicillin and cefradine showed weak efficacy(inhibition zone diameters≤10 mm).Four extensively drug-resistant strains were detected:three from Chengbei WWTP(amoxicillin-resistant Shewanella xiame-nensis,erythromycin-resistant Aeromonas rivipollensis,and sulfadiazine-resistant Aeromonas media)and one from Shawo WWTP(amox-icillin-resistant Pseudomonas weihenstephanensis).qPCR analysis revealed the ubiquitous presence of multiple ARGs(e.g.blaTEM,aadA-01,and tetG)and MGEs(intI1 and tnpA-IS4)across representative strains,with relative abundances ranging from 9.226×10-8 to 1.186×10-3.Correlation analysis demonstrated significant positive correlations between the relative abundance of ARGs and integron intI1(r=0.519,P=0.039 4),and tnpA-IS4(r=0.507,P=0.031 9). [Conclusion]Aeromonas media and Aeromonas rivipollensis constitute the dominant antibiotic-resistant bacterial populations in typical municipal wastewater in Weifang City.The composition of these drug-resistant bacteria is highly diverse,with certain strains exhibiting severe multidrug-resistant phenotypes.Furthermore,MGEs such as integron intI1 and transposon tnpA-IS4 carried by these bacteria play a critical role in mediating the horizontal transfer of ARGs within the sewage environment.