blaTEM and vanA as indicator genes of antibiotic resistance contamination in a hospital–urban wastewater treatment plant system

摘要

Four indicator genes were monitored by quantitative PCR in hospital effluent (HE) and in the raw andtreated wastewater of the municipal wastewater treatment plant receiving the hospital discharge. Theindicator genes were the class 1 integrase gene intI1, to assess the capacity of bacteria to be involved inhorizontal gene transfer processes; blaTEM, one of the most widespread antibiotic resistance genes in theenvironment, associated with Enterobacteriaceae; vanA, an antibiotic resistance gene uncommon in theenvironment and frequent in clinical isolates; and marA, part of a locus related to the stress response inEnterobacteriaceae. Variation in the abundance of these genes was analysed as a function of the type ofwater, and possible correlations with cultivable bacteria, antimicrobial residue concentrations, andbacterial community composition and structure were analysed. HE was confirmed as an importantsource of blaTEM and vanA genes, and wastewater treatment showed a limited capacity to remove theseresistance genes. The genes blaTEM and vanA presented the strongest correlations with culturablebacteria, antimicrobial residues and some bacterial populations, representing interesting candidates asindicator genes to monitor resistance in environmental samples. The intI1 gene was the most abundantin all samples, demonstrating that wastewater bacterial populations hold a high potential for geneacquisition