title: Sulfonamide and tetracycline resistance genes in total- and culturable-bacterial assemblages in South African aquatic environments.
abstract: Antibiotic resistant bacteria are ubiquitous in the natural environment. The introduction of eﬄuent derived antibiotic resistance genes (ARGs) into aquatic environments is of concern in the spreading of genetic risk. This study showed the prevalence of sulfonamide and tetracycline resistance genes, sul1, sul2, sul3, and tet(M), in the total bacterial assemblage and colony forming bacterial assemblage in river and estuarine water and sewage treatment plants (STP) in South Africa. There was no correlation between antibiotic concentrations and ARGs, suggesting the targeted ARGs are spread in a wide area without connection to selection pressure. Among sul genes, sul1 and sul2 were major genes in the total (over 10(-2) copies/16S) and colony forming bacteria assemblages (∼10(-1) copies/16S). In urban waters, the sul3 gene was mostly not detectable in total and culturable assemblages, suggesting sul3 is not abundant. tet(M) was found in natural assemblages with 10(-3) copies/16S level in STP, but was not detected in colony forming bacteria, suggesting the non-culturable (yet-to-be cultured) bacterial community in urban surface waters and STP eﬄuent possess the tet(M) gene. Sulfamethoxazole (SMX) resistant (SMX(r)) and oxytetracycline (OTC) resistant (OTC(r)) bacterial communities in urban waters possessed not only sul1 and sul2 but also sul3 and tet(M) genes. These genes are widely distributed in SMX(r) and OTC(r) bacteria. In conclusion, urban river and estuarine water and STP eﬄuent in the Durban area were highly contaminated with ARGs, and the yet-to-be cultured bacterial community may act as a non-visible ARG reservoir in certain situations.
authors: Center for Marine Environmental Studies, Ehime University Matsuyama, Japan.
authors: Satoru
authors: S
authors: Suzuki
authors: Center for Marine Environmental Studies, Ehime University Matsuyama, Japan.
authors: Mitsuko
authors: M
authors: Ogo
authors: Tokyo University of Agriculture and Technology Fuchu, Japan.
authors: Tatsuya
authors: T
authors: Koike
authors: Tokyo University of Agriculture and Technology Fuchu, Japan.
authors: Hideshige
authors: H
authors: Takada
authors: Coastal Systems Research Group, Natural Resources and the Environment, The Council for Scientific and Industrial Research Durban, South Africa.
authors: Brent
authors: B
authors: Newman
keywords: South Africa; antibiotic resistance; sewage treatment plant; sul; tet(M); yet-to-be cultured