Are Sewage Treatment Plants Promoting Antibiotic Resistance?

There is widespread speculation that sewage treatment plants (STPs) and aquatic environments in general may be breeding grounds for antibiotic resistant bacteria. We examine the question of whether low concentrations of antibiotics in STPs can provide or contribute to a selective pressure facilitating the acquisition or proliferation of antibiotic resistance among bacteria in the receiving environment. Examination of available literature suggests that relative levels of antibiotic resistance may be increased during sewage treatment processes. However, it is unclear whether this may be partially the result of horizontal gene transfer or entirely due to clonal propagation. While there is circumstantial evidence that the presence of antibiotics or other related genetic promoters in STP wastewaters may contribute to selective pressures for these processes, a definite role is yet to be demonstrated. Future researchers would benefit from the application of non-culture-based techniques because culture limits the possible observations to a small subset of STP microbial diversity.