Antimicrobial Residues and Antimicrobial-Resistant Bacteria: Impact on the Microbial Environment and Risk to Human Health-A Review

Water quality has become a major environmental concern due to the presence of potentially harmful bacteria, protozoa, and chemicals. In particular, pharmaceuticals have recently gained prominence due to their potential negative effects on both the aquatic environment and on human health. The antimicrobial classes of penicillins, cephalosporins, macrolides, and fluoroquinolones are among the most frequent pharmaceuticals detected in the environment in Europe. The common route of entry of these antimicrobials into the environment is thought to be through wastewater treatment plant (WWTP) effluent. The main concern with regard to antimicrobial agents is the potential formation of antimicrobial resistance. Evidence suggests WWTPs may promote development of antimicrobial resistance. This study reviews antimicrobial residues typically found in treated water, their sources, process barriers, entry into the environment, and consequent human health concerns. The effects of WWTP on residues and the formation of antimicrobial-resistant bacteria are also discussed in addition to current risk assessment approaches for evaluating human health concerns, including development of antimicrobial resistance and resultant therapeutic failure. The uncertainty surrounding the fate and impact of different classes of antimicrobials in the environment is highlighted in addition to the lack of standardised methods to detect antimicrobials and to assess selective pressures.