Antibiotic resistance profiles and polystyrene biofilm formation capabilities of bacteria isolated from wastewater in Tromsø

Abstract

Pollution of plastic in itself has become a growing focus in the last 15 years. In addition, the impact of plastic as a reservoir for pathogenic bacteria and transfer of antibiotic resistance genes has become a global concern, for individuals, organizations, policymakers and health organizations. It is important to document the relationship of microbiota associated to different types of plastic material. This project is part of a larger project (MICROPLASTRESIST) and aims to document the connection between antibiotic resistance patterns in bacteria, identify potential pathogens in wastewater, and further document biofilm formation capabilities on polystyrene (PS) plastic. Antibiotic resistant bacteria were isolated from two wastewater treatment plants in Tromsø, Norway, using ampicillin agar. The identities of the pure isolated strains of bacteria were confirmed using mass spectrometric analysis (MALDI-TOF) that is mainly based on species specific ribosomal proteins. The result showed an abundance of bacteria from genus Pseudomonas, followed by Aeromonas, Klebsiella, Raoultella and Acinetobacter, which are all Gram-negative bacteria. Some of the species were closely related to known pathogens like A. salmonicida. Others were characterized within the same genus, but being non-pathogens, like A. media. This implies that the bacteria are able to exchange genetic material, both resistance and pathogenicity from pathogens to non-pathogenic bacteria. Biofilms in particular are believed to create opportunities for this exchange of genetic material and thus form resistance reservoirs. Antibiotic resistance patterns were mapped out using 8 of the most prescribed antibiotics used at the University Hospital of North Norway (UNN). In total, 13/55 of the identified bacterial species contained antibiotic resistant genes to ≥ 5 of these 8 antibiotics. Most of the identified strains were able to form biofilm on polystyrene microtiter plates at 30°C and 35°C. Most biofilm mass was formed using TSB and BHI broth for the raw wastewater, whereas bacteria in wastewater without any added nutrients form biofilm after 24 h at 30°C. This pilot study confirms existence of multi-resistant bacteria, both human and fish pathogens, at both wastewater stations in Tromsø. Most of them are also biofilm forming on polystyrene at 30°C and 35°C.