Thesis title: An investigation of the presence of antibiotic resistance determinants and resistant bacteria in the Norwegian environment by examination of water treatment plant sludge.
Trial lecture title: The genetic basis of aminoglycoside resistance across different bacterial species and reservoirs.
The ordinary opponents are:
- First opponent: Professor Luca Guardabassi, University of Copenhagen, Denmark
- Second opponent: Assistant Professor Isabel Henriques, University of Coimbra, Portugal
- Leader of the evaluation committee: Associate Professor Yury Kiselev, OsloMet
The leader of the public defense is Professor Kaare Magne Nielsen, OsloMet.
The main supervisor is Professor Colin Charnock, Department of Life Sciences and Health, OsloMet.
The co-supervisors are Associate Professor Hege Tunsjø, OsloMet and Professor Kaare Magne Nielsen, OsloMet.
Abstract
The dissemination of antimicrobial resistant bacteria and determinants in natural environments has received more attention over the last decades. It has been shown that resistance is widespread in environments such as surface water, soil, marine ecosystems and waste water to mention a few.
However, there are still many uncertainties on the prevalence, development and spread of genes related to resistance in these environments.
Moreover, even though the situation in Norway, regarding use of antibiotics in animal and human medicine is limited, and the prevalence of resistant pathogens in clinics are promising, there is only sporadic knowledge on the situation of the natural environments.
Antimicrobial resistant bacteria and resistant determinants
Through culture-based and HTS approaches using sludge from drinking water treatment plants, this study reports on the presence of antimicrobial resistant bacteria and resistant determinants at 23 different geographical locations in Norway.
Sludge samples are derived from a large environmental area including drinking water sources and their surrounding catchment areas. Phenotypic and genotypic analyses showed that efflux pumps, reduced membrane permeability and genes coding for aminoglycoside modifying enzymes could explain some of the observed resistance.
Multi-drug resistant
Four strains of the "environmental superbug" Pedobacter isolated from the sludge samples were characterized by whole genome sequencing and antibiotic disc diffusion assays.
As with previous studies on members of this genus, we found that the isolates were multi-drug resistant, and that this resistance included clinically important beta-lactams, aminoglycosides and the fluoroquinolone ciprofloxacin.
Whole genome sequencing analysis of the four selected Pedobacter strains revealed a putative metallo-betalactamase gene resembling pedo-2.
Shotgun metagenomic analyses of water and sludge samples affiliated with wastewater treatment plant (WWTP) outflows in six Norwegian municipalities could identify a higher occurrence of antibiotic resistance genes in untreated sewage solids (Troms) relative to fjord surface sediments proximal to municipal wastewater treatment discharge locations (Bergen) and selected WTPs.
Furthermore, genes frequently detected in clinical isolates were also identified in the metagenomic data.
First large scale nationwide investigation
The present study suggests that antimicrobial resistant bacteria are present in Norwegian environments with limited anthropogenic exposures.
This is, to our knowledge, the first large scale nationwide investigation of antibiotic resistance in the Norwegian environment.
