Spread of antibiotic resistance markers in Lake Ceresio and tributary rivers. Monitoring results 2016

Mauri, Federica and Demarta Aeschbacher, Antonella (2017) Spread of antibiotic resistance markers in Lake Ceresio and tributary rivers. Monitoring results 2016. In: Joint annual meeting, 2017 SSM, SGM, 30.08.2017, Basel, Switzerland. (Unpublished)

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Aims Antibiotic resistant bacteria and antibiotic resistance genes (ARGs) are considered important environmental contaminants but little is known yet about their fate in the environment or about how they affect the natural microbial populations. In the environment, especially in water affected by anthropic activities (discharge of hospital, urban and industrial waste water treatment plant and agricultural run-off), antibiotic determinants may become part of the environmental gene pool, may spread horizontally, and may move back to humans and animals via contaminated food and drinking water. However, there are scarce information about the presence and distribution of antibiotic resistance genes in aquatic ecosystems. The aim of this work was to observe if anthropic activities could influence the bacterial populations naturally present in water environments in terms of antibiotic resistance. To reach our objective we investigate the presence of antibiotic resistance genes and antibiotic resistance bacteria in water samples collected from Lake Ceresio and some tributary rivers. Methods We analyzed water samples by PCR to investigated the presence or absence of integrase gene and of 10 antibiotics resistance genes that confers resistance to the major classes of antibiotics used in clinical and veterinary (β-lactams, tetracycline, quinolones and sulphonamides). After the qualitative screening we quantified resistance genes using qPCR. Total count of viable cells in all water samples were evaluated by flow-cytometry and agar plate count. To investigate the prevalence of mesophilic resistant bacteria, selected colonies were identified by MALDI-TOF and plated on selective agar. Results We found at least four quantifiable genes sulII, qnrS, tetA, blaTEM (104 – 101 copies/ml) especially in the rivers influenced by waste water treatment plants and in the lake near the potable water uptake plant. Pseudomonas spp., Acinetobacter spp., Stenotrophomonas spp., Aeromonas spp., Enterobacteriaceae and Flavobacteriaceae were the resistant bacterial population frequently found in water samples. Conclusion Our results indicate that rivers and lake are reservoir of ARGs and could be considered the ideal settings for the transmission of resistance from environmental non-pathogenic or potentially pathogenic bacteria to human pathogens. The presence of resistance genes near potable water uptake plant needs further investigations to evaluate the risk of their diffusion by drinking water.

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