INSIGHTS INTO THE ENVIRONMENTAL DISTRIBUTION, DIVERSITY AND MOBILITY OF β-LACTAMASE GENES

Antibiotics are the most important therapeutic discovery in medical history, and currently are an essential part of modern medicine. However, antibiotic resistance (AR) has emerged as an important threat to human and animal health. AR research has principally focused on clinical settings, leaving aside natural environments and their role in the dynamics affecting the spread of AR. We assessed the distribution of β-lactamase genes across different ecological and geographical compartments through massive screening of 232 metagenomes. Metagenomic reads were screened against a compiled comprehensive (EX-B) β-lactamase database. Subsequently we applied network analyses in attempt to elucidate β-lactamase dynamics within and across ecological boundaries. Finally, in order to evaluate ARG transfer between environments, we assessed ARG content in integrons obtained from different steps in the Shafdan wastewater treatment plant and several effluents from European wastewater treatment plants. For this task, we developed a novel high-throughput amplicon sequencing pipeline that enables characterization of thousands of integron gene cassette-associated reads.

Our findings indicate that: i) β-lactamase genes are highly diverse in less anthropogenically impacted environments than in more anthropogenically impacted environments; ii) there are high levels of intra-habitat connectivity between β-lactamase genes; iii) high similarity in β-lactamase content among effluents; iv) blaGES gene was highly predominant only in Israel and Cyprus effluents; iv) β-lactamase gene content is significantly reduced in Shafdan’s wastewater processes; v) there is no evidence of significant transfer of β-lactamase genes into integrons, to downstream environments.

On the whole our results suggest a characteristic β-lactamase fingerprint according environments, with low frequency of gene transfer events between environments.