Analysing diversity among beta-lactamase encoding genes in aquatic environments

Area of Science:

• Microbiology
• Environmental Science
• Genetics

Background:

• Beta-lactamase enzymes are a primary mechanism for bacterial resistance to beta-lactam antibiotics.
• The genes encoding beta-lactamases exhibit rapid evolution and significant molecular diversity.
• Previous studies primarily identified beta-lactamase resistance genes from clinical isolates.

Purpose of the Study:

• To investigate the presence and characteristics of beta-lactamase gene sequences in an aquatic environment.
• To compare genetic features of beta-lactamase genes from aquatic samples with those in existing databases.
• To explore the potential of aquatic ecosystems as reservoirs for antibiotic resistance genes.

Main Methods:

• DNA extraction from water samples from the Ria de Aveiro lagoon.
• Polymerase Chain Reaction (PCR) and hybridization to detect specific beta-lactamase gene families (TEM, IMP, OXA-2 derivatives).
• Cloning, sequence analysis, and PCR-denaturing gradient gel electrophoresis (PCR-DGGE) to assess molecular diversity.

Main Results:

• Beta-lactamase gene sequences from the TEM, IMP, and OXA-2 families were detected in the aquatic samples.
• Most retrieved sequences were highly similar or identical to those previously identified in clinical isolates.
• Phylogenetic analysis indicated the aquatic ecosystem acts as a reservoir for diverse beta-lactamase gene sequences.
• Observed patterns of molecular diversity differed from those typically found in clinical settings.

Conclusions:

• Aquatic environments, such as the Ria de Aveiro lagoon, harbor a diverse array of beta-lactamase gene sequences.
• These environmental reservoirs contain genes similar to those conferring antibiotic resistance in clinical settings.
• The distinct molecular diversity patterns suggest unique evolutionary dynamics of these genes in aquatic ecosystems.