Transposition of a gene encoding OXA-2 beta-lactamase

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• The bla gene encodes OXA-2 beta-lactamase, an enzyme conferring resistance to beta-lactam antibiotics.
• R plasmids are extrachromosomal DNA molecules in bacteria that often carry antibiotic resistance genes.
• Transposable elements facilitate the spread of genetic material, including resistance genes, within and between bacterial genomes.

Purpose of the Study:

• To characterize a novel transposable element, Tn2410, identified in Salmonella typhimurium.
• To determine the genetic makeup and functional properties of Tn2410, including the genes it carries and its resistance profiles.
• To compare Tn2410 with other known transposable elements to understand its evolutionary context.

Main Methods:

• Isolation and characterization of the transposable element Tn2410 from Salmonella typhimurium R plasmid R1767.
• Determination of the size and flanking sequences of Tn2410 using restriction enzyme analysis.
• Mapping of resistance genes (bla, sulphonamide, mercury) within the Tn2410 element.

Main Results:

• Tn2410 is an 18.5 kb transposable element encoding OXA-2 beta-lactamase, sulphonamide resistance, and mercury resistance.
• Tn2410 is flanked by small inverted repeats.
• Restriction enzyme analysis revealed significant similarity between Tn2410 and Tn2603 (encoding OXA-1 beta-lactamase).
• Ampicillin and sulphonamide resistance genes were mapped to a specific region within Tn2410.

Conclusions:

• Tn2410 represents a significant new transposable element contributing to antibiotic resistance.
• The structural similarity between Tn2410 and Tn2603 suggests a potential shared origin or horizontal gene transfer mechanism for these resistance elements.
• Understanding the characteristics of Tn2410 is crucial for monitoring and combating the spread of antibiotic resistance in bacterial populations.