blaTn3

blaTn3 is a designation used in microbiology to refer to a genetic element in which the beta-lactamase gene bla is embedded within a transposon of the Tn3 family. Elements of this type are mobile and can move between DNA molecules, most often onto plasmids, contributing to the spread of beta-lactam antibiotic resistance among Gram-negative bacteria.

In terms of structure, blaTn3 elements typically include the transposase gene tnpA, the resolvase gene tnpR, and a res site, flanked by inverted repeats. The beta-lactamase gene is carried as cargo and may be a variant such as blaTEM or other bla alleles. Like other Tn3-family transposons, blaTn3 elements are capable of replicative transposition, producing a duplicate copy at the new site while leaving the original intact.

Mobility is often supported by nearby insertion sequences and by association with plasmids that facilitate horizontal transfer. This arrangement enables rapid dissemination of beta-lactam resistance across bacterial populations, especially in settings with antibiotic pressure.

Occurrences have been reported in enterobacterial species, including Escherichia coli and Klebsiella, though the exact distribution varies by region and over time. The presence of blaTn3 can complicate treatment, as beta-lactamase activity can inactivate penicillins and, depending on the allele, some cephalosporins.

Research on blaTn3 focuses on its genetic context, mechanisms of transposition, and its contribution to the wider resistome. Molecular surveillance often targets elements such as the bla gene and transposase genes to track dissemination.