A new tetracycline-resistance determinant, class E, isolated from Enterobacteriaceae

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Tetracycline resistance is a growing concern in bacterial infections.
• Several tetracycline resistance determinants (classes A-D) are known in Enterobacteriaceae.
• The emergence of novel resistance mechanisms necessitates continuous surveillance.

Purpose of the Study:

• To identify and characterize a novel tetracycline resistance determinant.
• To investigate the genetic basis and prevalence of this new determinant.

Main Methods:

• Plasmid isolation and characterization from Escherichia coli.
• DNA-DNA hybridization to assess homology with known determinants.
• Determination of minimum inhibitory concentrations (MICs) for tetracycline and minocycline.
• Gene cloning and detection using labeled DNA fragments.

Main Results:

• A fifth tetracycline resistance determinant, class E, was identified on a transferable plasmid in E. coli.
• Class E showed no homology to previously described determinants (A-D) via DNA hybridization.
• Resistance was inducible by tetracycline and significantly increased MICs for tetracycline and minocycline.
• The mechanism of resistance appears to involve active drug efflux.
• The class E determinant was detected in Aeromonas but not in over 200 other E. coli strains.

Conclusions:

• A novel tetracycline resistance determinant (class E) has been identified, expanding the known repertoire of resistance mechanisms.
• This determinant confers resistance via an efflux mechanism and is transferable.
• The presence of class E in Aeromonas suggests potential inter-species transfer and broader dissemination.