Plasmids encoding trimethoprim resistance in bacterial isolates from man and pigs

Area of Science:

• Microbiology
• Genetics
• Public Health

Background:

• Trimethoprim (Tp) resistance is a growing concern in Gram-negative bacteria.
• Understanding the epidemiology and genetic basis of Tp resistance is crucial for effective treatment strategies.

Purpose of the Study:

• To investigate the prevalence and characteristics of transferable trimethoprim resistance plasmids in Gram-negative bacteria from human and porcine sources.
• To determine the diversity of resistance determinants and plasmid incompatibility groups.
• To assess the evolutionary origins and local spread of these plasmids.

Main Methods:

• Isolation and characterization of Gram-negative bacteria from human and porcine samples.
• Determination of bacterial resistance patterns and biotypes.
• Plasmid isolation and transferability assays.
• Agarose gel electrophoresis for molecular weight determination.
• Incompatibility typing of resistance plasmids.

Main Results:

• Transferable Tp resistance plasmids were detected in 86% of porcine and 37% of human isolates.
• Plasmids carried various resistance determinants including tetracycline (Tc), chloramphenicol (Cm), spectinomycin (Sp), streptomycin (Sm), and sulfonamide (Su).
• Two major plasmid incompatibility groups, Inc FIV and Inc N, were identified, with distinct molecular weights.

Conclusions:

• Tp resistance plasmids in Perth appear to have evolved independently from those in Europe and the UK.
• Evidence suggests local dissemination of these plasmids among various Gram-negative species in humans and animals.
• The findings highlight the importance of monitoring transferable antibiotic resistance in both clinical and animal settings.