Plasmid-determined epistatic susceptibility to kasugamycin

Area of Science:

• Microbiology
• Genetics
• Antibiotic Resistance

Background:

• Plasmids are extrachromosomal DNA elements that can confer new traits to host bacteria.
• Understanding plasmid-mediated effects on antibiotic susceptibility is crucial for combating bacterial infections.

Purpose of the Study:

• To investigate the impact of plasmids R100 and F8-gal on the susceptibility of Escherichia coli to the antibiotic kasugamycin.
• To determine if plasmid carriage directly influences bacterial response to kasugamycin.

Main Methods:

• Comparative analysis of kasugamycin susceptibility in plasmid-containing (R100+, F8-gal+) versus plasmid-free (R100-, F8-gal-) Escherichia coli strains.
• Plasmid retransfer and curing experiments to confirm plasmid-specific effects.
• Monitoring bacterial population dynamics during kasugamycin treatment.

Main Results:

• Escherichia coli strains harboring R100 or F8-gal plasmids exhibited increased susceptibility to kasugamycin compared to plasmid-free strains.
• Plasmid carriage was confirmed as the cause of this heightened susceptibility.
• In the presence of kasugamycin, R100+ cells initially showed overgrowth of plasmid-free segregants, followed by the emergence of kasugamycin-resistant R100+ mutants.

Conclusions:

• Plasmids R100 and F8-gal significantly alter Escherichia coli susceptibility to kasugamycin.
• The R100 plasmid appears to not only increase susceptibility but also enhance spontaneous mutation rates to kasugamycin resistance.
• These findings have implications for understanding bacterial evolution under antibiotic pressure and plasmid biology.