Mutation rates to 4-quinolone resistance.

Area of Science:

• Microbiology
• Pharmacology
• Bacterial Genetics

Background:

• The emergence of antibiotic resistance is a significant global health concern.
• Quinolone antibacterials are crucial in treating bacterial infections.
• Understanding resistance mechanisms and their impact on bacterial virulence is essential.

Purpose of the Study:

• To compare the efficacy of eleven 4-quinolone antibacterials against five bacterial species.
• To investigate the frequency of 4-quinolone-resistant mutant development.
• To assess the impact of resistance on bacterial pathogenicity.

Main Methods:

• Determined minimum inhibitory concentrations (MICs) for eleven 4-quinolones against Staphylococcus aureus, Staphylococcus warneri, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Streptococcus faecalis.
• Estimated the frequency of resistant mutant emergence at 5, 10, and 20 times the MIC.
• Assessed the coagulase production in resistant mutants.

Main Results:

• Ciprofloxacin and ofloxacin demonstrated the highest potency against all tested bacteria.
• No resistant mutants were detected in 10^12 bacteria for ciprofloxacin or ofloxacin against S. warneri, S. pneumoniae, and S. faecalis.
• Pseudomonas aeruginosa and Staphylococcus aureus exhibited resistant mutants at specific concentrations, with ofloxacin-resistant mutants showing reduced coagulase production.

Conclusions:

• Ciprofloxacin and ofloxacin are highly effective against the studied bacteria, with low rates of resistance.
• Ofloxacin resistance in Staphylococcus aureus is associated with a loss of coagulase production, suggesting decreased pathogenicity.
• Ciprofloxacin resistance in Staphylococcus aureus does not appear to affect coagulase production, preserving pathogenicity.