Comparative in vitro killing activity of meropenem versus imipenem against multiresistant nosocomial Pseudomonas...

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Multiresistant Pseudomonas aeruginosa poses a significant threat in healthcare settings.
• Carbapenems, including meropenem and imipenem, are crucial for treating serious P. aeruginosa infections.
• Understanding the comparative efficacy and resistance development of these agents is vital.

Purpose of the Study:

• To compare the in vitro killing activity of meropenem and imipenem against multiresistant P. aeruginosa strains.
• To evaluate the rate of resistance development to meropenem and imipenem during prolonged exposure.

Main Methods:

• Utilized 14 multiresistant P. aeruginosa clinical isolates, all susceptible to meropenem and imipenem (MIC ≤ 4 µg/ml).
• Performed 42 killing curves by exposing log-phase bacteria (5 x 10^5 CFU/ml) to 1x minimum bactericidal concentration (MBC) of each carbapenem.
• Assessed bacterial viability over 24 hours of incubation.

Main Results:

• Meropenem exhibited a slower initial killing rate than imipenem within the first 5 hours.
• Both carbapenems demonstrated equal effectiveness after 24 hours of incubation.
• Resistance developed in 40% of P. aeruginosa strains to imipenem versus 11.1% to meropenem after 24-hour exposure.

Conclusions:

• Meropenem and imipenem are both effective against susceptible multiresistant P. aeruginosa in vitro over 24 hours.
• Meropenem appears to induce resistance at a lower rate than imipenem.
• Further investigation into the mechanisms underlying differential resistance development is warranted.