In-vitro studies of meropenem.

Area of Science:

• Microbiology
• Pharmacology
• Infectious Diseases

Background:

• Meropenem is a novel carbapenem antibiotic.
• Broad-spectrum antimicrobial agents are crucial for combating diverse bacterial infections.

Purpose of the Study:

• To compare the in vitro activity of meropenem against imipenem and other broad-spectrum agents.
• To evaluate meropenem's efficacy against a wide range of clinical isolates, including anaerobes and beta-lactamase-producing strains.

Main Methods:

• Comparative in vitro susceptibility testing of meropenem, imipenem, and seven other antimicrobials against approximately 1000 clinical isolates.
• Minimum Inhibitory Concentration (MIC) determination using broth and agar dilution methods.
• Evaluation of meropenem's activity against specific bacterial groups (Gram-negative, Gram-positive, anaerobes) and beta-lactamase producers.

Main Results:

• Meropenem demonstrated 2- to 4-fold greater activity than imipenem against Gram-negative organisms and possessed a wider spectrum.
• Imipenem was more potent against staphylococci, Streptococcus spp., and enterococci.
• Meropenem showed potent activity against anaerobic bacteria and was generally bactericidal, with MICs unaffected by high inocula.
• Susceptibility to meropenem was observed in strains producing various beta-lactamases, though an inoculum effect was noted in some high-level producers.
• Antagonism was observed between meropenem and other beta-lactams against strains producing Type I cephalosporinases.
• High cross-susceptibility was found between imipenem and meropenem.

Conclusions:

• Meropenem offers a broader spectrum of activity than imipenem, particularly against Gram-negative pathogens.
• Meropenem is a potent and generally bactericidal agent effective against a wide array of bacteria, including anaerobes.
• Standardized susceptibility testing methods provide reliable results for meropenem, with established breakpoints for disc diffusion assays.