Differences between the activity of penicillin, amoxycillin, and co-amoxyclav against 5,252 Streptococcus pneumoniae...

Area of Science:

• Microbiology
• Infectious Diseases
• Pharmacology

Background:

• Conflicting published data exists regarding the comparative activity of amoxycillin and co-amoxyclav versus penicillin against Streptococcus pneumoniae.
• Understanding antimicrobial susceptibility patterns is crucial for effective treatment of pneumococcal infections.

Purpose of the Study:

• To analyze and compare the minimum inhibitory concentrations (MICs) of penicillin, amoxycillin, and co-amoxyclav for a large collection of Streptococcus pneumoniae isolates.
• To determine if amoxycillin and co-amoxyclav exhibit lower MICs than penicillin, especially in penicillin-intermediate and penicillin-resistant strains.

Main Methods:

• Analysis of 5252 Streptococcus pneumoniae isolates collected over a 5-year period (1992-1996).
• Determination of MIC distributions and simultaneous 95% confidence intervals (CIs) for penicillin, amoxycillin, and co-amoxyclav.
• Specific analysis of penicillin-intermediate and -resistant isolates to compare their MICs to amoxycillin and co-amoxyclav.

Main Results:

• Amoxycillin and co-amoxyclav MIC90s were consistently one two-fold dilution lower than penicillin MIC90s across all analyzed isolates and time periods (1992-1993 and 1994-1996).
• Simultaneous 95% CIs indicated that the mean MIC differences favored amoxycillin and co-amoxyclav over penicillin (differences were less than zero).
• A majority of penicillin-intermediate and penicillin-resistant isolates showed lower amoxycillin and co-amoxyclav MICs compared to their penicillin MICs.

Conclusions:

• Amoxycillin and co-amoxyclav exhibit lower MICs than penicillin for the studied Streptococcus pneumoniae isolates.
• These findings suggest amoxycillin and co-amoxyclav may offer improved in vitro activity against Streptococcus pneumoniae, including resistant strains, compared to penicillin.