Differences between the activity of penicillin, amoxycillin, and co-amoxyclav against 5,252 Streptococcus pneumoniae isolates tested in the Alexander Project 1992-1996.
A number of published studies have shown that the MICs of amoxycillin and/or co-amoxyclav are lower than those of ampicillin and/or penicillin for Streptococcus pneumoniae. Other published studies have concluded that the activities of amoxycillin and co-amoxyclav are comparable with that of penicillin for S. pneumoniae. A collection of 5252 S. pneumoniae isolates obtained during a 5 year period (1992-1996) was analysed to determine differences between the MICs of penicillin, amoxycillin and co-amoxyclav. Among the isolates analysed, 3788 (72%) were penicillin-susceptible, 615 (12%) were penicillin-intermediate and 849 (16%) were penicillin-resistant. Differences between the agents were assessed by examination of MIC distribution functions and simultaneous 95% CIs. In addition, penicillin-intermediate and -resistant isolates were analysed to determine the number and percentage of isolates which had an amoxycillin and co-amoxyclav MIC less than, equal to, or greater than the penicillin MIC. Results showed that the amoxycillin and co-amoxyclav MIC90s were one two-fold dilution lower than those of penicillin for all isolates collected between 1992-1993 and 1994-1996. Simultaneous 95% CIs showed that the mean differences between MICs of amoxycillin and penicillin, and between MICs of co-amoxyclav and penicillin, were less than zero. The majority of the penicillin-intermediate and penicillin-resistant isolates had an amoxycillin and co-amoxyclav MIC less than the penicillin MIC. In conclusion, amoxycillin and co-amoxyclav MICs were shown to be lower than the penicillin MICs for the S. pneumoniae isolates analysed in this study.
Department of Anti-Infectives, SmithKline Beecham Pharmaceuticals, Collegeville, PA 19426-0989, USA.
D L
DL
Butler
R C
RC
Gagnon
L A
LA
Miller
J A
JA
Poupard
D
D
Felmingham
R N
RN
Grüneberg
D000658:Amoxicillin / Q000494:pharmacology*; D019980:Amoxicillin-Potassium Clavulanate Combination / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D010406:Penicillins / Q000494:pharmacology*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D010406:Penicillins; D019980:Amoxicillin-Potassium Clavulanate Combination; D000658:Amoxicillin