THE IN-VITRO ACTIVITY OF FAROPENEM, A NOVEL ORAL PENEM

The in-vitro activity of faropenem, a novel oral penem, was studied in comparison with other beta-lactam antimicrobials against 711 recent c linical isolates including Gram-negative, Grampositive and anaerobic b acteria. MIC data showed that faropenem was active against most member s of the Enterobacteriaceae (MICs less than or equal to 4 mg/L), with reduced activity against Serratia spp. (MIC90 = 32 mg/L). In common wi th its comparators, faropenem had weak activity against Pseudomonas ae ruginosa and Stenotrophomonas maltophilia (MIG > 128 mg/L). Faropenem was active against staphylococci, although for MRSA MICs were raised ( MIG(90) = 2 mg/L) compared with those for MSSA (MIC90 = 0.12 mg/L). Fa ropenem was also found to be active against streptococci, Neisseria sp p., Enterococcus faecalis and beta-lactamase-producing and non-produci ng strains of Haemophilus influenzae and Moraxella catarrhalis. Of the anaerobic bacteria studied, faropenem was most active against peptost reptococci and Clostridium perfringens (MIG(90) less than or equal to 1 mg/L) and Bacteroides fragilis (MIG(90) = 4 mg/L). An increase in in oculum from 10(4) to 10(6) cfu raised faropenem MICs for Morganella mo rganii from 0.06-1 mg/L to 2-4 mg/L and for MRSA from 0.25-2 mg/L to 8 mg/L (a similar increase was not observed for MSSA). The MICs of faro penem were not affected by the presence of either 20% or 70% (v/v) ser um. MICs for faropenem to 11 well characterized beta-lactamase produce rs were similar to those of non-producers. In hydrolysis studies, faro penem was shown to be highly stable to a number of beta-lactamases, in cluding TEM-1, SHV-1, the extended spectrum beta-lactamases, TEM-3 and TEM-9, and the beta-lactamase produced by Staphylococcus aureus (NCTC 11561).