Antimicrobial Activity in Vitro of Cefaclor, A New Oral Cephalosporin

Abstract

Antimicrobial activity of cefaclor, a new orally administered cephalosporin derivative, was studied in vitro against a variety of gram-positive and gram-negative clinical isolates. Penicillin-resistant and penicillin-susceptible strains of Staphylococcus aureus were susceptible to cefaclor, with mean MIC [minimum inhibitory concentrations] of 1.44 and 0.93 .mu.g/ml, respectively. The MBC [minimum bactericidal concentration] for penicillin-resistant S. aureus was higher than that for penicillin-susceptible strains. All strains of Streptococcus [St.] pyogenes, St. sp. and St. pneumoniae tested were highly susceptible to cefaclor; all strains of St. faecalis were highly resistant to cefaclor. Strains of Escherichia coli, Klebsiella sp., Proteus mirabilis and Haemophilus influenzae were susceptible to cefaclor. Eighty per cent of strains of H. influenzae were inhibited by 5 .mu.g/ml of cefaclor. Most strains of Enterobacter sp., indole-positive Proteus, Pseudomonas sp. and Serratia sp. were resistant to cefaclor.