In-vitro activity of pefloxacin compared to enoxacin, norfioxacin, gentamicin and newβ-lactams

Abstract

The in-vitro activity of pefloxacin was compared with that of norfloxacin, enoxacin, nalidixic acid, gentamicin, cefotaxime, ceftazddime and, where appropriate, other β-lactams against a total of 363 recent clinical isolates. An agar dilution procedure was used to determine MICs and two inocula (10⁴ and 10⁶ cfu) were used throughout. Pefloxacin inhibited 90% of isolates of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, indole-positive Proteus spp., Enterobacter spp., Shigella sonnei, Salmonella typhi, Campylobacter jejuni, Staphylococcus aureus and Haemophilus influenzae at ≤0-5 mg/1. Senatia marcescens and Providencia stuartii were somewhat more resistant, 2 mg/1 of pefloxacin being required to inhibit 90% of isolates of these species. Pefloxacin inhibited 90% of isolates of Pseudomonas aeruginosa at 4 mg/1 and 90% of isolates of the Bacteroides fragilis group at 16 mg/1. The activity of enoxacin was similar to that of pefloxacin, with enoxacin being four-fold less active against Staph. aureus. two-fold less active against the Bacteroides fragilis group and most species of the Enterobacteriaceae, and two-fold more active against Ps. aeruginosa. Pefloxacin showed good activity against gentamicin-resistant Ps. aeruginosa and Enterobacteriaceae and against methicillin-resistant Staph. aureus. Strains with decreased suscepUbility to norfloxacin tended to be less susceptible to both pefloxacin and enoxacin.