A REASSESSMENT OF THE IN-VITRO ACTIVITY OF COLISTIN SULPHOMETHATE SODIUM

The in-vitro activity of colistin sulphomethate sodium was compared wi th that of other commonly used antimicrobial agents against 377 recent clinical isolates of Gram-negative bacteria (including 94 strains of Pseudomonas aeruginosa from patients with cystic fibrosis) and 16 orga nisms with defined resistance patterns. Colistin was active against mo st strains of P. aeruginosa (MIC90 4 mg/L), Shigella spp. (MIC90 0.5 m g/L), Salmonella spp. (MIC90 1 mg/L), Acinetobacter spp. (MIC90 2 mg/L ), Citrobacter spp. (MIC90 1 mg/L), Escherichia coli (MIC90 1 mg/L), K lebsiella spp. (MIC90 8 mg/L) and Enterobacter spp. (MIC90 1 mg/L), No useful activity was demonstrated against Providentia spp. or Serratia spp. The results show that colistin remains a useful antimicrobial ag ent against Gram-negative bacteria, particularly those strains which a re resistant to more commonly used antibiotics.