Overview of Scandinavian in vitro studies with ciprofloxacin.

Scandinavian studies have confirmed that ciprofloxacin is highly active against most Gram-negative bacterial species with extremely low minimal inhibitory concentrations (MIC-values) except for Pseudomonas aeruginosa. The antibacterial activity is approximately four times higher than that of norfloxacin. Gram-positive cocci are less sensitive with MIC-values of 0.5 to 1 mg/l. For pneumococci the ciprofloxacin concentration inhibiting 90% of clinical isolates (MIC90) is approximately 2 mg/l. The antibacterial activity of ciprofloxacin is influenced very little by an increased inoculum and culture conditions. However, urine reduces the antibacterial activity. Resistance to ciprofloxacin occurs extremely rarely among E. coli, but development of resistance among species like P. aeruginosa and Staphylococcus aureus may be more frequent. Ciprofloxacin is a bacterial antibiotic but killing of staphylococci was poor when studied kinetically. Ciprofloxacin plus piperacillin act synergistically against strains of P. aeruginosa. Ciprofloxacin has a post-antibiotic effect (PAE) of approximately 2h against both Gram-negative rods and Gram-positive cocci.