Microbiological perspectives of co-trimoxazole

Trimethoprim-sulfamethoxazole in vitro activity was compared with ampicillin, tetracycline, sulfonamide and trimethoprim against isolates of 24 gram-negative and 11 gram-positive species. The incidence of more than 10% of strains with minimal inhibitory concentrations above 32 mg/l was restricted to Escherichia coli, Shigella spp., Klebsiella pneumoniae, Providencia rettgeri, Morganella morganii, methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis. Occasionally, Streptococcus pneumoniae and Haemophilus influenzae strains with MICs above 32 mg/l were identified. Co-trimoxazole in vitro activity was superior to the comparative drugs for the majority of species. Co-trimoxazole remains an active combination against major pathogens of infections of the upper and lower respiratory, urinary tract and enteric infections with a still low incidence of resistant organisms.