Activity of 18 antimicrobial agents against multi-resistant strains of Staphylococcus aureus isolated from intensive care patients.

During an outbreak of infections with multiple-resistant Staphylococcus aureus, 22 strains were isolated from 12 patients between November 1983 and March 1984 on two surgical intensive care units at Kiel University Hospital. Susceptibility of all strains was tested with the disc diffusion method and a microdilution test using different inocula of 10(2) and 10(5) cfu/ml. All strains were resistant to beta-lactam antibiotics, including thienamycin as well as to gentamicin, clindamycin, doxycycline, erythromycin and fosfomycin. Rifampicin was the most active substance in terms of w/v, followed by fusidic acid, ciprofloxacin, vancomycin, and trimethoprim/sulfamethoxazole. Netilmicin and chloramphenicol showed only moderate activity in relation to the antibiotic breakpoint, but were considered sensitive according to the disc diffusion test. Caution should be reserved for the use of imipenem against multiply-resistant staphylococci.