Microbiological, pharmacokinetic and clinical studies on sulbactam/cefoperazone (SBT/CPZ) were carried out in the field of pediatrics. Antimicrobial activity The MIC80 of SBT/CPZ was 6.25 micrograms/ml for clinically isolated 24 strains of S. aureus (24 beta-lactamase producing strains), 0.39 micrograms/ml for 17 strains of S. pyogenes, 3.13 micrograms/ml for 24 strains of E. coli (22 beta-lactamase producing strains), 3.13 micrograms/ml for 22 strains of K. pneumoniae (22 beta-lactamase producing strains), 1.56 micrograms/ml for 22 strains of P. mirabilis and 0.20 microgram/ml for 15 strains of H. influenzae (13 beta-lactamase producing strains). In comparison with CPZ in respect to the MIC, SBT/CPZ exhibited synergistic effect on 31 strains out of 81 beta-lactamase producing strains (included 6 strains of S. aureus, 9 of E. coli, 5 of K. pneumoniae and 11 of H. influenzae) which was scarcely observed against 43 non-beta-lactamase producing strains. Absorption and excretion Serum levels and urinary excretion of SBT/CPZ were studied in 7 children aged 5 to 12 years. The mean serum concentration of SBT at 15 minutes following a single intravenous injection of 10 mg/kg of SBT/CPZ was 14.2 micrograms/ml and that of CPZ was 30.4 micrograms/ml. The mean urinary recovery rates at 6 hours following the intravenous injection were 57.8% and 18.3%, respectively. The mean serum concentrations of SBT and CPZ after 1-hour infusion of 10 mg/kg of SBT/CPZ were 10.9 micrograms/ml and 17.6 micrograms/ml, respectively. The urinary recovery rates of SBT and CPZ at 7 hours after the infusion were 100.0% and 27.7% on average, respectively. The mean serum levels of SBT and CPZ at 15 minutes after a single intravenous injection of 20 mg/kg of SBT/CPZ were 25.6 micrograms/ml and 66.0 micrograms/ml, respectively and urinary elimination until up to 6 hours were 72.5% on average for SBT and 21.1% for CPZ. Clinical study SBT/CPZ was used for the treatment of a total of 20 pediatric patients aged 1 month to 14 years to evaluate its clinical effectiveness, bacteriological efficacy and adverse effects. The clinical efficacy in 6 patients with acute pneumonia, 3 with staphylococcal scalded skin syndrome, 2 each with acute purulent tonsillitis and acute pyelonephritis, 1 each with acute purulent lymphadenitis, acute sinusitis, acute bronchitis, peritonitis and acute enteritis was judged to be excellent in 15 cases and good in 3 cases with an efficacy ratio of 100%. The clinical efficacy in 6 patients whose infections were caused by beta-lactamase producing strains was judged to be excellent in all the cases.(ABSTRACT TRUNCATED AT 400 WORDS)