Serum bactericidal activity against aerobes and anaerobes of volunteers receiving cefoxitin or cefotetan.

Six volunteers received intravenously a single 1 g dose of cefoxitin or cefotetan. The 2 groups were crossed after a week of washout. Five strains each of Escherichia coli, Klebsiella pneumoniae, Bacteroides fragilis and Bacteroides thetaiotaomicron susceptible to the administered drugs were tested for serum bactericidal activity (SBA). Blood samples were obtained before and 0.5, 3.0 and 12.0 hours after antibiotic injection. SBA was determined using microtitre procedures. Anaerobic bacteria were incubated in an anaerobic chamber. Cefotetan showed a very high SBA both against aerobes and anaerobes over the 12 hour sampling time. Cefoxitin reached satisfactory SBA values only 0.5 hours after administration.