Bactericidal effects of cefotetan and other antibiotics in human fluids

Antibiotics were added at final concentrations of 0.5 to 10 mg/l to either human blood, serum, urine, bile or ascitic fluid inoculated with sensitive cultures. Bactericidal effects were monitored by estimation of viable counts over 24 h at 37 degrees C. Cefotetan was reliably bactericidal to bacteria suspended in human urine over a wide range of conditions. Gentamicin, cefotaxime, cefotetan and azthreonam were predominantly bactericidal against Enterobacteriaceae in serum and blood; gentamicin, cefotetan and cefotaxime were bactericidal in bile, and cefotetan bactericidal in ascitic fluid. The above antibiotics all also produced a bactericidal effect against Haemophilus influenzae in serum, and the macrolides erythromycin and rosaramicin destroyed haemophilus in serum more rapidly than did ampicillin or amoxycillin. In most of these fluids, destruction (reduction in viable counts by greater than 10-fold) of the inoculum occurred within 2 to 4 h for gentamicin and 4 to 6 h for similar concentrations of beta-lactam agents.