[Importance of the study of the minimal bactericidal time of serum in the choice of optimal treatment of neonatal septicemias].

Rapid eradication of bacteria in bloodstream is critical for the outcome in neonatal bacterial sepsis. Two groups of neonates with E. coli K1 sepsis without purulent meningitis were studied. Group I (n = 14) received cefotaxime IV (100 mg.kg-1 D-1) plus netilmicin (4 mg.kg-1 D-1); group II (n = 8) received amoxicillin/clavulanic acid IV (100/10 mg.kg-1 D-1) plus netilmicin (4 mg.kg-1 D-1). Both groups were identical. For all strains MICs of cefotaxime, amoxicillin/clavulanic acid, netilmicin were less than 0.2, 4 and 1 mg/l respectively. Serum bactericidal activity (SBA) was determined for each patient (peak sample). The SBA was defined as the greatest dilution in which 99,99% of the inoculum was killed. Time-kill curves were performed with 1:16 dilutions of peak serum samples to measure the kinetic of bacterial killing. The minimal bactericidal time of serum (MBTS) was defined as the minimal time required to observe a decrease of more than 4 log CFU/ml of the bacterial inoculum. Samples (10 microliters) were taken at 1 h intervals over a 6 h period and at 24 h for quantitative culture. All patients cured. Median SBA were respectively 1/128 and 1/64 for group I and II. However, mean MBTS for groups I and II were respectively 1.2 h +/- 0.8 and 3.9 h +/- 1.4. Killing was more rapid in group I (p less than 0.01). The MBTS may be a clinically useful adjunctive test when optimal therapy would be expected.