INFLUENCE OF ANTIMICROBIAL THERAPY ON KINETICS OF TUMOR-NECROSIS-FACTOR LEVELS IN EXPERIMENTAL ENDOCARDITIS CAUSED BY KLEBSIELLA-PNEUMONIAE

The kinetics of tumor necrosis factor (TNF) levels in serum during therapy with cell wall-active agents (ceftriaxone, imipenem) and gentamicin were investigated in rabbits with experimental endocarditis caused by an isogenic pair of Klebsiella pneumoniae strains: a TEM-3 beta-lactamase-producing strain (KpR) or its susceptible variant (KpS). In vitro, KpR was resistant to ceftriaxone and was susceptible to gentamicin and imipenem, while KpS was susceptible to all three antibiotics. Serum TNF levels were determined in control rabbits hourly after bacterial inoculation and then daily; they were determined in treated animals hourly after the first antibiotic injection and then daily during a 4-day therapy with either imipenem (60 mg/kg of body weight four times daily), ceftriaxone (75 mg/kg once daily), or gentamicin (4 mg/kg once daily) alone or in combination with ceftriaxone. After a transient peak (10.2 +/- 3.1 ng/ml) at 90 min following bacterial challenge, serum TNF levels remained low and stable in control animals. The peak in the serum TNF levels occurred 4 h after the first antibiotic injection and with ceftriaxone was significantly higher (P < 0.05) against KpS (1.99 +/- 0.52 ng/ml) than against KpR (1.40 +/- 0.17 ng/ml). Against the KpR strain, the levels observed with ceftriaxone were significantly higher (P < 0.05) than those obtained with the other therapeutic regimens (0.70 to 0.80 ng/ml). On the day of sacrifice, effective regimens were associated with low TNF levels. We concluded that TNF production depends on (i) the antibiotic's mechanism of action and the susceptibility of the strain at the early phase of therapy, without any effect of the rapidity of bacterial killing, and (ii) the final reduction of the bacterial count at a later stage of therapy.