[In vitro bactericidal effect of a piperacillin-pefloxacin combination against isolated strains of nosocomial pneumopathies in intensive care]. / Activité bactéricide in vitro de l'association pipéracilline-péfloxacine sur des souches isolées de pneumopathies nosocomiales en réanimation.

Combinations of piperacillin and pefloxacin are evaluated in vitro using checkerboard and killing-curves methods against 19 clinical isolates: S. aureus, K. pneumoniae, K. oxytoca, C. freundii, P. stuartii, Ps. aeruginosa, Ps. maltophilia and Ac. anitratum. The static checkerboard method showed more synergistic antibacterial effects than the killing curves method. The best synergistic effects appeared against S. aureus, K. oxytoca, P. stuartii, Ps. aeruginosa Ac. anitratum, including a notable increase of the rapidity of bactericidal activity. The combination PIP 64 micrograms - PEF 4 micrograms prevents the frequent secondary regrowth seen after 6 hours with the antibiotics used alone. No activity is obtained against S. aureus meti-R and Ps. maltophilia.

Interaction of ceftriaxone with human polymorphonuclear neutrophil function.

Ceftriaxone, an amino-2-thiazolyl cephalosporin, has been shown to cooperate in vitro with human neutrophils for the killing of some bacteria. In this work the direct interaction with human leucocyte bactericidal function has been studied. Ceftriaxone (1000 to 1 mg/l) did not alter neutrophil chemotaxis or superoxide anion production. It also did not interfere with the chemiluminescence response of isolated PMN although a paradoxical depressive effect was observed with whole human blood in the case of zymosan stimulation. The killing of Staphylococcus aureus and Klebsiella pneumoniae was not enhanced by ceftriaxone and phagocytosis was significantly depressed only with adherent neutrophils but not when using neutrophils in liquid medium. It is concluded that the synergy observed between leucocyte and ceftriaxone for bacterial killing cannot be related to a direct stimulation of neutrophil functions and should depend on bacterial alteration.

Effect of ceftriaxone-induced alterations of bacteria on neutrophil bactericidal function.

Two bacterial strains (Staphylococcus aureus and Klebsiella pneumoniae) were exposed to subinhibitory concentrations of ceftriaxone. After an overnight culture in presence of 1 MIC of ceftriaxone either in broth or on solid medium S. aureus showed enlarged forms which were better phagocytosed (increase about 40%) and killed (increase about 50%) than control staphylococci. Exposure of K. pneumoniae to 0.1 MIC ceftriaxone resulted in filamentation of bacteria. When grown in the presence of 0.01 MIC, K. pneumoniae did not elongate into filaments but were significantly more phagocytosed (increase about 40%) or killed (increase about 170%) than control bacilli. The mechanism of the greater sensitivity to PMN killing of the altered S. aureus and K. pneumoniae was assessed either with phenylbutazone-treated PMN or by in-vitro exposure to crude granule extracts of PMN. The altered bacteria displayed a significant susceptibility to the non-oxidative killing mechanism while untreated bacteria were unaffected by the non-oxidative system. These data could explain the synergy observed between ceftriaxone and leucocytes in the killing of some micro-organisms.

[In vitro study of ceftriaxone binding to blood]. / Etude in vitro de la fixation sanguine de la ceftriaxone.

Binding of ceftriaxone, a new third generation cephalosporin, to blood was studied in vitro. Steady state dialysis with 14C-ceftriaxone was used. Percentages of ceftriaxone bound to plasma within the range of therapeutic concentrations (10 to 1,000 microM) varied widely (80 to 50%). Indicating that the binding process is saturable, investigations performed with various isolated plasma proteins in physiologic concentrations show that ceftriaxone binds mainly to albumin, and marginally or not at all to alpha-1-acid glycoprotein, gammaglobulins, transferrin, haptoglobin, and lipoproteins. Albumin has a single binding site (n = 0.7) with moderate affinity (Ka = 72,000 M-1) for ceftriaxone. The presence of this site explains why ceftriaxone binds to plasma according to a saturable process. Only a small proportion (5%) of ceftriaxone (75-450 microM) binds to red blood cells in whole blood with a 50% hematocrit. A strongly significant inhibition of ceftriaxone (520 microM) binding to plasma was found with high bilirubin levels (230 microM) (24% decrease; p less than 0.01). A small but significant decrease in ceftriaxone (380 microM) binding to plasma was found with high serum oleic acid (1014 microM) or uric acid (1,800 microM) concentrations (2% decrease; p less than 0.05).