Post-antibiotic effect of ceftazidime, ciprofloxacin, imipenem, piperacillin and tobramycin for Pseudomonas cepacia.

The post-antibiotic effects (PAE) of ceftazidime, ciprofloxacin, imipenem, piperacillin and tobramycin were studied for ten strains of Pseudomonas cepacia isolated from patients with cystic fibrosis. Antibiotic concentrations used for exposure were either the MIC of each agent for the sensitive isolates or the recommended sensitivity breakpoint concentrations for the resistant isolates. After 2 h of exposure, cultures were rapidly diluted 1000-fold to eliminate the antibiotic. Out of the ten isolates, there were eight sensitive to ceftazidime, six to ciprofloxacin, six to imipenem, nine to piperacillin and five to tobramycin. All antibiotics tested demonstrated PAE for some isolates of P. cepacia, however, each antibiotic failed to produce a PAE for at least one isolate. The mean PAE was 1.35 h for ceftazidime, 2.38 h for ciprofloxacin, 2.39 h for imipenem, 2.16 h for piperacillin and 1.77 h for tobramycin. Imipenem demonstrated PAE of > or = 0.5 h for all sensitive isolates tested; ceftazidime, piperacillin, ciprofloxacin and tobramycin demonstrated PAE of > or = 0.5 h for 6/8, 8/9, 5/6 and 2/5 sensitive isolates, respectively. These data indicate that several antibiotics have significant (> or = 0.5 h) PAE for isolates of P. cepacia.

Abrogation of adriamycin-induced cardiotoxicity by selenium in rabbits.

Adriamycin-induced cardiomyopathy in rabbits was produced by intravenous injections of the drug with a short therapeutic schedule (3 mg/kg body wt administered as four intermittent doses). Animals receiving selenium supplementation of Adriamycin showed preservation of the normal pattern of the heart histologic picture. The protective effect of selenium was accompanied by increased selenium levels in the plasma and the heart muscle. An eventual interaction between the antitumor effect of Adriamycin and the protective effect of selenium was ruled out by in vitro experiments using the L1210 cell line. Selenium did not abrogate the antiproliferative effect of Adriamycin when the cells were treated simultaneously with both agents. The results from this study indicate that Adriamycin-induced cardiotoxicity could be prevented by selenium if the animals were pretreated with selenium, rather than simultaneous administration of both agents. The mechanism of this effect is not entirely understood.