Sitafloxacin (DU-6859a) and trovafloxacin: postantibiotic effect and in vitro interactions with rifampin on methicillin-resistant Staphylococcus aureus.

Sitafloxacin (DU-6859a) and trovafloxacin are novel quinolones potent on methicillin-resistant Staphylococcus aureus (MRSA) that are designed for once daily administration. In order to define the adequacy of the above regimen for the therapy of infections by multiple drug-resistant MRSA, their postantibiotic effect (PAE), their bactericidal activity, and their interactions with rifampin were determined on 14 MRSA isolates resistant to both ciprofloxacin and rifampin. PAE was defined after 1-h exposure to 1x, 4x, and 10x MIC and the killing effect after exposure to 1x and 4x MIC. Rifampin was applied for interactive studies at a concentration of 2 micrograms/mL, which is equal to its mean serum level. Median PAEs produced by 1x, 4x, and 10x MIC of sitafloxacin were 1.39, 3.75, and 6.61 h respectively, and by 1x, 4x, and 10x MIC of trovafloxacin 0.87, 2.07, and 2.23 h respectively. PAEs achieved by sitafloxacin were statistically shown to be longer than those achieved by trovafloxacin; PAEs achieved by a concentration of 10x MIC of each quinolone did not differ significantly from those achieved by a concentration of 4x MIC. Both the 4x and 10x MIC concentrations produced a more prolonged PAE than the 1x MIC concentration. A rapid bactericidal activity was expressed over the first 6 h of growth by each quinolone involving 80% of isolates enhanced in some isolates by their interaction with rifampin. The above findings revealed an extended PAE and a rapid killing effect of both sitafloxacin and trovafloxacin on MRSA resistant to ciprofloxacin and to rifampin, thus supporting their once daily administration in the therapy of infections by multiple drug-resistant MRSA. However little in vitro benefit is derived by their interaction with rifampin.

Impact of cefuroxime administration on endotoxin (LPS) and tumour necrosis factor-alpha (TNFalpha) blood levels in patients suffering from acute pyelonephritis: a preliminary report.

It has been suggested that treatment of systemic infections caused by Gram-negative bacteria with beta-lactam agents might add to the inflammatory process by resulting in the release of endotoxins (LPS) upon death of the Gram-negative bacteria. To evaluate that hypothesis, 25 patients with acute pyelonephritis of Gram-negative aetiology were given intravenous cefuroxime 1.5 g tid. Blood samples were collected at various time intervals for blood culture and for the determination of LPS, tumour necrosis factor-alpha (TNFalpha) and cefuroxime levels. LPS remained elevated at levels equal to those before the administration of cefuroxime over the first 24 h of therapy. A positive correlation was detected between LPS and drug levels 6 h after the initiation of therapy. Fever persisted in 50, 37.5 and 16.7% of patients 48, 72 and 96 h after the start of treatment, respectively, followed by a rise of LPS at levels above the baseline. Blood cultures taken at the same time were sterile. A wide range of TNFalpha levels were found at similar times of sampling, indicating that LPS triggers considerable TNFalpha production in the serum of some patients but not in others. It is concluded that antibiotic-induced endotoxaemia is a phenomenon that might be observed in patients receiving cefuroxime and that might be responsible for the persistence of fever despite negative blood cultures.