Lipid peroxidation in Gram-negative bacteremia modulates the risk for septic shock and infections by resistant Klebsiella pneumoniae.

Controversies in outcomes with the parenteral administration of antioxidants as adjuvant therapies led to the measurement of malondialdehyde (MDA), a product of lipid peroxidation, in serum collected from 120 patients with primary Gram-negative bacteremia during the first 24 h from sepsis onset. MDA was measured by the thiobarbiturate assay, followed by high-performance liquid chromatography (HPLC) analysis. After receiver operator characteristic (ROC) curve analysis, patients were divided into those with high levels of MDA and low levels of MDA. The primary endpoint was the association of the level of MDA with septic shock. The level of MDA as an index of neutrophil function and associations with outcome and with infections by carbapenem-resistant Klebsiella pneumoniae were the secondary endpoints. In total, 63 patients had high and 57 had low MDA levels; 27% and 49.1%, respectively, had septic shock (p = 0.015). The rate of the concentration of MDA to the total neutrophil count was used as an expression of neutrophil function; this was lower among patients with septic shock. The odds ratio (OR) for death among patients without septic shock and low level of MDA was 4.00; this was 0.48 for patients with septic shock (p = 0.020 between the two ORs). The OR for resistance to carbapenems among patients with bacteremia by K. pneumoniae and low level of MDA was 7.50 (p = 0.011 compared to patients with bacteremia by other pathogens). Low level of circulating MDA is associated with susceptibility to septic shock and infections by carbapenem-resistant K. pneumoniae.

Time-kill effect of levofloxacin on multidrug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii: synergism with imipenem and colistin.

In the present study, we challenged the concept that levofloxacin should not be used for the management of ventilator-associated pneumonia (VAP) when minimum inhibitory concentrations (MICs) exceed 2 µg/ml. Multidrug-resistant (MDR) and genetically distinct isolates of Pseudomonas aeruginosa (n = 49) and Acinetobacter baumannii (n = 29) from patients with VAP were exposed over time to levofloxacin, imipenem, colistin and their combinations. Synergy between levofloxacin and imipenem was found in 55.3 % and between levofloxacin and colistin in 90.9 % of isolates of P. aeruginosa within the first 4 h of growth. Synergy with imipenem but not with colistin was dependent of the MIC. Synergy between levofloxacin and imipenem was found in 58.6 % of isolates of A. baumannii after 24 h of growth. Considerable synergy was found between levofloxacin and colistin, reaching 84.8 % of isolates of A.baumannii after 6 h of growth. Synergy was independent from the MIC. These results create hopes that levofloxacin can be used as combination therapy for infections by MDR bacteria.