Synergistic activity of ceftobiprole and vancomycin in a rat model of infective endocarditis caused by methicillin-resistant and glycopeptide-intermediate Staphylococcus aureus.

The therapeutic activity of ceftobiprole medocaril, the prodrug of ceftobiprole, was compared to that of vancomycin, daptomycin, and the combination of a subtherapeutic dose of ceftobiprole and vancomycin in a rat model of infective endocarditis due to methicillin-resistant Staphylococcus aureus (MRSA) (ATCC 43300) or glycopeptide-intermediate Staphylococcus aureus (GISA) (NRS4 and HIP 5836) strains. The minimum bactericidal concentrations of ceftobiprole, vancomycin, and daptomycin at bacterial cell densities similar to those encountered in the cardiac vegetation in the rat endocarditis model were 2, >64, and 8 µg/ml, respectively, for MRSA ATCC 43300 and 4, >64, and 8 µg/ml, respectively, for the GISA strain. Ceftobiprole medocaril administered in doses of 100 mg/kg of body weight given intravenously (i.v.) twice a day (BID) every 8 h (q8h) (equivalent to a human therapeutic dose of ceftobiprole [500 mg given three times a day [TID]) was the most effective monotherapy, eradicating nearly 5 log(10) CFU/g MRSA or 6 log(10) CFU/g GISA organisms from the cardiac vegetation and had the highest incidence of sterile vegetation compared to the other monotherapies in the endocarditis model. In in vitro time-kill studies, synergistic effects were observed with ceftobiprole and vancomycin on MRSA and GISA strains, and in vivo synergy was noted with combinations of subtherapeutic doses of these agents for the same strains. Additionally, sterile vegetations were achieved in 33 and 60%, respectively, of the animals infected with MRSA ATCC 43300 or GISA NRS4 receiving ceftobiprole-vancomycin combination therapy. In summary, ceftobiprole was efficacious both as monotherapy and in combination with vancomycin in treating MRSA and GISA infections in a rat infective endocarditis model and warrants further evaluation.

Efficacy of a new fluoroquinolone, JNJ-Q2, in murine models of Staphylococcus aureus and Streptococcus pneumoniae skin, respiratory, and systemic infections.

The in vivo efficacy of JNJ-Q2, a new broad-spectrum fluoroquinolone (FQ), was evaluated in a murine septicemia model with methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) and in a Streptococcus pneumoniae lower respiratory tract infection model. JNJ-Q2 and comparators were also evaluated in an acute murine skin infection model using a community-acquired MRSA strain and in an established skin infection (ESI) model using a hospital-acquired strain, for which the selection of resistant mutants was also determined. JNJ-Q2 demonstrated activity in the MSSA septicemia model that was comparable to that moxifloxacin (JNJ-Q2 50% effective dose [ED(50)], 0.2 mg/kg of body weight administered subcutaneously [s.c.] and 2 mg/kg administered orally [p.o.]) and activity in the MRSA septicemia model that was superior to that of vancomycin (JNJ-Q2 ED(50), 1.6 mg/kg administered s.c.). In an S. pneumoniae lower respiratory tract infection model, JNJ-Q2 displayed activity (ED(50), 1.9 mg/kg administered s.c. and 7.4 mg/kg administered p.o.) that was comparable to that of gemifloxacin and superior to that of moxifloxacin. In both MRSA skin infection models, treatment with JNJ-Q2 resulted in dose-dependent reductions in bacterial titers in the skin, with the response to JNJ-Q2 at each dose exceeding the responses of the comparators ciprofloxacin, moxifloxacin, linezolid, and vancomycin. Additionally, in the ESI model, JNJ-Q2 showed a low or nondetectable propensity for ciprofloxacin resistance selection, in contrast to the selection of ciprofloxacin-resistant mutants observed for both ciprofloxacin and moxifloxacin. JNJ-Q2 demonstrated activity that was comparable or superior to the activity of fluoroquinolone or antistaphylococcal comparators in several local and systemic skin infection models performed with both S. aureus and S. pneumoniae and is currently being evaluated in phase II human clinical trials.

Hepatic expression of heme oxygenase-1 and antioxidant response element-mediated genes following administration of ethinyl estradiol to rats.

Heme oxygenase-1 (HO-1) is one of several enzymes induced by hepatotoxicants, and is thought to have an important protective role against cellular stress during liver inflammation and injury. The objective of the present study was to evaluate the role of HO-1 in estradiol-induced liver injury. A single dose of ethinyl estradiol (500 mg/kg, po) resulted in mild liver injury. Repeated administration of ethinyl estradiol (500 mg/kg/day for 4 days, po) resulted in no detectable liver injury or dysfunction. Using RT-PCR analysis, we demonstrate that HO-1 gene expression in whole liver tissue is elevated (>20-fold) after the single dose of ethinyl estradiol. The number and intensity of HO-1 immunoreactive macrophages were increased after the single dose of ethinyl estradiol. HO-1 expression was undetectable in hepatic parenchymal cells from rats receiving Methocel control or a single dose of ethinyl estradiol, however cytosolic HO-1 immunoreactivity in these cells after repeated dosing of ethinyl estradiol was pronounced. The increases in HO-1 mRNA and HO-1 immunoreactivity following administration of a single dose of ethinyl estradiol suggested that this enzyme might be responsible for the observed protection of the liver during repeated dosing. To investigate the effect of HO-1 expression on ethinyl estradiol-induced hepatotoxicity, rats were pretreated with hemin (50 micromol/kg, ip, a substrate and inducer of HO-1), with tin protoporphyrin IX (60 micromol/kg, ip, an HO-1 inhibitor), or with gadolinium chloride (10 mg/kg, iv, an inhibitor/toxin of Kupffer cells) 24 h before ethinyl estradiol treatment. Pretreatment with modulators of HO-1 expression and activity had generally minimal effects on ethinyl estradiol-induced liver injury. These data suggest that HO-1 plays a limited role in antioxidant defense against ethinyl estradiol-induced oxidative stress and hepatotoxicity, and suggests that other coordinately induced enzymes are responsible for protection observed with repeated administration of high doses of this compound.