Jeffrey Fernandez

Synthesis and topoisomerase inhibitory activities of novel aza-analogues of flavones

Abstract Aseries of aza-flavones (3-hydroxy-2-phenyl-4-quinolones) were designed and synthesized as inhibitors of bacterial DNA-gyrase and mammalian topoisomerase II. Structure activity relationships of the compounds against each of the enzymes are discussed.

In Vivo Activity of Ceftobiprole in Murine Skin Infections Due to Staphylococcus aureus and Pseudomonas aeruginosa

ABSTRACT Ceftobiprole, a broad-spectrum cephalosporin with activity against methicillin-resistant Staphylococcus aureus (MRSA) (P. Hebeisen et al., Antimicrob. Agents Chemother. 45:825-836, 2001), was evaluated in a subcutaneous skin infection model with Staphylococcus aureus Smith OC 4172 (methicillin-susceptible S. aureus [MSSA]), S. aureus OC 8525 (MRSA), Pseudomonas aeruginosa OC 4351 (having an inducible AmpC β-lactamase), and P. aeruginosa OC 4354 (overproducing AmpC β-lactamase). In the MSSA and MRSA infection models, ceftobiprole, administered as the prodrug ceftobiprole medocaril, was more effective in reducing CFU/g skin (P < 0.001) than were cefazolin, vancomycin, or linezolid based on the dose-response profiles. Skin lesion volumes in MSSA-infected animals treated with ceftobiprole were 19 to 29% lower than those for cefazolin-, vancomycin-, or linezolid-treated animals (P < 0.001). In MRSA infections, lesion size in ceftobiprole-treated mice was 34% less than that with cefazolin or linezolid treatment (P < 0.001). Against P. aeruginosa, ceftobiprole at similar doses was as effective as meropenem-cilastatin in reductions of CFU/g skin, despite 8- and 32-fold-lower MICs for meropenem; both treatments were more effective than was cefepime (P < 0.001) against the inducible and overproducing AmpC β-lactamase strains of P. aeruginosa. Ceftobiprole was similar to meropenem-cilastatin and 47 to 54% more effective than cefepime (P < 0.01) in reducing the size of the lesion caused by either strain of P. aeruginosa in this study. These studies indicate that ceftobiprole is effective in reducing both bacterial load and lesion volume associated with infections due to MSSA, MRSA, and P. aeruginosa in this murine model of skin and soft tissue infection.

Synergistic Activity of Ceftobiprole and Vancomycin in a Rat Model of Infective Endocarditis Caused by Methicillin-Resistant and Glycopeptide-Intermediate Staphylococcus aureus

ABSTRACT 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 log10 CFU/g MRSA or 6 log10 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.

In Vivo Activity of the Pyrrolopyrazolyl-Substituted Oxazolidinone RWJ-416457

ABSTRACT RWJ-416457 is an investigational pyrrolopyrazolyl-substituted oxazolidinone with activity against antibiotic-susceptible and -resistant gram-positive pathogens. Efficacies of RWJ-416457, linezolid, and vancomycin against methicillin-susceptible Staphylococcus aureus (MSSA) and community-associated methicillin-resistant S. aureus (CA-MRSA) in murine skin and systemic infections were compared, as were efficacies against Streptococcus pneumoniae in a lower respiratory infection. In staphylococcal systemic infections, RWJ-416457 was equipotent with to twofold more potent than linezolid, with 50% effective dose values ranging from 1.5 to 5 mg/kg of body weight/day. RWJ-416457 was two- to fourfold less potent than vancomycin against MSSA but up to fourfold more potent than vancomycin against CA-MRSA. In MSSA and CA-MRSA skin infections, RWJ-416457 demonstrated an efficacy similar to that of linezolid, reducing CFU/g skin approximately 1.0 log10 at all doses tested; vancomycin yielded greater reductions than the oxazolidinones, with decreases in CFU/g skin of 3 log10 (MSSA) and 2 log10 (CA-MRSA). In the pneumococcal model, RWJ-416457 was two- to fourfold more potent than linezolid. The free-drug area under the concentration-time curves at 24 h (fAUC24) were similar for RWJ-416457 and linezolid. The half-life of RWJ-416457 was up to threefold longer than that of linezolid for all routes of administration. The fAUC24/MIC ratio, the pharmacodynamic parameter considered predictive of oxazolidinone efficacy, was approximately twofold greater for RWJ-416457 than for linezolid. Since the fAUC values were similar for both compounds, the higher fAUC/MIC ratios of RWJ-416457 appear to result from its greater in vitro potency. These results demonstrate that RWJ-416457 is a promising new oxazolidinone with efficacy in S. aureus or S. pneumoniae mouse infection models.

6-Oxa isosteres of anacardic acids as potent inhibitors of bacterial histidine protein kinase (HPK)-mediated two-component regulatory systems

A series of 6-oxa isosteres of anacardic acids (6-higher alkyl/alkenyl-2-hydroxybenzoic acids) was synthesised and several members were discovered to be among the most potent inhibitors (IC50 values < or = 5 microM) of the bacterial two-component regulatory systems, KinA/SpoOF and NRII/NRI, reported to date. The Gram-positive antibacterial activity in selected strains is also presented.

A Meningococcal Outer Membrane Vesicle Vaccine Incorporating Genetically Attenuated Endotoxin Dissociates Inflammation from Immunogenicity

Background Group B Neisseria meningitidis, an endotoxin-producing Gram-negative bacterium, causes the highest incidence of group B meningococcus (MenB) disease in the first year of life. The Bexsero vaccine is indicated in Europe from 8 weeks of age. Endotoxin components of outer membrane vesicles (OMVs) or soluble lipopolysaccharide (LPS) represent a potential source of inflammation and residual reactogenicity. The purpose of this study was to compare novel candidate MenB vaccine formulations with licensed vaccines, including Bexsero, using age-specific human in vitro culture systems. Methods OMVs from wild type- and inactivated lpxL1 gene mutant-N. meningitidis strains were characterized in human neonatal and adult in vitro whole blood assays and dendritic cell (DC) arrays. OMVs were benchmarked against licensed vaccines, including Bexsero and whole cell pertussis formulations, with respect to Th-polarizing cytokine and prostaglandin E2 production, as well as cell surface activation markers (HLA-DR, CD86, and CCR7). OMV immunogenicity was assessed in mice. Results ΔlpxLI native OMVs (nOMVs) demonstrated significantly less cytokine induction in human blood and DCs than Bexsero and most of the other pediatric vaccines (e.g., PedvaxHib, EasyFive, and bacillus Calmette–Guérin) tested. Despite a much lower inflammatory profile in vitro than Bexsero, ΔlpxLI nOMVs still had moderate DC maturing ability and induced robust anti-N. meningitidis antibody responses after murine immunization. Conclusion A meningococcal vaccine comprised of attenuated LPS-based OMVs with a limited inflammatory profile in vitro induces robust antigen-specific immunogenicity in vivo.

A peptide immunization approach to counteract a Staphylococcus aureus protease defense against host immunity

Pathogens that induce acute and chronic infections, as well as certain cancers, employ numerous strategies to thwart host cellular and humoral immune defenses. One proposed evasion mechanism against humoral immunity is a localized expression of extracellular proteases that cleave the IgG hinge and disable host IgG functions. Host immunity appears to be prepared to counter such a proteolytic tactic by providing a group of autoantibodies, denoted anti-hinge antibodies that specifically bind to cleaved IgGs and provide compensating functional restoration in vitro. These respective counter-measures highlight the complex interrelationships among pathogens and host immunity and suggested to us a possible means for therapeutic intervention. In this study, we combined an investigation of pathogen-mediated proteolysis of host IgGs with an immunization strategy to boost host anti-hinge antibodies. In a Staphylococcus aureus infection model using an artificial tissue cage (wiffle ball) implanted into rabbits, cleaved rabbit IgGs were detected in abundance in the abscesses of untreated animals early after infection. However, in animals previously immunized with peptide analogs of the cleaved IgG hinge to generate substantial anti-hinge antibody titers, S. aureus colony formation was markedly reduced compared to control animals or those similarly immunized with a scrambled peptide sequence. The results of this study demonstrate that extensive local proteolysis of IgGs occurs in a test abscess setting and that immunization to increase host anti-hinge antibodies provided substantial acute protection against bacterial growth.

The mouse intranasal challenge model for potency testing of whole-cell pertussis vaccines

Introduction: A mouse intracerebral challenge model is used for potency testing of whole-cell pertussis (wP) vaccines. We investigated the use of a mouse nasopharyngeal challenge model, which better reflects the clinical features of pertussis disease, to differentiate between efficacy of wP vaccines. Methods: Efficacy of three wP vaccines (Quinvaxem®, Easyfive® and Pentavac®) was tested in the nasopharyngeal challenge model. Mice were vaccinated at 4 and 7 weeks and challenged with Bordetella pertussis at 9 weeks. Vaccine efficacy was determined based on CFU in the lungs 5 days after challenge. Results: The mouse nasopharyngeal challenge model has the capacity to differentiate between the efficacy of whole cell pertussis vaccines. Conclusion: The mouse nasopharyngeal challenge model could be considered as a potency and release assay for wP vaccines. Whether this model directly correlates with clinical vaccine efficacy requires further investigations. Whether this model directly correlates with clinical vaccine efficacy requires further investigations. The mouse nasopharyngeal challenge model could be considered as a potency and release assay for wP vaccines.