In Vitro and In Vivo Evaluation of APX001A/APX001 and Other Gwt1 Inhibitors against Cryptococcus.

Cryptococcal meningitis (CM), caused primarily by Cryptococcus neoformans, is uniformly fatal if not treated. Treatment options are limited, especially in resource-poor geographical regions, and mortality rates remain high despite current therapies. Here we evaluated the in vitro and in vivo activity of several compounds, including APX001A and its prodrug, APX001, currently in clinical development for the treatment of invasive fungal infections. These compounds target the conserved Gwt1 enzyme that is required for the localization of glycosylphosphatidylinositol (GPI)-anchored cell wall mannoproteins in fungi. The Gwt1 inhibitors had low MIC values, ranging from 0.004 µg/ml to 0.5 µg/ml, against both C. neoformans and C. gattii APX001A and APX2020 demonstrated in vitro synergy with fluconazole (fractional inhibitory concentration index, 0.37 for both). In a CM model, APX001 and fluconazole each alone reduced the fungal burden in brain tissue (0.78 and 1.04 log10 CFU/g, respectively), whereas the combination resulted in a reduction of 3.52 log10 CFU/g brain tissue. Efficacy, as measured by a reduction in the brain and lung tissue fungal burden, was also observed for another Gwt1 inhibitor prodrug, APX2096, where dose-dependent reductions in the fungal burden ranged from 5.91 to 1.79 log10 CFU/g lung tissue and from 7.00 and 0.92 log10 CFU/g brain tissue, representing the nearly complete or complete sterilization of lung and brain tissue at the higher doses. These data support the further clinical evaluation of this new class of antifungal agents for the treatment of CM.

Comparison of disc diffusion, Etest and broth microdilution for testing susceptibility of carbapenem-resistant P. aeruginosa to polymyxins.

BACKGROUND: Considering the increasing use of polymyxins to treat infections due to multidrug resistant Gram-negative in many countries, it is important to evaluate different susceptibility testing methods to this class of antibiotic. METHODS: Susceptibility of 109 carbapenem-resistant P. aeruginosa to polymyxins was tested comparing broth microdilution (reference method), disc diffusion, and Etest using the new interpretative breakpoints of Clinical and Laboratory Standards Institute. RESULTS: Twenty-nine percent of isolates belonged to endemic clone and thus, these strains were excluded of analysis. Among 78 strains evaluated, only one isolate was resistant to polymyxin B by the reference method (MIC: 8.0 microg/mL). Very major and major error rates of 1.2% and 11.5% were detected comparing polymyxin B disc diffusion with the broth microdilution (reference method). Agreement within 1 twofold dilution between Etest and the broth microdilution were 33% for polymyxin B and 79.5% for colistin. One major error and 48.7% minor errors were found comparing polymyxin B Etest with broth microdilution and only 6.4% minor errors with colistin. The concordance between Etest and the broth microdilution (reference method) was respectively 100% for colistin and 90% for polymyxin B. CONCLUSION: Resistance to polymyxins seems to be rare among hospital carbapenem-resistant P. aeruginosa isolates over a six-year period. Our results showed, using the new CLSI criteria, that the disc diffusion susceptibility does not report major errors (false-resistant results) for colistin. On the other hand, showed a high frequency of minor errors and 1 very major error for polymyxin B. Etest presented better results for colistin than polymyxin B. Until these results are reproduced with a large number of polymyxins-resistant P. aeruginosa isolates, susceptibility to polymyxins should be confirmed by a reference method.

Outcome predictors of 84 patients with hematologic malignancies and Fusarium infection.

BACKGROUND: Invasive infection by Fusarium sp. is associated with high mortality in patients with hematologic cancer. Yet to the authors' knowledge, little is known regarding predictors of adverse outcome. METHODS: The authors conducted a retrospective review of the records of patients with hematologic carcinoma and invasive fusariosis who were treated at one institution in the U.S. and at 11 centers in Brazil. RESULTS: The records of 84 patients were evaluated. Neutropenia was present in 83% and 33 patients had undergone stem cell transplantation. Only 18 patients (21%) were alive 90 days after the diagnosis of fusariosis. Multivariate predictors of poor outcome were persistent neutropenia (hazard ratio [HR] of 5.43; 95% confidence interval [95% CI], 2.64-11.11) and use of corticosteroids (HR of 2.18; 95% CI, 1.98-3.96). The actuarial survival rate of patients without any of these factors was 67% compared with 30% for patients who recovered from neutropenia but were receiving corticosteroids and 4% for patients with persistent neutropenia only. None of the patients with both risk factors survived (P<0.0001). CONCLUSIONS: Measures to reduce the duration of neutropenia, as well as the judicious use of corticosteroids, may reduce the high mortality rate of fusariosis in patients with hematologic cancer.