Caspofungin in combination with itraconazole and amphotericin B for the treatment of invasive Aspergillosis in humans, with a method to test ex vivo synergism

Evaluation of the efficacy of a posaconazole and anidulafungin combination in a murine model of pulmonary aspergillosis due to infection with Aspergillus fumigatus

Posaconazole (PSC) in combination with anidulafungin (AFG) was evaluated in a murine model of pulmonary aspergillosis. Immunosuppressed animals were infected via the nasal cavity with 2 different A. fumigatus strains. The animals received PSC (oral, 20mg/kg per day) and/or AFG (i.p., 10mg/kg per day) for 7days. On Day 8, the mice were euthanized and fungal burdens were determined from the lungs. Survival curves were constructed for mortality analysis. Compared to untreated groups, groups singly treated with PSC or AFG showed a reduced fungal burden in the lungs (P=0.0001-0.006) and prevention of mortality (66.66-83.33% of survival). Combination treatment with PSC and AFG significantly reduced the fungal burden (or sterilized the lungs) compared to the findings in the untreated and monotherapy groups and improved the survival rate to 100%. The PSC and AFG combination therapy was highly effective and should be evaluated in larger-scale experiments.

Comparison Between Etest and Broth Microdilution Methods for Testing Itraconazole-Resistant Aspergillus fumigatus Susceptibility to Antifungal Combinations

The checkerboard broth microdilution assay (BMD) is the most frequently used method for the in vitro evaluation of drug combinations. However, its use to evaluate the effect of antifungal drugs on filamentous fungi is sometimes associated with endpoint-reading difficulties, and different degrees of interaction are assigned to the same drug combination. We evaluated combinations of the azoles, itraconazole, posaconazole, and voriconazole, with the echinocandins, anidulafungin, caspofungin, and micafungin, against 15 itraconazole-resistant Aspergillus fumigatus clinical strains via the checkerboard BMD and Etest assay. Readings after 24 and 48 h, considering the two reading endpoints, the minimum inhibitory concentration (MIC) and minimum effective concentration (MEC), were performed for both methods. Our results showed that the correlation coefficients between the BMD and Etest methods were quite diverse to the drug combinations tested. The highest correlation coefficients of the Etest with the BMD assays (MEC and MIC reading) were the Etest-MIC reading at 24 h and the Etest-MEC reading at 48 h. Improvements in experimental conditions may increase the correlation between the two methods and ensure that Etest assay can be safely used in the evaluation of antifungal combinations against Aspergillus species.

Does a triple combination have better activity than double combinations against multiresistant fungi? Experimental in vitro evaluation

In this study, the in vitro interactions of amphotericin B (AmB), voriconazole (VRC) and anidulafungin (AFG) in double and triple combinations against four species of multiresistant fungi (Fusarium solani, Lomentospora prolificans, Scopulariopsis brevicaulis and Scopulariopsis brumptii) were evaluated. In general, AmB combined with AFG was the most synergistic, especially against F. solani (7/8; 87.5%) when low concentrations of AmB were used, i.e. 0.125-0.5 µg/mL. The least active combination was AmB + VRC, with the lowest percentage of synergy against S. brevicaulis (2/11; 18.2%) and, in general, high concentrations of both antifungals were needed to achieve synergy. The triple combination was also highly synergistic against F. solani and S. brevicaulis, especially when the lowest concentrations of AmB were used, suggesting that use of combined therapies would reduce the toxicity of therapy. The triple combination was more effective than the double combinations in some cases, but not against all strains, suggesting that administration of three drugs is not always useful in the treatment of infections due to multiresistant fungi.

Efficacy of the Combination Ampicillin Plus Ceftriaxone in the Treatment of a Case of Enterococcal Endocarditis Due toEnterococcus faecalisHighly Resistant to Gentamicin: Efficacy of the “Ex Vivo” Synergism Method

The case of a patient with highly gentamicin-resistant Enterococcus faecalis endocarditis treated with an ampicillin + ceftriaxone combination is described. We have designed a method to evaluate synergism between the antibacterial activity of patient's serum taken during a given antibiotic regimen (ampicillin) to which another antibiotic (ceftriaxone) is added in vitro. In this patient the two-drug combination was able to stop the bacteremia and prevent the infection of the prosthetic valve.

Concentration-dependent synergy and antagonism within a triple antifungal drug combination against Aspergillus species: analysis by a new response surface model

Triple antifungal combinations are used against refractory invasive aspergillosis without an adequate understanding of their pharmacodynamic interactions. We initially studied the in vitro triple combination of voriconazole, amphotericin B, and caspofungin against Aspergillus fumigatus, A. flavus, and A. terreus by a spectrophotometric microdilution broth method after 48 h of incubation. We then analyzed these results with a recently described nonlinear mixture response surface E(max)-based model modified to assess pharmacodynamic interactions at various growth levels. The new model allows flexibility in all four parameters of the E(max) model and is able to describe complex pharmacodynamic interactions. Concentration-dependent pharmacodynamic interactions were found within the triple antifungal combination. At the 50% growth level, synergy (median interaction indices of 0.43 to 0.82) was observed at low concentrations of voriconazole (<0.03 mg/liter) and amphotericin B (</=0.20 mg/liter) and at intermediate concentrations of caspofungin (0.95 to 14.88 mg/liter), whereas antagonism (median interaction indices of 1.17 to 1.80) was found at higher concentrations of voriconazole and amphotericin B. Ternary plot and interaction surface analysis further revealed the complexity of these concentration-dependent interactions. With increasing concentrations of amphotericin B, the synergistic interactions of voriconazole-caspofungin double combination decreased while the antagonistic interactions increased. A similar effect was observed when voriconazole was added to the double combination of amphotericin B and caspofungin. In conclusion, the new nonlinear mixture-amount response surface modeling of the triple antifungal combination demonstrated a net antagonism or synergy against Aspergillus species depending upon drug concentrations and species.

Clinical and microbiological efficacy of colistin therapy in combination with rifampin and imipenem in multidrug-resistant Pseudomonas aeruginosa diabetic foot infection with osteomyelitis

The evaluation of the safety and effectiveness of colistin in association with rifampin and imipenem in 1 diabetic patient with severe diabetic foot infection (DFI) due to multidrug-resistant (MDR) Pseudomonas aeruginosa, complicated by osteomyelitis, is presented in this "Case Report". The patient received colistin after other ineffective antimicrobial treatment when an MDR P aeruginosa strain was isolated by cultural examination, together with a multidisciplinary care approach including surgical debridement and adequate offloading. The efficacy of combination colistin plus rifampin plus imipenem was observed with a checkerboard method and bactericidal activity of the serum. The patient received colistin combination therapy for 6 weeks with cure of the infection and without renal toxicity. These data suggest that colistin, in combination with rifampin and imipenem, is safe and effective, in promoting healing in DFI due to MDR P aeruginosa and suggest the need for controlled clinical studies.

Inflammatory pseudotumor of the lung following invasive aspergillosis in a patient with chronic graft-vs.-host disease

Inflammatory myofibroblastic tumor (IMT) is an uncommon cause of solitary or multifocal lung nodules and can also be rarely found in various other extrapulmonary sites. Although this pseudotumor is benign, it can be locally very aggressive. The pathogenesis of IMT remains unclear; autoimmune or infectious origins have been hypothesized, so far. Here, we report a case of inflammatory pseudotumor of the lung secondary to invasive pulmonary aspergillosis in a patient with chronic graft-vs.-host disease. The 42-year-old patient presented with coughing and hemoptysis as major clinical signs 1 yr after successful HLA-identical stem cell transplantation. Aspergillus fumigatus was cultured from the bronchoscopic lavage, but intensive antifungal treatment could only initially improve the clinical situation. Diagnostic re-evaluation by open-chest biopsy surprisingly revealed an inflammatory pseudotumor responsible for clinical and radiographical deterioration. Both clinical and radiographical signs resolved under long-term steroids and secondary antifungal prophylaxis.

Aspergillus infections in transplant recipients

Aspergillus infections are occurring with an increasing frequency in transplant recipients. Notable changes in the epidemiologic characteristics of this infection have occurred; these include a change in risk factors and later onset of infection. Management of invasive aspergillosis continues to be challenging, and the mortality rate, despite the use of newer antifungal agents, remains unacceptably high. Performing molecular studies to discern new targets for antifungal activity, identifying signaling pathways that may be amenable to immunologic interventions, assessing combination regimens of antifungal agents or combining antifungal agents with modulation of the host defense mechanisms, and devising diagnostic assays that can rapidly and reliably diagnose infections represent areas for future investigations that may lead to further improvement in outcomes.