Efficacy of caspofungin and voriconazole combinations in experimental aspergillosis

In vitro and in vivo evaluation of antifungal combinations against azole-resistant Aspergillus fumigatus isolates

Azole resistance in Aspergillus fumigatus (Af) has become a widespread threat and a major concern for optimal management of patients with invasive aspergillosis (IA). Combination of echinocandins with azoles is an attractive alternative option for the treatment of IA due to azole-resistant Af strains. The aim of this study was to evaluate the in vitro and in vivo combination of caspofungin (CAS) with either voriconazole (VRZ) or posaconazole (PSZ). In vitro interactions were assessed by two methods, and an animal model of IA in Galleria mellonella was used for in vivo evaluation. Assessment of efficacy was based on larvae mortality. Groups of 10 larvae were infected by 3 clinical strains of Af (azole susceptible, AfS; PSZ resistant, AfR1; VRZ and PSZ resistant strain, AfR2). In vitro, combination of CAS and azoles was indifferent against AfS, and AfR2, and a synergy was found for AfR1. When compared to VRZ monotherapy, the combination of VRZ at 4 µg/larva with CAS at 4 µg/larva improved survival of AfR2-infected larvae (p=0.0066). Combination of PSZ at 4µg/larva with CAS at 4 µg/larva improved survival of AfR1-infected larvae compared to CAS (p=0.0002) and PSZ (0.0024) monotherapy. Antagonism was never observed. In conclusion, the combination of caspofungin with azoles is a promising alternative for the treatment of azole resistant strains of Af.

Rodent Models of Invasive Aspergillosis due to Aspergillus fumigatus: Still a Long Path toward Standardization

Invasive aspergillosis has been studied in laboratory by the means of plethora of distinct animal models. They were developed to address pathophysiology, therapy, diagnosis, or miscellaneous other concerns associated. However, there are great discrepancies regarding all the experimental variables of animal models, and a thorough focus on them is needed. This systematic review completed a comprehensive bibliographic analysis specifically-based on the technical features of rodent models infected with Aspergillus fumigatus. Out the 800 articles reviewed, it was shown that mice remained the preferred model (85.8% of the referenced reports), above rats (10.8%), and guinea pigs (3.8%). Three quarters of the models involved immunocompromised status, mainly by steroids (44.4%) and/or alkylating drugs (42.9%), but only 27.7% were reported to receive antibiotic prophylaxis to prevent from bacterial infection. Injection of spores (30.0%) and inhalation/deposition into respiratory airways (66.9%) were the most used routes for experimental inoculation. Overall, more than 230 distinct A. fumigatus strains were used in models. Of all the published studies, 18.4% did not mention usage of any diagnostic tool, like histopathology or mycological culture, to control correct implementation of the disease and to measure outcome. In light of these findings, a consensus discussion should be engaged to establish a minimum standardization, although this may not be consistently suitable for addressing all the specific aspects of invasive aspergillosis.

Antifungal pharmacokinetics and pharmacodynamics

Successful treatment of infectious diseases requires choice of the most suitable antimicrobial agent, comprising consideration of drug pharmacokinetics (PK), including penetration into infection site, pathogen susceptibility, optimal route of drug administration, drug dose, frequency of administration, duration of therapy, and drug toxicity. Antimicrobial pharmacokinetic/pharmacodynamic (PK/PD) studies consider these variables and have been useful in drug development, optimizing dosing regimens, determining susceptibility breakpoints, and limiting toxicity of antifungal therapy. Here the concepts of antifungal PK/PD studies are reviewed, with emphasis on methodology and application. The initial sections of this review focus on principles and methodology. Then the pharmacodynamics of each major antifungal drug class (polyenes, flucytosine, azoles, and echinocandins) is discussed. Finally, the review discusses novel areas of pharmacodynamic investigation in the study and application of combination therapy.

Meropenem/colistin synergy testing for multidrug-resistant Acinetobacter baumannii strains by a two-dimensional gradient technique applicable in routine microbiology

OBJECTIVES

Precise assessment of potential therapeutic synergy, antagonism or indifference between antimicrobial agents currently depends on time-consuming and hard-to-standardize in vitro chequerboard titration methods. We here present a method based on a novel two-dimensional antibiotic gradient technique named Xact™.

METHODS

We used a test comprising a combination of perpendicular gradients of meropenem and colistin in a single quadrant. We compared test outcomes with those obtained with classical chequerboard microbroth dilution testing in a study involving 27 unique strains of multidrug-resistant Acinetobacter baumannii from diverse origins.

RESULTS

We were able to demonstrate 92% concordance between the new technology and classical chequerboard titration using the A. baumannii collection. Two strains could not be analysed by Xact™ due to their out-of-range MIC of meropenem (>128 mg/L).

CONCLUSIONS

The new test was shown to be diagnostically useful, easy to implement and less labour intensive than the classical method.

Efficacy of combination therapy of triazole and echinocandin in treatment of invasive aspergillosis: a systematic review of animal and human studies

OBJECTIVE

The effectiveness of the combination therapy of triazole and echinocandin in treatment of invasive aspergillosis (IA) remains controversial. The objective of this systematic review was to assess the efficacy of combination therapy of triazole and echinocandin in treatment of IA.

METHODS

Relevant articles on the combination therapy of triazole and echinocandin in IA, including the animal studies and clinical studies from January 1966 to October 2013, were searched on Web of Science, PubMed and Cochrane Library. The prolongation of survival of the combination therapy of triazole and echinocandin in IA was performed as risk ratio (RR) with 95% confidence interval (95% CI).

RESULTS

Nine animal studies with a total of 1,582 animals and five clinical trials totaling 872 patients were included. The survival of the included animal studies with combination therapy was significantly prolonged compared with echinocandin alone [RR =2.26, (95% CI, 1.79-2.87; P<0.00001)], but no statistical difference compared with monotherapy of triazole [RR =1.19, (95% CI, 0.98-1.44; P=0.08)]. Of the four human cohort studies, two studies observed that the combination therapy of triazole and echinocandin was associated with a significant reduction in mortality compared with other treatments, and one study might be considered as a preferable therapy [HR =0.58, (95% CI, 0.3-1.14; P=0.117)]. While another study revealed that there was no significant difference among the combination therapy of triazole and echinocandin and either of the monotherapy. In the randomized clinical trial (RCT), of the 135 patients who received the combination therapy, 39 died, while 55 died out of 142 patients who received monotherapy (P=0.08, 95% CI, -21.4, 1.09) by week 12.

CONCLUSIONS

The combination therapy of triazole and echinocandin in treating IA results in a trend towards improved overall survival in animals' studies and clinical studies. Well-designed RCTs and further improved clinical trials are necessary to study the effectiveness of the combination therapy.

Multicentre surveillance study on feasibility, safety and efficacy of antifungal combination therapy for proven or probable invasive fungal diseases in haematological patients: the SEIFEM real-life combo study

This multicentre observational study evaluated the feasibility, efficacy and toxicity of antifungal combination therapy (combo) as treatment of proven or probable invasive fungal diseases (IFDs) in patients with haematological malignancies. Between January 2005 and January 2010, 84 cases of IFDs (39 proven and 45 probable) treated with combo were collected in 20 Hematological Italian Centres, in patients who underwent chemotherapy or allogeneic haematopoietic stem cell transplantation for haematological diseases. Median age of patients was 34 years (range 1-73) and 37% had less than 18 years. Acute leukaemia was the most common underlying haematological disease (68/84; 81%). The phase of treatment was as follows: first induction in 21/84 (25%), consolidation phase in 18/84 (21%) and reinduction/salvage in 45/84 (54%). The main site of infection was lung with or without other sites. The principal fungal pathogens were as follows: Aspergillus sp. 68 cases (81%), Candida sp. six cases (8%), Zygomycetes four cases (5%) and Fusarium sp. four cases (5%). The most used combo was caspofungin+voriconazole 35/84 (42%), caspofungin + liposomal amphotericin B (L-AmB) 20/84 (24%) and L-AmB+voriconazole 15/84 (18%). The median duration of combo was 19 days (range 3-180). The overall response rate (ORR) was 73% (61/84 responders) without significant differences between the combo regimens. The most important factor that significantly influenced the response was granulocyte (PMN) recovery (P 0.009). Only one patient discontinued therapy (voriconazole-related neurotoxicity) and 22% experienced mild and reversible adverse events (hypokalaemia, ALT/AST increase and creatinine increase). The IFDs-attributable mortality was 17%. This study indicates that combo was both well tolerated and effective in haematological patients. The most used combo regimens were caspofungin + voriconazole (ORR 80%) and caspofungin + L-AmB (ORR 70%). The ORR was 73% and the mortality IFD related was 17%. PMN recovery during combo predicts a favourable outcome.

CLINICAL TRIALS REGISTRATION

NCT00906633.

High-dose caspofungin as a component of combination antifungal therapy in 91 patients with neoplastic diseases and hematopoietic stem cell transplantation: a critical review of short-term and long-term adverse events

The antifungal activity of echinocandins is concentration dependent. Previously, we demonstrated that high-dose caspofungin (HD-CSP; 100 mg daily) was well tolerated in 34 immunosuppressed patients with cancer and may have favorably influenced outcomes. We retrospectively assessed all 91 patients in whom HD-CSP was given for the treatment of invasive fungal disease (IFD). The median number of doses was 18.5 ± 21.5, and in 8 (9%) patients more than 40 doses were given. Most (62%) of the patients had leukemia. A total of 45 (49%) patients had undergone stem cell transplantation; 80% received allogeneic grafts and 47% had graft-versus-host disease. High-dose corticosteroids were given during antifungal therapy in 26 (29%) patients. In all, 8 (9%) patients had new elevation in serum bilirubin during HD-CSP therapy; normalization occurred after voriconazole and HD-CSP were discontinued in 4 patients each. No other short-term or delayed adverse events were observed. In all, 40 (44%) patients died of IFD. High-dose corticosteroids during HD-CSP (odds ratio [OR] 8, 95% confidence interval [CI] 2.1-30.4; P < .002) and starting HD-CSP in the critical care unit (OR 67.5, 95% CI 5.25-868.9; P < .001) were associated with death from fungal disease. Prolonged HD-CSP therapy was well tolerated. Drug-induced hyperbilirubinemia may pose a potential limitation for continued HD-CSP use in highly susceptible patients with hematologic neoplasms and stem cell transplantation.

Efficacy of the combination of voriconazole and caspofungin in experimental pulmonary aspergillosis by different Aspergillus species

Objectives

Invasive pulmonary aspergillosis (IPA) caused by Aspergillus fumigatus, Aspergillus flavus, or Aspergillus niger is associated with high mortality. We evaluated the efficacy and compared the therapeutic effect differences of voriconazole (VRC) in combination with caspofungin (CAS) in transiently neutropenic rats infected by A. fumigatus, A. flavus, or A. niger.

Methods

Treatment groups consisted of VRC (10 mg/kg q12 h) monotherapy, CAS (1 mg/kg/day) monotherapy, combination of VRC (10 mg/kg q12 h) + CAS (1 mg/kg/day), and no drug for 10 consecutive days. The efficacy and the difference in the treatments were evaluated through prolongation of survival, reduction in serum galactomannan levels and residual fungal burden, and histological studies.

Results

For all the strains, the combination of VRC and CAS led to significant prolongation in survival (P < 0.05) and reduction in residual fungal burden (P < 0.05) compared with CAS alone, and decrease in serum galactomannan levels (P < 0.05) compared with either agent alone. The survival in the combined therapy groups was significantly improved compared to VRC monotherapy for the strains of A. flavus and A. niger (P < 0.05), but no significant difference for the strains of A. fumigatus (P > 0.05).

Conclusions

Combination of VRC and CAS was synergistic in IPA by A. flavus and A. niger, but small efficacy benefits in IPA by A. fumigatus.

Impact of in vivo triazole and echinocandin combination therapy for invasive pulmonary aspergillosis: enhanced efficacy against Cyp51 mutant isolates

Previous studies examining combination therapy for invasive pulmonary aspergillosis (IPA) have revealed conflicting results, including antagonism, indifference, and enhanced effects. The most commonly employed combination for this infection includes a mold-active triazole and echinocandin. Few studies have evaluated combination therapy from a pharmacodynamic (PD) perspective, and even fewer have examined combination therapy against both wild-type and azole-resistant Cyp51 mutant isolates. The current studies aim to fill this gap in knowledge. Four Aspergillus fumigatus isolates were utilized, including a wild-type strain, an Fks1 mutant (posaconazole susceptible and caspofungin resistant), and two Cyp51 mutants (posaconazole resistant). A neutropenic murine model of IPA was used for the treatment studies. The dosing design included monotherapy with posaconazole, monotherapy with caspofungin, and combination therapy with both. Efficacy was determined using quantitative PCR, and results were normalized to known quantities of conidia (conidial equivalents [CE]). The static dose, 1-log kill dose, and associated PD target area under the curve (AUC)/MIC ratio were determined for monotherapy and combination therapy. Monotherapy experiments revealed potent activity for posaconazole, with reductions of 3 to 4 log10 Aspergillus CE/ml with the two "low"-MIC isolates. Posaconazole alone was less effective for the two isolates with higher MICs. Caspofungin monotherapy did not produce a significant decrease in fungal burden for any strain. Combination therapy with the two antifungals did not enhance efficacy for the two posaconazole-susceptible isolates. However, the drug combination produced synergistic activity against both posaconazole-resistant isolates. Specifically, the combination resulted in a 1- to 2-log10 decline in burden that would not have been predicted based on the monotherapy results for each drug. This corresponded to a reduction in the free-drug posaconazole AUC/MIC ratio needed for stasis of up to 17-fold. The data suggest that combination therapy using a triazole and an echinocandin may be a beneficial treatment strategy for triazole-resistant isolates.

Amphotericin B- and voriconazole-echinocandin combinations against Aspergillus spp.: Effect of serum on inhibitory and fungicidal interactions

Antifungal combination therapy with voriconazole or amphotericin B and an echinocandin is often employed as primary or salvage therapy for management particularly of refractory aspergillosis. The pharmacodynamic interactions of amphotericin B- and voriconazole-based combinations with the three echinocandins caspofungin, micafungin, and anidulafungin in the presence of serum were tested against 15 Aspergillus fumigatus complex, A. flavus complex, and A. terreus complex isolates to assess both their growth-inhibitory and fungicidal activities. The in vitro activity of each drug alone and in combination at a 1:1 fixed concentration ratio was tested with a broth microdilution colorimetric method, and interactions were assessed by isobolographic analysis. Synergy was found for all amphotericin B- and voriconazole-based combinations, with amphotericin B-based combinations showing strong inhibitory synergistic interactions (interaction indices of 0.20 to 0.52) and with voriconazole-based combinations demonstrating strong fungicidal synergistic interactions (interaction indices of 0.10 to 0.29) (P < 0.001). Drug- and species-specific differences were found, with caspofungin and the A. fumigatus complex exhibiting the weakest synergistic interactions. In the presence of serum, the synergistic interactions were reduced in the order (from largest to smallest decrease) micafungin > anidulafungin > caspofungin, and A. flavus complex > A. fumigatus complex > A. terreus complex, resulting in additive interactions, particularly for inhibitory activities of amphotericin B-echinocandin combinations and fungicidal activities of voriconazole-echinocandin combinations. Drug- and species-specific differences were found in the presence of serum for inhibitory activities of antifungal drugs, with the lowest interaction indices being observed for amphotericin B-caspofungin (median, 0.77) and for the A. terreus complex (median, 0.56). The present in vitro data showed that serum had a major impact on synergistic interactions of amphotericin B-echinocandin and voriconazole-echinocandin combinations, resulting in additive interactions and explaining the indifferent outcomes usually observed in vivo.

Combination of voriconazole and anidulafungin for treatment of triazole-resistant aspergillus fumigatus in an in vitro model of invasive pulmonary aspergillosis

Voriconazole is a first-line agent for the treatment of invasive pulmonary aspergillosis. Isolates with elevated voriconazole MICs are increasingly being seen, and the optimal treatment regimen is not defined. We investigated whether the combination of voriconazole with anidulafungin may be beneficial for the treatment of A. fumigatus strains with elevated voriconazole MICs. We used an in vitro model of the human alveolus to define the exposure-response relationships for a wild-type strain (voriconazole MIC, 0.5 mg/liter) and strains with defined molecular mechanisms of triazole resistance (MICs, 4 to 16 mg/liter). All strains had anidulafungin minimum effective concentrations (MECs) of 0.0078 mg/liter. Exposure-response relationships were estimated using galactomannan as a biomarker. Concentrations of voriconazole and anidulafungin were measured using high-performance liquid chromatography (HPLC). The interaction of voriconazole and anidulafungin was described using the Greco model. Fungal growth was progressively inhibited with higher drug exposures of voriconazole. Strains with elevated voriconazole MICs required proportionally greater voriconazole exposures to achieve a comparable antifungal effect. Galactomannan concentrations were only marginally reduced by anidulafungin monotherapy. An additive effect between voriconazole and anidulafungin was apparent. In conclusion, the addition of anidulafungin does not markedly alter the exposure-response relationship of voriconazole. A rise in serum galactomannan during combination therapy with voriconazole and anidulafungin should be interpreted as treatment failure and not attributed to a paradoxical reaction related to echinocandin treatment.

Assessment of efficacy of antifungals in experimental models of invasive aspergillosis in an era of emerging resistance: the value of real-time quantitative PCR

Experimental models of invasive aspergillosis (IA) have been used to explore pharmacokinetic and pharmacodynamic (PK/PD) properties of antifungal agents. Survival is still considered the golden standard effect measure but has the disadvantage that a large number of animals are needed to determine the dose-response relationships and PK/PD of antifungals. The feasibility of using fungal load by real-time quantitative PCR (qPCR) as an effect measure has been explored recently. The majority of studies reported convincingly demonstrate a larger dynamic range for qPCR compared to conventional assays. However interpretation and translating the results to guidance in clinical decision making need further study. It is expected that the use of qPCR will become the primary outcome measure for assessment of PK/PD relationships of antifungals in experimental models of IA.

Therapeutic and toxicologic studies in a murine model of invasive pulmonary aspergillosis

Invasive pulmonary aspergillosis remains problematic in immunocompromised patient populations. We studied potential therapeutic options in a murine model of pulmonary aspergillosis in triamcinolone-suppressed DBA/2 mice infected intranasally with conidia from Aspergillus fumigatus. Mice were treated with liposomal-amphotericin B (AmBi; AmBisome), lipid-complexed amphotericin B (ABLC; Abelcet), voriconazole (VCZ), micafungin (MICA), caspofungin (CAS) or deoxycholate amphotericin B (AMBd) given alone or in combination. Monotherapy with AmBi, ABLC, AMBd, CAS or MICA had activity in prolonging survival; however, only AMBd or CAS reduced fungal burden in the lungs and kidneys. Combinations of AmBi plus CAS or MICA prolonged survival, but were not better than monotherapy. VCZ was ineffective and AMBd plus CAS showed a possible antagonism. AmBi or ABLC at higher dosages, or loading-doses of AmBi resulted in reduced survival. Histopathology showed increased incidence of serious renal and mild hepatic toxicity in triamcinolone-treated mice given an amphotericin B regimen compared to no or only triamcinolone (minimal renal changes occurred with CAS or VCZ with or without triamcinolone); suggestive of combined toxicity of triamcinolone and the amphotericin B in AmBi or ABLC. Infected treated mice showed progressive pulmonary disease including abscesses, angioinvasion and abundant intralesional fungi. High loading-doses of AmBi were associated with nephrosis and damage to other tissues. No monotherapy or combination regimen showed superiority for the treatment of pulmonary aspergillosis in corticosteroid suppressed mice and the potential for combined drug toxicity was enhanced in these mice. High dosages of lipid-formulated amphotericin B also proved unsatisfactory. Additional studies are needed to evaluate improved treatment.

Newer combination antifungal therapies for invasive aspergillosis

Optimal therapy for invasive aspergillosis is unknown, and many clinicians have attempted to utilize a combination antifungal approach to improve outcomes. However, while numerous in vitro studies, animal models, and clinical reports suggest the possibility that combination antifungal therapy might offer improved results, there is no definitive accepted strategy. The currently available antifungals used in various combination approaches have not demonstrated clear improvement over monotherapy. The current classes of drugs targeting the cell wall and cell membrane may need adjunctive agents focused on separate cellular pathways, such as cell stress response or cellular signaling, to maximize efficacy. The calcineurin and the Hsp90 pathways are two such untouched arenas in which targeted manipulation may lead to great advances against aspergillosis.

Emergence of opportunistic mould infections in the hematopoietic stem cell transplant patient

Infection due to opportunistic moulds is an emerging problem in hematopoietic stem cell recipients. Through the 1990s, the incidence of invasive aspergillosis in allogenic graft recipients climbed steadily, peaking at 10% to 15%. In this decade, other opportunistic mould infections are emerging, including zygomycosis, fusariosis, and scedosporiosis. These epidemiologic changes are likely due to greater or different types of host immune suppression, medical interventions such as antifungal prophylaxis, and more successful treatment of aspergillosis, keeping immunosuppressed patients alive and at risk. The non-Aspergillus moulds generally exhibit variable susceptibility to antifungal agents, and outcomes continue to be disappointing. Thus, prevention of infection becomes a prominent concern in the care of these patients.

Helicobacter pylori: prevalence and antibiotic susceptibility among Kenyans

BACKGROUND

Helicobacter pylori infection in Kenya is staggeringly high. Evidence links infection of the gastric mucosa by H. pylori with subsequent development of gastric pathologies.

AIM

We investigated the prevalence of H. pylori in dyspeptic patients, its relationship with gastric pathologies, and associated antibiotic susceptibility profiles, and compared two media to find the appropriate medium that enhances growth and expedites culture and isolation.

METHODS

Rapid urease and histological tests were used to screen for H. pylori. Culture was performed to test sensitivity and evaluate media. Selective and nutritional supplements were added to culture media (Colombia blood agar and brain-heart infusion agar) for growth enhancement. E-test strips for metronidazole, amoxicillin and clarithromycin were used for susceptibility testing.

RESULTS

The prevalence of H. pylori infection in children was 73.3%, and 54.8% in adults. All the H. pylori investigated in this study were largely sensitive to clarithromycin (100%, minimum inhibiting concentration (MIC) <2 microg/ml), amoxicillin (100%, MIC <2 microg/ml) and metronidazole (95.4%, MIC <8 microg/ml). There was, however, occasional resistance to metronidazole (4.6%, MIC >8 microg/ml). Both Colombia blood and brain-heart infusion agar, with the supplements, effectively supported H. pylori growth. Growth was achieved in an average of 36 hours for primary isolations and 24 hours for subcultures.

CONCLUSION

The media described here reduce the time required to culture and isolate bacteria and perform susceptibility testing. Despite the high prevalence of H. pylori infection, the associated pathology is low and does not parallel H. pylori prevalence in the population.

Use of Antifungal Combination Therapy: Agents, Order, and Timing

Given the substantial morbidity and mortality related to invasive fungal infections, treatment with a combination of antifungal agents is often considered. A growing body of literature from in vitro studies, animal models, and clinical experience provides data evaluating this approach. This review describes combination antifungal strategies for the management of cryptococcal meningitis, invasive candidiasis, invasive aspergillosis, and rare mold infections. The potential effects that sequencing and timing have on the efficacy of such approaches are discussed, with a focus on recent clinical data in this arena.

Defining fractional inhibitory concentration index cutoffs for additive interactions based on self-drug additive combinations, Monte Carlo simulation analysis, and in vitro-in vivo correlation data for antifungal drug combinations against Aspergillus fumigatus

The fractional inhibitory concentration (FIC) index range of 0.5 to 4 that is commonly used to define additivity results in no interactions in most combination studies of antifungal agents. These results may differ from those of in vivo studies, where positive and negative interactions may be observed. We reassessed this in vitro FIC index range based on (i) the experimental variation of the checkerboard technique using multiple replicates, (ii) the ability to correctly determine purely additive self-drug and two-drug antagonistic combinations of amphotericin B (AMB) and voriconazole (VRC), (iii) Monte Carlo simulation analysis, and (iv) in vitro-in vivo correlation using experimental models of invasive pulmonary aspergillosis against the same Aspergillus fumigatus isolate based on visual, spectrophotometric, and colorimetric determinations of FICs after 24 and 48 h of incubation. FICs obtained after 24 h of incubation ranged from 0.5 to 1.25 for the self-drug additive combinations of AMB plus AMB and VRC plus VRC and from 2.25 to 4.25 for the antagonistic combination of AMB plus VRC. Monte Carlo simulation analysis showed that self-drug combinations were correctly classified as additive and that the combination of AMB plus VRC was correctly classified as antagonistic for >85% of the simulated FICs when deviation of the 95% confidence interval (CI) of replicate FICs from the additivity range of 1 to 1.25 was used to assess interactions after 24 h. In vitro-in vivo correlation analysis showed that the 95% CIs of the FICs of the in vivo synergistic combination anidulafungin plus VRC determined after 24 h were lower than 1 and the 95% CIs of the FICs of the in vivo antagonistic combination AMB plus ravuconazole were higher than 1.25. Adequate insight into weak pharmacodynamic interactions with in vivo relevance may be obtained by demonstrating that triplicate FICs at 24 h are outside an inclusive additivity range of 1 to 1.25.

Aspergillus fumigatus endocarditis in a pediatric liver transplant recipient: favorable outcome without cardiac surgery

Transplant recipients are very susceptible to invasive aspergillosis, which increases mortality rate. Disseminated aspergillosis in the liver transplant recipient can affect virtually any organ and endocarditis is often lethal despite cardiac surgery and antifungal therapy. We report the case of a eight-month-old girl who presented with Aspergillus fumigatus endocarditis 18 days after liver transplantation that was successfully treated by a combination of antifungal drugs associated to a low dosage of immunosuppressive therapy.

Combination therapy of advanced invasive pulmonary aspergillosis in transiently neutropenic rats using human pharmacokinetic equivalent doses of voriconazole and anidulafungin

At present, voriconazole (VOR) is the drug of first choice for treating invasive pulmonary aspergillosis (IPA). However, particularly in advanced stages of disease and in the severely immunocompromised host, the mortality remains substantial. The combination of VOR with an echinocandin may improve the therapeutic outcome. We investigate here whether combining VOR and anidulafungin (ANI) in advanced IPA in transiently neutropenic rats results in a higher therapeutic efficacy. Since VOR is metabolized more rapidly in rodents than in humans, dosage adjustment for VOR is necessary to obtain an area under the plasma concentration-time curve (AUC) in rodents that is equivalent to that of humans. In this study, the pharmacokinetics of VOR and ANI in rats were elucidated, and dosage schedules were applied that produced AUCs similar to those of humans. The developed dose schedules were well tolerated by the rats, without effects on renal and hepatic functions. VOR showed excellent efficacy in early IPA (100% rat survival). In advanced IPA, VOR was less efficacious (50% rat survival), whereas a significant decrease in galactomannan concentrations in lungs and sera was found in surviving rats. ANI administered in advanced IPA resulted in 22% rat survival, and the serum concentrations of fungal galactomannan were slightly but not significantly decreased. The addition of ANI to VOR did not result in significantly increased therapeutic efficacy in advanced IPA, resulting in 67% rat survival and a significant decrease in galactomannan concentration in serum. In conclusion, VOR monotherapy is therapeutically effective in the treatment of advanced-stage IPA and superior to the use of ANI. Combining both agents does not significantly improve the therapeutic outcome.

Fungicidal versus Fungistatic: what's in a word?

BACKGROUND

Historically clinicians have preferred to use 'cidal' antifungal agents, particularly in critically ill patients. However, data to support the belief that the preferential use of a 'cidal' agent results in better patient outcomes has been lacking.

OBJECTIVE

This review examined the in vitro definitions of fungicidal and fungistatic as well as their strengths and limitations.

METHODS

A Medline search was performed in order to identify literature that examined the in vitro or in vivo impact of fungicidal and fungistatic activity. The study examined three common invasive fungal infections, namely cryptococcal meningitis, candidemia and invasive aspergillosis, where sufficient comparisons of fungicidal and fungistatic agents have been performed to allow for the evaluation of the clinical importance of these in vitro findings.

RESULTS AND CONCLUSION

A clear clinical benefit of fungicidal agents over those with fungistatic activity remains elusive. Patients with cryptococcal meningitis clearly benefit from early fungicidal therapy but require long-term suppression. The data in invasive Candida sp. infections are tantalizing and suggest that fungicidal therapy may be important. However, the data for invasive aspergillosis do not support the hypothesis that fungicidal activity improves outcomes.

[In vitro antifungal activity of voriconazole: New data after the first years of clinical experience]

Voriconazole has been developed to meet the increasing need for new and useful antifungal agents for the treatment of invasive mycoses. This review describes the spectrum of voriconazole antifungal activity based on data from in vitro studies published during the last three years. This survey demonstrates that voriconazole has a broad antifungal spectrum against the most common fungal pathogens being its action fungistatic for Candida and fungicidal for Aspergillus and other filamentous fungi. Overall, more than 95% of all Candida isolates tested are susceptible to voriconazole and less than 3% are resistant. Similar or even better activity rates have been described for Aspergillus, Cryptococcus and most of yeasts and moulds of medical importance. We also discuss the limitations related to the azole cross-resistance observed in some Candida glabrata isolates, the poor activity of voriconazole against Scedosporium prolificans, its activity against fungal biofilms and the great potential usefulness of combination of voriconazole with other antifungal drugs.

The pharmacology and clinical use of caspofungin

Caspofungin was the first echinocandin to be licensed for the treatment of invasive fungal infections. Caspofungin has in vitro and in vivo activity against Candida spp. and Aspergillus spp., which constitute the majority of medically important opportunistic fungal pathogens. Caspofungin inhibits the synthesis of the 1,3-beta-glucan, with resultant osmotic instability and lysis. The pharmacology of caspofungin is relatively complex. Trafficking of drug into tissues is an important determinant of the shape of the concentration-time relationship. Caspofungin has demonstrated efficacy in experimental models of invasive candidiasis and aspergillosis, which reflect its activity in the treatment of oropharyngeal, esophageal and disseminated candidiasis, as well as salvage therapy for patients with invasive aspergillosis.

A comparative evaluation of properties and clinical efficacy of the echinocandins

With the increase in prevalence of fungal infections, newer antifungal agents are needed to effectively treat invasive disease, and at the same time minimize adverse effects from therapy. The echinocandins comprise a novel class of antifungals; their mechanism of action involves inhibiting 1,3-beta-D-glucan synthase, which is essential in cell wall synthesis for certain fungi. All three echinocandins are US FDA-approved for the treatment of esophageal candidiasis. Caspofungin and anidulafungin are licensed for the treatment of candidemia, and other select forms of invasive candidiasis. Micafungin is at present the only echinocandin approved for prophylaxis of fungal infections in hematopoietic stem cell transplants; whereas caspofungin is approved for empiric therapy of febrile neutropenia. Although all three echinocandins are active against Aspergillus, only caspofungin is presently approved for salvage therapy in invasive aspergillosis. Combination therapy with echinocandins plus other licensed antifungal therapy shows promise in treating invasive aspergillosis. This article will explore the similarities and differences among the echinocandins.

Measurement of voriconazole activity against Candida albicans, C. glabrata, and C. parapsilosis isolates using time-kill methods validated by high-performance liquid chromatography

We developed a high-performance liquid chromatography (HPLC) assay to validate time-kill and postantifungal-effect (PAFE) experiments for voriconazole against Candida albicans, Candida glabrata, and Candida parapsilosis isolates. Voriconazole exerted prolonged fungistatic activity but no PAFE at concentrations achievable in human sera. HPLC confirmed that experiments were conducted at the desired steady-state voriconazole concentrations.

Voriconazole : a review of its use in the management of invasive fungal infections

Voriconazole (VFEND), a synthetic second-generation, broad-spectrum triazole derivative of fluconazole, inhibits the cytochrome P450 (CYP)-dependent enzyme 14-alpha-sterol demethylase, thereby disrupting the cell membrane and halting fungal growth. In the US, intravenous and/or oral voriconazole is recommended in adults for the treatment of invasive aspergillosis, candidaemia in non-neutropenic patients, disseminated infections caused by Candida spp., oesophageal candidiasis, and in patients with scedosporiosis and fusariosis who are refractory to or intolerant of other antifungal therapy. In Europe, intravenous and/or oral voriconazole is recommended in adults and paediatric patients of at least 2 years of age for the treatment of invasive aspergillosis, candidaemia in non-neutropenic patients, fluconazole-resistant serious invasive Candida spp. infections, scedosporiosis and fusariosis. In large randomised trials, voriconazole was an effective and generally well tolerated primary treatment for candidiasis and invasive aspergillosis in adults and adolescents. More limited data also support the use of voriconazole for the treatment of invasive fungal infections in children, in those with rare fungal infections, such as Fusarium spp. or Scedosporium spp., and in those refractory to or intolerant of other standard antifungal therapies. The availability of both parenteral and oral formulations and the almost complete absorption of the drug after oral administration provide for ease of use and potential cost savings, and ensure that therapeutic plasma concentrations are maintained when switching from intravenous to oral therapy. On the other hand, the numerous drug interactions associated with voriconazole may limit its usefulness in some patients. Further clinical experience will help to more fully determine the position of voriconazole in relation to other licensed antifungal agents. In the meantime, voriconazole is a valuable emerging option for the treatment of invasive aspergillosis and rare fungal infections, including Fusarium spp. and Scedosporium spp. infections, and provides an alternative option for the treatment of candidiasis, particularly where the causative organism is inherently resistant to other licensed antifungal agents.

High-dose caspofungin combination antifungal therapy in patients with hematologic malignancies and hematopoietic stem cell transplantation

Pneumocandins have concentration-dependent antifungal activity and higher dose of caspofungin (HD-CAP) in combination with other licensed antifungal therapy (OLAT) may improve response. Thirty-four patients who received HD-CAP were compared with 63 patients who received standard dose (SD)-CAP. There were no differences between the groups in either patient or disease characteristics. Significantly more patients in the HD-CAP arm had extrapulmonary infections (29 vs 8% in SD group; P=0.0053), and non-Aspergillus species infection (21 vs 6%; P=0.05) and had received prior antifungal therapy (71 vs 33%; P=0.0004). No serious adverse reactions were noted in patients receiving HD- or SD-CAP therapy. Twelve weeks after treatment commenced 44% had a complete or partial response compared with 29% in SD-CAP group (P=0.1). Logistic regression analysis showed a significant probability of a favorable outcome at 12 weeks in patients who received HD-CAP (OR 3.066, 95% CI, 1.092-8.61; P=0.033). This may in part reflect higher number of patients in HD group had received granulocyte-macrophage colony-stimulating factor (41 vs 14% in SD group; P=0.04) and/or interferon gamma (26 vs 5% in SD group; P=0.003) immune enhancement. Further studies are needed to evaluate efficacy of HD-CAP in severely immunosuppressed cancer patients with invasive fungal infections.

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.

Aerosolized nanostructured itraconazole as prophylaxis against invasive pulmonary aspergillosis

OBJECTIVE

Prophylactic strategies against invasive pulmonary aspergillosis are often limited by drug interactions and toxicities. Targeted airway delivery of antifungals to the lungs may avoid these pitfalls. We evaluated the effectiveness of an aerosolized nanostructured formulation of itraconazole produced by spray freezing into liquid (SFL) as prophylaxis against invasive pulmonary aspergillosis caused by A. fumigatus.

METHODS

Immunocompromised Balb/C mice received either itraconazole by oral gavage (Sporanox Oral Liquid [SOL] 30 mg/kg TID) or by aerosolization (SFL 30 mg/kg via 20 min aerosolizations, or control, BID). Dosing began 2 days prior to pulmonary inoculation with A. fumigatus and continued for 7 days post-inoculation. Changes in lung histopathology were also assessed. In the survival arm, mice were monitored over a 5 day period following discontinuation of therapy and survival was assessed by Kaplan-Meier analysis.

RESULTS

SFL survival (35%) was greater compared to control (10%; p=0.03) and SOL (0%; p=0.02). Histopathology demonstrated severe invasive disease involving vessels and small airways in control and SOL animals. SFL animals demonstrated colonization with some invasion predominately of large airways.

CONCLUSIONS

Prophylactic aerosolization of nanostructured SFL significantly improved survival and limited invasive disease of small airways due to A. fumigatus.

Pharmacokinetics and pharmacodynamics of antifungals

Application of pharmacodynamic principles to antifungal drug therapy of Candida and Aspergillus infections has provided and understanding of the relationship between drug dosing and treatment efficacy. Observations of the pharmacodynamics of triazoles and AmB have correlated with the results of clinical trials and have proven useful for validation of in vitro susceptibility breakpoints. Although there remain many unanswered questions regarding antifungal pharmacodynamics, available data suggest usefulness in the application of pharmacodynamics to antifungal clinical development. Future application of these principles should aid in the design of optimal combination antifungal therapies.

Standardization of an experimental murine model of invasive pulmonary aspergillosis

Evaluating new therapeutic agents for invasive aspergillosis requires animal models that are reproducible among different laboratories. We therefore evaluated a murine model of aerosol infection in two independent laboratories and found a high level of both intra- and interlaboratory reproducibility of survival, fungal burden over time, and the efficacy of liposomal amphotericin B.

New strategies of antifungal therapy in hematopoietic stem cell transplant recipients and patients with hematological malignancies

Invasive fungal infections (IFIs) are associated with considerable morbidity and mortality among high-risk individuals. Outcomes for IFI historically have been suboptimal and associated with a high mortality rate, hence global prophylaxis strategies have been applied to at-risk populations. Among certain populations, fluconazole prophylaxis has reduced systemic and superficial infections caused by Candida species. Newer azoles are currently being evaluated as prophylaxis and have the potential to provide protection against mould pathogens that are more troublesome to treat once they occur. Global prophylaxis strategies have the shortcoming of subjecting patients to therapy that ultimately will not need it. Targeted prophylaxis has the advantage of treating only patients at highest risk using some parameter of greater host susceptibility. Prophylaxis strategies are most suitable in patients at the highest risk for IFI. For patient groups whose risk is somewhat lower or when suspicion of IFI occurs in patients receiving prophylaxis, empirical antifungal therapy is often employed following a predefined period of fever. Again this approach subjects many non-infected patients to unnecessary and toxic therapy. A more refined approach such as presumptive or pre-emptive therapy whereby treatment is only initiated upon positive identification of a surrogate marker of infection in combination with clinical and radiological signs will subject fewer patients to toxic and expensive treatments.

Emerging echinocandins for treatment of invasive fungal infections

The echinocandins are a new class of antifungals, developed in response to the need for safe and effective antifungals for the treatment of invasive fungal infections. These agents work by inhibiting 1,3-beta-d-glucan synthase, an enzyme essential for production of cell walls in select fungi. Echinocandins appear to demonstrate favourable activity in vitro against a variety of yeasts (including both Candida albicans and non-albicans Candida) as well as select moulds (including Aspergillus spp.) In general, all echninocandins demonstrate a favourable safety profile and require once-daily parenteral administration. Caspofungin is the first of these agents to be available in the US, and is approved for empirical antifungal therapy in febrile neutropenic patients, candidaemia and select forms of invasive candidiasis, and for management of invasive aspergillosis in patients refractory to or intolerant of other therapies. Micafungin was recently approved by the FDA for treatment of oesophageal candidiasis, and for the prophylaxis of fungal infections in haematopoietic stem cell transplant recipients. Emerging data indicate micafungin may have an important role in the treatment of invasive forms of candidiasis. Anidulafungin is an echinocandin approved in the US for treatment of candidaemia and oesophageal candidiasis. Aminocandin (HMR-3702, IP-960) is an investigational agent, with published experience limited to in vitro studies and animal models of infection.

Is combination antifungal therapy for invasive aspergillosis a necessity in hematopoietic stem-cell transplant recipients?

PURPOSE OF REVIEW

The use of combination antifungal therapy in hematopoietic stem-cell transplantation patients is controversial and limited by a paucity of controlled data. The recent literature is reviewed and the relative arguments for and against combination antifungal therapy are outlined with summative recommendations to assist practitioners in decision-making.

RECENT FINDINGS

There is an abundance of in-vitro and murine in-vivo combination antifungal literature, whereas clinical data are less abundant and controlled. Of the published case series there is a suggested benefit to combination therapy over monotherapy, although there are limitations to the available literature. Other issues in the combination debate that are addressed include the following: improved response rates and a survival advantage have been demonstrated in recent monotherapy studies; response rates in most published combination therapy studies do not suggest large gains over monotherapy; the lack of sustained survival advantage to combination therapy studies; and finally the consideration of host defenses in treatment responses.

SUMMARY

Based on available data, combination therapy is not warranted at the initial diagnosis of invasive aspergillosis. Randomized, controlled trials with rigorous study design are needed.

Aspergillus fumigatus tricuspid native valve endocarditis in a non-intravenous drug user

Invasive aspergillosis is an emerging infection mainly affecting immunocompromised patients. This report details a case of Aspergillus fumigatus tricuspid native valve endocarditis complicated by recurrent septic pulmonary emboli in a young, non-intravenous drug user. He was treated by surgical resection of the posterior leaflet of the tricuspid valve and the vegetations, as well as by valvuloplasty, which was followed by a combination of liposomal amphotericin B and voriconazole as acute-phase therapy and voriconazole alone as suppression therapy.

Combination of Voriconazole and Caspofungin as Primary Therapy for Invasive Aspergillosis in Solid Organ Transplant Recipients: A Prospective, Multicenter, Observational Study

BACKGROUND

: The efficacy of the combination of voriconazole and caspofungin when used as primary therapy for invasive aspergillosis in organ transplant recipients has not been defined.

METHODS

: Transplant recipients who received voriconazole and caspofungin (n=40) as primary therapy for invasive aspergillosis (proven or probable) in a prospective multicenter study between 2003 and 2005 were compared to a control group comprising a cohort of consecutive transplant recipients between 1999 and 2002 who had received a lipid formulation of AmB as primary therapy (n=47). In vitro antifungal testing of Aspergillus isolates to combination therapy was correlated with clinical outcome.

RESULTS

: Survival at 90 days was 67.5% (27/40) in the cases, and 51% (24/47) in the control group (HR 0.58, 95% CI, 0.30-1.14, P=0.117). However, in transplant recipients with renal failure (adjusted HR 0.32, 95% CI: 0.12-0.85, P=0.022), and in those with A. fumigatus infection (adjusted HR 0.37, 95% CI: 0.16-0.84, P=0.019), combination therapy was independently associated with an improved 90-day survival in multivariate analysis. No correlation was found between in vitro antifungal interactions of the Aspergillus isolates to the combination of voriconazole and caspofungin and clinical outcome.

CONCLUSIONS

: Combination of voriconazole and caspofungin might be considered preferable therapy for subsets of organ transplant recipients with invasive aspergillosis, such as those with renal failure or A. fumigatus infection.