In vitro interaction of caspofungin acetate with voriconazole against clinical isolates of Aspergillus spp

Pulmonary aspergillosis: diagnosis and treatment

Aspergillusspecies are the most frequent cause of fungal infections of the lungs with a broad spectrum of clinical presentations including invasive pulmonary aspergillosis (IPA) and chronic pulmonary aspergillosis (CPA). IPA affects immunocompromised populations, which are increasing in number and diversity with the advent of novel anti-cancer therapies. Moreover, IPA has emerged as a complication of severe influenza and coronavirus disease 2019 in apparently immunocompetent hosts. CPA mainly affects patients with pre-existing lung lesions and is recognised increasingly frequently among patients with long-term survival following cure of tuberculosis or lung cancer. The diagnosis of pulmonary aspergillosis is complex as it relies on the presence of clinical, radiological and microbiological criteria, which differ according to the type of pulmonary aspergillosis (IPA or CPA) and the type of patient population. The management of pulmonary aspergillosis is complicated by the limited number of treatment options, drug interactions, adverse events and the emergence of antifungal resistance.

Efficacy and Safety of Combination Antifungals as Empirical, Preemptive, and Targeted Therapies for Invasive Fungal Infections in Intensive-Care Units

Purpose

To determine whether combinations of antifungal drugs are effective and safe for patients in intensive-care units.

Methods

This study compared the efficacy and safety of caspofungin (CAS), voriconazole (VOR), amphotericin B liposome (L-AmB), CAS+VOR, and CAS+L-AmB as empirical, preemptive, and targeted therapies for invasive fungal infection (IFI).

Results

Comparing the CAS, VOR, and CAS+VOR groups revealed that there were no differences in response rates between all therapy types, IFI-associated death within 90 days was less common in the CAS+VOR group (1.8%) than the VOR group (14.3%), and there were more adverse events in the VOR group than in the CAS group (P < 0.05). For empirical or preemptive therapy, the CAS group had a better response rate (80.0%) than the CAS+VOR group (47.1%), and there were more adverse events in the VOR group than in the CAS group (P < 0.05). For targeted therapy, no differences were found for efficacy and safety. There were no differences among the CAS, L-AmB, and CAS+L-AmB groups in efficacy and safety.

Conclusion

Patients who received CAS monotherapy as an empirical or preemptive therapy could achieve good outcomes. Patients who received CAS+VOR or CAS+L-AmB achieved almost the same outcomes when compared with those who received CAS, VOR, and L-AmB monotherapy as targeted therapies, but those who received CAS+VOR had a lower IFI mortality rate than did those who received VOR monotherapy.

In vitro synergistic antifungal activities with caspofungin plus fluconazole or voricanazole against Candida species determined by Etest method

OBJECTIVES

Increased resistance of Candida species, especially C.glabrata is problematic. Combination antifungal therapies were studied to solve the problem.

METHODS

In this study, combinations of caspofungin with fluconazole and voricanazole were evaluated in 28 Candida species (included 15 C.glabrata and 12 with FKS mutation) at 24 and 48 h by two Etest methods (direct cover method and MIC/MIC method).

RESULTS

For Candida isolates, direct cover method showed synergy of caspofungin-fluconazole and caspofungin-voriconazole against 12/28 (43%) isolates at 24 h, and against 16/28 (57%) isolates at 48 h. MIC/MIC method showed synergy of caspofungin-fluconazole and caspofungin-voriconazole against 11/28 (39%) and 12/28 (43%) isolates at 24 h, and against 16/28 (57%) and 17/28 (61%) isolates at 48 h, respectively. For C.glabrata, direct cover method showed synergy of caspofungin-fluconazole and caspofungin-voriconazole against 11/15 (73%) and 10/15 (67%) isolates at 24 h, and 11/15 (73%) and 13/15 (87%) isolates at 48 h, respectively. MIC/MIC method showed synergy of caspofungin-fluconazole and caspofungin-voriconazole against both 11/15 (73%) isolates at 24 h, and 10/15 (67%) and 14/15 (93%) isolates at 48 h, respectively.

CONCLUSION

A combination of caspofungin and fluconazole or voriconazole might be effective in infections due to Candida species, especially for C.glabrata with FKS mutation.

Aspergillus tubingensis Endocarditis: A Case Report and Review of the Literature

Aspergillus endocarditis is a rare infection that may affect immunocompetent patients following heart valve replacement or heart surgery. We report the case of a 39 year old woman with a history of intravenous drug use who developed endocarditis with direct examination of the resected valve and vegetation showing the presence of mycelia. Cultures were positive for an Aspergillus of section Nigri, which was subsequently identified as Aspergillus tubingensis by sequencing. The clinical course was favorable following surgery and prolonged antifungal therapy (8 months in total). Antifungal susceptibility testing showed good in vitro activity of amphotericin B, voriconazole and echinocandins against planktonic cells of this A. tubingensis isolate. However, only amphotericin B displayed significant activity against biofilms. In vitro combinations of voriconazole or amphotericin B with echinocandins did not meet the criteria of synergism. Our review of the literature identified 17 other cases of endocarditis attributed to Aspergillus of section Nigri with an overall mortality rate of 57% (100% in the absence of surgery). Endocarditis caused by Aspergillus niger and related cryptic species are rare events, for which surgical management appears to be crucial for outcome. While amphotericin B was the only antifungal drug displaying significant anti-biofilm activity, the type and duration of antifungal therapy remain to be determined.

Review on Current Status of Echinocandins Use

Fungal infections are rising all over the world every year. There are only five medical compound classes for treatment: triazoles, echinocandins, polyenes, flucytosine and allylamine. Currently, echinocandins are the most important compounds, because of their wide activity spectrum and much lower sides effects that may occur during therapy with other drugs. Echinocandins are secondary metabolites of fungi, which can inhibit the biosynthesis of β-(1,3)-D-glucan. These compounds have fungicidal and fungistatic activity depending on different genera of fungi, against which they are used. Echinocandin resistance is rare—the major cause of resistance is mutations in the gene encoding the β-(1,3)-D-glucan synthase enzyme. In this review of the literature we have summarized the characteristics of echinocandins, the mechanism of their antifungal activity with pharmacokinetics and pharmacodynamics, and the resistance issue.

Echinocandins for the Treatment of Invasive Aspergillosis: from Laboratory to Bedside

Echinocandins (caspofungin, micafungin, anidulafungin), targeting β-1,3-glucan synthesis of the cell wall, represent one of the three currently available antifungal drug classes for the treatment of invasive fungal infections. Despite their limited antifungal activity against Aspergillus spp., echinocandins are considered an alternative option for the treatment of invasive aspergillosis (IA). This drug class exhibits several advantages, such as excellent tolerability and its potential for synergistic interactions with some other antifungals. The objective of this review is to discuss the in vitro and clinical efficacy of echinocandins against Aspergillus spp., considering the complex interactions between the drug, the mold, and the host. The antifungal effect of echinocandins is not limited to direct inhibition of hyphal growth but also induces an immunomodulatory effect on the host's response. Moreover, Aspergillus spp. have developed important adaptive mechanisms of tolerance to survive and overcome the action of echinocandins, such as paradoxical growth at increased concentrations. This stress response can be abolished by several compounds that potentiate the activity of echinocandins, such as drugs targeting the heat shock protein 90 (Hsp90)-calcineurin axis, opening perspectives for adjuvant therapies. Finally, the present and future places of echinocandins as prophylaxis, monotherapy, or combination therapy of IA are discussed in view of the emergence of pan-azole resistance among Aspergillus fumigatus isolates, the occurrence of breakthrough IA, and the advent of new long-lasting echinocandins (rezafungin) or other β-1,3-glucan synthase inhibitors (ibrexafungerp).

In vitro activities of six antifungal agents and their combinations against Chaetomium spp

PURPOSE

To assess in vitro activities of six antifungal agents (amphotericin B, itraconazole, voriconazole, posaconazole, caspofungin and terbinafine) and the combined effects of eight pairs of them (caspofungin or terbinafine with amphotericin B, itraconazole, voriconazole or posaconazole) against 22 isolates of Chaetomium spp.

METHODOLOGY

The broth microdilution method drafted by the Clinical and Laboratory Standards Institute and the checkerboard method were used in this study to evaluate in vitro activities of antifungal drugs both alone and in combination against Chaetomium spp.

RESULTS

Amphotericin B and triazoles exhibited lower geometric mean, MIC50 and MIC90 than caspofungin and terbinafine. Besides, all the paired drugs displayed varying degrees of synergism, with the interactions between caspofungin and itraconazole ranking first (86.36 %).

CONCLUSION

Our study illustrated varying degrees of synergism between caspofungin or terbinafine and itraconazole, voriconazole, posaconazole or amphotericin B towards Chaetomium spp., which could be a reference for the clinical treatment of Chaetomium spp. infections.

Azole-induced cell wall carbohydrate patches kill Aspergillus fumigatus

Azole antifungals inhibit the fungal ergosterol biosynthesis pathway, resulting in either growth inhibition or killing of the pathogen, depending on the species. Here we report that azoles have an initial growth-inhibitory (fungistatic) activity against the pathogen Aspergillus fumigatus that can be separated from the succeeding fungicidal effects. At a later stage, the cell wall salvage system is induced. This correlates with successive cell integrity loss and death of hyphal compartments. Time-lapse fluorescence microscopy reveals excessive synthesis of cell wall carbohydrates at defined spots along the hyphae, leading to formation of membrane invaginations and eventually rupture of the plasma membrane. Inhibition of β-1,3-glucan synthesis reduces the formation of cell wall carbohydrate patches and delays cell integrity failure and fungal death. We propose that azole antifungals exert their fungicidal activity by triggering synthesis of cell wall carbohydrate patches that penetrate the plasma membrane, thereby killing the fungus. The elucidated mechanism may be potentially exploited as a novel approach for azole susceptibility testing.

Azole antifungals inhibit fungal ergosterol biosynthesis. Here, Geißel et al. show that the fungicidal activity of azoles involves excessive synthesis of cell wall carbohydrates at defined spots along the hyphae, leading to formation of membrane invaginations and eventually rupture of the plasma membrane.

Voriconazole plus caspofungin for treatment of invasive fungal infection in children with acute leukemia

Background

Invasive fungal infections (IFIs) are a life-threatening problem in immunocompromised patients. Despite timely diagnosis and appropriate antifungal therapy, clinical outcomes of IFIs remain unsatisfactory, necessitating treatment with a combination of antifungal agents. Therefore, childhood leukemic patients treated with voriconazole plus caspofungin were evaluated for the safety and efficacy of the combination antifungal therapy to treat IFIs.

Methods

In this retrospective study, medical records were retrieved for patients admitted to the Pediatric Department of Yeungnam University Hospital, Daegu, South Korea, between April 2009 and May 2013. Medical records of 22 patients were analyzed.

Results

Of the 22 patients studied, nine (41%) had been diagnosed with probable IFI, and 13 (59%) with possible IFI. All patients, except one, were already receiving antifungal monotherapy for the treatment of neutropenic fever. After a diagnosis of IFI was confirmed, antifungal monotherapy was replaced with combination therapy. The study's overall response rate was 90.9%, with complete responses in 86.3% of the patients. Two patients experienced a side effect of a small increase in liver enzyme levels.

Conclusion

Voriconazole plus caspofungin combination therapy is an effective and safe treatment for serious IFI in pediatric patients with acute leukemia.

Echinocandins: The Expanding Antifungal Armamentarium

The echinocandins are large lipopeptide molecules that, since their discovery approximately 41 years ago, have emerged as important additions to the expanding armamentarium against invasive fungal diseases. Echinocandins exert in vitro and in vivo fungicidal action against most Candida species and fungistatic action against Aspergillus species. However, the population of patients at risk for developing invasive fungal infections continues to increase. New therapeutic strategies using echinocandins are needed to improve clinical outcomes in patients with invasive fungal disease.

Caspofungin: Pharmacodynamics, pharmacokinetics, clinical uses and treatment outcomes

Over the past decade, echinocandins have emerged as first-line antifungal agents for many Candida infections. The echinocandins have a unique mechanism of action, inhibiting the synthesis of β-1,3-d-glucan polymers, key components of the cell wall in pathogenic fungi. Caspofungin was the first echinocandin antifungal agent to become licensed for use. The objectives of this review are to summarize the existing published data on caspofungin, under the subject headings of chemistry and mechanism of action, spectrum of activity, pharmacodynamics, pharmacokinetics, clinical studies, safety, drug interactions, dosing, and an overview of the drug's current place in therapy.

Consensus guidelines for the treatment of invasive mould infections in haematological malignancy and haemopoietic stem cell transplantation, 2014

Mould species represent the pathogens most commonly associated with invasive fungal disease in patients with haematological malignancies and patients of haemopoietic stem cell transplants. Invasive mould infections in these patient populations, particularly in the setting of neutropenia, are associated with high morbidity and mortality, and significantly increase the complexity of management. While Aspergillus species remain the most prevalent cause of invasive mould infections, Scedosporium and Fusarium species and the Mucormycetes continue to place a significant burden on the immunocompromised host. Evidence also suggests that infections caused by rare and emerging pathogens are increasing within the setting of broad-spectrum antifungal prophylaxis and improved survival times placing immunosuppressed patients at risk for longer. These guidelines present evidence-based recommendations for the antifungal management of common, rare and emerging mould infections in both adult and paediatric populations. Where relevant, the role of surgery, adjunctive therapy and immunotherapy is also discussed.

Successful treatment of Batrachochytrium salamandrivorans infections in salamanders requires synergy between voriconazole, polymyxin E and temperature

Chytridiomycosis caused by the chytrid fungus Batrachochytrium salamandrivorans (Bsal) poses a serious threat to urodelan diversity worldwide. Antimycotic treatment of this disease using protocols developed for the related fungus Batrachochytrium dendrobatidis (Bd), results in therapeutic failure. Here, we reveal that this therapeutic failure is partly due to different minimum inhibitory concentrations (MICs) of antimycotics against Bsal and Bd. In vitro growth inhibition of Bsal occurs after exposure to voriconazole, polymyxin E, itraconazole and terbinafine but not to florfenicol. Synergistic effects between polymyxin E and voriconazole or itraconazole significantly decreased the combined MICs necessary to inhibit Bsal growth. Topical treatment of infected fire salamanders (Salamandra salamandra), with voriconazole or itraconazole alone (12.5 μg/ml and 0.6 μg/ml respectively) or in combination with polymyxin E (2000 IU/ml) at an ambient temperature of 15 °C during 10 days decreased fungal loads but did not clear Bsal infections. However, topical treatment of Bsal infected animals with a combination of polymyxin E (2000 IU/ml) and voriconazole (12.5 μg/ml) at an ambient temperature of 20 °C resulted in clearance of Bsal infections. This treatment protocol was validated in 12 fire salamanders infected with Bsal during a field outbreak and resulted in clearance of infection in all animals.

Septic-Metastasizing Aspergillus-Encephalitis Mimicking Massive Cerebral Infarction in a Heart Transplant Recipient: A Case Report

Invasive fungal infection after solid-organ transplantation is known as a severe complication and carries with it a high risk of infection-related mortality. Among patients after heart transplant Aspergillus species most often cause atypical pneumonia. The incidence of invasive aspergillosis after heart transplant has been reported from 3% to 14%. It is the opportunistic pathogen with the highest mortality, ranging from 50% to 80%. Prompt antifungal therapy is crucial, but rapid diagnostic procedures with sufficient sensitivity and specificity are lacking at the moment. We present a rare case of a patient with massive metastasizing invasive aspergillosis within 1 month after heart transplant, undetected before death.

Clinical experience of the use of voriconazole, caspofungin or the combination in primary and salvage therapy of invasive aspergillosis in haematological malignancies

Invasive aspergillosis (IA) is a life-threatening infection in severely immunocompromised haematological malignancy patients. In this study, the efficacy and safety of caspofungin, voriconazole or the combination as primary and salvage therapy in patients with IA were compared. The study included 181 patients with haematological malignancies and IA who received primary or salvage therapy with caspofungin, voriconazole or the combination. In total, 138 patients who received treatment for ≥7 days were analysed; 86 underwent primary antifungal therapy (15 with caspofungin, 38 with voriconazole and 33 with both). Among the salvage therapy patients, 17 received caspofungin, 24 received voriconazole and 35 received both. In the primary therapy group, no difference in therapy response was found, but caspofungin was associated with higher IA mortality rates. A multivariate competing risk analysis of primary antifungal therapy revealed that voriconazole was independently associated with lower IA-associated mortality rates than caspofungin (hazard ratio=0.2, 95% confidence interval 0.06-0.96; P=0.04). In the salvage therapy group, the three treatment groups had similar responses and IA-associated mortality rates. The combination of voriconazole and caspofungin did not result in better outcomes compared with voriconazole alone, as primary or salvage therapy, in haematological malignancy patients. However, voriconazole was associated with a lower Aspergillus-associated mortality rate compared with caspofungin monotherapy.

Studies of the in vitro antibacterial activities of several polyphenols against clinical isolates of methicillin-resistant Staphylococcus aureus

In this study, we report the antibacterial activities of six polyphenols (i.e., luteolin, quercetin, scutellarin, apigenin, chlorogenic acid, and resveratrol) against 29 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), and in vitro antibacterial activities of two-drug combinations. All of the MRSA strains evaluated were clinical isolates from patients with MRSA bacteremia. The antibacterial activities were determined by agar dilution method, and the two-drug antibacterial activities were determined by the checkerboard agar dilution method. It was found that luteolin, quercetin and resveratrol show obvious antibacterial activities against MRSA, and the results of two-drug antibacterial activity show either synergy or additivity, without evidences of antagonistic effects.

Treatment of Aspergillus terreus infections: a clinical problem not yet resolved

Despite the use of recommended therapies, invasive infections by Aspergillus terreus show a poor response. For years, investigative studies on the failure of therapy of fungal infections have focused on in vitro susceptibility data. However, it is well known that low minimum inhibitory concentrations (MICs) are not always predictive of response to therapy despite a correct dosage schedule. Many experimental and clinical studies have tried to establish a relationship between MICs and outcome in serious fungal infections but have come to contradictory and even surprising conclusions. The success or failure of treatment is determined by many factors, including the in vitro susceptibility of the causative fungal isolate, the pharmacokinetics/pharmacodynamics of the drug used for treatment, pharmacokinetic variability in the population, and the underlying disease that patients suffer. To try to understand this poor response to treatment, available data on the in vitro susceptibility of A. terreus, the experimental and clinical response to amphotericin B, triazoles and echinocandins, and the pharmacokinetics/pharmacodynamics of these antifungals have been reviewed. Of special interest are the fungistatic activites of these drugs against A. terreus and the high interpatient variability of serum drug levels observed in therapy based on triazoles, which make monitoring of infected patients necessary.

Current and future therapies for invasive aspergillosis

Invasive fungal infections have increase worldwide and represent a threat for immunocompromised patients including HIV-infected, recipients of solid organ and stem cell transplants, and patients receiving immunosuppressive therapies. High mortality rates and difficulties in early diagnosis characterize pulmonary fungal infections. Invasive pulmonary aspergillosis has been reviewed focussing on therapeutic management. Although new compounds have become available in the past years (i.e., amphotericin B lipid formulations, last-generation azoles, and echinocandines), new diagnostic tools and careful therapeutic management are mandatory to assure an early appropriate targeted treatment that represents the key factor for a successful conservative approach in respiratory fungal infections.

Population pharmacokinetic analysis of voriconazole and anidulafungin in adult patients with invasive aspergillosis

To assess the pharmacokinetics (PK) of voriconazole and anidulafungin in patients with invasive aspergillosis (IA) in comparison with other populations, sparse PK data were obtained for 305 adults from a prospective phase 3 study comparing voriconazole and anidulafungin in combination versus voriconazole monotherapy (voriconazole, 6 mg/kg intravenously [IV] every 12 h [q12h] for 24 h followed by 4 mg/kg IV q12h, switched to 300 mg orally q12h as appropriate; with placebo or anidulafungin IV, a 200-mg loading dose followed by 100 mg q24h). Voriconazole PK was described by a two-compartment model with first-order absorption and mixed linear and time-dependent nonlinear (Michaelis-Menten) elimination; anidulafungin PK was described by a two-compartment model with first-order elimination. For voriconazole, the normal inverse Wishart prior approach was implemented to stabilize the model. Compared to previous models, no new covariates were identified for voriconazole or anidulafungin. PK parameter estimates of voriconazole and anidulafungin are in agreement with those reported previously except for voriconazole clearance (the nonlinear clearance component became minimal). At a 4-mg/kg IV dose, voriconazole exposure tended to increase slightly as age, weight, or body mass index increased, but the difference was not considered clinically relevant. Estimated voriconazole exposures in IA patients at 4 mg/kg IV were higher than those reported for healthy adults (e.g., the average area under the curve over a 12-hour dosing interval [AUC0-12] at steady state was 46% higher); while it is not definitive, age and concomitant medications may impact this difference. Estimated anidulafungin exposures in IA patients were comparable to those reported for the general patient population. This study was approved by the appropriate institutional review boards or ethics committees and registered on ClinicalTrials.gov (NCT00531479).

Invasive pulmonary aspergillosis

In susceptible patients, invasive aspergillosis has a high incidence and a mortality of up to 80%. The diagnosis of this condition is difficult, especially in the early stages of the disease and, as a consequence, antifungal therapy, despite its expense and toxicity, is often initiated empirically. Until recently, there were very few effective antifungal agents for established invasive aspergillosis, but the introduction of two new drugs, voriconazole and caspofungin, has increased the treatment options. These newer antifungal therapies, combined with improved early diagnosis due to the introduction of newer microbiologic techniques, offer the hope that there will be a significant improvement in the substantial morbidity and mortality associated with invasive aspergillosis over the next 5 years.

Caspofungin: an overview

The echinocandins are a novel class of antifungal agents that have come into use over the past 10 years. The mechanism of action of these lipopeptide agents is via noncompetitive inhibition of the synthesis of 1,3-beta-glucans, which are fungal cell wall constituents. All agents of this class are only available in an intravenous formulation. The first approved agent of this class was caspofungin (Cancidas). Caspofungin is a therapeutic option for patients with candidal esophagitis and deep-seated candidal infections, and is an alternative therapy for Aspergillus infections, especially in the salvage setting. In addition, it is a therapeutic option for the empiric therapy of febrile neutropenia. The usefulness of this agent in treating less common fungal infections has been cited in anecdotal reports. One major limitation of this drug is the lack of an oral formulation. Caspofungin may be considered as a component of combination antifungal regimens. Caspofungin represents a significant advance in the care of patients with serious fungal infections.

Echinocandin antifungals: review and update

The echinocandins are a new and unique class of antifungal agents that act on the fungal cell wall by way of noncompetitive inhibition of the synthesis of 1,3-beta-glucans. All agents of this class are of parenteral formulation, with no oral preparations available. Caspofungin (Cancidas) was the first approved echinocandin, followed recently by micafungin (Mycamine) and anidulafungin (Eraxis). The precise role of the echinocandins in the antifungal armamentarium is still unfolding. Caspofungin is approved for the treatment of candidal esophagitis and candidemia, salvage therapy of Aspergillus infections and for empirical therapy of febrile neutropenia. Micafungin is likewise approved for candidal esophagitis, in addition to antifungal prophylaxis for hematopoietic stem cell transplant recipients. Anidulafungin is also approved for treatment of candidal esophagitis, as well as therapy of candidemia. There has been anecdotal use of these agents to treat less common fungal pathogens, as well as limited use as a component of combination antifungal therapy. The echinocandins are an important addition to the antifungal armamentarium in the treatment of fungal infections in both immunocompromised patients and those with normal immunity.

Primary hepatic aspergillosis following induction chemotherapy for acute leukemia

Invasive aspergillosis (IA) contributes significantly to the burden of infectious complications in heavily immunosuppressed patients with acute leukemia. The infection is typically acquired via inhalation into the respiratory tract, and the lungs are most commonly involved. However, disseminated disease may occur and reports of isolated extrapulmonary infection suggest the gastrointestinal tract is likely an additional portal of entry for this organism. We describe a case of primary hepatic aspergillosis in a patient with acute myelogenous leukemia. The patient did not respond to medical therapy with antifungals and ultimately required surgical exploration and drainage. IA should be considered in an immunosuppressed patient with hepatic abscesses and may require a combined surgical and medical approach to therapy.

Aspergillus tracheobronchitis causing subtotal tracheal stenosis in a liver transplant recipient

Invasive aspergillosis is recognized as one of the most significant opportunistic infections after liver transplantation. Diagnosis of invasive aspergillosis in transplant recipients has been proven to be challenging, and optimal approach to the treatment of invasive aspergillosis is still controversial. We here present an unusual case of Aspergillus tracheobronchitis in the setting of liver transplantation. A 47-year-old female patient with persistent dry cough after liver transplantation developed respiratory insufficiency and was readmitted to the intensive care unit 55 days after liver transplantation. A CT scan revealed subtotal tracheal stenosis; bronchoscopy was performed, and extended white mucus coverings causative of the tracheal stenosis were removed. Microbiological assessment isolated Aspergillus fumigatus. The diagnosis was obstructive Aspergillus tracheobronchitis. The patient was started on a treatment of voriconazole 200 mg orally twice daily, adjusted to a trough level of 1-4 mg/L. For further airway management, a tracheal stent had to be implanted. The patient is alive and well 28 months after liver transplantation. Invasive aspergillosis should be considered a possible etiology in liver transplant patients presenting with unspecific symptoms such as persistent dry cough. Optimal strategies for improved and early diagnosis as well as prophylaxis need to be defined.

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.

In vitro interaction of voriconazole and anidulafungin against triazole-resistant Aspergillus fumigatus

Voriconazole is the recommended drug of first choice to treat infections caused by Aspergillus fumigatus. The efficacy of voriconazole might be hampered by the emergence of azole resistance. However, the combination of voriconazole with anidulafungin could improve therapeutic outcomes in azole-resistant invasive aspergillosis (IA). The in vitro interaction between voriconazole and anidulafungin was determined against voriconazole-susceptible and voriconazole-resistant (substitutions in the cyp51A gene, including single point [M220I and G54W] and tandem repeat [34-bp tandem repeat in the promoter region of the cyp51A gene in combination with substitutions at codon L98 and 46-bp tandem repeat in the promoter region of the cyp51A gene in combination with mutation at codons Y121 and T289] mutations) clinical A. fumigatus isolates using a checkerboard microdilution method with spectrophotometric analysis and a viability-based XTT {2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide} assay within 2 h of exposure after 24 and 48 h of incubation at 35 °C to 37 °C. Fractional inhibitory concentration (FIC) indexes (FICis) were determined using different MIC endpoints and Bliss independence analysis performed based on the response surface calculation of the no-drug interaction. Significant synergistic interactions obtained based on measuring the FIC index were dependent on the MIC endpoint, in which FICs were inversely related to voriconazole and anidulafungin MICs and were influenced by the CYP51A genotype. A statistically significant difference was observed between FIC indexes of isolates harboring tandem repeat mutations and wild-type controls (P = 0.006 by one-way analysis of variance [ANOVA]), indicating that synergy is decreased in azole-resistant strains. Our results indicated that a combination of voriconazole and anidulafungin might be effective against infections caused by both azole-susceptible and azole-resistant A. fumigatus isolates, but the combination could possibly be less effective in voriconazole-resistant strains with high MICs. Studies in vivo and in vitro-in vivo correlation investigations are required to validate the potential synergy of voriconazole and anidulafungin.

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.

Voriconazole in the management of nosocomial invasive fungal infections

Voriconazole is a new triazole developed for the treatment of life-threatening fungal infections. The drug is available for both oral and intravenous administration; the oral formulation has excellent bioavailability. The side-effect profile of voriconazole presents an acceptable safety and tolerability spectrum: transient visual disturbances, liver enzyme abnormalities, and skin rashes are the most frequently reported side effects but rarely lead to discontinuation. The potential for drug–drug interactions is high, because of its extensive hepatic metabolism. Careful attention to dosage is required, and serum levels and the effects of interacting drugs should be monitored. Review of 25 470 isolates of yeasts and 3216 isolates of filamentous fungi showed voriconazole to have broad-spectrum activity against pathogenic yeasts including intrinsically fluconazole-resistant isolates such as Candida krusei, dimorphic fungi, and opportunistic moulds like Aspergillus spp, amphotericin-B-resistant Aspergillus terreus, Fusarium spp, and Scedosporium apiospermum. It displays excellent clinical efficacy in patients with fluconazole-resistant and -susceptible Candida infections, invasive bone and central nervous system aspergillosis, and various refractory fungal infections. Voriconazole has been approved by the US Food and Drug Administration and by the European Medicines Agency for the treatment of invasive aspergillosis, serious infections caused by Fusarium and S. apiospermum, fluconazole-resistant invasive Candida infections, and candidemia in nonneutropenic patients.

Approaches to the early treatment of invasive fungal infection

Invasive fungal infections account for significant morbidity and mortality in the seriously immunocompromised host, especially those suffering from hematologic malignancies and the recipients of hematopoietic cell transplant. One of the reasons for the continuing high mortality rates due to invasive fungal infection is the delay in administering appropriate therapy. As preemptive antifungal therapy is not feasible for lack of a predictive test, early empiric therapy is currently the only approach likely to result in improvement in survival. Here, we present our approach to both invasive candidiasis and invasive mold infection. Therapy should be initiated at the first signs and symptoms of disease, utilizing knowledge of local fungal epidemiology, the patient's recent antifungal agent exposure, and the diagnostic tests immediately available, to select an appropriate antifungal agent most likely to be effective against the suspected fungal species.

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.

Fluconazole, caspofungin, voriconazole in combination with amphotericin B

Combined antifungal therapy has been suggested to enhance the efficacy and reduce the toxicity of antifungal agents. The aim of the study was to investigate the in vitro synergistic activity of caspofungin, voriconazole, and fluconazole with amphotericin B against ten isolates of Candida parapsilosis and Candida albicans strains which were resistant to azoles or amphotericin B. Three different antifungal combinations (amphotericin B [AP] — caspofungin [CS], amphotericin B — fluconazole [FL], and AP — voriconazole [VO]) were evaluated for in vitro synergistic effect by the microdilution checkerboard and E-test methods. For the majority of strains, the combination test showed indifferent activity. Via the E-test method, synergistic activity was seen in 3 strains in response to AP-CS combination treatment and in one strain after administration of AP-FL; however, no synergy was observed in response to combination treatment with P-VO. Antagonistic activity was the result in 1 strain treated with AP-CS as well as in 6 strains treated with AP-FL and AP-VO combinations. Via the microdilution test, no synergistic activity was seen after treatment with all 3 combinations. Antagonistic activity was the result in 2 strains with AP-CS, in 6 strains with AP-VO and in 5 strains with AP-FL combinations. Agreement between the checkerboard and E-test methods was observed to be approximately 72%. These combinations may be used in the case of antifungal resistance.

Echinocandin pharmacodynamics: review and clinical implications

Echinocandins have made a significant impact in the treatment of select invasive fungal infections, most notably invasive candidiasis and aspergillosis. However, treatment outcomes for such infections are still less than optimal, prompting an examination of dosing and administration techniques in an attempt to exploit known pharmacodynamic properties and improve outcomes. Echinocandins generally exhibit concentration-dependent, fungicidal activity against Candida spp. and fungistatic activity against Aspergillus spp. However, increasing drug concentrations of echinocandins above the organism's MIC may result in a paradoxical increase in fungal growth as demonstrated in some in vitro and in vivo models (known most commonly as the 'Eagle effect'). Therefore, the potential impact of dose escalations on improving the clinical efficacy of echinocandins based on in vitro and animal models are uncertain and are still being evaluated. In addition, such strategies have to consider the potential for increased treatment-related toxicities and costs. To date, published clinical studies (both superiority and non-inferiority) demonstrating the potential for dose-related improvements in treatment outcomes have been limited to mucocutaneous and oesophageal candidiasis. Further research is needed to determine if a role exists for optimizing echinocandin pharmacodynamics in various clinical settings.

Synergistic activities of three triazoles with caspofungin against Candida glabrata isolates determined by time-kill, Etest, and disk diffusion methods

Combinations of voriconazole, fluconazole, and itraconazole with caspofungin were evaluated against 50 Candida glabrata isolates by the time-kill, disk diffusion, and Etest methods. The majority of antifungal combinations were indifferent. By the time-kill method, synergistic activity was detected with eight (16%) of the caspofungin-voriconazole and seven (14%) of the caspofungin-fluconazole combinations, but synergy was not seen with the caspofungin-itraconazole combination. Further comparisons of the Etest and disk diffusion synergy techniques with the time-kill method are warranted.

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.

Assessment of the in vitro kinetic activity of caspofungin against Candida glabrata

Echinocandins have become the drug of choice in infections caused by Candida glabrata. The objective of this study was to evaluate the in vitro activity of caspofungin alone and in combination against C. glabrata. In vitro assays demonstrated that caspofungin alone showed excellent fungicidal activity against C. glabrata, including fluconazole-resistant strains. The combination of caspofungin and azole antifungals showed potential synergy against C. glabrata. Overall, caspofungin demonstrated excellent in vitro activity, alone and in combination, against strains of C. glabrata.