Seyedmojtaba Seyedmousavi

International expert opinion on the management of infection caused by azole-resistant Aspergillus fumigatus

An international expert panel was convened to deliberate the management of azole-resistant aspergillosis. In culture-positive cases, in vitro susceptibility testing should always be performed if antifungal therapy is intended. Different patterns of resistance are seen, with multi-azole and pan-azole resistance more common than resistance to a single triazole. In confirmed invasive pulmonary aspergillosis due to an azole-resistant Aspergillus, the experts recommended a switch from voriconazole to liposomal amphotericin B (L-AmB; Ambisome(®)). In regions with environmental resistance rates of ≥10%, a voriconazole-echinocandin combination or L-AmB were favoured as initial therapy. All experts recommended L-AmB as core therapy for central nervous system aspergillosis suspected to be due to an azole-resistant Aspergillus, and considered the addition of a second agent with the majority favouring flucytosine. Intravenous therapy with either micafungin or L-AmB given as either intermittent or continuous therapy was recommended for chronic pulmonary aspergillosis due to a pan-azole-resistant Aspergillus. Local and national surveillance with identification of clinical and environmental resistance patterns, rapid diagnostics, better quality clinical outcome data, and a greater understanding of the factors driving or minimising environmental resistance are areas where research is urgently needed, as well as the development of new oral agents outside the azole drug class.

Efficacy and pharmacodynamics of voriconazole combined with anidulafungin in azole-resistant invasive aspergillosis

OBJECTIVES Azole resistance is an emerging problem in the treatment of Aspergillus fumigatus infections. Combination therapy may be an alternative approach to improve therapeutic outcome in azole-resistant invasive aspergillosis (IA). The in vivo efficacy of voriconazole and anidulafungin was investigated in a non-neutropenic murine model of IA using voriconazole-susceptible and voriconazole-resistant A. fumigatus clinical isolates. METHODS Treatment groups consisted of voriconazole monotherapy, anidulafungin monotherapy and voriconazole + anidulafungin at 2.5, 5, 10 and 20 mg/kg body weight/day for 7 consecutive days. In vitro and in vivo drug interactions were analysed by non-parametric Bliss independence and non-linear regression analysis. RESULTS Synergistic interaction between voriconazole and anidulafungin against the voriconazole-susceptible isolate (AZN 8196) was observed in vitro and in vivo. However, among animals infected with the voriconazole-resistant isolate (V 52-35), 100% survival was observed only in groups receiving the highest doses (20 mg/kg voriconazole + 20 mg/kg anidulafungin). For this isolate, additivity, but not synergy, was observed in vivo. CONCLUSIONS Combination of voriconazole and anidulafungin was synergistic in voriconazole-susceptible IA, but additive in voriconazole-resistant IA. There is a clear benefit of combining voriconazole and anidulafungin, but the reduced effect of combination therapy in azole-resistant IA raises some concern.

The role of azoles in the management of azole-resistant aspergillosis: From the bench to the bedside

Azole resistance is an emerging problem in Aspergillus fumigatus and is associated with a high probability of treatment failure. An azole resistance mechanism typically decreases the activity of multiple azole compounds, depending on the mutation. As alternative treatment options are limited and in some isolates the minimum inhibitory concentration (MIC) increases by only a few two-fold dilutions steps, we investigated if voriconazole and posaconazole have a role in treating azole-resistant Aspergillus disease. The relation between resistance genotype and phenotype, pharmacokinetic and pharmacodynamic properties, and (pre)clinical treatment efficacy were reviewed. The results were used to estimate the exposure needed to achieve the pharmacodynamic target for each MIC. For posaconazole adequate exposure can be achieved only for wild type isolates as dose escalation does not allow PD target attainment. However, the new intravenous formulation might result in sufficient exposure to treat isolates with a MIC of 0.5 mg/L. For voriconazole our analysis indicated that the exposure needed to treat infection due to isolates with a MIC of 2 mg/L is feasible and maybe isolates with a MIC of 4 mg/L. However, extreme caution and strict monitoring of drug levels would be required, as the probability of toxicity will also increase.

Therapeutic drug monitoring of voriconazole and posaconazole for invasive aspergillosis

Voriconazole and posaconazole are extended-spectrum triazoles recommended for treatment, prophylaxis and salvage therapy of Aspergillus diseases. Over the past decade many papers have emerged supporting the use of therapeutic drug monitoring (TDM) for azole antifungals. TDM is used to tailor the exposure of a specific drug to the individuals to optimize treatment response and minimize side effects. We reviewed the pharmacokinetics and pharmacodynamics (PK-PD) characteristics of voriconazole and posaconazole. We present the available evidence on target concentrations defining maximal efficacy and minimal toxicity. Finally we provide some practical recommendations how to best perform TDM in clinical practice.

Azole-Resistant Aspergillus fumigatus, Iran

To the Editor: Aspergillus fumigatus causes a variety of diseases in humans. The drugs recommended for treatment of Aspergillus diseases are the mold-active azole antifungal drugs (1). However, a wide range of mutations in A. fumigatus confer azole resistance, which commonly involves modifications in the cyp51A gene (2), the target for azole antifungal drugs. Azole resistance is thought to be selected for as a result of patient therapy or exposure to azole compounds in the environment; resistance in clinical A. fumigatus isolates has been increasingly reported in several European countries, Asia, and the United States (3–7). The most frequently reported resistance mechanism is a 34-bp tandem repeat (TR34) in combination with a substitution at codon 98 (TR34/L98H) (4); this mechanism is believed to have been selected for through environmental exposure to azole fungicides. Because routine in vitro susceptibility testing of clinical Aspergillus isolates is not common in many centers worldwide, the prevalence of azole resistance might be underestimated. We investigated the prevalence of azole resistance in clinical A. fumigatus isolates stored for 6 years (2003–2009) at Tehran University Mycology Reference Centre and Islamic Azad University, Ardabil Branch, Iran. We investigated 124 clinical A. fumigatus isolates obtained from patients with Aspergillus diseases (Technical Appendix Table 1). We conducted strain identification, in vitro antifungal susceptibility testing, and sequence-based analysis of the Cyp51A gene, as described (4). We performed microsatellite genotyping of all A. fumigatus isolates for which the MIC of itraconazole was ≥16 mg/L (8) by using a short tandem repeat A. fumigatus assay, and we compared the results with those reported for the Netherlands (20 isolates) and other European countries (24 isolates) (Technical Appendix Figure). The distribution of azole-resistant and wild-type A. fumigatus isolates examined in this study, according to year of isolation, is shown in online Technical Appendix Table 1. Of 124 A. fumigatus isolates, 4 grew on the wells containing itraconazole and voriconazole, indicating a multidrug-resistant phenotype. Of these resistant isolates, 3 were from patients with chronic pulmonary aspergillosis and 1 was from a patient with allergic bronchopulmonary aspergillosis (Table). Table Characteristics of 4 azole-resistant clinical Aspergillus fumigatus isolates, Iran* Sequence analysis of the CYP51A gene indicated the presence of TR34/L98H in 3 isolates and no mutations in the other isolate (Table). The first TR34/L98H isolate had been recovered in 2005, which is relatively early compared with reported isolations in other countries (Technical Appendix Table 2). Microsatellite typing of 6 short tandem repeat loci demonstrated identical patterns for 2 of the 3 azole-resistant isolates from Iran, but the TR34/L98H isolates from Iran did not cluster with those from the Netherlands and other European countries, indicating no close genetic relatedness (Technical Appendix Figure). The TR34/L98H azole resistance mechanism was first described in 1998 in the Netherlands; since then, its presence in clinical and environmental A. fumigatus isolates in multiple European countries and recently in Asia has been increasingly reported (Technical Appendix Table 2) (3–7). In the study reported here, prevalence of azole resistance in clinical A. fumigatus isolates obtained from patients in Iran was 3.2%; most isolates exhibited the TR34/L98H resistance mechanism. The fact that the first TR34/L98H isolate was found relatively early, in 2005, underscores the possibility that prevalence of azole resistance might be underestimated in many countries because in vitro susceptibility testing of A. fumigatus is not routinely performed. Microsatellite genotypic analysis of A. fumigatus isolates from the Netherlands and various European countries showed that the genetic diversity of TR34/L98H isolates is lower than that of wild-type controls (8). It has been suggested that TR34/L98H isolates might have a common ancestor that developed locally and subsequently migrated across Europe. In contrast, genotyping of TR34/L98H originating from India suggested a different dynamic; all environmental and clinical TR34/L98H isolates from India shared the same multilocus microsatellite genotype not found in any other analyzed samples, from within India or from the Netherlands, France, Germany, or the People’s Republic of China (9). The molecular epidemiology of the TR34/L98H isolates from Iran suggests that they cluster apart from the European isolates, indicating that migration from Europe to Iran, or vice versa, is unlikely. Genotyping of more TR34/L98H isolates from the Middle East and comparison with those from India would enhance understanding of the origin and geographic spread of TR34/L98H. Our study indicates that TR34/L98H was in Iran in 2005; this finding adds to the growing list of regions where acquired resistance in A. fumigatus of environmental origin is documented. From a global perspective, fungicide use is second highest in the Asia–Pacific regions (24%), preceded only by western Europe (37%) (10). For a bettering understand of the scale of this emerging public health problem and for insight into the dynamics of geographic migration, surveys of fungal culture collections for TR34/L98H and molecular typing studies are warranted. These data would be useful not only for clinical management of Aspergillus diseases but also for enabling policy makers to develop strategies that prevent resistance selection by the environmental route. Technical Appendix: Distribution of azole-resistant and azole-susceptible Aspergillus fumigatus isolates, Iran, 2003–2009; first reports of multiple-triazole-resistant A. fumigatus isolate(s) carrying the TR34/L98H mutations in the CYP51A gene, by country; and minimum spanning tree comparing genotypic relatedness of clinical azole-resistant A. fumigatus isolates carrying TR34/L98H alteration in the CYP51A gene from Iran with those reported from European countries. TR, tandem repeat. Click here to view.(160K, pdf)

Exophiala sideris, a novel black yeast isolated from environments polluted with toxic alkyl benzenes and arsenic

A novel species of the black yeast genus Exophiala (order Chaetothyriales) is described. Strains were repeatedly obtained by enriching samples of wild berries from different plants, guano-rich soil and from oak railway ties treated with arsenic creosote under a toluene-rich atmosphere. An identical strain was encountered in a closed arsenic mine polluted by alkyl benzenes. Its potential use for purposes of bioremediation is discussed.

Aspergillus and aspergilloses in wild and domestic animals: a global health concern with parallels to human disease

The importance of aspergillosis in humans and various animal species has increased over the last decades. Aspergillus species are found worldwide in humans and in almost all domestic animals and birds as well as in many wild species, causing a wide range of diseases from localized infections to fatal disseminated diseases, as well as allergic responses to inhaled conidia. Some prevalent forms of animal aspergillosis are invasive fatal infections in sea fan corals, stonebrood mummification in honey bees, pulmonary and air sac infection in birds, mycotic abortion and mammary gland infections in cattle, guttural pouch mycoses in horses, sinonasal infections in dogs and cats, and invasive pulmonary and cerebral infections in marine mammals and nonhuman primates. This article represents a comprehensive overview of the most common infections reported by Aspergillus species and the corresponding diseases in various types of animals.

Phaeohyphomycoses, Emerging Opportunistic Diseases in Animals

SUMMARY Emerging fungal diseases due to black yeasts and relatives in domestic or wild animals and in invertebrates or cold- and warm-blooded vertebrates are continually being reported, either as novel pathogens or as familiar pathogens affecting new species of hosts. Different epidemiological situations can be distinguished, i.e., occurrence as single infections or as zoonoses, and infection may occur sporadically in otherwise healthy hosts. Such infections are found mostly in mammals but also in cold-blooded animals, are frequently subcutaneous or cerebral, and bear much similarity to human primary disorders. Infections of the nervous system are mostly fatal, and the source and route of infection are currently unknown. A third epidemiological situation corresponds to pseudoepidemics, i.e., infection of a large host population due to a common source. It is often observed and generally hypothesized that the susceptible animals are under stress, e.g., due to poor housing conditions of mammals or to a change of basins in the case of fishes. The descriptions in this article represent an overview of the more commonly reported and recurring black fungi and the corresponding diseases in different types of animals.

Pharmacodynamics of Isavuconazole in an Aspergillus fumigatus Mouse Infection Model

ABSTRACT Azole resistance is an emerging problem in Aspergillus fumigatus which translates into treatment failure. Alternative treatments with new azoles may improve therapeutic outcome in invasive aspergillosis (IA) even for strains with decreased susceptibility to current azoles. The in vivo efficacy of 0.25, 1, 4, 16, 64, 128, 256, and 512 mg/kg of body weight/day prodrug isavuconazonium sulfate (BAL8557) (isavuconazole [ISA]-equivalent doses of 0.12, 0.48, 1.92, 7.68, 30.7, 61.4, 122.9, and 245.8 mg/kg/day, respectively) administered by oral gavage was assessed in an immunocompetent murine model of IA against four clinical A. fumigatus isolates: a wild-type isolate (ISA MICEUCAST, 0.5 mg/liter) and three azole-resistant isolates harboring substitutions in the cyp51A gene: G54W (ISA MICEUCAST, 0.5 mg/liter), M220I (ISA MICEUCAST, 4 mg/liter), and TR34/L98H (ISA MICEUCAST, 8 mg/liter). The maximum effect (100% survival) was reached at a prodrug isavuconazonium sulfate dose of 64 mg/kg for the wild-type isolate, 128 mg/kg for the G54W mutant, and 256 mg/kg two times per day (q12) for the M220I mutant. A maximum response was not achieved with the TR34/L98H isolates with the highest dose of prodrug isavuconazonium sulfate (256 mg/kg q12). For a survival rate of 50%, the effective AUC0–24/MICEUCAST ratio for ISA total drug was 24.73 (95% confidence interval, 22.50 to 27.18). The efficacy of isavuconazole depended on both the drug exposure and the isavuconazole MIC of the isolates. The quantitative relationship between exposure and effect (AUC0–24/MIC) can be used to optimize the treatment of human infections by A. fumigatus, including strains with decreased susceptibility.

Pharmacodynamics of Ceftazidime and Avibactam in Neutropenic Mice with Thigh or Lung Infection

ABSTRACT Avibactam is a new non-β-lactam β-lactamase inhibitor that shows promising restoration of ceftazidime activity against microorganisms producing Ambler class A extended-spectrum β-lactamases (ESBLs) and carbapenemases such as KPCs, class C β-lactamases (AmpC), and some class D enzymes. To determine optimal dosing combinations of ceftazidime-avibactam for treating infections with ceftazidime-resistant Pseudomonas aeruginosa, pharmacodynamic responses were explored in murine neutropenic thigh and lung infection models. Exposure-response relationships for ceftazidime monotherapy were determined first. Subsequently, the efficacy of adding avibactam every 2 h (q2h) or q8h to a fixed q2h dose of ceftazidime was determined in lung infection for two strains. Dosing avibactam q2h was significantly more efficacious, reducing the avibactam daily dose for static effect by factors of 2.7 and 10.1, whereas the mean percentage of the dosing interval that free drug concentrations remain above the threshold concentration of 1 mg/liter (%fT>CT 1 mg/liter) yielding bacteriostasis was similar for both regimens, with mean values of 21.6 (q2h) and 18.5 (q8h). Dose fractionation studies of avibactam in both the thigh and lung models indicated that the effect of avibactam correlated well with %fT>CT 1 mg/liter. This parameter of avibactam was further explored for four P. aeruginosa strains in the lung model and six in the thigh model. Parameter estimates of %fT>CT 1 mg/liter for avibactam ranged from 0 to 21.4% in the lung model and from 14.1 to 62.5% in the thigh model to achieve stasis. In conclusion, addition of avibactam enhanced the effect of ceftazidime, which was more pronounced at frequent dosing and well related with %fT>CT 1 mg/liter. The thigh model appeared more stringent, with higher values, ranging up to 62.5% fT>CT 1 mg/liter, required for a static effect.