Evolving strategies in the management of aspergillosis

Catastrophic Brain Aspergillosis after Liver Transplantation

Background. Liver transplantation has many complications. Because of receiving immunosuppressive regimens, infectious complications in these patients may have fatal results. Aspergillosis in solid organ recipients is one of the most common fungal infections that usually occur 1 month after transplantation. Aspergillus infection mainly involves the lungs. Although the central nervous system may get involved due to hematogenous spreading from lungs, isolated central nervous system involvement is rarely reported. Case Presentation. The patient was an 8-year-old boy, with a case of Wilson disease, who underwent liver transplantation due to acute fulminant hepatic failure. Four days after the surgery, he was affected by fever, agitation, loss of consciousness, hemiparesis, and focal seizure. Brain MRI showed abscess formation, whereas chest X-ray was normal. Intravenous antibiotics were initiated but the patient's condition was not improving; therefore, surgical drainage of the abscess was performed. The pathological investigation was compatible with aspergillosis. Antifungal therapy with voriconazole was administrated. His symptoms were resolved but unfortunately, brain lesions caused persistent vegetative state. Discussion. Aspergillus is a ubiquitous organism that mainly occurs in immunocompromised patients. Aspergillosis could be prevented by environmental modification such as installing high-efficiency particulate air filters. Chemoprevention with triazoles, echinocandins, and polyenes is also effective. Voriconazole is the drug of choice for aspergillosis treatment. Although voriconazole is a highly effective antifungal drug, cerebral aspergillosis is often fatal.

Role of therapeutic drug monitoring of voriconazole in the treatment of invasive fungal infections

BACKGROUND

Voriconazole is a broad-spectrum, second-generation triazole antifungal agent with demonstrated efficacy in the treatment of invasive fungal infections caused by Aspergillus spp. and Candida spp. Given the characteristically poor prognosis of patients with invasive fungal infections and the protracted duration of treatment required, therapeutic monitoring of voriconazole is, in theory, an attractive method to optimize antifungal therapy.

OBJECTIVE

To determine the utility of therapeutic drug monitoring for voriconazole.

METHODS

A previously published decision-making algorithm was used to assess the currently available literature on therapeutic drug monitoring of voriconazole.

RESULTS

Several analytical methods can be used to quantify plasma or serum concentrations of voriconazole. Reasons for therapeutic monitoring of this drug include wide variability both within and between individuals secondary to drug properties, drug-drug interactions, and disease states. Furthermore, voriconazole follows nonlinear pharmacokinetics with saturable hepatic clearance. Another potential factor in favour of therapeutic drug monitoring for voriconazole is genetic polymorphism of CYP2C19, whereby patients who are homozygous for poor metabolism (about 19% of non-Indian Asians) can have 4-fold greater exposure to voriconazole. The concentrations of this drug are also greater in patients with hepatic impairment. Drug-drug interactions with other substrates of CYP2C9, CYP2C19, and CYP3A4 can also alter voriconazole concentrations. However, the correlations between plasma concentrations of voriconazole and its efficacy and toxicity are not well defined. Although lower and upper target thresholds of 0.25-2 mg/L and 4-6 mg/L, respectively, have been suggested, studies to date have not been appropriately designed or powered to reveal any definitive association.

CONCLUSIONS

Routine therapeutic drug monitoring of voriconazole is not recommended except in certain circumstances, such as lack of response to therapy or evidence of toxicity, in which case selective monitoring of voriconazole concentrations may be of clinical utility.

A role for macrophage migration inhibitory factor in protective immunity against Aspergillus fumigatus

Inflammation plays an important role in protective immunity against fungi, including the opportunistic pathogen, Aspergillus fumigatus. The balance between pro-inflammatory and anti-inflammatory cytokines is a key determinant of infection outcome. Since macrophage migration inhibitory factor (MIF) is an upstream regulator of many cytokines, we analyzed herein the role of endogenous MIF in the host control of hematogenously disseminated aspergillosis using MIF⁻/⁻ mice. As revealed by their mortality rate, MIF⁻/⁻ mice were more susceptible to disseminated infection than WT mice. Moreover, pharmacologic inhibition of MIF with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester, (ISO-1) increased the susceptibility of WT mice to lethal infection. The higher tissue fungal burden early in sublethal infection indicated increased susceptibility of MIF⁻/⁻ mice to sublethal infection as well. Substantial down-regulation of innate and acquired antifungal responses, characterized by decreased production of IL-1β, IL-6, TNF-α, IFN-γ and IL-17 in the spleen was noted in sublethally infected MIF⁻/⁻ mice. In contrast, IL-4 was higher in MIF⁻/⁻ than in WT mice. Taken together, our findings show that MIF contributes to host resistance against progressive invasive A. fumigatus infection by controlling downstream pro-inflammatory versus anti-inflammatory cytokine production thus determining the outcome of infection.

Aspergillus terreus accessory conidia are unique in surface architecture, cell wall composition and germination kinetics

Infection with Aspergillus terreus is more likely to result in invasive, disseminated disease when compared to other Aspergillus species; importantly this species appears to be less susceptible to the antifungal drug amphotericin B. Unique to this species is the ability to produce specialized structures denoted as accessory conidia (AC) directly on hyphae both in vitro and in vivo. With the hypothesis that production of AC by A. terreus may enhance virulence of this organism, we analyzed the phenotype, structure and metabolic potential of these conidia. Comparison of A. terreus phialidic conidia (conidia that arise from conidiophores, PC) and AC architecture by electron microscopy revealed distinct morphological differences between the two conidial forms; AC have a smoother, thicker outer cell surface with no apparent pigment-like layer. Further, AC germinated rapidly, had enhanced adherence to microspheres, and were metabolically more active compared to PC. Additionally, AC contained less cell membrane ergosterol, which correlated with decreased susceptibility to AMB as determined using a flow cytometry based analysis. Furthermore, AC exhibited surface patches of β1-3 glucan, suggestive of attachment scarring. Collectively, the findings of this study suggest a possible role for AC in A. terreus pathogenesis.

[Problematics of fungal infections in the paranasal sinuses]

Fungal infections of the ear and paranasal sinus, are recognised quite rarely, but they make sometimes, for many reasons, very important diagnostic-therapy issue. Cantagion may developes near every paranasal sinus. Facilities to invasion give every states, which weaken general and punctual immunity (like immunosupression, chemo-sterydotherapy, blood disease, pregnancy and HIV). After penetrated organism, course of infections, in case of type of patogens, trim of the patient and localization, can have without symptoms, sharp, chronic or fulminant shape. The hardest course with the highest mortality occur in the cases of mucormycosis and aspergillosis. Actually curiosity occur cases of fungal infections, since this times consider to be unpathogenic for humans. For treatment of sinus mycosis in majority chirurgical treatment is required. In addition or the sake of morphological differentiation fungal, in their developing cycle, treatment mycosis recommends serious difficulty, extra factor, which impeds therapy, is a must of prolongely antifungal treatment and repeated (to total elimination) remove hyphae from sinus, which stay sometimes even for week. Progress of the mycotic infections in paranasal sinus, remain bacterial infections and is often reason of bad diagnosis and incorrect treatment.

Conidiation color mutants of Aspergillus fumigatus are highly pathogenic to the heterologous insect host Galleria mellonella

The greater wax moth Galleria mellonella has been widely used as a heterologous host for a number of fungal pathogens including Candida albicans and Cryptococcus neoformans. A positive correlation in pathogenicity of these yeasts in this insect model and animal models has been observed. However, very few studies have evaluated the possibility of applying this heterologous insect model to investigate virulence traits of the filamentous fungal pathogen Aspergillus fumigatus, the leading cause of invasive aspergillosis. Here, we have examined the impact of mutations in genes involved in melanin biosynthesis on the pathogenicity of A. fumigatus in the G. mellonella model. Melanization in A. fumigatus confers bluish-grey color to conidia and is a known virulence factor in mammal models. Surprisingly, conidial color mutants in B5233 background that have deletions in the defined six-gene cluster required for DHN-melanin biosynthesis caused enhanced insect mortality compared to the parent strain. To further examine and confirm the relationship between melanization defects and enhanced virulence in the wax moth model, we performed random insertional mutagenesis in the Af293 genetic background to isolate mutants producing altered conidia colors. Strains producing conidia of previously identified colors and of novel colors were isolated. Interestingly, these color mutants displayed a higher level of pathogenicity in the insect model compared to the wild type. Although some of the more virulent color mutants showed increased resistance to hydrogen peroxide, overall phenotypic characterizations including secondary metabolite production, metalloproteinase activity, and germination rate did not reveal a general mechanism accountable for the enhanced virulence of these color mutants observed in the insect model. Our observations indicate instead, that exacerbated immune response of the wax moth induced by increased exposure of PAMPs (pathogen-associated molecular patterns) may cause self-damage that results in increased mortality of larvae infected with the color mutants. The current study underscores the limitations of using this insect model for inferring the pathogenic potential of A. fumigatus strains in mammals, but also points to the importance of understanding the innate immunity of the insect host in providing insights into the pathogenicity level of different fungal strains in this model. Additionally, our observations that melanization defective color mutants demonstrate increased virulence in the insect wax moth, suggest the potential of using melanization defective mutants of native insect fungal pathogens in the biological control of insect populations.

[Problematics of fungal infections in the ear]

Fungal infections of the ear are recognised quite rarely, but they make sometimes, for many reasons, very important diagnostic-therapy issue. Cantagion may developes in every elements of the ear, ranging from external ear (external canal ear, sometimes auricle), middle ear (every pneumatic structure) to iner ear (extra ordinary rarely). Every states, which weaken general and punctual immunity (like immunosupression, chemo-sterydotherapy, blood disease, pregnancy and HIV) are circles, which give facilities to invansion. After penetrated organism, course of infections, in case of type of patogens, trim of the patient and localization, can have without symptoms, sharp, chronic or fulminant shape. For the sake of morphological differentiation fungal, in their developing cycle, treatment mycosis recommends serious difficulty, extra factor, which impeds therapy, is a must of prolongely antifungal treatment and repeated (to total elimination) remove hyphae from ear, which stay sometimes even for week. Progress of the mycotic infections ear, remain bacterial infections and is often reason of bad diagnosis and incorrect treatment.