Épidémiologie et facteurs de risque de l’aspergillose invasive du sujet non neutropénique

Invasive and Subcutaneous Infections Caused by Filamentous Fungi: Report from a Portuguese Multicentric Surveillance Program

Invasive fungal infections (IFI) have significantly increased over the past years due to advances in medical care for the at-risk immunocompromised population. IFI are often difficult to diagnose and manage, and can be associated with substantial morbidity and mortality. This study aims to contribute to understanding the etiology of invasive and subcutaneous fungal infections, their associated risk factors, and to perceive the outcome of patients who developed invasive disease, raising awareness of these infections at a local level but also in a global context. A laboratory surveillance approach was conducted over a seven-year period and included: (i) cases of invasive and subcutaneous fungal infections caused by filamentous/dimorphic fungi, confirmed by either microscopy or positive culture from sterile samples, (ii) cases diagnosed as probable IFI according to the criteria established by EORTC/MSG when duly substantiated. Fourteen Portuguese laboratories were enrolled. Cases included in this study were classified according to the new consensus definitions of invasive fungal diseases (IFD) published in 2020 as follows: proven IFI (N = 31), subcutaneous fungal infection (N = 23). Those proven deep fungal infections (N = 54) totalized 71.1% of the total cases, whereas 28.9% were classified as probable IFI (N = 22). It was possible to identify the etiological fungal agent in 73 cases (96%). Aspergillus was the most frequent genera detected, but endemic dimorphic fungi represented 14.47% (N = 11) of the total cases. Despite the small number of cases, a high diversity of species were involved in deep fungal infections. This fact has implications for clinical and laboratory diagnosis, and on the therapeutic management of these infections, since different species, even within the same genus, can present diverse patterns of susceptibility to antifungals.

A computational model of invasive aspergillosis in the lung and the role of iron

Background

Invasive aspergillosis is a severe infection of immunocompromised hosts, caused by the inhalation of the spores of the ubiquitous environmental molds of the Aspergillus genus. The innate immune response in this infection entails a series of complex and inter-related interactions between multiple recruited and resident cell populations with each other and with the fungal cell; in particular, iron is critical for fungal growth.

Results

A computational model of invasive aspergillosis is presented here; the model can be used as a rational hypothesis-generating tool to investigate host responses to this infection. Using a combination of laboratory data and published literature, an in silico model of a section of lung tissue was generated that includes an alveolar duct, adjacent capillaries, and surrounding lung parenchyma. The three-dimensional agent-based model integrates temporal events in fungal cells, epithelial cells, monocytes, and neutrophils after inhalation of spores with cellular dynamics at the tissue level, comprising part of the innate immune response. Iron levels in the blood and tissue play a key role in the fungus’ ability to grow, and the model includes iron recruitment and consumption by the different types of cells included. Parameter sensitivity analysis suggests the model is robust with respect to unvalidated parameters, and thus is a viable tool for an in silico investigation of invasive aspergillosis.

Conclusions

Using laboratory data from a mouse model of invasive aspergillosis in the context of transient neutropenia as validation, the model predicted qualitatively similar time course changes in fungal burden, monocyte and neutrophil populations, and tissue iron levels. This model lays the groundwork for a multi-scale dynamic mathematical model of the immune response to Aspergillus species.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-016-0275-2) contains supplementary material, which is available to authorized users.

Miliary nodules: An unusual presentation of allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is an immune-mediated inflammatory disease caused by hypersensitivity to Aspergillus fumigatus. A wide spectrum of plain radiographic appearances has been described in ABPA, though none are pathognomonic of ABPA. The common radiological abnormalities encountered are fleeting pulmonary opacities, bronchiectasis, and mucoid impaction. Uncommon radiological findings encountered in ABPA include pulmonary masses, perihilar opacities simulating hilar adenopathy, and pleural effusions. However, miliary nodules as a radiological presentation of ABPA are very rare and only one case has been reported in literature. It is often misdiagnosed and mismanaged as tuberculosis; thus, the clinician should be vigilant enough to diagnose this very rare entity.

[Epidemiological transition of mycosis diseases in sub-Saharan Africa: from surface to depth]

Fungi are schematically responsible for three distinct kinds of infections: superficial mycoses, subcutaneous and deep ones. The current socio-epidemiological transition observed in sub-Saharan Africa does not actually lead to similar consequences regarding these three categories of fungal entities. For instance, it has long been known that superficial mycoses are very prevalent in tropical areas, since they are partly due to the warm climate and the promiscuity. They are mostly caused by dermatophytic fungi or Malassezia sp. (Pityriasis versicolor). Subcutaneous mycoses are rarer, and usually due to dimorphic fungi which are accidentally inoculated into the body after a skin injury or a trauma. Sometimes very spectacular, the clinical outcome is then described as chronic. Thus, chromoblastomycosis, rhinoentomophtoromycosis or mycetoma are some examples of subcutaneous mycoses which remain well-known by practitioners of endemic countries. Deep mycoses (or invasive / systemic mycoses) are defined by fungal infections of deep anatomical sites that should be normally sterile. By contrast with the other entities mentioned above, the outcome may be rapidly fatal for the patient. One of the most outstanding examples was the great increasing of cryptococcal meningitis during the HIV outbreak in the 80'. A few other similar mycoses may be feared in a near future, since they usually occur in contexts of important immunosuppression which are about to be definitely experienced in Africa: overall increase of chronic diseases like diabetes, lengthening life expectancy and its associated diseases, widespread medical practices which were only seen in advanced intensive care units, onco-haematology departments or graft centers so far. Thus, the deep mycoses will inevitably increase in Africa, as they did in all developed countries over the last two decades. The consequences will not only be limited to the clinical management as described above: the diagnostic approach is also quite particular, since the identification of the involved fungal species should be established in emergency, if not the outcome will be fatal. Besides, the antifungal drugs are expensive, and their therapeutic monitoring is quite challenging all along the follow up. Overall, we have to thoroughly take into account the emergence of invasive mycoses right now in Intertropical Africa, in order to successfully achieve the socio-economic development of this continent.

[Could pleural aspergillosis happen to be a complication of pleural drainage?]

Four cases of nosocomial aspergillosis are described where the responsibility of pleural drainage is advocated. Infection was pulmonary once, pleural three times. Pleural suction had been long lasting with incomplete re-expansion of the lung and major air leaks. The hypothesis of the responsibility of pleural drainage in the advent of aspergillosis is reinforced by the revision of medical papers, which leads to the conviction that similar cases have been described yet, even though the mechanism of the contamination had not been understood. Prevention needs to limitate the lasting of the suction, especially if there are major air leaks. Cure needs total re-expansion of the lung and suppression of any pleural cavity, even if a thoracoplasty is needed. An anti-fungal therapy is not always needed.

[Lung mycosis in non neuropenic patients]

Lung mycosis is rare. Diagnosis and treatment must be done the earliest possible.

METHODS

It is about a retrospective study on clinical records including patients hospitalized for lung infection.

RESULTS

From 2008 to 2011, 16 patients (13 men and three women, average age 42 years) developed a pulmonary infection. Twelve of our patients had respiratory or extrarespiratory histories. None of our patients had a neutropenia. The diagnoses were lung aspergilloma in four cases, invasive lung aspergillosis in three cases, allergic bronchopulmonary aspergillosis in three cases, mucormycosis in three cases, trichosporonosis in a case, actinomycosis in one case and penicilliosis in one case. An antifungal treatment consisting in amphotericin B or itraconazole was given to four patients and six patients, respectively. Surgery was chosen for six patients. The evolution was good for 12 patients, one presented renal failure, and three patients died.

[Guidelines for the treatment of invasive fungal disease by Aspergillus spp. and other fungi issued by the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC). 2011 Update]

The guidelines on the treatment of invasive fungal disease by Aspergillus spp. and other fungi issued by the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) are presented. These recommendations are focused on four clinical categories: oncology-haematology patients, solid organ transplant recipients, patients admitted to intensive care units, and children. An extensive review is made of therapeutical advances and scientific evidence in these settings. These guidelines have been prepared according the SEIMC consensus rules by a working group composed of specialists in infectious diseases, clinical microbiology, critical care medicine, paediatrics and oncology-haematology. Specific recommendations on the prevention of fungal infections in these patients are included.

[Primitive aspergillosis of the posterior cerebral fossa in immunocompetent patient]

Cerebral aspergillosis arises in the great majority of cases during an invasive aspergillosis with hematogene scattering from the lung hurts. The cerebral, not rare location is one of the worse criteria forecast during the invasive aspergillosis. We report the case of patient who was hospitalized in the neurosurgery department for syndrome of increased intracranial pressure, hemiparesis and cerebellar syndrome in febrile context. The radiological exploration objectified a collection of the posterior fossa. A stereotactic biopsy was performed. It collected fragments biopsy and pus. The pathological and microbiological analysis allowed the identification of Aspergillus fumigatus. The originality of this observation comes from the rare location in the posterior fossa of aspergillosis and because the patient is immunocompetent and no primary location is found. The patient presents however a viral hepatitis B of fortuitous discovery. He is put under treatment by amphotericin B. The evolution is marked by meningitis comment-diversion. Antibiotics are prescribed, and then the patient is operated for total ablation of the tumor. He dies following an osmolar coma associated with thrombopenia and a secondary renal insufficiency due to his treatment by the amphotericin B.

Distinct roles for Dectin-1 and TLR4 in the pathogenesis of Aspergillus fumigatus keratitis

Aspergillus species are a major worldwide cause of corneal ulcers, resulting in visual impairment and blindness in immunocompetent individuals. To enhance our understanding of the pathogenesis of Aspergillus keratitis, we developed a murine model in which red fluorescent protein (RFP)-expressing A. fumigatus (Af293.1RFP) conidia are injected into the corneal stroma, and disease progression and fungal survival are tracked over time. Using Mafia mice in which c-fms expressing macrophages and dendritic cells can be induced to undergo apoptosis, we demonstrated that the presence of resident corneal macrophages is essential for production of IL-1beta and CXCL1/KC, and for recruitment of neutrophils and mononuclear cells into the corneal stroma. We found that beta-glucan was highly expressed on germinating conidia and hyphae in the cornea stroma, and that both Dectin-1 and phospho-Syk were up-regulated in infected corneas. Additionally, we show that infected Dectin-1(-/-) corneas have impaired IL-1beta and CXCL1/KC production, resulting in diminished cellular infiltration and fungal clearance compared with control mice, especially during infection with clinical isolates expressing high beta-glucan. In contrast to Dectin 1(-/-) mice, cellular infiltration into infected TLR2(-/-), TLR4(-/-), and MD-2(-/-) mice corneas was unimpaired, indicating no role for these receptors in cell recruitment; however, fungal killing was significantly reduced in TLR4(-/-) mice, but not TLR2(-/-) or MD-2(-/-) mice. We also found that TRIF(-/-) and TIRAP(-/-) mice exhibited no fungal-killing defects, but that MyD88(-/-) and IL-1R1(-/-) mice were unable to regulate fungal growth. In conclusion, these data are consistent with a model in which beta-glucan on A.fumigatus germinating conidia activates Dectin-1 on corneal macrophages to produce IL-1beta, and CXCL1, which together with IL-1R1/MyD88-dependent activation, results in recruitment of neutrophils to the corneal stroma and TLR4-dependent fungal killing.

[Diagnosis of invasive pulmonary aspergillosis: value of bronchoalveolar lavage galactomannan for immunocompromised patients]

Invasive pulmonary aspergillosis (IPA) is an emerging disease associated with high mortality. The diagnosis is difficult, based on a combination of elements that are clinical, radiological and biological. For early detection of cases of IPA, during 25 months, we have systematically carried out on the LBA (N=355) of immunocompromised patients (N=313) a determination of Aspergillus galactomannan (GM) by ELISA (PlateliaAspergillus, BioRad). We observed 14 cases of probable API. The sensitivity of GM compared to direct examination (DE) and culture is, respectively, 64% versus 29% and 57%. The determination of GM is definitely more sensitive than the ED. Excellent specificity (98%) allows its implementation as a screening test in patients at risk.

The biocontaminants and complexity of damp indoor spaces: more than what meets the eyes

Nine types of biocontaminants in damp indoor environments from microbial growth are discussed: (1) indicator molds; (2) Gram negative and positive bacteria; (3) microbial particulates; (4) mycotoxins; (5) volatile organic compounds, both microbial (MVOCs) and non-microbial (VOCs); (6) proteins; (7) galactomannans; (8) 1-3-β-D-glucans (glucans) and (9) lipopolysaccharides (LPS — endotoxins). When mold species exceed those outdoors contamination is deduced. Gram negative bacterial endotoxins, LPS in indoor environments, synergize with mycotoxins. The gram positive Bacillus species, Actinomycetes (Streptomyces, Nocardia and Mycobacterium), produce exotoxins. The Actinomycetes are associated with hypersensitivity pneumonitis, lung and invasive infections. Mycobacterial mycobacterium infections not from M. tuberculosis are increasing in immunocompetent individuals. In animal models, LPS enhance the toxicity of roridin A, satratoxins G and aflatoxin B1 to damage the olfactory epithelium, tract and bulbs (roridin A, satratoxin G) and liver (aflatoxin B1). Aflatoxin B1 and probably trichothecenes are transported along the olfactory tract to the temporal lobe. Co-cultured Streptomyces californicus and Stachybotrys chartarum produce a cytotoxin similar to doxorubicin and actinomycin D (chemotherapeutic agents). Trichothecenes, aflatoxins, gliotoxin and other mycotoxins are found in dust, bulk samples, air and ventilation systems of infested buildings. Macrocyclic trichothecenes are present in airborne particles <2 μm. Trichothecenes and stachylysin are present in the sera of individuals exposed to S. chartarum in contaminated indoor environments. Haemolysins are produced by S. chartarum, Memnoniella echinata and several species of Aspergillus and Penicillium. Galactomannans, glucans and LPS are upper and lower respiratory tract irritants. Gliotoxin, an immunosuppressive mycotoxin, was identified in the lung secretions and sera of cancer patients with aspergillosis produced by A. fumigatus, A. terreus, A. niger and A. flavus.

Isavuconazole: a new and promising antifungal triazole for the treatment of invasive fungal infections

Invasive fungal infections (IFIs) are an important cause of morbidity and mortality. Isavuconazole (BAL4815) is a promising novel broad-spectrum triazole in late-stage clinical development that has proven to be active in vitro against Aspergillus, Candida and Cryptococcus neoformans, the most common agents of IFIs. Furthermore, isavuconazole has a pharmacokinetic profile that allows oral and intravenous administration with no severe toxicity. In vivo data from animal models are also encouraging. However, very little information on clinical efficacy is available. Four clinical trials are currently in progress to demonstrate the safety and efficacy of isavuconazole for the treatment and prevention of IFIs. In the absence of clinical and cost data, the real possibilities of this agent as a competitor for the treatment and prevention of IFIs in the clinical setting are still unknown.