1. Introduction
Aspergillus infections in humans were firstly reported in the eighteenth century [1, 2]. Aspergillus was first described in 1729 by Micheli, an Italian priest and biologist, who was the first person to attempt the scientific study of fungi [3]. A. flavus was named and reported by Link in 1809. John Hughes Bennett (1812–1875) was the first to describe aspergillosis. In his seminal paper published in 1842, he made the very first description of Aspergillus growing in the lung tissue of humans [4]. Paranasal sinus mycosis in 1893 and since then numerous cases have been reported from different parts of the world. In 1926, the genus Aspergillus was first classified and accepted in 69 Aspergillus species in 11 groups. By the year 1965, the previous classification of Aspergillus was declared outdated, and detailed 151 species in 18 different groups were introduced. Additional research led to further refined species designations with the use of new technologies such as thin-layer chromatography of secondary metabolites and DNA hybridization.
The genus Aspergillus consists of numerous species gathered in a diverse group with environmental and public health importance [5, 6]. The members of this genus are cosmopolitan fungi frequently found in various natural habitats especially in soil as the main reservoir and they are responsible for food spoilage, mycotoxin contamination, and various types of human and animal mycoses [7, 8]. Moreover, they are rich sources of beneficial metabolites such as antibiotics, organic acids, enzymes, and additives. At present, there are more than 300 species which are now accepted, and new species continue to be described and added to this list. The taxonomy of species within the Aspergillus genus is gradually undergoing emendation with the use of molecular methods and is not yet complete. Of the known Aspergillus species, only 20 have been confirmed to cause human infections and three of them are consistently and regularly encountered as etiological agents of over 95% of diseases caused by members of the genus including A. fumigatus, A. niger, and A. flavus [9]. The other species of this genus related to human lesions are A. terreus, A. glaucus, A. nidulans, A. oryzae, and A. clavatus. Mode of infection is the inhalation of airborne conidia, exposure to contaminated water (contact with conidia during showering), and nosocomial infections (hospital fabrics and plastics may serve as important sources of Aspergillus species). The incubation period is between 2 days and 3 months.
Aspergillosis is a common term used to describe infections caused by different species of Aspergillus [10]. Aspergillosis was described as a clinical human disease under the name of bronchopulmonary Aspergillus. The species A. fumigatus, with A. flavus and A. niger are responsible for more than 90% of aspergillosis worldwide. A wide array of clinical forms from allergic reactions (allergic bronchopulmonary aspergillosis, rhinitis, Farmer’s lung) to superficial and cutaneous infections, localized aspergilloma, and invasive infections have been reported. Invasive life-threatening aspergillosis occurs mainly in immunocompromised individuals who have undergone widespread antibiotics, cancers, or autoimmune underlying disorders. Invasive infections initiate by entering air-borne conidia to lungs with clinical entities such as invasive sinusitis, fever, facial pain, headache, cough, and dyspnea with subsequent spread to the central nervous system (CNS), leading to seizures or death.
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2. Description
In the current book which comprises five distinct chapters, different aspects of the genus Aspergillus from Aspergillus-host interactions to the immunopathogenesis of aspergillosis, mycotoxin production, and industrial applications of the beneficial species have gained special attention.
It has been shown that host immune status and previous underlying diseases act as important determinants of clinical outcomes and disease spectra of aspergillosis which is life-threatening in the invasive form where the etiologic fungus affects lung tissue and disseminates to different organs with high morbidity and mortality. The role of influenza and COVID-19 infections in ICU patients has been noticed as the new risk factors of invasive aspergillosis. In relation to the immunopathogenesis of aspergillosis, documents demonstrated that following entry of causative Aspergillus species, fungal elements are affected by pulmonary host defense in order to clearance of infective conidia. In conditions of poor host immune response, where the neutrophils and macrophages fail to recognize the etiologic fungus, Aspergillus conidia attack and destroy airway epithelium and neutrophils play an important role in the clearance of fungal hyphae via oxidative and non-oxidative mechanisms. As an amazing topic in mycotoxin research, the relationship between mycovirus-containing Aspergillus flavus and acute lymphoblastic leukemia as carcinogenesis beyond mycotoxin production has been noticed. The role of aflatoxin in Aspergillus flavus resistance to stress conditions is a very interesting subject in the importance of members of Aspergillus section Flavi. In this context, it has been shown that Aspergillus employs a considerable amount of energy to synthesize aflatoxins which are not so obviously linked to an enhancement of population fitness. Another important aspect of the genus Aspergillus is the industrial application of nanomaterials produced by Aspergillus species. These fungi produce a large number of beneficial metabolites enabling the producing fungus to the successful synthesis of nanoparticles.
In conclusion, we would like to thank all authors for their invaluable contribution and hard work to make the successful endeavor on the goals of the present book. We are also grateful to the “In-Tech” Publisher personnel, especially Ms. Karmen Ðaleta, who kindly assisted us in the arrangement of the book and scheduling our activities.
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