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Veterinary Mycology
Abstract
This book is a comprehensive overview of the fungi that are clinically relevant for animals and humans. It is divided in three major parts: the first part comprises the history of veterinary and medical mycology, general aspects of morphology, growth, nutrition, reproduction and classification of fungi. In the second part, the etiologic agents of cutaneous, subcutaneous and systemic mycoses are described in detail with special emphasis on emerging and uncommon pathogenic fungi. Each chapter consists of a brief history and the morphology, classification, reproduction, susceptibility to disinfectants, natural habitat, distribution, genome, isolation, growth and colony characteristics, antigenic characteristics, virulence factors. The major diseases and their routes of transmission, pathogenesis, immunity, diagnosis and treatment are also covered. The third part focuses on laboratory diagnosis including clinical sample collection, their processing for fungal isolation, special stains for microscopic visualization, culture media composition and a relevant glossary. Each chapter includes color photographs, schematic diagrams and tables for better understanding. For details: http://www.springer.com/life+sciences/microbiology/book/978-81-322-2279-8
Chapters (6)
The term ‘mycology’ was coined by H.S. Berkley (1834) as a study of fungi. Medical or veterinary mycology is the study of medically or veterinary important fungi and fungal diseases in human and animals, respectively. The term ‘mycosis’ (mykes = mushroom) is used to describe the infection of human, animal, birds and plants which is caused by numerous pathogenic fungi. The ‘mycotoxicosis’ describes the diseased condition produced by the ingestion of mycotoxins (intoxication) present in the feed. When the fungi produce the pathogenesis due to in vivo toxin production after entry within the host, it is known as ‘mycetism’.
The fungi are eukaryotic, heterogeneous, unicellular to filamentous, spore bearing, and chemoorganotrophic organisms which lack chlorophyll. The fungi have three major morphological forms, i.e. unicellular yeast, filamentous mould (mold) and yeast-like form (pseudohyphae form). The dimorphic fungi (Blastomyces dermatitidis, Coccidioides immitis, Histoplasma, Sporothrix schenckii) are able to produce both the forms (yeast and mould) depending on the temperature (thermal dimorphism). The yeast form is produced within the body of the host (in vitro at 37 °C) and the mould form is observed either in the environment or in artificial culture medium (at room temperature). The pseudohyphae form is chains of elongated ellipsoidal cells with constriction between them and it is produced by Candida albicans.
The classification of fungi relies mostly on morphological criteria such as the pigmentation, shape of hyphae, presence or absence of septa and types of spores. The taxonomy of mould and yeasts is governed by International Code of Botanical Nomenclature (ICBN). Any new proposal for classification of fungi is published in official journal of International Association for Plant Taxonomy (Taxon) and is discussed in annual meeting before acceptance. The classification of clinically relevant fungi is described in Table 3.1.
The first description of dermatophytosis was recorded by Celsus, a Roman encyclopaedist who described a suppurative infection of scalp (‘porrigo’ or ‘kerion of Celsus’) in De Re Medicina (30 A.D.). Throughout the middle ages, several descriptions of dermatophytosis were produced where it is described as ‘tinea’. The keratin-destroying moths which made circular holes in the woollen garments are known as Tinea. Due to similarity in the structure of circular lesion of dermatophytosis on the smooth skin with the circular hole made by moth, Cassius Felix introduced the term ‘tinea’ to describe the lesions. In 1806, Alibert used the term ‘favus’ to describe the honey-like exudate in some scalp infections. However, the fungal aetiology of tinea was first detected by Robert Remak, a Polish physician who first observed the presence of hyphae in the crusts of favus. This detection is also a landmark in medical history because this is the first description of a microbe causing a human disease. He himself did not publish his work, but he permitted the reference of his observations in a dissertation by Xavier Hube in 1837. Remak gave all the credits of his discovery to his mentor Schoenlein who first published the fungal etiological report of favus in 1839. He observed the infectious nature of the favus by autoinoculation into his own hands and also successfully isolated the fungus later (1945) and named Achorion schoenleinii (Trichophyton schoenleinii) in honour of his mentor. In 1844, Gruby described the etiologic agent of tinea endothrix, later became known as Trichophyton tonsurans. The genus Trichophyton was created and described by Malmsten (1845) with its representative species T. tonsurans. Charles Robin identified T. mentagrophytes in 1847 and T. equinum was identified by Matruchot and Dassonville in 1898. Raymond Jacques Adrien Sabouraud (France) first compiled the description of Trichophyton in his book (Les Teignes) in 1910 which was based on his observation in artificial culture. The sexual state of dermatophyte was described by Nannizzi (1927). Emmons (1934) first reported the classification of dermatophytes based on vegetative structures and conidia. Gentles (1958) established the successful treatment of tinea capitis with griseofulvin.
The collection of proper clinical specimens with sterile instruments and their timely shipment with appropriate arrangements into the laboratory is a crucial matter for isolation and identification of fungi. The correct type of specimen with sufficient quantity is required for proper identification. Table 5.1 describes the types of clinical specimens that can be collected from different body systems and types of fungal infection that can be identified from those specimens. The collection methods of clinical materials and their despatch are mentioned below.
The conventional and modern diagnostic techniques which are used for identification of fungi are discussed below.
... Arthrospores are widely spread by dust particles, even in room without entering pet animal (Frymus et al. 2013). This type of skin disease is an occupational infection of Veterinarians, abattoir and tannery workers, farmers, and pet owners particularly the teenagers who care the infected cat and dog (Samanta 2015). Animal is commonly an asymptomatic carrier of dermatophytes because of the pathogen adaptation to the immune system of the host subsequently; zoophilic species cause severe inflammatory reactions. ...
... The vertical transmission of infection is much more common than the horizontal spread. T. schoenleinii can survive in homes for numerous generations without appropriate cleaning (Samanta 2015). It has been shown that shared wet surfaces (patios, balconies, showers, bathtubs) and shared tools may contribute to the transmission of dermatophytes among family member, as dermatophytes groups can persist on a variety of surfaces for up to 18 months (Jazdarehee et al. 2022). ...
... Branching, septate hyphae can be visualized best in the stratum corneum with a special stain such as periodic acid-Schiff (PAS) with diastase predigestion, Grocott methenamine silver and calcofluor white (CFW) stains (Jartarkar et al. 2022), Although, they may also be seen in Hematoxylin and Eosin stained preparations. The diagnostic sensitivity can be increased with biopsy which is not always possible to conduct especially in human patients suffering with diabetes (Samanta 2015). ...
... The hyphae are observed under the microscope invading the hair and producing arthrospores which arranged in three types of hair invasion, known as ectothrix, endothrix and ecto-endotherix arrangement of arthrospores. In ectothrix invasion, the arthrospores are observed on the surface of the hair, and in endothrix invasion within the hair, whereas, in ecto-endotherix invasion the spores are found within and out the hair (11). ...
... The Petri dishes were incubated upside down in an incubator in the dark at a constant temperature of 28 0 C and examined daily for three weeks. After three weeks the colonies in the medium were macroscopically and microscopically examined and identified to dermatophytes species (Samanta, 2015). ...
Feline dermatophytosis is a specific fungal disease of the epidermal tissues in the skin and these are the most common agents of fungal infections worldwide. During a period of 12 months from first January to last December, 407 asymptomatic and clinical domestic cats with different age, breed, sex, habitat and hair coat were examined clinically to detection of ringworm. Moreover, 170 of 407 domestic cats were suggested with cutaneous mycosis and 120 cases were resulted in positive cultures for feline dermatophytosis and 76 samples positive for saprobe fungi or non-dermatophytes sp. The mycological analyses were conducted by direct microscopy and by fungal culture on SDA supplemented with chloramphenicol & actidione and DTM agar. Our survey was identified two genera of dermatophytes Microsporum sp. (93.91%), represented Microsporum canis (79.3%); M. audounii (10.8%); M. gypseum (9.9%) and Trichophyton spp (7.5%) represented Trichophyton ruburum 12 (60.0%) and T. terrestre 8 (40.0%). Distribution of dermatophytosis and dermatomycosis from various parts region of Baghdad city were Al Kurkh district 45 of 60 (75.0%), 15 of 60 (25.0%) and Al Rusafa district 75 of 110 (68.18%), 35 of 101 (31.8%), respectively. A high prevalence rate of ringworm was recorded in young age (73.94%) and lower infection in old age (50.0%) significantly at P< 0.05. The effect of breeds on the prevalence of feline dermatophytosis show high percentage of infection in Shiraz Persian cats (75.47%) and Himalayan Persian (69.23%) and lower infection in local cats (54.55%). Ringworm in long hair coat was higher (96.12%) than short hair coat (57.14%) significantly. The study show no significant difference between the sex and infection while, recorded a high prevalence in shelters habitat (77.36%) and low (68.33%) in household habitat. Feline dermatophytosis was more frequently isolated in January (88.23%) and lower frequently isolated in November (25.0%). Moreover, the effect of season on the prevalence of dermatophytosis showed a higher prevalence rate of infection in winter (81.54%) and lower in autumn (48.15%). Other dermatomycosis isolated were Chrysosporium ophiodiicola (6.6%) Malassezia pacydermatis (7.9%) and saprobe fungi from domestic cats represented by Alternaria alternate (7.1%); Aspergillus flavus (23.3%); Aspergillus fumigatus (34.9%); Aspergillus niger (37.2%); Aspergillus nidulus (4.7%); Penicillium sp. (5.3%); Rhizopus sp (3.9%) and Curvularia sp (3.9%).
... The hyphae are observed under the microscope invading the hair and producing arthrospores which arranged in three types of hair invasion, known as ectothrix, endothrix and ecto-endotherix arrangement of arthrospores. In ectothrix invasion, the arthrospores are observed on the surface of the hair, and in endothrix invasion within the hair, whereas, in ecto-endotherix invasion the spores are found within and out the hair (11). ...
The aim of the present study was to isolate and identify of the pathogenic fungi of canine dermatophytosis in Baghdad governorate Iraq, also study the epidemiology and describe the clinical signs of dermatophytosis, from January 2018 till December 2018. Out of 653 dogs 165 (25.3%) were with dermatomycoses and 103 (62.42%) dogs with dermatophytosis. The mycological diagnosis were conducted by direct microscopy and by culture the specimens on each sabouraud dextrose agar supplemented with chloramphenicol and cyclohxemide and dermatophytes test media. The identified dermatophytes were represented Microsporum sp.(80.6%) appeared Microsporum canis (87.9%); M. audounii (8.4% );M. gypseum (3. 6 %) and Trichophyton spp (19.4%) in which divided between Trichophyton ruburum (60.0 %) and T. terrestre (40.0%). Microsporum canis and Trichophyton ruburum were the most common species isolated (87.9%),(60.0 %) respectively. The overall prevalence of dermatomycosis and dermatophytosis from various parts region of Baghdad city were Al Karkh district (32.0%), (64.6%) and Al Rusafa district (22.4%), (60.4%) respectively. Moreover, a higher percentage of infection in young age 55 of 84 (65.47%) and lower infection in old age 8 of 18 (44.44%) with significant difference at P< 0.05. The effect of breeds on the prevalence of canine mycosis show high percentage of infection in German shepherd dog (47.96%) and lower infection in Bulldog breed (10.63%) as well as, high prevalence of dermatophytosis recorded in Rottweiler (100%), Pomeranian (83.3%) and lower prevalence (40.0 %) in each of Boxer and local dog breed. The relation of hair coat showed significantly high percentage of infection in long hair dogs (69.0%) than short hair coat (48.0%). There were no significant difference between the sex and habitat but, recorded a high (%) in shelters habitat (67.19%) and low (%) in plantation habitat (56.25%). The prevalence of infection was showed no signficantly high percentage of infection in cold climate winter (67.74%) in which low temperature and high humidity while low percentage of infection in dry climate autumn (44.4%). In addition the effect of season on the prevalence of dermatophytosis recognized by a higher (%) of infection in cold weather, winter (67.74%) and lower infection in dry weather, autumn (50.0%). Other dermatomycosis isolated were Chrysosporium Nannizziopsis dermatitidis (9.1%); Malassezia pacydermatis (7.9 %) and saprobe fungi from domestic dogs represented by Alternaria alternate (21.4%); Aspergillus spp (60.7%); Aspergillus flavus (25.9%); Aspergillus fumigatus (28.2%); Aspergillus niger (23.5 %); Aspergillus nidulans (22.4 %); Penicillium sp. (4.3%); Curvularia sp (3.6%) and Rhizopus sp (2.1%).
Chitinolytic bacteria were isolated from guts and shells of the termite Microcerotermes sp. Among the nineteen morphologically different chitinolytic isolates, three isolates with highest extracellular chitinase production ratio (≥ 2.26) were selected. Based on molecular identification of 16S rRNA gene sequences and biochemical characterizations using API test kits and MALDI-TOF MS, these isolates were closely related to Bacillus thuringiensis (Mc_E02) and Paenibacillus species (Mc_E07 and Mc_G06). Isolate Mc_E02 exhibited the highest chitinase specific activity (2.45 U/mg protein) at 96 h of cultivation and the enzyme activity was optimized at pH 7.0 and 45°C. The isolate showed highest and broad-spectrum inhibitory effect against three phytopathogenic fungi (Curvularia lunata, Colletotrichum capsici, and Fusarium oxysporum). Its 36-kDa chitinase exhibited the biomass reduction and mycelium inhibition against all fungi, with highest effects to Curvularia lunata. This research provides novel information about termite chitinolytic bacteria and their effective chitinase, with potential use as biocontrol tool.
Background:
Dermatophytes are infectious zoonotic fungal agents that are common in animals worldwide. A new loop-mediated isothermal amplification (LAMP) method and quantitative (q)PCR can be used for identifying these agents. Both methods have high specificity and sensitivity, and are simple and quick to use.
Hypothesis/objectives:
To develop a LAMP and a rapid multiplex qPCR method for detecting Microsporum canis and Trichophyton mentagrophytes, which are the most common fungal species isolated from cats and dogs.
Material and methods:
Both methods targeted the CHS-1 gene. Their specificity and sensitivity were tested using 64 M. canis and 44 T. mentagrophytes field strains. The validation of the methods was performed using 250 clinical fungal-positive hair samples.
Results:
The specificity value was 100% for both methods. For LAMP, the sensitivity value was 96.9% for M. canis and 93.2% for T. mentagrophytes. For qPCR, the sensitivity values were 98.4% for M. canis and 97.7% for T. mentagrophytes. Similar specificity and sensitivity results were obtained from the validation study using 250 clinical hair samples. LAMP and multiplex qPCR took 30 and 45 min (respectively) for both targets. The limit of detection (LOD) assays for both targets were 10 and 1 spore/mL for LAMP and multiplex qPCR, respectively.
Conclusion:
These findings demonstrate that the LAMP and multiplex qPCR methods targeting CHS-1 gene developed in this study can be used both for point-of-care testing and in the laboratory for detecting M. canis and T. mentagrophytes with high specificity and sensitivity with an internal control.
Aflatoxin B1 (AFB1) is a hazardous component that can seriously threaten the public health. Terxine is a component used in traditional soup and found in the western mountainous regions of Iran. Several microorganisms have been reported to bind or degrade aflatoxins (AFs) in foods and feeds. This research aimed to investigate the effect of Terxine fermentation by Lactobacillus plantarum strains AF1 and LU5 on AFB1. Fermentation was carried out, and pH, lactic acid, and AFB1 amount and microbial count were further determined. In addition, the kinetic experimental data of AFB1 by Lactobacillus plantarum AF1 and LU5 (obtained at 37°C) were fitted to the zero-order, first-order, and parabolic diffusion models. According to the coefficient of determination (R2) and root mean square of errors (RMSE), the zero-order model best described aflatoxin (AF) degradation. The growth of Lactobacillus strains was increased by the rise in the fermentation time; in this regard, the number of L. plantarum AF1 increased from 4.2 to 5.1 log cfu/g and that of L. plantarum LU5 increased from 4.1 to 5.2 log cfu/g in the first 8 h, reaching 7.2 and 7.4 log cfu/g in the next 8 h, respectively. The results also showed that the amount of lactic acid increased whereas the pH value decreased during the 24 h fermentation. Both microorganisms reduced the amount of AFB1 while L. plantarum AF1 was more effective. Therefore, Lactobacillus plantarum strains AF1 and LU5 can be effectively used to reduce AFB1 in fermented foods.
This study aimed to compare fungal contamination of poultry litter between warm and cold seasons. It was carried out in commercial production conditions over two five-week fattening periods: one in the summer (July-August) and one in the winter (December-January). Broilers were reared on a litter composed of chopped straw and sawdust. Litter fungal concentration and composition were investigated weekly, along with litter temperature, moisture, and pH. Litter concentration of total fungi increased over both fattening periods, with no differences in median concentrations between them. Season also had no effect on yeast, Aspergillus section Nigri , and Cladosporium , Fusarium , and Rhizopus spp. concentrations, while the Aspergillus section Flavi and Aspergillus spp. combined showed higher concentrations in the summer, and Mucor and Penicillium spp. in the winter. Total fungal concentration highly correlated with litter temperature, moisture, and pH, regardless of the season. Our findings can be useful in the assessment and control of potential harmful effect of fungi on the health of poultry and poultry farm workers.
Background:
Due to the limited range of antifungals available to treat genital Candida infections and the emergence of resistant isolates, attention has focused on the antifungal potency of natural compounds with promising biological properties.
Objectives:
To examine whether eugenol synergises the in vitro efficacy of voriconazole against Candida strains isolated from the genital tract of mares.
Study design:
In vitro experiment.
Methods:
The antifungal activity of eugenol and voriconazole was evaluated using the broth microdilution assay (CLSI- M27-A3). Synergism of eugenol and voriconazole against genital Candida isolates was evaluated by the microdilution checkerboard method.
Results:
Minimum inhibitory concentration (MIC) values for eugenol and voriconazole ranged from 400 to 800 µg/mL and 1 to 8 µg/mL, respectively, for C. tropicalis isolates, and from 200 to 400 µg/mL for eugenol and 2 to 16 µg/mL for voriconazole against C. krusei isolates. Eugenol decreased the arithmetic mean MIC for voriconazole against C. tropicalis and C. krusei isolates from 2.66 to 0.46 µg/mL and 7.77 to 0.41 µg/mL respectively. The fractional inhibitory concentration index (FICI) values for the eugenol-voriconazole combination ranged from 0.25 to 0.88 and 0.19 to 0.63 for C. tropicalis and C. krusei isolates respectively. A synergistic effect of eugenol in combination with voriconazole was observed for 83.3% of C. tropicalis and 77.7% of C. krusei isolates. Antagonistic activity was not seen in any of the isolates tested.
Main limitations:
Since in vitro antifungal susceptibility tests are not systematic analyses, any selection bias could influence the results. In addition, in vitro susceptibility does not uniformly predict clinical success in vivo.
Conclusions:
Eugenol showed fungistatic and fungicidal effects against genital Candida isolates and, in combination, synergised the antifungal effects of voriconazole. The eugenol-voriconazole combination can lay the foundation for a therapeutic approach against isolates in which azole resistance has increased over time.