''Cochliobolus lunatus'' is a

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

plant pathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...

that can cause disease in humans and other animals. The anamorph of this fungus is known as ''Curvularia lunata'', while ''Cochliobolus lunatus'' denotes the

teleomorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an ase ...

or sexual state. They are, however, the same biological entity. ''Cochliobolus lunatus'' is the most commonly reported species in clinical cases of reported ''Cochliobolus'' infection.

Morphology

Macroscopic features of ''C. lunatus'' include brown to black colour, hairy, velvety or woolly texture, and loosely arranged and rapidly growing colonies on

potato dextrose agar Potato dextrose agar (BAM Media M127
from the U.S.

medium. Microscopically, there is great variety in the arrangement of the septate

conidiophore A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are al ...

s, as they can be isolated or in groups, straight or bent, show simple or geniculate growth pattern, and vary in colour ranging from pale to dark brown. Conidiophore length can reach 650 μm and are often 5-9 μm wide, with swollen bases ranging from 10-15 μm in diameter. Conidia develop at the tips and sides of the spores and have a smooth texture. ''Cochliobolus lunatus'' is differentiated from other Cochliobolus species by its 3 septa and 4 cells, with the first and last cell usually of a paler shade of brown than those in the middle. Conidia range from 9-15 μm in diameter and have a curved appearance.

Phylogeny

The order

Pleosporales The Pleosporales is the largest order in the fungal class Dothideomycetes. By a 2008 estimate it contains 23 families, 332 genera and more than 4700 species. The majority of species are saprobes on decaying plant material in fresh water, marin ...

includes many

s of economic importance. ''C. lunatus'' belongs to Clade-II in the family

Pleosporaceae Pleosporaceae is a family of sac fungi. The taxonomic relationship of this family to associated genera is still not determined. Genera As accepted by GBIF; * '' Acrothecium'' (13) * ''Alternaria'' Nees ex Wallroth, 1816 (841) * '' Alternariast ...

, which is the largest family in its order. The ''Clk1''

MAPK A mitogen-activated protein kinase (MAPK or MAP kinase) is a type of protein kinase that is specific to the amino acids serine and threonine (i.e., a serine/threonine-specific protein kinase). MAPKs are involved in directing cellular responses to ...

gene in ''C. lunatus'' is homologous to MAPK genes such as ''Pmk1'', ''Cmk1'', ''Chk1'' and ''Ptk1'' of other fungal pathogens, which are highly conserved in eukaryotic lineages. There are over 80 species in the genus ''

Cochliobolus The fungal genus ''Cochliobolus'' includes 55 species, including the following plant pathogenic species: '' C. carbonum'', '' C. heterostrophus'', '' C. miyabeanus'', '' C. sativus'' and '' C. lunatus''. Heterothallism and homothallism Those ...

''.

Ecology

''Cochliobolus lunatus'' has a widespread distribution, though it is especially prevalent in the tropics and subtropics. Infection is caused by airborne conidia and

ascospore An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...

s, however, sclerotioid ''C. lunatus'' can also survive in the soil. The optimal temperature for ''in vitro'' growth and infection ranges from while death results from exposure at for a 1 minute duration, or for a 5 minute duration. Successful plant host infection requires the host surface to be wet for 13 hours. The majority of clinical cases have been reported in India, the United States, Brazil, Japan and Australia.

Pathogenicity and therapy

Plant diseases

''Cochliobolus lunatus'' is best known as the causative agent of seedling blight and seed germination failure in

monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...

crops such as

sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with ...

rice Rice is the seed of the grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima ''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown i ...

millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most species generally referred to as millets belong to the tribe Paniceae, but some millets al ...

and

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...

. ''Cochliobolus lunatus'' also causes leaf spot on a wide variety of

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

hosts, where each lesion contains a sporulating mass of fungi at its center. The ''Clk1'' gene plays an important role in fungal growth during the infection process, specifically conidiation, which is vital to the process of foliar infection.

Fungicides Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...

, in particular those with organo-mercurial compounds, have been associated with effective eradication of this pathogen.

Human diseases

Phaeohyphomycoses

''Cochliobolus lunatus'' is one of the main causative agents of

phaeohyphomycosis Phaeohyphomycosis is a diverse group of fungal infections, caused by dematiaceous fungi whose morphologic characteristics in tissue include hyphae, yeast-like cells, or a combination of these. It can be associated an array of melanistic filamento ...

. Initial infection via breaks to the epidermal barrier or the inhalation of spores can lead to disseminated infections, which are often associated with a poor prognosis. ''C. lunatus'' is an

opportunistic pathogen An opportunistic infection is an infection caused by pathogens (bacteria, fungi, parasites or viruses) that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened immune ...

, infecting immunocompromised patients and those on rigorous steroid drug regimens such as solid organ transplant recipients, advanced AIDS patients and cancer patients.

Dematiaceous “Black yeasts”, sometimes also black fungi, dematiaceous fungi, microcolonial fungi or meristematic fungi is a diverse group of slow-growing microfungi which reproduce mostly asexually (fungi imperfecti). Only few genera reproduce by budding ...

fungi such as ''C. lunatus'' can facilitate foreign body infections of

catheter In medicine, a catheter (/ˈkæθətər/) is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. Cath ...

heart valve A heart valve is a one-way valve that allows blood to flow in one direction through the chambers of the heart. Four valves are usually present in a mammalian heart and together they determine the pathway of blood flow through the heart. A heart v ...

s and

pacemaker An artificial cardiac pacemaker (or artificial pacemaker, so as not to be confused with the natural cardiac pacemaker) or pacemaker is a medical device that generates electrical impulses delivered by electrodes to the chambers of the heart eith ...

s, for example. With regards to treatment, surgical excision using a method similar to

Mohs surgery Mohs surgery, developed in 1938 by a general surgeon, Frederic E. Mohs, is microscopically controlled surgery used to treat both common and rare types of skin cancer. During the surgery, after each removal of tissue and while the patient waits, t ...

is preferred if the mycosis is accessible, especially for abscesses in the brain. Administration of antifungals is commonly indicated as secondary management therapy, though the specific best regimen depends on the nature and location of the phaeohyphomycosis. When treating immunocompromised patients, it is critical that the underlying disease is controlled, and immune modulators such as

granulocyte-macrophage colony-stimulating factor Granulocyte-macrophage colony-stimulating factor (GM-CSF), also known as colony-stimulating factor 2 (CSF2), is a monomeric glycoprotein secreted by macrophages, T cells, mast cells, natural killer cells, endothelial cells and fibroblasts that ...

and

gamma interferon Interferon gamma (IFN-γ) is a dimerized soluble cytokine that is the only member of the type II class of interferons. The existence of this interferon, which early in its history was known as immune interferon, was described by E. F. Wheelock ...

can be indicated when surgery or antifungals are not feasible alternatives.

Allergy

Allergic fungal manifestations include asthma, rhinitis, sinusitis and bronchopulmonary

mycoses Fungal infection, also known as mycosis, is disease caused by fungi. Different types are traditionally divided according to the part of the body affected; superficial, subcutaneous, and systemic. Superficial fungal infections include common ti ...

caused by a variety of etiological fungal agents including ''C. lunatus''. These agents provoke humoral immune responses, characterized by type I (immediate) and type III (immune complex mediated) hypersensitivity reactions. Prevalence of these diseases among the atopic population is 20-30 % and 6% in the general population.

Allergic rhinitis Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, i ...

, more commonly known as hay fever, is less frequently encountered in clinic compared to allergic fungal sinusitis.

Differential diagnosis In healthcare, a differential diagnosis (abbreviated DDx) is a method of analysis of a patient's history and physical examination to arrive at the correct diagnosis. It involves distinguishing a particular disease or condition from others that p ...

of allergic bronchopulmonary mycosis is difficult, and it is often misdiagnosed as

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...

bronchiectasis Bronchiectasis is a disease in which there is permanent enlargement of parts of the bronchi, airways of the lung. Symptoms typically include a chronic cough with sputum, mucus production. Other symptoms include shortness of breath, hemoptysis, co ...

, lung

abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends b ...

or bronchial

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...

. Several serological tests can be performed to assess total IgE and allergen specific

IgE Immunoglobulin E (IgE) is a type of antibody (or immunoglobulin (Ig) " isotype") that has been found only in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains (ε chain) and two light chains, with the ε c ...

and

IgG Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG ...

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...

, MAST, HIA, and CAP RAST. However, more conventional allergy testing such as skin-prick tests can provide rapid results and are easy to conduct and inexpensive, though they may indicate false-positive or false-negative results. Current research has shown that there is an association between allergic fungal sinusitis and

MHC II MHC Class II molecules are a class of major histocompatibility complex (MHC) molecules normally found only on professional antigen-presenting cells such as dendritic cells, mononuclear phagocytes, some endothelial cells, thymic epithelial cells, ...

alleles, suggesting a genetic component to this chronic inflammatory respiratory tract disorder. Treatment for allergic fungal sinusitis includes post-operative corticosteroid and aggressive anti-allergic inflammatory regimen including

itraconazole Itraconazole, sometimes abbreviated ITZ, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, blastomycosis, coccidioidomycosis, histoplasmosis, and paracoccidioidomycosis. It may be given by mouth ...

amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococcosis. Fo ...

, while treatment for bronchopulmonary mycosis usually does not include surgery.

Eye infection

Mycotic

keratitis Keratitis is a condition in which the eye's cornea, the clear dome on the front surface of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves any of the following symptoms: pain, impaired e ...

and

conjunctivitis Conjunctivitis, also known as pink eye, is inflammation of the conjunctiva, outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may ...

are more commonly reported in tropical climates. Environmental factors such as wind, temperature, rainfall and humidity have been found to influence the ecology of filamentous fungi. In the Gulf of Mexico for example, increased numbers of airborne spores of ''C. lunatus'' during hot, humid months has been linked to increased clinical reports of keratitis. ''C. lunatus'' commonly infects the

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...

, and

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

of the eye, and infection can result from trauma, surgery or dissemination from paranasal sinuses.

Endophthalmitis Endophthalmitis is inflammation of the interior cavity of the eye, usually caused by infection. It is a possible complication of all intraocular surgeries, particularly cataract surgery, and can result in loss of vision or loss of the eye itself ...

can result from deep fungal keratitis caused by ''C. lunatus'', where the Descemet's membrane is penetrated and compromised. In immunocompetent atopic individuals, 17% of those affected with allergic fungal sinusitis can develop orbital mycotic symptoms, where the fungus acts as an allergen causing allergic mucin. Pre-existing allergic fungal sinusitis, allergic conjunctivitis and use of soft contact lenses are risk factors for development of ophthalmomycosis. Typical therapy includes administration of

natamycin Natamycin, also known as pimaricin, is an antifungal medication used to treat fungal infections around the eye. This includes infections of the eyelids, conjunctiva, and cornea. It is used as eyedrops. Natamycin is also used in the food industr ...

and

azoles Azoles are a class of five-membered heterocyclic compounds containing a nitrogen atom and at least one other non-carbon atom (i.e. nitrogen, sulfur, or oxygen) as part of the ring. Their names originate from the Hantzsch–Widman nomenclature. T ...

such as

fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. This includes candidiasis, blastomycosis, coccidiodomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor. It is also used to prevent ...

posaconazole Posaconazole, sold under the brand name Noxafil among others, is a triazole antifungal medication. It was approved for medical use in the United States in September 2006, and is available as a generic medication. Medical uses Posaconazole is u ...

and

voriconazole Voriconazole, sold under the brand name Vfend among others, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, candidiasis, coccidioidomycosis, histoplasmosis, penicilliosis, and infections by '' ...

References

External links

Index Fungorum

USDA ARS Fungal Database
{{DEFAULTSORT:Cochliobolus Lunatus Fungal plant pathogens and diseases Cochliobolus Fungi described in 1898