Conidiobolus incongruus Drechsler 1960

Conidiobolus incongruus grows rapidly in culture at 30-35°C. The colonies are flat, cream-colored, radially folded, and glabrous (smooth). Mature colonies will darken in color, becoming tan to brown, with a white reverse side. Primary and secondary conidia are produced. Characteristic ballistoconidia are produced on short conidiophores. These forcibly discharged asexual spores are round to pyriform (pear-shaped). In culture, they will coat the lid of the Petri dish (Reiss, Shadomy, & Lyon, 2011). Round, thick-walled zygospores similar in size to the primary conidia are produced (Stephens & Gibson, 1997).

As agents of infection in humans, Conidiobolus incongruus and the related species C. coronatus produce similar symptoms and must be differentiated in culture or using molecular techniques. Conidiobolus incongruus is a homothallic species that produces zygospores but does not produce villous (finely hairy) sporangioles that are found in some other species. Conidiobolus coronatus can be differentiated from C. incongruus because C. coronatus is heterothallic and does not produce zygospores in culture. Furthermore, C. coronatus produces resting villous sporangioles (Reiss et al., 2011; Temple, Brady, Koranyi, & Nahata, 2001). The conidial papillae of Conidiobolus incongruus are also pointed, whereas those of C. coronatus are more rounded (Walsh et al., 1994).

Conidiobolus species occur worldwide as saprobes on plant detritus and as parasites on arthropods (Gryganskyi et al., 2012). Conidiobolus incongruus is an opportunistic pathogen (Madson, Loynachan, Kariyawasam, & Opriessnig, 2009) known to very rarely infect humans and other mammals. Nasofacial zygomycosis caused by Conidiobolus incongruus has been described in a herd of sheep. Disseminated zygomycosis has been observed in a young male red deer (Cervus elapus) in Australia (Stephens & Gibson, 1997) and a white-tailed deer (Odocoileus virginianus) in North America (Madson et al., 2009). Mackey et al. (2015) recorded a case of disseminated zygomycosis in a dog in the United States.

Recent molecular analyses indicate that the genus Conidiobolus is a polyphyletic assemblage. Ancestral state reconstruction suggests that the ancestor of all members of the phylum Entomophthoromycota was morphologically similar to extant species of Conidiobolus (Gryganskyi et al., 2012).

Conidiobolus incongruus is an uncommon cause of zygomycosis in humans; the majority of cases are caused by Conidiobolus coronatus (Reiss et al., 2011; Sharma, Mahajan, & Singh, 2003). Infections by Conidiobolus have traditionally been referred to as zygomycosis because Conidiobolus was originally placed in the (now defunct) phylum Zygomycota. However, these infections are sometimes also referred to as conidiobolomycosis or rhinoentomophthoromycosis (Sharma et al., 2003).

Conidiobolus infections in humans most often occur in tropical and subtropical regions (Mackey et al., 2015), particularly in Sub-Saharan Africa and Southeast Asia. The majority (60%) of Conidiobolus infections occur in adults between the ages of 20 and 29 (Temple et al., 2001). Males are disproportionately infected, with a 10:1 ratio of males to females (Pfaller & Diekema, 2005).

Classical presentation is chronic subcutaneous mycosis of the nasofacial area. Infection begins following inhalation of spores through the nose. These spores germinate in the nasal mucosa and grow slowly, causing chronic sinusitis. Left untreated, lesions will develop and spread, resulting in facial disfigurement. Insect bites may play a role in transmission, but the exact mechanism of infection is unclear in most human cases (Reiss et al., 2011). Infection in a 20-year-old tuba player suggests that stress, injury, or trauma to the mucous membranes may facilitate infection (Sharma et al., 2003).

Biopsy for histology and tissue culture are preferred for diagnosis. There is no standard treatment protocol for zygomycosis caused by C. incongruus (Temple et al., 2001). Long-term oral use of saturated solution of potassium iodide (SSKI) is an effective and inexpensive treatment favored in developing countries. Azole antifungal agents may be employed, sometimes in conjunction with SSKI treatment (Reiss et al., 2011), as well as hyperbaric oxygen and surgery (Temple et al., 2001). Multisystem dissemination of Conidiobolus incongruus is extremely rare and is typically only found in immunocompromised patients (Reiss et al., 2011). Walsh et al. (2014) reported the fatal case of a 32-year-old female cancer patient with pneumonia caused by C. incongruus; the strain was resistant to amphotericin B and flucytosine.

Conidiobolus incongruus is an uncommon cause of zygomycosis in humans; the majority of cases are caused by Conidiobolus coronatus (Reiss et al., 2011; Sharma, Mahajan, & Singh, 2003). Infections by Conidiobolus have traditionally been referred to as zygomycosis because Conidiobolus was originally placed in the (now defunct) phylum Zygomycota. However, these infections are sometimes also referred to as conidiobolomycosis or rhinoentomophthoromycosis (Sharma et al., 2003).

Conidiobolus infections in humans most often occur in tropical and subtropical regions (Mackey et al., 2015), particularly in Sub-Saharan Africa and Southeast Asia. The majority (60%) of Conidiobolus infections occur in adults between the ages of 20 and 29 (Temple et al., 2001). Males are disproportionately infected, with a 10:1 ratio of males to females (Pfaller & Diekema, 2005).

Classical presentation is chronic subcutaneous mycosis of the nasofacial area. Infection begins following inhalation of spores through the nose. These spores germinate in the nasal mucosa and grow slowly, causing chronic sinusitis. Left untreated, lesions will develop and spread, resulting in facial disfigurement. Insect bites may play a role in transmission, but the exact mechanism of infection is unclear in most human cases (Reiss et al., 2011). Infection in a 20-year-old tuba player suggests that stress, injury, or trauma to the mucous membranes may facilitate infection (Sharma et al., 2003).

Biopsy for histology and tissue culture are preferred for diagnosis. There is no standard treatment protocol for zygomycosis caused by C. incongruus (Temple et al., 2001). Long-term oral use of saturated solution of potassium iodide (SSKI) is an effective and inexpensive treatment favored in developing countries. Azole antifungal agents may be employed, sometimes in conjunction with SSKI treatment (Reiss et al., 2011), as well as hyperbaric oxygen and surgery (Temple et al., 2001). Multisystem dissemination of Conidiobolus incongruus is extremely rare and is typically only found in immunocompromised patients (Reiss et al., 2011). Walsh et al. (2014) reported the fatal case of a 32-year-old female cancer patient with pneumonia caused by C. incongruus; the strain was resistant to amphotericin B and flucytosine.

Conidiobolus incongruus is a zygomycete fungus in the family Ancylistaceae, in the order Entomophthorales. Drechsler first described the species in 1960. It was isolated from leaf litter collected in Colorado (Hernandez et al., 2007). Conidiobolus incongruus is sometimes misspelled as Conidiobolus incongruous in literature (Kwon-Chung, 2012; Pfaller & Diekema, 2005).

Biology and relevance for humans

C. incongruus is known as a pathogen of animals and humans. In wild or domestic mammals, it has been reported to infect sheep and deer in Australia and the United States. In these cases, the C. incongruus can cause nasal swelling, rhinocerebral mycosis, exophthalmia, and disseminated disease. Most recently, Mackey et al. (2015) reported the isolation of C. incongruus from a 17-month-old male English Mastiff dog. It was the first isolation of this fungus from a non-Artiodactyla animal.

Although the infection of C. incongruus is uncommon in humans, it is fatal for immunocompromised patients. The first fatal case of disseminated infection due to C. incongruus happened in a 20-year-old female Thai student. In this case the patient displayed fever, weight loss, a cough with hemoptysis, and a subcutaneous mass. The symptoms lasted about 2 months. The broad hyphae were detected in subcutaneous tissue, lung, lymph nodes, esophagus, liver, and jejunum. Another case of C. incongruus infection in an immunocompromised patient was reported in Germany. A 32-year-old woman with granulocyteopenic due to lymphoytic lymphoma was diagnosed with pulmonary and pericardial zygomycosis caused by the infection of C. incongruus. The patient died on the third day after treatment with amphotericin B and pericardiocentesis. Additionally, Jaffey et al. reported a case of disseminated C. incongruus infection with endocarditis in a cocaine abuser. So far, the mode of transmission of C. incongruus is still unknown. One accepted hypothesis of infection claims that built up by inhalation of fungal spores implanted in the nasal mucosa or from a minor trauma such as an insect bite.

Introduction

In taxonomy, Conidiobolus incongruus (Fig 1.) belongs to the genus of Conidiobolus. The genus Conidiobolus was first discovered by Brefeld in 1884 and includs over 150 species. Although most species of Conidiobolus have been identified as saprophytic fungi, a substantial quantity of species has been isolated from insects as well. Additionally, some species, such as C. incongruus and C. coronatus, can infect mammals and humans.

Kingdom-Fungi

Phylum-Zoopagomycota

Subphylum-Entomophthoromycotina

Order-Entomophthorales

Family-Ancylistaceae

Genus-Conidiobolus

Species-incongruus

Fig 1. The taxonomy of Conidiobolus incongruus

Conidiobolus

Conidiobolus is known as a morphologically complex genus. Under artificial culture condition, species of this genus display three types of vegetative growth and eight types of spores (Fig 2.). In culture, the coenocytic hyphae can usually be divided into multinucleate segments. Under certain condition, the protoplast is separated into chains of hyphal bodies. In others, as the elongation of hypha, a septum would be formed behind the advancing protoplasm.The first two types of vegetative growth are quite common in all species. However, the third type of vegetative growth is rarely seen. The eight types of spores include primary conidium on the conidiophore, globose replicative conidium on the conidiophore, forcibly discharged elongate repetition conidium, microconidia produced from globose conidium, passively detached elongate conidium, zygospore, chlamydospore, and villose resting spores. Compared with other types of spores, only the primary conidium and replicative conidium are characteristics of all species.

Conidiobolus incongruus

C. incongruus exists widely in every continent. It was first identified by Charles Drechsler from friable duff collected from woods near Durango, Colorado, at an elevation of about 2000m and decomposed leaf mold collected from the woods near Fort Collins, Colorado. Initially, Charles Drechsler considered C. incongruus and C. gonimodes as two different species, since compared with C. gonimodes there were no microconidia produced by C. incongruus that had been observed. The micrconidium is known as a very important character for the taxonomy of Conidiobolus. However, according to King, the C. incongruus can readily produce microconidium when cultured on water agar media. Therefore, the C. incongruus and C. gonimodes are synonyms now.

Morphology and nutrition

Currently, the most comprehensive description of C. incongruus was reported by King. A colony of C. incongruus has a diameter of about 20mm and shows opaque growth in 3 days on PDA media at 2℃. There are multiple small colonies developing around the original colony. Under a microscope, the mycelia are usually compact. Assimilative hyphae are filamentous and branched, the terminal portion of which is arranged from 40 to 400μm in length, and soon septate and segments 15 to 200μm delimited. The primary conidia (Fig 3a-b) (11-37 × 12-42μm) produced on conidiophores (Fig 3a) (5-12× 20-130μm) are globose or ellipsoidal. Only globose replicative conidia are produced from primary conidia. Microconidia (Fig. 3c) (5.5-11 × 8-16μm) with shape of globose to ellipsoidal are produced on sterigmata (2-3 × 2-4μm) readily on water agar media.Zygospores (Fig 3d) (11-25 × 15-30 μm) are a result from the conjugation of adjacent segments of the same hypha and globose or less often slightly elongated. Nutritionally, asparagine is unnecessary or moderately needed; NH₄⁺ and urea are unnecessary.

Phylogenetic

Phylogenetically, the Entomophthoromycotina is a subphylum of Zoopagomycota along with Kickxellomycotina and Zoopagomytina. There are five major lineages have been detected within Entomophthoromycotina. The monophyletic Basidiobolus and paraphyletic Conidiobolus act as either saprotrophs or facultative parasites pathogens of insects and mammals. The other three lineages including Batkoa, Entomophthora, and Zoophthora are together consisting of a monophyletic family of Entomophthoraceae that is mainly obligate pathogens of insects and arthropods (Fig 4).

Ecology

The Conidioblous species is so-called opportunistic fungal pathogens and widely distributed around the world. It can be found in soil and decaying organic material. Despite the wide distribution, this species is more concentrated in warm, wet climates, especially in tropical countries. The organism concentrations increase as a result of increased rainfall. The C. incongruus is a homothallic species, it is morphologically similar to C. coronatus. Together with C. lamprauges, the C. incongruus and C. coronatus are able to cause illness and death in humans and animals. However, unlike C. coronatus, C. incongruus does not produce villose resting spores. Additionally, compared with Basidiobolus the C. incongruus does not produce conjugation beaks on the thick-walled zygospores (Fig 5).

Conidiobolus incongruus is a species of Conidiobolus.

It is associated with conidiobolomycosis.

Conidiobolus incongruus je grzib, co go ôpisoł Drechsler 1960. Conidiobolus incongruus nŏleży do zorty Conidiobolus i familije Ancylistaceae. Żŏdne podgatōnki niy sōm wymianowane we Catalogue of Life.

异孢耳霉（学名：Conidiobolus incongruus）是属于虫霉目新月霉科耳霉属的一种真菌，腐生在植物的腐烂组织、枯枝落叶及土壤中。该种分布于中国、印度、美国。