Part A:
1) Filobasidiella neoformans
2) Cryptococcus neoformans
3) Christensen’s Urea agar
4) Person to person through inhaling the aerosol droplets.
Part B: Similarities and individualities between Cryptococcus sp. vs Histoplasma sp.
Cryptococcus sp. belongs to basidiomycetes that consist of dimorphic life cycles, one is prominent yeast form and second is the hyphal form that produces infectious basidiospores. Similarly, Histoplasma sp. also is a dimorphic fungus with yeast forms and hyphal forms. These both species are responsible for meningoencephalitis and meningitis that is caused by its encapsulated form.
The most prevalent etiologic agent of Cryptococcus sp. is Cryptococcus neoformans while another species is C. gatti which is found attributable to less than 5% cases. The geographical niche of Cryptococcus sp. includes rural as well as urban regions worldwide. C. gatti is found to be endemic to South Africa, Australia, British Columbia, California, Vancouver Island, Several European parts and several Asian regions like India. The ecologically existence of Cryptococcus neoformans is evidently noticed in soil mixed with pigeon droppings while other C. gattii is found in the decay hollows of several trees like Eucalyptus.
Histoplasma sp. also have somewhat similar ecological niche that means it also develops in soil in the mold forms while in human and animal hosts it lives in its yeast form. These are prevalently found in the regions full of the droppings of blackbirds, pigeons, and bats, near chicken house litters, caves and bird roosting sites. The geographical distribution of Histoplasma sp. is been spread to worldwide particularly to the river valleys, such as in the regions of North America, near Mississippi and Ohio rivers, South America, Netherlands, Africa, Europe, and Asia.
Epidemiological evidence regarding Cryptococcus are obtained from the epidemic curve of AIDS while the non-AIDS patient’s show evidence of Cryptococcus in the case of Hodgkin’s disease, collagen-vascular disease or immunosuppression after organ transplantation. The transmission of Cryptococcus may occur through respiratory exposure linked to host. The pathogenicity of the disease is determined through melanin, mannitol and polysaccharide capsule. Some of the clinical forms of Cryptococcus are meningitis, pulmonary and meningoencephalitis. In the case of AIDS- Cryptococcus there is skin dissemination and cryptococcemia. AmB+ flucytosine (5FC) with Fluconazole (FLC) is used for Cryptococcus as a maintenance therapy. The laboratory detection of the disease is performed through culturing the CSF specimens (Reiss, Shadomy and Lyon Ch. 12).
The epidemiological evidence of Histoplasma sp. shows that people exposed to damp areas filled with birds and bats nests are highly susceptible to develop histoplasmosis. The people living near construction and mining sites are also at high risks. Moreover, people who are engaged in farming, cleaning chimneys, roofing, demolition, and maintenance of air-conditions are highly susceptible of catching the infection. Histoplasma transmits through its microconidia propagules that are mixed into the air and inhaled by individuals near the damp and dusty habitats of birds and bats. Once entering the host it transforms into yeast form.
Most of these species develop a granulomatous response in lungs. It may survive there without showing symptoms for longer periods and form calcifications. The skeleton and skin are the highest impacted organs by Histoplasmosis while the pulmonary invasion is seen rarely. The most common affected region is the central nervous system with histoplasmosis. Children also show severe or mild histoplasmosis. Immune normal children show symptoms like fever, mild cough, nonpleuritic chest pain along with weight loss, appetite loss, and weakness (Reiss, Shadomy and Lyon Ch. 6).
Works Cited
Reiss, Errol, H. Jean Shadomy, and G. Marshall Lyon. Fundamental medical mycology. John
Wiley & Sons, 2011.
