Lec. Dr. Ahmed Yaseen Abed

Viruses are the smallest infectious agents and contain only one kind of nucleic acid (RNA or DNA) as their genome. The nucleic acid is encased in a protein shell, which may be surrounded by a lipid-containing membrane (envelop). Viruses are inert in the extracellular environment; they replicate only in living cells, being parasites at the genetic level. The term virus, which come from the latin word for venom (poison). Because the viruses pass through bacterial filters, therefore the viruses were known as (filterable agents).

Histoplasmosis: is an infection caused by breathing in spores of a fungus often found in bird and bat droppings. Histoplasmosis is most commonly transmitted when these spores become airborne, often during cleanup or demolition projects. 1. Introduction and Epidemiology • Causative Agent: Histoplasmosis is caused by the dimorphic fungus Histoplasma capsulatum. • Geographical Distribution: Endemic in the Ohio and Mississippi River valleys in the United States, as well as parts of Central and South America, Africa, Asia, and Australia.

Penicillium :- is a genus of ascomycetous fungi of major importance in the natural environment as well as food and drug production. Some members of the genus produce penicillin, a molecule that is used as an antibiotic, which kills or stops the growth of certain kinds of bacteria inside the body. Other species are used in cheesemaking. Penicillium marneffei:- Penicillium species are usually regarded as unimportant in terms of causing human disease. Penicillium marneffei, discovered in 1956, is different.

Candidiasis:- is a fungal infection caused by yeasts that belong to the genus Candida. Species:- There are over 20 species of Candida yeasts that can cause infection in humans, the mostcommon of which is Candida albicans. Candida yeasts normally live on the skin and mucous membranes without causing infection; however, overgrowth of these organisms can cause symptoms to develop. Symptoms of candidiasis vary depending on the area of the body that is infected. There is an increasing incidence of infections caused by C. glabrata and C.

Zygomycosis (Mucormycosis) A. Overview and Pathogenesis Zygomycosis, also called mucormycosis, is a rare but aggressive fungal infection. Fungi of the Mucorales group are ubiquitous in nature and typically enter the body via inhalation or through skin injuries. Pathogenesis: Spores germinate in host tissues, forming hyphae that invade blood vessels, causing tissue necrosis.

These are infections confined to the dermis, subcutaneous tissue or adjacent structures. infection may arise following the wounding of the skin and the introduction of vegetable matter. these mycoses are rare and confined mainly to tropical regions. they tend to be slow in onset and chronic in duration. an example is sporotrichosis caused by sporothrix schenckii. the fungus is dimorphic, being a mould that can convert to a yeast form at 37°c on rich laboratory media or in infection.

Fungal diseases that affects the skin, hair and nails. They are generally restricted the keratinized tissue. They cause inflammatory response. DERMATOPHYTOSES Etiological fungi are called “dermatophytes” (They are keratinophilic fungi) • There are 3 genera:- Microsporum Trichophyton Epidermophyton

Reproduction in fungi:

Morphology 

Introduction to medical mycology 

Medical mycology is the study of fungi that cause diseases in humans. Fungi, a kingdom of eukaryotic organisms, are characterized by their cell walls made of chitin and the ability to obtain nutrients by absorption. While many fungi are beneficial to humans, such as those involved in the production of antibiotics and food, some can cause serious infections.