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Mycology is the study of yeasts and molds

"Infections caused by fungi are..." Infections caused by fungi are called mycoses (singular = mycosis) Only a small minority of the 100,000 species is pathogenic in humans

"Mycoses used to be rare..." Mycoses used to be rare and still are But there are more now because more people are immunosuppressed Many of these infections are oral infections

THE FUNGAL CELL All fungi are Gram-positive 2 cell shapes in fungi of medical or dental importance

Budding Yeast Yeast or blastospore Round or oval, 5-25 mm in diameter

Hyphae

"Yeasts usually occur as single..." Yeasts usually occur as single cells or as clusters

"Some organisms grow as yeast..." Some organisms grow as yeast at 37OC and form mycelia at room temperature This ability to have two forms is called dimorphism Organisms able to grow this way are called dimorphic

Candida germ tube

"Fungi differ," Fungi differ, in part, from bacteria in

VEGETATIVE  GROWTH  IN FUNGI

Yeast Growth Yeasts are eukaryotic Most pathogenic yeasts reproduce by budding A few reproduce by binary fission like bacteria

"Budding" Budding Large cell forms a small bud Bud gradually increases in size When it is almost as large as the parent cell- The cells undergo mitosis and completely separate Germ Tubes Yeast cells can also form germ   tubes and then mycelia

Mycelial Growth Hyphal cells Multiply similar to the yeasts except they elongate rather than bud

Laboratory Identification of Fungi Many methods used for bacteria are used for fungi Grow on many of the same media, i.e. blood agar Selective and differential media are available They ferment sugars and produce or break down a few other biochemical materials

"Shapes and sizes are of..." Shapes and sizes are of more value in identifying fungi The fungi contain chitin in their cell walls Thus, withstand treatments that would dissolve bacteria In this way, pretreatment of a tissue with 10% KOH (potassium hydroxide) clears the tissue and any mycelia in the tissues can be easily seen

KOH of tissue

Mechanism of fungal pathogenesis Most fungi cause disease via hypersensitivity (cell-mediated) Most fungi do not produce bacterial-type toxins However, many produce a variety of enzymes

MYCOSES WITH OROFACIAL MANIFESTATIONS

"Mycoses can be classified as" Mycoses can be classified as

Superficial Mycoses The fungi Grow on the surface of the skin or hair In numbers large enough to actually be seen (on skin and hair) Seldom cause any symptoms

Tinea versicolor

"Disease Organisms" Disease Organisms Pityriasis versicolor Malassezia furfur (AKA Tinea versicolor) Malassezia ovalis White piedra Trichosporon beigelii Black piedra Piedraia hortae

Cutaneous Mycoses Organisms responsible for cutaneous mycoses are called dermatophytes They are also referred to as tineas (ringworm) The terms tinea and ringworm date back to the Middle Ages and refer to the circular holes in cloth produced by the clothes moth larvae (worm)

"Athlete's foot is a fungal..." Athlete's foot is a fungal infection in this group Ringworm of the scalp can be encountered in dentistry and is one of the major reasons we use a headrest cover on the dental chair

Ringworm

Ringworm

Ringworm

"These organisms are" These organisms are keratinolytic - they lyse keratin, a protein in skin, hair and nails elastolytic - lyse elastin collagenolytic - lyse collagen All of these are important skin substances

"Disease Organisms" Disease Organisms Tinea, Ringworm, Trichophyton sp. Athlete's Foot Microsporum sp. Epidermophyton sp.

Subcutaneous Mycoses Usually result from a puncture wound The three major pathologic entities Sporotrichosis Entomophthoromycosis conidiobolae Rhinosporidiosis are seldom seen in dentistry

"Disease Organisms" Disease Organisms Sporotrichosis Sporothrix schenckii Entomophthoromycosis Conidiobolus coronatus conidiobolae Rhinosporidiosis Rhinosporidium seeberi

Systemic Mycoses Are often involved in pulmonary infections and are often fatal Again, we seldom see these in dentistry (but they may appear on board exams)

"Disease Organisms" Disease Organisms Histoplasmosis Histoplasma capsulatum Coccidioidomycosis Coccidioides immitis Blastomycosis Blastomyces dermatitidis Paracoccidioidomycosis Paracoccidioides brasiliensis

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Opportunistic Mycoses Usually don’t occur in healthy people Occur in immunocompromised persons May result from indiscriminate use of broad spectrum antibiotics (Candidiasis) We are seeing a great increase in patients infected with these agents, particularly AIDS patients

"Disease Organisms" Disease Organisms Cryptococcosis Cryptococcus neoformans Candidiasis Candida albicans Aspergillosis Aspergillus sp., A. fumigatus Mucormycosis Mucor, Absidia, Rhizopus Pneumocystis carinii Pneumocystis carinii pneumonia (PCP)

All Mycoses All of these organisms in all the groups can be involved in oral or facial lesions Rarely seen in healthy patients, except for perhaps ringworm and candidiasis

"But they are seen in..." But they are seen in immunosuppressed patients and therefore let’s look at each one

CANDIDA

"Candida - found in the..." Candida - found in the mouths of almost half the normal population - usually in the yeast phase When involved in an infection - usually in the mycelial phase Former name for genus was “Monilia” Thus “Moniliasis” was used for these infections

"Yeast infections following prolonged use..." Yeast infections following prolonged use of antibiotics, are usually Candida infections The species most often implicated is   C. albicans But there are other species that have occasionally been found

Most common Candida species in oral infections C. albicans C. tropicalis C. glabrata C. parapsilosis C. dubliniensis C. guilliermondii

Genus Candida All are Gram-positive Facultative anaerobes

Chlamydospores Can form a characteristic spore called a chlamydospore when grown on special media

Major Orofacial Candida infections

Acute Pseudomembranous Candidosis Also called monilia, moniliasis and thrush It is a subepithelial invasion of lingual and buccal surfaces with the formation of a white opaque pseudomembrane Removal of pseudomembrane exposes a raw, bleeding area underneath

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Treatment Topical application of nystatin or miconazole usually resolves this except in AIDS patients where the condition progresses to involve the tonsils and the back of the throat From there it can progress to affect the esophagus or the trachea and the lungs Therefore, AIDS patients are usually given systemic antifungal agents such as fluconazole or ketoconazole

"Was seen most often following..." Was seen most often following prolonged therapy with broad-spectrum antibiotics such as tetracycline Now commonly seen in severely immunocompromised individuals

Major Orofacial Candida infections

Acute Atrophic Candidosis Caused by the suppression of the oral bacterial microflora by broad-spectrum antibiotics, usually tetracyclines The tongue and cheek mucosa become thin, inflamed and atrophic in appearance Resolved by ending the broad spectrum antibiotics and using topical antifungal agents

Acute Atrophic Candidosis

Major Orofacial Candida infections

Chronic Atrophic Candidosis Also called denture stomatitis Affects 50-60% of denture wearers Usually the upper denture is the one affected Occurs when the denture becomes colonized with Candida The organisms penetrate the denture and they also penetrate the palatal epithelium

"Often painless so patient is..." Often painless so patient is often unaware of the problem Difficult to cure because it is difficult to kill the Candida inside the denture material

Major Orofacial Candida infections

Chronic Hyperplastic Candidosis First seen as a white patch intraoraly usually at the angles of the cheeks The white patches cannot be rubbed off They consist of grossly thickened epithelium penetrated by hyphal elements of C. albicans

"5-11%" 5-11% of lesions may become cancerous Can be treated with antifungal agents topically, systemically or both with some success

Major Orofacial Candida infections

Chronic Mucocutaneous Candidosis Characterized by widespread hyperplastic outgrowths, usually occurring in the mouth Particularly disfiguring when they spread to the face Can also affect the nails

"An underlying immunodeficiency is generally..." An underlying immunodeficiency is generally necessary Treatment with systemic ketoconazole has often resulted in a complete cure

Major Orofacial Candida infections

Angular Cheilitis Also called perlèche

"In some patients it is..." In some patients it is the result of folic acid deficiency and replacement therapy often results in a cure Often the lesion is also infected with S. aureus and/or S. pyogenes Antifungal agents having some bacteriostatic properties, e.g. miconazole, are most effective

Candida Armamentarium Lipases Phospholipase Proteases: mucin IgG C'3 serum albumin alpha2 macroglobulin (helps regulate inflammation) alpha1 protease inhibitor (helps regulate inflammation)

Treatment of Candida infections Nystatin and Fluconazole are the antibiotics most commonly used

Cryptococcus

Cryptococcus The organism, Cryptococcus neoformans, is prevalent in soil containing bird droppings, especially pigeon droppings Human infection results from inhalation of the organisms

"Cryptococcosis is seen as either..." Cryptococcosis is seen as either a Lung infection - asymptomatic or pneumonia Meningitis Systemic infections are usually fatal

"Capsule stains show a very..." Capsule stains show a very large capsule around budding yeasts This is diagnostic for Cryptococcosis

Aspergillus, Mucor

Aspergillus, Mucor Aspergillosis, and Mucormycosis occur most often as infections of the paranasal sinuses or the lung but can occur as oral epithelial infections Most commonly seen in immunocompromised individuals

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"Aspergillus flavus produces a toxin..." Aspergillus flavus produces a toxin called aflatoxin when growing on cereals or nuts When eaten, this toxin can cause liver damage and is carcinogenic

Pneumocystis carinii

Pneumocystis carinii Pneumocystis carinii was originally thought to be a parasite It is fungus

"It is the etiologic agent..." It is the etiologic agent of a pneumonia occurring frequently in AIDS patients - Pneumocystis carinii Pneumonia or PCP

"Not known how it is..." Not known how it is transmitted but can be transmitted by the airborne route It is normal flora in some people It infects the lungs and causes much damage in immunocompromised people

Antibiotics used in the treatment of fungal infections Amphotericin B Hydroxystilbamide Nystatin Sulfonamides Clotrimazole Fluconazole Itraconazole Ketoconazole Miconazole

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