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1

Tinea

Group of superficial fungal infections. 

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Fungal Infections Categories

 

  • Superficial mycoses- involve the outermost layers of the skin and hair
  • Cutaneous mycoses- penetrate deeper into the epidermis, hair, and nails
  • Subcutaneous mycoses - involve the dermis, subcutaneous tissue, muscle, and fascia (tinea pedis, tinea cruris, and tinea corporis)
  • Systemic or endemic mycoses - extend beyond a local site of infectio into organs, such as the lungs or blood

 

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Fascia

Sheet of fibrous tissue that covers the body beneath the skin, also encloses muscles and groupos of muscles seperating them

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Erythematous 

Redness of the skin

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Types of Tinea

  • Tinea Pedis (athletes foot)- affects the foot and toes
  • Tinea Corporis (RIngworm) - affects the trunk and extremities
  • Tinea Cruris ( Jock itch) - Affects the groin 

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Tinea Presentation

Scaling patch with raised margin showing variable inflammation, ith diminished infammation toward the center of the lesion 

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Diagnostic methods of Infections

  • KOH - aids in visualizing hypae and confirming diagnosis of dermatophyte infection
  • Woods lamp (ultraviolet light) - limited usefullness, most dermatophytes currently see in the US do not fluoresce 
  • Fungal Culture - slow and expensive but useful to confirm a diagnosis when long-term oral therapy is being considered

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Antifungal Spectrum

describes the range of activity of an antifungal agent against fungi. 

 

Broad spectrum- antifungal agent that inhibits a wide variety of fungi, including both yeast and molds. 

 

Narrow-spectrum -  agent that is active against a limited number of fungi 

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Fungistatic Activity

Describes the level of antifungal activity that inhibits growth of an organism. It is determined in vitri by testing a standardized concentration of organisms against a series of antifungal dilutions 

 

Minimum Inhibitory Concentration (MIC) - lowest concentration of the drug that inhibits growth of the organism

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Fungicidal Activity 

Describes the ability of an antifungal agent to kill an organism in vitro or in in vivo. 

 

Minimum Fungicidal Concentration (MFC) - Lowest concentration of the drug that kills 99.9% of the test population 

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In Vitro

Studies in experimental biology are those that are conducted using components of an organism that have been isolated from their usual biological surroundings in order to permit a more detalied or more convenient analysis than can be done with whole organism. 

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In Vivo

Studies are those that are conducted with living organisms in their normal intact state

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Antifungal Combinations

Combination of agents that may be used to :

  • Enhance efficacy in the treatment of refractory fungal infection
  • broaden the spectrum of empiric antifungal therapy
  • prevent the emerence of resistant organisms
  • achieve a synergistic killing effect

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Topical Therapy

  • Tinea infections are most commonly treated with topical agents
    • Most topical drugs indicated for cutaneous infections are fungistatic, they increase the permeability of th efungal cell wall, causing the contents of the cell to leak out and the cell to die
  • Classes Most widely used
    • Imidazoles 
    • Allylamines
    • Pyridones

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Imidazoles

  • belong to the class of antifungal agents called azoles. In the treatment of fungal infections of the skin,  imidazoles are used both topically and systemically. 
  • Agents block the synthesis of Ergosterol, which is critical in the development and maintenance of fungal cell membranes and hyperpermeability. 

 

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Ergosterol

Primary steroid found in the cell membrane of some fungi. It stabilizes membrane as cholesterol does in human cells. 

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Topical Imidazoles

Luliconazole - LUZU - 1% Cream

Sertaconazole nitrate - Ertazo- 2% Cream

Econazole - Spectazole, Ecoza - 1 % Cream

Oxiconazole - Oxistat- 2% Cream

Ketoconazole - Nizoral - 2% cream

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Tinea Pedis

Fungal infection of the the foot that affect men more than women. Most commonly casued by dermatophyte T. rubrum. 

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Three Identified Tinea Pedis Conditions

  • Interdigital
  • Moccasin-type 
  • Vesiculobullous

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Interdigital 

Characterized by mild to severe interdigital scaling with underlying weepy erythemic wrosions and maceration with fissures

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Fissures

Deep roove, cleft, or slit; gap between bones or bony elements. 

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Pruritus

Itching

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Moccasin-Type

Second most common type of tinea pedis. Characterized by widespread scaling in a "moccasin-foot" pattern, SCaling commonly spreads onto the sides of the feet and the lower heel. 

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Vesiculobullous

Least common form of tinea pedis, characterized by bullous eruptions with large blisters. 

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Tinea Cruris

superficial infection of the groin. Most common symptoms are burning and pruritus. 

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Tinea Corporis

Type of cutaneous mycosis, fungi release enzymes into the skin tha dissolve keratin. typically limited to the epidermis.