MYCOLOGY - SUPERFICIAL MYCOSES - DERMATOPHYTOSES

1. CHAP 66
MEDICAL MYCOLOGY
PART 2.1

2. CLASSIFICATION OF FUNGAL DISEASES
• Mycoses
• Infection caused by fungus
• Types
• Superficial mycoses
• Strictly surf infection
• Deep mycoses
• Subcutaneous mycoses
• By saprophytic fungi of soil/decaying vegetation
• Introduced into s.c. tissue
• Producing progressive local disease w tissue destruction & sinus formation
• Systemic mycoses
• By fungi of soil
• Acquired by inhalation
• Disseminate to bones, CNS, other organs

3. SUPERFICIAL MYCOSES
SURFACE INFECTIONS
Tinea/Pityriasis
versicolor
Tinea nigra Piedra
Black White
CUTANEOUS
INFECTIONS
Dermatophytoses
SURFACE INFECTIONS CUTANEOUS INFECTIONS
 Fungi live on dead layers of skin & its appendages  Confined to cornified layer of skin & its appendages
 No inflammatory response
 As no contact w living tissue
 Inflammatory & allergic responses induced
 Due to fungi and their metabolic products

4. TINEA/PITYRIASIS VERSICOLOR

5. CAUSATIVE FUNGUS:
Pityrosporum orbiculare/Malassezia furfur
• Lipophilic yeast-like fungus
• Forms normal skin flora
• ∴ Most infections thought to be endogenous
• CHARACTERISED BY MILD CHRONIC INFECTION OF STRATUM CORNEUM
• COMMON SITES: Neck, Chest, Abdomen, Back, Upper arm
• MANIFESTATION: Patchy discolouration of skin

6. LAB DIAGNOSIS
• SPECIMEN
• Skin scales
• DIRECT MICROSCOPY
• PROC – KOH preparation
• RESULT –
• Clusters of round yeast cells
• Curved, non-branched, short hyphae
• CULTURE (rarely necessary for diagnosis)
• PROC –
• SDA overlaid w layer of olive oil
• Incubate at 37℃ for 5-7 days
• COLONY MORPHO: Creamy colonies
• LACTOPHENOL COTTON BLUE WET MOUNT OF COLONIES:
• Budding yeast cells w no of bottle shaped cells

7. DERMATOPHYTOSES

8. CAUSATIVE AGENT – DERMATOPHYTES @ RINGWORM/TINEA (LATIN; TINEA = WORM)
• Group of fungi infecting only superficial keratinized tissue (hair, nail, skin)
• Breakdown & utilize keratin
• Incapable of penetrating s.c. tissue
GENUS IMP. SPECIES INFECTION OF
 Trichophyton
 More microconidia
 Few macroconidia
 H N S
 T. mentagrophytes
 T. rubrum
 T. schoenleinii
 T. tonsurans
 T. verrucosum
 T. violaceum
 Hair
 Nail
 Skin
 Microsporum
 Predominant macroconidia
 H S
 M. gypseum
 M. canis
 M. audouinii
 Hair
 Skin
 Epidermophyton
 Macroconidia
 N S
 E. floccosum  Nail
 Skin

10. CLASSIFICATION ON THE BASIS OF NATURAL HABITAT & HOST PREFERENCES
NATURAL HABITAT HOST PREFERENCES EXAMPLES
 Anthropophilic (Man)  Man  T. rubrum
 M. audouinii
 E. floccosum
 Zoophilic (Animals)  Animals  M. canis
 Geophilic  Soil  M. gypseum

11. CLINICAL CLASSIFICATION DEPENDING ON SITE INVOLVED
CLINICAL TYPE SITE INVOLVED EXAMPLES
 Tinea pedis/athlete’s foot  Foot
 Tinea cruris  Groin
 Tinea corporis  Non-hairy skin of body  T. rubrum
 Tinea capitis  Scalp  Trichophyton (most spp)
 Microsporum (any spp)
 Tinea barbae/barber’s itch  Bearded areas of face & neck
 Favus  Hair follicles  T. schoenleinii
 T. violaceum
 M. gypseum
 Hair infection
 Endothrix  Fig. 66.10
 Arthospore formation entirely within
hair shaft
 T. schoenleinii
 T. tonsurans
 T. violaceum
 Ectothrix  Fig. 66.10
 Sheath of arthospores present on
surface of hair shaft
 T. mentagrophytes
 T. rubrum
 Microsporum

12. LAB DIAGNOSIS
(SPECIMEN, DIRECT MICROSCOPY, CULTURE)
SPECIMEN
• Skin, Nail, Hair
DIRECT MICROSCOPY
• PROC – Direct 10 % KOH mount
• RESULT – Fungal hyphae seen

13. CULTURE
• SDA, SDA w antibiotics
• PROC –
• Culture media incubated at 25-30℃ for 3 weeks
• Identify dermatophytes based on
• Colony morphology
• Pigment production
• Microconidia & Macroconidia
• Lactophenol cotton blue prep from colony reveals microconidia & macroconidia
• RESULT –
• Colony morphology
• White to creamy cottony growth
• Pigment production
• Microconidia & Macroconidia
• Genus Trichophyton
• More microconidia
• Few macroconidia
• Genus Microsporum
• Predominant macroconidia
• Genus Epidermophyton
• Macroconidia

14. TREATMENT
• DOC
• Oral griseofulvin
• GENERALLY USED
• Topical antifungal agents