2. Dermatophytes :
• Dermatophytes are the cutaneous fungi which infect only the
keratinised tissues by liberating keratinase enzyme.
• These are plant like organisms, living on the top of the skin.
• Invade superficial keratinised structures like hair, horns, skin, claws.
• They are restricted to non-viable skin because most are unable to grow
at 37 degree Celsius or in the presence of serum.
5. Classification based on Habitat
Ecological classification
• Depending on the usual habitat(Humans, animals, and soil).
1. Anthrophilic:Infected humans.
2.Zoophilic:infect animals as well as birds.
3.Geophilic:frequently isolated from soil.
8. Differences between trichophyton,
microsporum, epidermophyton.
Type of
dermatophyte
Shape Macroconidia Microconidia Septae
Microsporum Spindle Numerous, thick
walled and rough
Rare Multiseptae
Trichophyton Cigar shape Rare thin walled and
smooth
Abundant Four to six
Epidermophyton Pear shape/ovoid Numerous, smooth
walled
Absent One or two septae
9.
10.
11. Cultural properties
• Medium:sabouraud dextrose agar(SDA) containing cycloheximide (Exerts its Effect
by interfering with the tranaslation. Step in protein synthesis) and incubated at 25°C,
30°C and for 4 weeks.
• Potato dextrose agar:better sporulation useful for the production of pigment.
Colonies appear in 10 days to 3 weeks, depending on the organism.
• Dermatophytes testing medium:useful for the presumptive identification of
dermatophytes from fungal or bacterial contamination found prevalent in cutaneous
lesions, incubation at 25°C
• When we grow on synthetic or artificial media produce microconidia/macroconidia
asexual spore. On germinating hypae gives ENTHYRSE in chains/clusters-
ENGRAPPE.
12. Trichophyton Agar
• Caesin Basal medium agar
• T1:controlled medium
• T3:add thiamine and Inositol
• T4:we add thiamine
• T5:Nicotonic acid
• T. Mentagrophyte-hydrolyses urea and we provide Christansen’s
agar.
• T. Verrucosam:T1+T3+T5
• T. Equinum:T5+T1 other serovar T. Equinumvar Autotrophium.
13. Transmission and Pathogenesis
• Direct contact, indirectly by epithelial debris is transmitted.
• Mostly effect young and aged animalsnand immunosupressed animals.
• Pathogenesis: is first they release Arthrospores then
• Germinate in 6 hrs
• Invade keratinised structures
• Straitum corneum of epidermis(hair shaft and
hair follicle)
• In poultry invade feathers.
14. Dermatophytes Growth on sabaroudes
dextrose agar
Macroconidium shape
M. Canis Outwardside:on petri dish
whole plate is white, buff
color(light orange)
Corner:orange color
Reverse side:yellowish orange
color
Rough, thickwalled, spindle
shape upto 15 septae
M. Gypseum Outward:buff, cinnamon
Periphery :white
Reverse:reddish brown
Boat shaped, 6septae, thick
walled
M. Nanum Outwardside :cream/tan,
powdery form
Reverse side:Reddish brown
Ovoid, pear shaped 1/2
sepatae, roughrough, thin
walled.
15.
16. T. Mentagrophyte Outside:cream/tan
color, powdery
Reverse :buff/dark
brown colour
Cigar shaped,
macroconidium
smooth, thin walled, 7
septae
T. Verrucosum Outward:white velvety
Reverse:white to pale
buff
Chlamydospore, large
chains
T. Equinum Outward :initial white
fluffy, later folded
Cigar shaped.
17. Species Causative agent Lesions and symptoms
Cattle T. Mentagrophyte Bovine dermatophytosis
Bovine dermomycosis
Scaly lesions on top of head, neck, flank
of limbs.
Crust-heavy hair loss
Equines T. Equinum Produce scaly lesions, inflamed on
saddle and girth region
Sheep and goat T. Mentagrophyte Scaly lesions on ears, horns, nose, tail
Dogs T. Canis
T. Gypseum
T. Mentagrophyte
Lesions on head, base of ears, abdomen,
scrotum
Pigs T. Mentagrophye(major)
T. Verrucosum(minor)
No hair or reddish brown hair
18. Species Causative organism Symptoms and lesions
Cats M. Canis In long haired cats produce
circular lesions
Fowl T. Gallinae Cause a condition called FAVUS.
Lesions on combs wattles, non
feathered areas emaciation and
finally death.
19.
20. Diagnosis
1. Based on symptoms and lesions
2. Wood lamp technique:in this first Hair is taken then
• Then U. V rays of mercuric vapour lamp(MVL)
• Vapors are filtered by Na, Ba, borosilicate
glass(SBBCG) contains Nio2.
• If hair has ectothrix produce floroscence of
GREENISH color.
21. • 3.KoH mounting :
• Take hairs
• Skin scrappings
• Hair follicles
• If present these dermatophytes produce
Arthrospores.
• Arthrospores can be demonstrated by 10_20%KoH.
• We can see clear structures of Arthrospores or visualization can be
enhanced by 36% di methyl sulphoxide(DMSO).
• Isolation and incubation for SDA 2-3 weeks.
22.
23.
24. 4.Dermatophyte testing medium
• It contains pH indicator is phenol red.
• Medium becomes alkaline red colour on DTM if dermatophytes are
present.
Treatment
• Orally-griseoflavin 20-40mg/kg. Bwt is given.
• Typical applications :
• Salicylic acid
• Benzoic acid
• Icthammol paraffin
25. Malassezia
• Malassezia is a type of yeast that
colonises the surface layers of
skin in healthy dogs and cats.
• It has a mutually beneficial
relationship with the many
species of bacteria that colonises
the surface of skin.
