Fungal and Mycobacterial infections of the skin, muscle and blood stream

Question 1

Superficial Mycoses

Answer 1

fungal growth on epithelial tissues such as human hair, skin or nails. no noticeble invasion of living tissue, doesn’t provoke an immune repsonse.

• when keartin is digested it can irriate adjacent living tissue due to fungal metabolites and byproducts.

Question 2

White piedra

Answer 2

Etiology: Trichosporon- yeast genus, arthroconidia(spore forming)

Pathogenesis: can infect cutaneous tissue, an also cause systemic infection.

Trichosporon Beigelli shows up on a PAS stain in systemic infection.

CLINICAL PRESENTATION: asymptomatic growth on outside of hair shaft. Soft noduels taht can easly be pulled off of hair, these are white, greenish or yellowsh and composed of compacted fungal elements. The Hair is not invaded but they may break if the fungy have been there for long periods of time. affects hairs on scalp, beard, eyelashes, eyebrows, axilla and groin.
-warm moist conditions predispose.

CONTROL- shaving and local application of antifungal agents, all clinically sifnificant Trichosporon show high in vitro susceptibilty to common antifungal agents- Amphotericin B, Clotrimazole, Ketoconazole, Itraconazole

Question 3

Black Piedra

Answer 3

ETIOLOGY– ascomycete genus, piedraia

asymptomatic visible colonization f the shaft of scapl hair, is restricted to humid tropical areas

• the nodules can’t be pulled off and treatment is difficult
• topical application of azole antifungals have been ued

Question 4

Tinea nigra

Answer 4

ETIOLOGY- Hortae werneckii (Exophiala weneckii),
-colonies are smooth with an oily clistening, olive back color, aged colonies become velvety as a result of prdocution of aerial hyphae and the hyphae become darker with age. it is somewhat halophilic and occasionally isolated from beach soil.

Superficial infection of SKIN- stratum corneum,

• brown to black lesions, mainly on palm but sometimes on sole of the foot. pigmentation is more intense near the border, only the outer layers of skin are affected, No invasion of living tissue occurs

Question 5

Pitryiasis Versicolor

Answer 5

Malassezia furfur infects outer layers of stratum corneum. usually superficial, chornic, and asymptomatic, MAcular rash or fine scaling of the upper trunk and sholders.

• lesions appear lighter or darker than surrounding skin.
• Erythematous follicular papules.

DIAGNOSIS- confirmed by microscopy, morphology of both filaments and yests, can be abundant in the scales and you will see spaghetti and metballs

TREATMENT- topical antifungals, frequently recurs.

May cause deep line catheter associated sepsis in neonates with M. Pachydermatis.

• may cause seborrheic dermatitis and dandruff
• isolation of yeast using lipid containing media, can also see yeast in tissues.

Question 6

Cutaneous mycoses:dermatophytes

Answer 6

fungi using keratin as a nutrient source, they invade skin, hair, and nails, typical skin lesion has an annular ring, scaly patch with raised margin, commonly called ring worm or jock itch.
-infection of har causes hair loss leaving a dry scaly patch of skin
-nail infections, nails become yellow thickened and crack
can have inflammation but no invasion of fungus into underlying tissue.
-they colonize keratinized tissue of the stratum corneum.

TRANSMISSION-

• predisposing conditions- immunological blind spots, old age, collagen vascular disease, diabetes mellitus, hematological malignancy
• 3 sources of infection- antrhopophilic, zoopihlic, geophilic
• infected by contact with skin scales form humans or animals. scales can be carried t the next host by way of dirty moist shower mats, shared nail and hair clippers, shared combs, used shoes.

Classified on basis of location of the lesions on the body,
-ringworm becasue of the worm like appearance of skin lesions with irregular inflammatory borders.

TREATMENT: must consider, extent,location and clinical type of infection, the infectious agent, and the specturm of activity of the antifungal.
-orally active triazoles, allylamines, (terbinafine), orally administered griseofulvin and ketoconazole, topical antifungals thiocarbonates, and numerous imidazoles

Question 7

Microsporum canis

Answer 7

attack skin and hair but not nails, distinguising features are macroconidia are more numerous than microconidia, macroconidia have rough walls ranging from spiny to warty.

Question 8

Epidermophyton

Answer 8

attacks skin and nails but doen’t invade hari.
E. Floccosum, is only pathogenic species and has spores
macroconidia have a smooth walled large, born singly or in a banana-like cluster
-microconidia are absent.

Question 9

Trichophyton

Answer 9

attacks skin, hair AND nails, noted for life long nail infections, micro more numerous than macroconidia, macroconidia present are smooth walled, pencil shaped, fusiform)
T. Rubrum has a red color on potato dextrose agar on teh reverse side.
T. tonsurans is a major cause of ringworm i skin.

Question 10

Tinea Corporis

Answer 10

ringworm of upper parts of covered body, usually involves the trunk, shoulders, axilla, chest and back,- have usually less hair. lesions are well marginated with raised erythematous, vesicular borders, may be mild or severe. most serious chornic infection most often due to T. Rubrum

Question 11

Tinea Cruris

Answer 11

infection of inguinal area involving groin, perianal and perineal areas, freqeuntly in adults casued by T. rubrum and E. Floccosum.

lesiosn are erythematous and scaly, raised inflamaed borders, often with vesicles.
usually bilateral extending down the sids and inner thighs, waist area and buttocks- itching and burning

Question 12

Tinea capitis

Answer 12

infection of scalp, eyebrows, eye lashes,

• ectochthrix invasion when fungus forms sheath of hyphae and arthroconidia around shafts of hair. infected hair is lusterless and brittle and breaks off of scalp.
• endothrix invasion when hyphae invade hair follicel and shaft and form many spores within the hair shaft. infected grayish white hairs break off easily at scalp giving black dot appearance

-secondary bacerial infections can result in scarring and complications

Commonly caused by microsporum, M. Audounini, m. Canis, Mgypseum (Ectothrix), T. Tonsurans (endothrix.

Question 13

tinea Pedis

Answer 13

ringowrm of the feet, involves chronic infection of the interdigital webs and soles. symptoms include scaling, fissuring, erythema, itching, and burning, less common clinical form is infection of the soles and heels extending up the sides of the foot ( Moccasin foot)

• acute condition has vesicles, inflammation and sterile pustules
• common agents- T mentagrophytes, T rubrum, E. Floccosum

Question 14

Tinea Barbae

Answer 14

infection of beard area, mild to severe forms occur, more severe from with pustular lesions. often caused by zoophilic trichopython verrucosum in cattle and T. mentagrophytes in mice and rodents.

Question 15

Tinea unguium

Answer 15

invasion of the nail plate, nail bed, and skin on the underside of the nail, causes lifting of the nail plate and its detachement from teh nail bed
-caused by T. rubrum, T. mentagrophyes, and e. flocossum

• most difficult to cure, agents applied diretly to the nal don’t work because it can’t penetrate the nail bed and nal removal plays a limited role in therapy
• best new treatment is oral systemic antifungal, effective when administered for long periods of time (3 months or more. Time to reach nail bed and incorporate into nail matrix, the healed nail slowly pushes away old infected nail, partial nail removal and topical therapy may augment systemic therapy
• new antifungals made systemic therapy possible, response rates of up to 90% for fingernails and 70=80% for toenails reported for itraconazole and terbinafine.