Fungal infections

Fungi (introduction)

• Study of fungi is mycology.
• All fungi are eukaryotic and its cell wall is composed of chitin,mannan and glucan.
• Ergosterol is the major membrane sterol.
• Hyphae is the filamentous cellular units of moulds and mushrooms (it can be septate and non-septate)
• Pseudo-hyphae: C.albicans

Dimorphic fungi:

Fungi which can convert from hypheal to yeast or yeast-like form.

Fungi which are in the from of mold in cold is thermally dimorphic.

Imp dimorphic fungi:

• Histoplasma
• Sporothrix
• Coccidioides
• Blastomyces

Superficial fungal infections

• Malassezia furfur
• Cutaneous fungal infection
• Yeast skin infection
• Dermatophytes

Candidiasis (Moniliasis)

• Is an infection caused by the yeast Candida albicans, or occasionally by other species of Candida. 
• C.albicans is an oval yeast 2-6 x 3-9 mm in size, which can produce budding cells, pseudohyphae and true hyphae.
• It most commonly causes superficial infections of the skin and mucous membranes.
• Can also involve internal organs as in septicemia, endocarditis and meningitis (particularly in AIDS patients and in patients in intensive care units).
• Candida albicans occurs as a normal commensal in humans and colonizes the gastrointestinal tract, vagina, intertriginous skin and the bronchial tree.

Clinical syndromes of candidiasis 

• Oral candidiasis
• Candida intertrigo (flexural candidosis)
• Vulvovaginitis (vulvovaginal thrush)
• Candidal balanoposthitis
• Napkin candidosis (diaper rash)
• Candida paronychia 

Oral candidiasis

• can occur in infants (oral thrush),
• immunocompromised patients, 
• patients wearing dentures (denture stomatitis),
• smokers & those applying intraoral steroid medications (mouthwashes,inhalers).
• Sharply defined patch of curd-like white pseudomembrane, which, when removed, leaves an underlying erythematous base.  

Candida intertrigo (flexural candidosis)

• Usually affects the skin folds in obese subjects.
• Typical lesions are moist, erythematous eroded areas with a fringed irregular edge and pustular or papular satellite lesions beyond the margins.  

Vulvovaginitis (vulvovaginal thrush)

• Itching, soreness and dusky red erythema of the vaginal mucosa and the vulval skin with a thick curdy white discharge per vagina.
• More common in pregnancy. 

Candidal balanoposthitis

• Is more commonly seen in the sexually active uncircumcised men or in patients with diabetes. 
• The sexual partners are usually carriers of candida. 
• Tiny papules or pustules develop on the glans penis a few hours after intercourse, and rupture, leaving a peeling edge, with mild soreness and irritation. 

Napkin candidiasis (diaper rash)

• Moist skin of the buttocks and genitalia infants and can cause disease in the napkin area when it is wet and occluded. 
• The affected area may show erythema with subcorneal pustules and satellite lesions.

Candida paronychia

• Candida is the most common cause of chronic paronychia. 
• condition is commonly found among those whose hands are frequently immersed in water (cooks, housemaids, washermen). 

                                        

Management of candidal infections

Remove the susceptibility factors. For example, maintenance of oral and dental hygiene and keeping the affected sites dry.

• Topical therapy

Clotrimazole, miconazole, econazole, nystatin, natamycin. These drugs are used in the form of creams, lotions, gels, mouth paints or lozenges.

• Oral therapy

The most useful treatments are with fluconazole (100-400 mg/day) and itraconazole (100-200 mg/day).

• Intravenous therapy

Amphotericin B and fluconazole are mainly used for systemic infections. 

Dermatophytes

• These are filamentous fungi and are monomorphic.
• It infect only skin, hair/nail.(Only superficial)
• Dermatophytic infections are known as Tineas or Ringworms.
• These belong to  three genera. They are:

Trichophyton: Infects skin, hair and nails.
Microsporum: Infects skin and hair.
Epidermophyton: Infects skin and nail.

Cutaneous infections:

• Tinea capitis: ringworm of scalp
• Tinea barbae: ringworm of the bearded region
• Tinea corporis: infection of the glaberous skin
• Tinea cruris: jock itch
• Tinea pedis: athlete’s foot

Tinea capitis

Ringworm of the scalp in which the essential feature is invasion of hair shafts by a dermatophyte fungus.

Have a distinct predilection for the hair shaft.

• Cause: M. audouinii, T. schoenleinii and T. violaceum

Clinical feature

• The appearance vary from a few dull grey, broken-off hairs with a little scaling, detectable only on careful inspection, to a severe, painful, inflammatory mass covering most of the scalp.
• In all types, the cardinal features are partial hair loss with inflammation of some degree.

Tinea capitis

Tinea barbae

Ringworm of the beard and moustache areas of the face with invasion of coarse hairs. It is thus a disease of the adult male.

• Causes: T. mentagrophytes  and T. verrucosum

Clinical features

• The affected men are commonly farm workers
• The clinical picture in these is that of a highly inflammatory pustular folliculitis.
• Hairs of the beard or moustache regions are surrounded by red inflammatory papules or pustules, usually with exudation or crusting.
• Many hairs within the affected areas are loose and easily removed with the forceps without causing pain. 

Tinea barbae

Tinea corporis

Dermatophytic infection of the glaberous skin, but can occur in any part of the body.

Cause:

• Microsporum canis
• Trichophyton verrucosum

Clinical features

• The lesions are erythematous, annular and scaly with a well defined edge with central clearing.
• May be single or multiple and are usually asymmetrical.
• Steroid use: leads to disguising and worsening of the signs.

Tinea corporis

Tinea cruris

Infection of the groins by a species of dermatophyte.

Cause: 

• T. rubrum is the main cause;
• T. mentagrophytes var. interdigitale and
• E. fl occosum

Clinical features

• Itching is a predominant feature.
• The lesions are erythematous plaques, curved with sharp margins extending from the groin down the thighs.

Tinea cruris

Tinea pedis

Infection of the feet or toes with a dermatophyte fungus.

Causes:

• T. rubrum,
• T. mentagrophytes var. interdigitale and
• E. floccosum

Clinical features

• The most common form of tinea pedis is an intertriginous dermatitis characterized by peeling, maceration and fissuring affecting the lateral toe clefts, and sometimes spreading to involve the undersurface of the toes.
• This picture may be produced by any of the three species. 
• Itching is a common complaint in warm weather. The condition is highly persistent. 
• In T. rubrum infections, a scaling hyperkeratotic variety, which is particularly chronic and resistant to treatment and which affects the soles, heels and sides of the feet, is often found. The affected areas are pink and covered with fine silvery white scales. If the foot is extensively involved, the term ‘moccasin foot’ or dry-type infection are sometimes applied.
• In T. mentagrophytes vesiculation or frank blistering is commonly seen.

Tinea pedis

• In all cases of suspected dermatophytic infection:

Skin scrapings/ nail clippings
Woods light examination
Direct examination
Fungal culture

Treatment

• Topical

Terbinafine or miconazole cream

• Systemic

terbinafine, griseofulvin or itraconazole