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BACTERIAL, VIRAL and FUNGAL Infections
1. BACTERIAL DISEASES OF SKIN
1.1 Impetigo Contagiosa
A contagious superficial pyogenic infection of the skin. There are two clinical forms, non-bullous impetigo (Staph. aureus & Strept. pyogenes) and bullous impetigo (Staph. aureus only).
Clinical features :
A typical lesion begins as a subcorneal thin walled vesicle on an erythematous base that ruptures and leaves a yellowish brown crust. Multiple lesions may coalesce. The crusts dry up and separate to leave erythema which fades on healing.
Children are commonly affected. The lesions usually occurs in the face, around nose and mouth. Mucous membrane involvement is rare. Other areas may be involved especially in children with atopic eczema and scabies. There is a tendency to spontaneous cure in 2-3 weeks. Heavily pigmented skin may have temporary hypopigmentation.
Complications :
Cellulitis, scarlet fever, post-streptococcal glomerulonephritis, urticaria, and erythema multiforme can complicate streptococcal impetigo.
Laboratory Diagnosis :
Cultures for Staph. aureus and Strept. pyogenes.
Urine for sugar, blood glucose level for those with recurrent attacks.
Nasal swab for detection of Staph. carrier in patients with recurrent Staph. impetigo.
Treatment :
(i) Mild and localized cases
Topical antibiotics e.g. Mupirocin, fusidic acid, neomycin, bacitracin.
(ii) Widespread and severe cases
Systemic antibiotics e.g. flucloxacillin, erythromycin, co-trimoxazole, tetracycline are required.
Prophylactic penicillin V orally in suspected nephrotoxigenic case.
(iii) For Staph. carrier
Topical application of chlorhexidine or povidone iodine to eradicate Staph. aureus harbouring in body folds before bathing.
A short course of topical mupirocin to eradicate Staph. aureus harbouring in nasal vestibules.
1.2 Furuncles, Boils and Carbuncles
Staph. aureus folliculitis (furuncle) is common in chronic dermatitis or after treatment of dermatitis or psoriasis with corticosteroid ointments. A spattered eruption of 1-5 mm pustules is seen with a halo of erythema, obviously follicular and often with a hair emerging from the centre of the pustule. A boil is produced by infection of multiple adjacent follicles. The coalescence of multiple adjacent boils form a carbuncle.
Management :
Any predisposing factors e.g. obesity, hyperhidrosis, friction, diabetes mellitus etc., should be sought and removed. Culture from lesions should be sent. Topical antibiotics can be given if the patient has just got a few lesions. For multiple lesions and carbuncle, an appropriate systemic antibiotic e.g. flucloxacillin, erythromycin and fusidic acid should be given. Eradication of a Staph. aureus carrier state is required for recurrent infection.
1.3 Ecthyma
In the debilitated, diabetic, or immunosuppressed, lesions of impetigo or folliculitis may ulcerate to produce multiple shallow or occasionally deep round ulcers.
Management : same as 1.2
1.4 Erysipelas
This is an acute, dermal infection caused by streptococcus pyogenes. Cellulitis is similar to erysipelas but lies deeper. Clinically, there is localized erythema, swelling and tenderness. Margin of the lesion is usually well defined and often palpable. Attack is typically heralded by malaise, fever, flu-like symptoms and pain in the affected area (usually face or one leg). Tenderness, pain and toxicity are crucial in differentiating the episode from urticaria or angio-oedema. Itching is absent.
Complications :
Streptococcal septicaemia is a serious hazard. Recurrent erysipelas may lead to damage to lymphatic vessels and subsequent lymphoedema oedema.
Treatment :
Topical therapy is ineffective. Systemic antibiotics should be started soon after taking a bacterial swab sent for culture and sensitivity. e.g. flucloxacillin, amoxicillin or erythromycin. In recurrent attacks, give long term penicillin 500 mg to 2 gm daily or erythromycin in patients allergic to penicillin.
1.5 Erysipeloid
This is an infection by Erysipelothrix insidiosa, a Gram-positive bacillus. It occurs in those who handle raw meat and fish and often follows a prick or scratch from a bone.
Clinical features :
It presents as a dull or purplish-red erythema with oedema at the inoculation site and spread peripherally with a well-marginated border. Vesicles may be present. Central fading occurs as the lesion enlarges. Adjacent joints may be involved. Hands, fingers are commonly affected. Pain, swelling and tenderness make movement difficult. Compared with cellulitis/erysipelas, constitutional symptoms and lymphangitis are usually absent. Lesions usually heal spontaneously in two weeks without treatment.
Treatment :
Penicillin V 500 mg qid x 1 week
Oxytetracycline 500 mg qid x 1 week
1.6 Erythrasma
This is a dry, pale, red-brown, flexural eruption in the axillae, groins or abdominal or submammary folds.
Diagnosis :
The lesions fluoresce coral-red under Wood's light due to porphyrin production by the causative diphtheroid, Corynebacterium minutissimum.
Treatment :
(i) Topical imidazole cream (e.g. 1% Clotrimazole cream).
(ii) Oral Erythromycin 250 mg qid x 1 week.
2. VIRAL DISEASES OF SKIN
2.1 Herpes Zoster (Shingles) (HZ)
This is an acute, painful, vesicular eruption characterized by a unilateral and segmental distribution confined to one or more sensory dermatones.
HZ affects both sex and is seen mainly in the second half of life and is rare in children. A higher incidence of HZ occurs patients who are immunosuppressed, and those with leukaemia, lymphoma.
One attack of shingles confers immunity for years and a second attack is uncommon. The virus can infect non-immune individuals who will manifest as chickenpox.
Clinical features :
Classically, the eruption is heralded by pain in a segmental distribution for up to a week. Areas of edematous erythema quickly develop which erupt and become vesicular. Enlargement of the draining lymph nodes is usual. Pain, paraesthesiae and numbness, persist in varying degrees throughout the attack and postherpetic neuralgia may be severe in the elderly. HZ usually leaves scarring and cicatricial alopecia is not uncommon if the scalp is involved.
Complications :
In immunosuppressed patients, viraemia may lead to fatal varicella pneumonia or encephalitis. Rarely, it may spread to involve the anterior horn cells of the spinal cord resulting in paralysis. Orbital structures like conjunctiva, cornea and sclera may be involved in ophthalmic zoster. Post-herpetic neuralgia is the persistence or recurrence of pain at the site previously affected by HZ for more than a month after the appearance of clinical leisons. This occur more commonly in adulthood older than 40 years of age. The pain can be very disabling.
Treatment :
(i) Topical
Useful for mild localized disease.
Acyclovir cream five times daily for 5 days.
Topical steroids are contraindicated.
(ii) Systemic
Oral acyclovir 200 mg to 800 mg five times daily for 1 week. This should preferably be given within the first 1-2 days of the clinical infection.
IV acyclovir required for patients who are immunocompromised or having a severe attack of herpes zoster.
2.2 Herpes Simplex (HS)
This is a localized herpetic eruptions which are unrelated to any dermatone.
Aetiology :
Herpesvirus Hominis
Two antigenic forms :
- HSV Type I - mostly oral and facial lesions
- HSV Type II - mostly anogenital lesions
Both types can cause primary and recurrent lesions, cross-infection is increasing.
Modes of Infection :
Virus shed in saliva and genital secretions from asymptomatic individuals, also from active lesions.
(i) Direct contact
(ii) Droplets from lesion
(iii) Autoinoculation, exogenous inoculation
(iv) Perinatal infection
Clinical Features :
Primary Infection :
Primary HS infection can be subclinical. However, if clinical lesions develop, constitutional symptoms, e.g. fever, malaise can be severe.
In herpetic gingivostomatitis, there are painful oral vesicles, erosions, blisters and superficial ulcers affecting young children. The gums are swollen, friable and bleed easily. Drinking, eating and swallowing are painful and difficult.
In Herpes genitalia, there are painful ulcers in the glans penis, prepuce, shaft of penis, vulva, vagina, cervix ulceration, cervicitis, and perianal lesions (in homosexuals). Pain, dysuria, lymphadenopathy are frequent.
In Herpetic whitlow, doctors and health care workers are commonly affected. Lesions appear as single or grouped painful blisters at distal parts of the fingers. The blisters contain clear fluid but then become purulent, these may break down and form crusts. Lesions usually resolve within three weeks.
Complications :
(i) Keratoconjunctivitis
(ii) Aseptic meningitis, encephalitis
(iii) Radiculopathy - sacral anaesthesia, urinary retention, constipation, and impotence in the male.
(iv) Hepatitis
Recurrent Infection :
Genital herpes recur more commonly than oral herpes. Type 2 recur more commonly than type 1. Trigger factors include minor trauma, infection, sexual activity, minor operation and stress. It usually occurs as a group of closely set small vesicles and constitutional symptoms are absent. Lesions heal in 7 to 10 days without scarring.
Complications :
(i) Keratoconjunctivitis
(ii) Cranial nerve palsy, Bell's palsy recurrent eczema herpeticum
(iii) Dendritic ulcers in cornea
(iv) Iridocyclitis
(v) Erythema multiforme
Diagnosis :
(i) Viral culture from scraped tissues or fluids
(ii) Immunofluorescence in scrapings from lesions to detect viral antigens
(iii) Electronmicroscopy to demonstrate the virus.
(iv) Serology
Not routinely performed in the social hygiene clinic. In primary infection, paired sera showed a seroconversion or a rising antibody titre. Recurrence tends to produce little or no change in the antibody titre and therefore serology is NOT useful in the diagnosis of a recurrent HS attack.
Treatment :
(i) Herpetic whitlow
(a) Oral Acyclovir 400 mg five times daily for five days
(b) KMnO4 wet compress.
(c) Acyclovir cream, if given early, may inhibit the chance of recurrence.
(ii) Herpetic Keratitis
- Idoxuridine 0.5% eye drops
- Acyclovir ophthalmic ointment
(iii) Lesions of lips, face, genitalia & lower limbs
- Acyclovir cream
(iv) Immunosuppressed or eczema herpeticum
- IV acyclovir
(v) Recurrent infection (> 6 attacks per year)
- Prophylactic oral low dose acyclovir for several months has been shown to reduce severity and frequency of relapse.
2.3 Warts (Verrucae)
These are papillomata affecting skin and mucosae caused by Human papilloma viruses (HPV), a group of DNA viruses. Over 60 types have now been identified. Lesions do not turn malignant, but genital lesions due to HPV-16 and HPV-18 are of importance because they have been implicated in premalignant dysplasia and squamous cell carcinoma of the cervix uteri; and HPV-5 and HPV-8 are associated with malignant transformation in lesions of epidermodysplasia verruciformis.
2.3.1 Common Warts (Verruca Vulgaris) HPV-2
These are papilliferous excrescences. They usually occur on the hands but may affect the elbows, face, knees and scalp.
Treatment :
(i) Topical application of salicylic acid and lactic acid e.g. Collomack, Duofilm
(ii) Cryotherapy using liquid nitrogen
(iii) Cauterization and curettage under local anaesthesia
2.3.2 Plane Warts (Verruca Plana) HPV-3
These are flat-topped yellowish papules, mainly on the backs of the hands, wrist and face.
Treatment :
Similar to the treatment of common warts but sometimes a more conservative method like topical retinoic acid can be effective.
2.3.3 Plantar Warts (Verruca Plantaris) HPV-1, HPV-2
These are yellowish white, flattened, tender papules, deeply embedded in hyperkeratotic epidermis. Tenderness on vertical pressure is usually minimal but lateral squeezing elicits marked tenderness (the reverse of the situation is a callosity).
Treatment :
(i) Single
- Cauterization and curettage under local anaesthesia
(ii) Multiple
- Topical application as in common warts
- Sodden keratin must be regularly removed with a pumice stone or by sand papering
- Liquid nitrogen may be useful for small or superficial plantar warts
- Topical retinoic acid (Retin A)
2.3.4 Genital Wart (Condylomata Acuminata)
Refer to STD
2.4 Molluscum Contagiosum
It is due to a pox virus which is transmitted either by direct contact or by fomites. It can also be transmitted sexually. A typical lesion is characterized by rounded, whitish elevations with an umbilicated centre, and frequently have a glistening, pearly-white appearance. Pultaceous material may be expressed from them. Itching is variable. If untreated, the lesions tend to increase in size and number for months. Spontaneous resolution may occur.
Treatment :
- Curettage and iodine application
- Lesions may be pierced with a spicule of wood which has been dipped in liquefied phenol
- Cryotherapy with liquid nitrogen
2.5 Pityriasis Rosea
This is a common disease of unknown cause, possibly viral, characterized by a centripetal rash which lasts for several weeks.
It occurs mainly between the ages of 15 and 40 years. Second attacks are rare. 'Herald patch' is the first sign which is a single erythematous oval or circular macule up to 3-4 cm in diameter and is often found on the trunk than the limbs. Itching is slight or absent (occasionally can be severe). Within 4-14 days, an exanthema follows in a centripetal distribution confined to the trunk, neck and the proximal part of the limbs. The eruption is symmetrical and often particularly profuse about the shoulder girdle, including the axillae, and the pelvic girdle. The rash may take up to 2 weeks to develop fully. The lesions slowly fades away, having run a total course of 4-8 weeks. Itching is variable.
Differential diagnoses include other papulosquamous eruptions e.g. secondary syphilis, guttae psoriasis.
Treatment :
The condition is almost not affected by treatment, oral antihistamines or a course of UVB can be useful in reducing the itchiness.
3. FUNGAL DISEASES OF SKIN
Approach to Diagnosis :
(i) Clinical features
(ii) Wood's light
(iii) Microscopic examination of scrapings and clippings in 10%-30% KOH
(iv) Culture
.1 Tinea Capitis
Treatment :
Griseofulvin oral 500 mg qd adult; 250 mg qd children for at least 2 months until Wood's light negative in ectothrix infection, until clinical features have resolved and mycological tests negative in endothrix infection.
3.2 Tinea Corporis
Many dermatophyte species can be responsible (e.g. Trichophyton rubrum). The eruption is typically sparse and asymmetrical, with one or more erythematous, scaly, discoid lesions, each sharply defined and spreading slowly centrifugally. Itching is variable. If topical corticosteroid creams have been used, the appearance may be atypical with the margins of the ringed lesions losing their continuity and with less scaling.
Treatment :
Topical and systemic (q.v.).
3.3 Tinea Cruis
It occurs in Intertriginous inguinal fold, caused by E floccosum, T mentagrophytes var. interdigitale or T rubrum. It may be due to autoinfection from the feet or to sharing of sports clothing or towels by young men.
In Tinea incognito, the natural appearance of tinea cruris is often masked by inappropriate topical steroid therapy which partly suppresses the inflammation and encourages its spread. The distinct margin of the infection is broken up and deeper, inflammatory, 'boil-like' lesions may be seen.
Treatment :
Topical and systemic (q.v.).
3.4 Tinea Pedis
It is caused by the same three species which cause tinea cruris and is extremely common but rare in those who go barefoot. There are 3 main clinical patterns :
(i) Intertrigo occurs especially between the fourth and fifth toes.
(ii) Vesicular patterns begin on the sides of toes or on the instep, side or dorsum of the foot.
(iii) Hyperkeratotic pattern, diffuse or patchy thickening of the sole is seen.
Id-reaction is an allergic vesicular dermatitis (pompholyx) that can occur at sites distant from the site of active dermatophyte infection may occur.
Treatment :
Topical and systemic (q.v.).
3.5 Tinea Faciei
It is an infection of the glabrous skin of the face and is caused by Trichophyton rubrum and T mentagrophytes and also Microsporum species. The small animal pets e.g. rabbit is the carrier of the fungus.
Clinical features include erythema, scaling, papules or marginated plaques. There may be itching, burning and sensitivity to light.
Treatment :
Topical and systemic (q.v.).
3.6 Tinea Manuum
T Rubrum is commonest, E floccosum and T interdigitale in a minority of cases.
There are five clinical patterns :
(i) Vesicular discoid patches
(ii) Crescentric exfoliating scaling lesions
(iii) Discrete red papular and follicular scaly patches on the backs of the hands or wrists
(iv) Erythematous scaly sheets on the backs of the hands, with well-defined margins, and
(v) Hyperkeratotic erythematous finely exfoliative lesions
Treatment :
Topical and systemic (q.v.).
3.7 Tinea Unguium
Onychomycosis of the toe nails is more common than the fingernails. T rubrum is the commonest cause in the fingernails and toenails. T interdigitale may also be isolated in the toenails. The infection begins at the free end of the nail, and gradually extends proximally until the whole nail plate is diseased. The affected nail loses its lustre and becomes brittle and opaque. Paronychia is not a feature. Subungual hyperkeratosis, yellow and brown dyschromia and onycholysis are commonly found.
Treatment :
Topical and systemic (q.v.).
3.8 Candidosis
Candidosis (moniliasis) is an infection of the skin, nails and mucosae, usually caused by the yeast-like fungus, Candida albicans, although rarely other Candida species are implicated. The yeast is a normal resident of the gastrointestinal and genital mucosae which becomes pathogenic only when an opportunity arises. The disease is seen at the extremes of life and in patients suffering from malnutrition.
Clinical situations favouring candidosis :
(i) Pregnancy
(ii) Oral contraceptives
(iii) Wide-spectrum antibiotics
(iv) Corticosteroids
(v) Immunosuppressive drugs
(vi) Diabetes mellitus
(vii) Hypoparathyroidism
(viii) Blood dyscrasia
(ix) HIV infection
Clinical patterns of candidosis :
(i) Oral thrush
(ii) Angular stomatitis
(iii) Candida granuloma (*lips)
(iv) Balanoposthitis
(v) Vulvovaginitis
(vi) Intertrigo
(vii) Erosio interdigitalis
(viii) Chronic paronychia
(ix) Chronic onychia
(x) Pruritus ani
Treatment :
(i) Oral candidiasis
Topical
- Suspensions of nystatin
- Miconazol gel
- Amphotericin lozenges
Systemic
- (immunocompromised)
- Oral ketoconazole, itraconazole or fluconazole
(ii) Genital candidiasis
Topical - clotrimazole, econazole, isoconazole, nystatin
Systemic - oral fluconazole, itraconazole
(iii) Intertriginous candidiasis
Topical - some as (ii)
(iv) Paronychia and onychia
Topical - same as (ii)
Systemic - oral ketoconazole, itraconazole
3.9 Pityriasis Versicolor (Tinea Versicolor)
It is caused by Malassezia furfur which is the mycelial phase of Pityrosporum orbiculare, a yeast which is a component of normal skin flora. It is slightly contagious but the disease is usually autogenous. It is common in young adults, uncommon in children and rare in old age. It affects both sexes equally. Systemic and topical steroid therapy predispose to this infection, as does Cushing's syndrome.
Clinical features include islands of hypopigmentation of the infected skin occur and the infected areas resemble the patches of leukoderma seen in vitiligo although the depigmentation is usually not complete. Wood's light examination shows a faint orange, gold or buff fluorescence in the affected areas.
Treatment :
(i) Topical Treatment
(a) Imidazoles - clotrimazole, miconazole etc.
(b) ketoconazole cream or shampoo
(c) 2.5% selenium sulphide (selsun shampoo)
(ii) Systemic Treatment
(a) Oral itraconazole
(b) Oral ketoconazole 200 mg daily x 3 to 7 days
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