bacterial infections of the skin

PRIMARY BACTERIAL INFECTIONS OF THE SKIN

DR. AKRETI SOBTI DEPT OF DERMATOLOGYK. J. SOMAIYA HOSPITAL

INTRODUCTION

Bacterial skin infections – also known as Pyodermas

Mostly superficial

Easy to diagnose and treat

Special investigations not required

Can be treated with topical antibiotics at most times

SKIN AS A BARRIER AGAINST INFECTIONS

CommensalsProtective role against external organismsMostly non-pathogenicRarely pathogenic or opportunisticDepends on immune status of host

pH of skin

Dryness with exfoliationUse of harsh soaps and cleansers remove the normal flora

and cause more harm

APPENDAGESSKIN

SebaceousGlands

BACTERIAL INFECTIONS

SweatGlandsNailsHair

Superficial Deep

Eccrine Apocrine•Sup. Folliculitis•Pseudo-folliculitis•Tri-myco-axillaris

•Furuncle•Carbuncle•Sycosis barbae

AcuteParonychia

Periporitis Hid. Supp.

Acne

Superficial Deep

•Impetigo•SSSS•Pitt. K’lysis•Erythrasma

•Ecthyma•Erysipelas•Cellulitis•Nec. Fascitis

IMPETIGO

Contagious, superficial bacterial infection

Commonly seen in Children

Most favoured sites : Face and extremities

Peri-nasal involvement could be dangerous.

IMPETIGO

2 TYPES OF CLINICAL PRESENTATIONS:Bullous impetigo-

Caused by Staph. aureus. Vesicle enlarge to form bullae

Nonbullous impetigo- Caused by Streptococcus Vesicle rupture to expose red, moist base with crust

formation as lesion expands radially. ‘Honey coloured’ crusting is diagnostic

Bullous impetigo

Non-bullous impetigo

STAPHYLOCOCCAL SCALDED SKIN SYNDROME

Also called “Ritter’s disease”

Staphylococcal epidermolytic toxin syndrome

Follows an episode of sore throat

Caused by lack of immunity to toxins and renal immaturity in children causing poor clearance of toxins

Characterized by peeling of skin after blister formation – similar to burns

STAPHYLOCOCCAL

SCALDED SKIN SYNDROME

STAPHYLOCOCCUS SCALDED SKIN SYNDROME

TREATMENT:

Hospitalization

Intravenous antibiotic therapy

Skin should be lubricated with bland lotions and washed infrequently

ECTHYMA

Characterized by formation of adherent crusts beneath which ulceration occurs

Begins as small pustule on erythematous base which is soon surrounded by a hard crust.

Crust can be removed with difficulty to reveal an irregular ulcer

More common on the legs, thighs and buttocks

Initiated by Group A Beta hemolytic Streptococci and contaminated with Staphylococci.

Ecthyma

CELLULITIS AND ERYSIPELAS

Both are deeper infections of skin

Cellulitis is applied to inflammation of subcutaneous tissue

Erysipelas is infection of dermis and lymphatics

Similar bacteriology – Streptococci and staphylococci

Erythema, heat, swelling and tenderness common in both

CELLULITIS AND ERYSIPELAS

In Erysipelas, edge of lesion is demarcated and raised.

In Cellulitis, diffuse blister formation with hemorrhage

Both can progress to dermal necrosis

Lower extremities and face commonest

Complications – subcutaneous abscess, septicaemia and nephritis(streptococcal)

Erysipelas Cellulitis

FOLLICULITIS

Inflammation of hair follicle

Can be :

Infective - bacterial/viral/fungal

Non infective - grease, oil or post waxing.

Characterized by multiple superficial follicular pustules

Folliculitis

PSEUDOFOLLICULITIS

Not a bacterial infection

Commonly seen in blacks

Results from penetration of sharp tips of shaved hair into the skin

Commonest site is the beard

Characterized by papules and pustules on shaven skin

May cause scarring, keloid formation and hyper pigmentation

PSEUDOFOLLICULITIS

More of a cosmetic problem

Stop shaving for 4-6 wks

Maintain beard hair at 1mm length

Avoid plucking of hair

Topical steroid - antibacterial combination

FURUNCLE

Acute, usually necrotic infection of a hair follicle with S. aureus

Presents initially as a small, follicular inflammatory nodule pustular necrotic

Single or multiple associated with tenderness

Sites involved – face and neck, arms and legs, buttocks and anogenital area

Furunculosis

CARBUNCLE

Deep bacterial infection involving group of furuncles

Most favoured area is nape of neck

Marker for Diabetes mellitus

May require aggressive therapy

Carbuncle

ACUTE PARONYCHIA

Caused by staphylococci

Entry is gained through break in the skin or cuticle as a result of minor trauma

Characterized by acute inflammation with the formation of pus in the nail fold

Treatment is with systemic antibiotics.

Surgical drainage maybe required

PERIPORITIS

Secondary infection of miliaria( the eccrine sweat glands) with staph.aureus

Commonly seen in children

Summer exacerbation

Characterized by multiple erythematous papules and nodules over the forehead face scalp and trunk

Progress to form nontender fluctuant abcess

D/D: furunculosis

ERYTHRASMA

Corynebacterial infection of the skin

Characterized by well demarcated reddish-brown scaly patches on moist body areas such as the axillae or groins.

Most commonly mistaken for Tinea cruris or intertrigo

Differentiated by Wood’s lamp – coral red flourescence

Erythrasma

PITTED KERATOLYSIS

Caused by corynebacterium minutisimum, micrococcus sedantareus & dermatophilus congolensis

Predisposing factors:Excessive sweatingProlonged immersion of hands and feet in waterOcclusive footwearCharacterized by cribriform pattern of fine

punched out depressions on the palms and soles associated with foul smell

TREATMENT

Counseling

Oral antibiotics – erythromycin, azithromycin

Topical antifungal and antibiotic creams

Treatment of hyperhidrosis

TRICHOMYCOSIS AXILLARE

MisnomerCaused by corynebacterium tenuisaxillary and pubic hair become beaded with concretions

(yellow, red or black), made up of tightly packed bacteria

This maybe associated with discoloration of sweat leading to staining of the undergarments and foul smell

Topical antibiotics or shaving will clear the condition

TREATMENT

Topical antibiotics for localized infections

Combination of Oral and Topical therapy for extensive infections.

Topical modalities include Fusidic acid, Mupirocin, Sisomycin, Nadifloxacin, Framycitin-B

Oral antibiotics preferred are Ampicillin, Cloxacillin, Amoxycillin, Cephalosporins or Azithromycin.

Hospitalization, IV antibiotics and /or surgical intervention for deeper infections like Cellulitis and Erysipelas

SECONDARY BACTERIAL INFECTION

Bacterial infection on an underlying conditionScabies / PediculosisEczemasVesiculo-bullous lesionsUlcers