Bacterial Skin Infections

Erysipelas Dermatology Definition

Erysipelas is an acute beta-hemolytic group A streptococcal infection of the skin involving the superficial dermal lymphatics that causes marked swelling. The resulting local changes are unique to erysipelas and are not seen in other forms of cellulitis. Erysipelas is characterized by local redness, heat, swelling, and a highly characteristic raised, indurated border. Skin lesions vary from transient hyperemia and slight desquamation to intense inflammation with vesicles or bullae, but there is no localized purulence. The eruption spreads by peripheral extension. Associated lymphangitis and local lymphadenopathy may occur. The legs and face are the most frequently affected sites. When erysipelas occurs on the face, a classic butterfly distribution involving the cheeks and the bridge of the nose is seen. When legs are affected, edema and bullous lesions are often present. Erysipelas can occur in children and adults, but infants and elderly are at increased risk. Group B streptococcus is often responsible in the newborn or postpartum woman. Predisposing medical or postsurgical conditions, such as skin ulcers or eczematous lesions, chronic fungal infections, fissures, local trauma, venous or lymphatic compromise, and obesity are present in many patients who develop erysipelas. The onset can be preceded by prodromal symptoms of malaise with or without chills, fever, headache, vomiting, and joint pain.

Impetigo Treatment

Hand washing to reduce spread Topical or oral antibiotics Wash the affected area with antibacterial soap Check to see if his niece still has her rash Topical therapy with mupirocin or retapamulin ointment may be equally effective to oral antibiotics if the lesions are localized in an otherwise healthy patient and there are not multiple outbreaks in a family or group Otherwise, oral antibiotics are used.

Treatment for Erysipelas

Immediate empiric antibiotic therapy should be started (cover most common pathogen - Streptococcus) Such as penicillin V, amoxicillin, clindamycin, macrolide, and others Monitor patients closely and revise therapy if there is a poor response to initial treatment Elevation of the involved area Treat tinea pedis, erythrasma, or strep of toe spaces if present 25

Folliculitis Treatment

Prescribe oral antibiotics Stop shaving that area Wash the area (antibacterial soap may be used) Check with his girlfriend to see if she has any breakout Cleanse with antibacterial soap Superficial pustules will rupture and drain spontaneously Oral or topical anti-staphylococcal agents as mupiricin or retapamulin ointment; topical clindamycin solution/lotion may be used Deep lesions of folliculitis represent small follicular abscesses and should be drained

Risk Factors for cellulitis include

Local trauma (bug bites, laceration, abrasion, puncture wound) • Spread of a preceding or concurrent skin lesion (furuncle, ulcer) • Secondary cellulitis from blood-borne infection or from direct spread of subjacent infections (e.g. osteomyelitis) is rare • Following a preexisting skin infection due to compromise of skin barrier (intrerdigital strep, tinea pedis) • Inflammation (local dermatitis, radiation therapy) • Edema and impaired lymphatics in the affected area

Carbunculosis

is a coalescence of several inflamed follicles into a single inflammatory mass with purulent drainage from multiple follicles

Folliculitis

is a superficial bacterial infection of the hair follicles Presents as small, raised, erythematous, occasionally pruritic pustules less than 5 mm in diameter Genital folliculitis may be sexually transmitted Pathogens: • Majority of cases are due to Staphyloccus aureus • If there has been exposure to a hot tub or swimming pool, consider pseudomonas as a possible cause • Pustules associated with marked erythema in the groin may represent candidiasis

MRSA Risk Factors

• Antibiotic use • Prolonged hospitalization • Surgical site infection • Intensive care • Hemodialysis • MRSA colonization • Proximity to others with MRSA colonization or infection • Skin trauma • Cosmetic body shaving • Group facilities • Sharing equipment that is not cleaned or laundered between users/body contact as in sports

Impetigo

Peri-oral papules and plaques with overlying honey-colored crust Minimal surrounding erythema is a common superficial bacterial skin infection Most commonly seen in children ages 2-5, but older children and adults can be affected Impetigo is contagious, easily spread among individuals in close contact Most cases are due to S. aureus with the remainder either being due to Strep pyogenes or a combination of these two organisms

Cellutilis Etiology

80% of cases are caused by gram positive organisms Group A streptococcus is most common; other strep less so Staphylococcus aureus is less common but occurs with open wound or penetrating trauma as with needle injection with drug abuse Think of other organisms if there have been unusual exposures or conditions: Pasteurella multocida (animal bites) Eikenella corrodens (human bites) MRSA (with concurrent MRSA elsewhere/illicit drug use/purulent drainage)

Take Home Points

Cellulitis is a bacterial infection of the dermis that often begins with a portal of entry that is usually a wound, insect bite, fungal infection (tinea pedis), or maceration with strep present Untreated cellulitis may lead to sepsis and death Lower extremity cellulitis has a deep differential Erysipelas is a superficial cellulitis with marked dermal lymphatic involvement A skin abscess is a loculated infection within the dermis and deeper skin tissues and is best treated with I&D Furuncles and carbuncles are subtypes of abscesses, which preferentially occur in skin areas containing hair follicles exposed to friction and perspiration Folliculitis is a superficial bacterial infection of the hair follicles presenting as follicular pustules In impetigo, papules and vesicles progress to form pustules that enlarge and break down to form thick, adherent crusts with a golden or honey-colored appearance Necrotizing fasciitis presents as an expanding dusky, edematous, red plaque with blue discoloration Anesthesia of the skin of the affected area is a characteristic finding of necrotizing fasciitis Necrotizing fasciitis is a medical/surgical emergency

Abscess

Erythematous, warm, fluctuant nodule with several small pustules throughout the surface Very tender to palpation A skin abscess is a collection of pus within the dermis and deeper skin tissues Present as painful, tender, fluctuant and erythematous nodules Often surmounted by a pustule and surrounded by a rim of erythematous edema Spontaneous drainage of purulent material may occur

Furuncle/ Carbuncle

Furuncles and carbuncles are a subtype of abscesses, which preferentially occur in skin areas containing hair follicles exposed to friction and perspiration • Common areas include the back of the neck, face, axillae, and buttocks Usually caused by Staphylococcus aureus Patients are commonly treated with oral antibiotics For a solitary small furuncle: warm compresses to promote drainage may be sufficient For larger furuncles and carbuncles: manage as you would an abscess

Stasis dermatitis

(Although found in similar location, stasis dermatitis often presents with pruritus and scale, which may erode or crust. Without fever or elevated wbc) Erythematous, pruritic, scaling patches on the lower extremities due to impaired venous circulation. Chronic changes in the lower extremities include edema, skin hyperpigmentation and ulcer formation. Venous insufficiency causes increased vascular hydrostatic pressure that leads to extravasation of serum and red blood cells. Over time, increased hemosiderin and fibrin deposition in the extracellular space leads to pigmentary and fibrotic changes in the skin as well as tissue hypoxia and ulcer formation. Inflammation with crusting and exudate may be present. Rapid onset can occur in cases of deep vein thrombosis. Treatment is targeted toward prevention of venous stasis and edema with weight loss, leg elevation, support stockings.

Tinea corporis

(Would expect annular plaque with elevated border and central clearing. Painless, without fever or elevated wbc) Fungal infection of the skin that presents as well-defined, erythematous, scaling papules or plaques. The lesions are often arranged in an annular configuration and often have an elevated, serpiginous border.

Bacterial folliculitis

(Would expect pustules and papules centered on hair follicles. Without systemic signs of infection) Inflammation of the hair follicle that appears clinically as an eruption of pustules and/or papules centered upon hair follicles. The distribution of pustules in folliculitis is often localized; favored areas are the buttocks, thigh, and beard area. Careful inspection reveals the presence of hairs piercing through the center of the pustules. The most common bacterial cause of folliculitis is Staphylococcus aureus. Chronic carriers of S. aureus may have recurrent outbreaks of folliculitis.

Necrotizing fascilitis

(Would expect rapidly expanding rash, usually appears as a dusky, edematous, red plaque. In this setting, it is always appropriate to ask the question, "Could this be necrotizing fasciitis?")

Seborrheic dermatitis

(would expect erythematous patches and plaques with a greasy, yellow scale) Seborrheic Dermatitis - A chronic inflammatory process commonly affecting the face, eyebrows, scalp (dandruff), chest, and perineum. The typical skin findings range from fine white scale to erythematous patches and plaques with greasy, yellowish scale. Seborrheic dermatitis is thought to be due to an inflammatory reaction against Pityrosporum ovale (called Malassezia furfur when in the infectious hyphal form),a yeast that is part of normal skin flora. The incidence of seborrheic dermatitis is associated with increased sebaceous gland activity and is found most commonly in infants and in post-pubertal patients. In infants, the process is expected to resolve with time. In adults, the course is chronic and unpredictable. May be associated with heredity, psoriasis, emotional stress, or immunocompromised conditions, like HIV infection. Therapy involves anti-seborrheic shampoos and/or steroids.

Orolibail HSV

(would expect grouped and confluent vesicles with an erythematous rim; can evolve to crusting and easily be confused with impetigo) Herpes Simplex - An acute, self-limited eruption of clustered vesicles, often with secondary crusting, caused by herpesvirus type 1 or type 2 infection.

Bullous Impetigo

A form of impetigo seen in young children is characterized by flaccid bullae with clear yellow fluid, which later becomes purulent. Ruptured bullae leave a thick brown crust Common locations are the face, extremities, and diaper area 56

Abscess dermatology glossary definition

Abscess - An abscess is a common infection characterized by a localized accumulation of polymorphonuclear leukocytes with tissue necrosis involving the dermis and subcutaneous tissue. Staphylococcus aureus is the most common causative agent, although abscesses can be caused by a variety of organisms. Abscesses and carbuncles are histologically similar but carbuncles (and furuncles) arise from infection of the hair follicles. Abscesses can arise from infection tracking in from the skin surface but are usually deeper than carbuncles and can also be a complication of bacteremia. Clinical features include local pain, swelling, erythema, and regional lymphadenopathy. Fever, chills, and systemic toxicity are unusual except in patients with concomitant cellulitis. Patients of all ages can develop skin abscess. A risk factor for development of this infection is relatively minor local trauma such as an insect bite, abrasion, or injection drug use. Patients may have a history of diabetes or immunosuppression but more often there is no demonstrable predisposing condition other than nasal or skin carriage of S. aureus.

Non-bullous Impetigo

Also called impetigo contagiosum; most common form Lesions begin as papules surrounded by erythema They progress to form pustules that enlarge and break down to form thick, adherent crusts with a characteristic honey-crusted appearance

Treatment for Cellulitis

Begin oral antibiotics immediately with coverage for gram positive bacteria and encourage leg elevation It is important to recognize and treat cellulitis early as untreated cellulitis may lead to sepsis and death The following guidelines are for empiric antibiotic therapy: • For outpatients with nonpurulent cellulitis: empirically treat for β-hemolytic streptococci (group A streptococcus) as cephalexin, amoxicillin, amoxicillin-clavulanate, dicloxacillin, or clindamycin • For outpatients with purulent cellulitis (purulent drainage or exudate in the absence of a drainable abscess)/injection drug use/other penetrating trauma/MRSA presence elsewhere: empirically choose treatment to cover community-associated MRSA as well as strep, as clindamycin; work with dermatology and infectious disease specialists • For unusual exposures: cover for additional bacterial species based on such exposure; work with dermatology and infectious disease specialists Monitor patients closely and revise therapy if there is a poor response to initial treatment; usually a 5 day course of antibiotics is sufficient Treat underlying derm disorder/condition, as venous eczema Elevation of the involved area Treat tinea pedis, toe maceration (strep) if present Consideration of concurrent oral steroid treatment to decrease post-inflammatory lymphatic damage; more studies needed For hospitalized patients: empiric therapy for MRSA should be considered Cultures from abscesses and other purulent skin and soft tissue infections (SSTIs) are recommended in patients to be treated with antibiotic therapy but if case has a typical presentation, they need not be performed

Carbuncle/Furuncle Dermatology Glossary

Carbuncle / Furuncle - A furuncle is an acute, round, firm, tender, circumscribed, perifollicular staphylococcal pyoderma that usually ends in central suppuration. A carbuncle is two or more confluent furuncles with separate heads. Furuncles, carbuncles, impetigo, and folliculitis are all considered to be primary pyodermas. These infections share certain features: they are usually caused by Staphylococcus aureus, they rarely require hospitalization, they may respond to local treatment, and recurrence may be prevented by decreasing S. aureus carriage. Furuncles and carbuncles begin in hair follicles, and often continue for a prolonged period by autoinoculation. Some lesions disappear before rupture, but most undergo central necrosis and rupture through the skin, discharging firm, purulent, necrotic debris. Predisposed sites include the nape, axilla, and buttocks, but lesions may occur anywhere. Local skin barrier compromise predisposes to infection by providing a portal of entry for the ubiquitous. The proximate cause is either contagion or autoinoculation from a carrier focus, usually in the nose or groin. Patients with certain systemic disorders including HIV, malnutrition, blood dyscrasias, and immunosupression may be predisposed to the S. aureus carrier state and furunculosis. Atopic dermatitis and renal dialysis also predisposes to the S. aureus carrier state. Treatment consists of warm compresses and oral antibiotics (penicillinase-resistant penicillin or a first-generation cephalosporin). Surgical drainage may be required in cases in which spontaneous drainage does not occur and antibiotic treatment does not achieve resolution of the lesion. Recurrent lesions are not uncommon.

Ecthyma

Ecthyma is an ulcerative lesion which extends through the epidermis and into the dermis. Consist of "punched out" ulcers covered with yellow crust surrounded by raised margins. Heals slowly and may scar S. aureus and/or Strep may be the cause 57

Treatment in Abscesses

Incision and drainage (incision and drainage is the treatment of choice for abscesses) Offer HIV test (patients with risk factors for HIV should be offered an HIV test, e.g. IVDU in this patient) Topical antibiotics not effective Abscesses require incision and drainage (I & D) • Most experts recommend clearing pus and debris and probing the entire cavity following incision and drainage Antibiotics are recommended for abscesses associated with: • Severe or extensive disease (e.g., involving multiple sites) • Rapid progression in presence of associated cellulitis • Signs and symptoms of systemic illness • Associated comorbidities or immunosuppression • Extremes of age • Abscess in an area difficult to drain (e.g., face, hand, or genitalia) • Associated septic phlebitis • Lack of response to I&D alone Recommended oral antibiotics include: clindamycin, TMP-SMZ, tetracyclines For hospitalized patients, consider vancomycin, linezolid, daptomycin, or telavancin Wound cultures should be sent Patients with recurrent skin infections should be referred to a dermatologist

Folliculitis Dermatology Glossary

Inflammation of the hair follicle that appears clinically as an eruption of pustules and/or papules centered upon hair follicles. The distribution of pustules in folliculitis is often localized; favored areas are the buttocks, thigh, and beard area. Careful inspection reveals the presence of hairs piercing through the center of the pustules. The most common bacterial cause of folliculitis is Staphylococcus aureus. Chronic carriers of S. aureus may have recurrent outbreaks of folliculitis.

Impetigo and Antibiotics

Oral antibiotics are used to treat impetigo when it's extensive or affecting several people (close contacts). Effective antibiotics include: Dicloxacillin •Cephalexin •Erythromycin (some strains of Staphyloccocus aureus and Streptococcal pyogenes may be resistant) Clindamycin Amoxicillin/clavulanate

Cellulitis

Skin: erythematous plaque with ill-defined borders over the right medial malleolus. Lesion is tender to palpation. Tender, slightly enlarged right inguinal lymph node Laboratory data: Wbc 12,000 (75% neutrophils, 10% bands) is a very common infection occurring in up to 3% of people per year Most do not require hospitalization Results from an infection of the dermis that often begins with a portal of entry that is usually a wound, maceration between toes (strep component), or fungal infection (e.g., tinea pedis) Presents as a spreading erythematous, non-fluctuant tender plaque More commonly found on the lower leg Streaks of lymphangitis may spread from the area to lymph nodes

Necrotizing Faciitis Treatment

Skin: ill-defined, large erythematous plaque with central patches of dusky blue discoloration, which is anesthetic; upon re-examination 60 minutes later the redness had spread; the subcu tissue had a woody induration An urgent surgical consult ( it is a surgical emergency) Considered a medical/surgical emergency with up to a 30-70% mortality rate with strep If you suspect necrotizing fasciitis: consult surgery immediately Necrotizing fasciitis is a clinical diagnosis. Treatment includes widespread debridement and broad-spectrum systemic antibiotics Do not delay treatment to obtain MRI Poor prognostic factors include: delay in diagnosis, age>50, diabetes, atherosclerosis, infection involving the trunk Necrotizing soft tissue infections can involve the skin, subcutaneous fat, superficial or deep fascia, and/or muscle.

Erysipelas Cellulitis

is a superficial cellulitis with marked dermal lymphatic involvement (causing the skin to be edematous or raised) • Main pathogen is group A streptococcus • Also caused by Staph aureus, Haemophilus, and others Usually affects the lower extremities and face Presents with pain, bright erythema, and plaque-like edema with a sharply defined margin to normal tissue Plaques may develop overlying blisters (bullae) May be associated with a high white count (>20,000/mcL) May be preceded by chills, fever, headache, vomiting, and joint pain

Furuncle (boil)

is an acute, round, tender, circumscribed, perifollicular abscess that generally ends in central suppuration