Bacterial Diseases of the Skin and Wounds

Sign and Symptoms of folliculitis, or “Ingrown Hair”

infection of the hair follicle; spread of infection into surrounding tissues can produce a furuncle (boil); common after shaving

Carbuncles

occur when multiple furuncles grow together

Pathogen and Virulence Factors of Folliculitis

most commonly caused by Staphylococcus; two species commonly found on the skin - Staphylococcus epidermidis + Staphylococcus aureus

Pathogenesis of Folliculitis 

Staphylococcus transmitted via direct contact or by fomites (microbes living on an inanimate object); injection can spread into the blood and move to organs beyond the skin

Epidemiology of Folliculitis 

S. epidermidis lacks virulence factors and rarely cause disease; S. aureus transiently colonizes the skin or mucous membranes of most people

Diagnosis, Treatment, and Prevention of Folliculitis 

Isolation of Gram-positive cocci bacteria in grape-like clusters from pus; infections treated with mupirocin or dicloxacillin; Vancomycin is used to treat resistant strains; Preventive measures included hand antisepsis and proper procedures in hospitals to minimize Methicillin-resistant S. aureus infections 

Signs and Symptoms of Staphylococcal Scalded Skin Syndrome (SSSS)

skin becomes red and wrinkled and forms blisters, causing skin to “sloth” off; only penetrates epidermis

Pathogen and Virulence Factors of Staphylococcal Scalded Skin Syndrome (SSSS)

some S. aureus strains; one or two different exfoliative toxins cause SSSS

Pathogenesis of Staphylococcal Scalded Skin Syndrome (SSSS)

circulation of toxins in the blood produces toxemia

Epidemiology of Staphylococcal Scalded Skin Syndrome (SSSS)

disease occurs primarily in infants and young children; transmitted by person-to-person spread of bacteria

Diagnosis, Treatment, and Prevention of Staphylococcal Scalded Skin Syndrome

diagnosed by characteristic sloughing of skin; treated by administration of penicillin-derived drugs; widespread presence of S. aureus makes prevention difficult 

Signs and Symptoms of Impetigo (Pyoderma)

usually S. aureus; red patches form on the face and limps; patches develop into pus-vesicles that crust

Signs and Symptoms of Erysipelas

usually Streptococcus; infection spreads to the lymph nodes; reddening occurs on the face, arms, or legs; potentially fatal if untreated

Signs and Symptoms of Cellulitis

infection of the deeper dermis and subcutaneous fat; appears as red, swollen area that is hot to the touch

Pathogens and Virulence Factors of Impetgo (Pyoderma), Erysipelas, and Cellulitis

S. aureus causes most cases of impetigo; Streptococcus pyogenes (group A Streptococcus) causes erysipelas, most cellulitis cases, and some cases of impetigo; S. pyogenes virulence factors contribute to impetigo (M protein, hyaluronic acid, pyrogenic toxins)

Pathogenesis of Impetigo (Pyoderma), Erysipelas, and Cellulitis

the bacteria invade where the skin is compromised; acute glomerulonephritis can result if infection spreads to the kidneys; cellulitis in adults usually occurs in the legs 

Epidemiology of Impetigo (Pyoderma), Erysipelas, and Cellulitis

transmitted by person-to-person contact or via fomites; impetigo occurs mostly in children; erysipelas can also occur in the elderly; cellulitis occurs most often in people with poorly controlled diabetes

Diagnosis, Treatment, and Prevention of Impetigo (Pyoderma), Erysipelas, and Cellulitis

the presence of vesicles is diagnostic for impetigo; impetigo is treated with oral and topical antimicrobials and careful cleaning of infected areas; erysipelas is treated with penicillin; cellulitis is treated with cephalexin; prevent with proper hygeine and cleanliness

Signs and Symptoms of Necrotizing Fasciitis, or “Flesh-Eating Disease”

redness, intense pain, and swelling at infection site; develop fever, nausea, malaise, and possible mental confusion

Pathogen and Virulence Factors of Necrotizing Fasciitis

most cases are caused by S. pyogenes; various enzymes facilitate invasion of tissues; exotoxin A and streptolysin S damage cells and tissues

Pathogenesis of Necrotizing Fasciitis

S. pyogenes enters through breaks in the skin 

Epidemiology of Necrotizing Fasciitis

usually spreads from person to person; death occurs in about 20% of patients

Diagnosis, Treatment, and Prevention of Necrotizing Fasciitis

early diagnosis is difficult because symptoms are nonspecific; affected tissue must be removed; treat with broad-spectrum antimicrobials (prevent secondary infections); difficult to prevent since S. pyogenes is common