Info

Streptococcus pyogenes

Staphylococcus aureus

Characteristics

Gram-positive cocci in chains; /-hemolytic colonies; cell wall contains group A polysaccharide and M protein

Gram-positive cocci in clusters; cream-colored colonies; cell wall contains protein A

Extracellular Products

Hemolysins: streptolysins O and S; streptokinase, DNase, hyaluronidase, and others

Hemolysins, leukocidin, hyaluronidase, nuclease, protease, penicillinase, and others

Disease Potential

Causes impetigo, strep throat, wound infections, scarlet fever, puerperal fever, toxic shock, and flesh-eating fasciitis. Complications: glomerulonephritis, rheumatic fever, and chorea

Causes boils, scalded skin syndrome, wound infections, abscesses, bone infections, impetigo, food poisoning, and toxic shock syndrome

22.3 Bacterial Skin Diseases 541

Figure 22.7 Pathogenesis of Post-Streptococcal Acute Glomerulonephritis Immune complexes are deposited in the kidney glomeruli, inciting an inflammatory response.

Glomerulus

Streptococcus pyogenes antigen

Complement _

Puffiness around the eyes (fluid retention)

Symptoms and Signs

• Fluid retention

High blood pressure

• Blood and protein in urine

Glomerulus

Streptococcus pyogenes antigen

Puffiness around the eyes (fluid retention)

Imagenes Estrechamiento Bronquial

Complement _

— Immune complex

■ Swollen ankles (fluid retention)

— Immune complex

■ Swollen ankles (fluid retention)

Prevention and Treatment

General cleanliness and avoiding people with impetigo help prevent the disease. Prompt cleansing of wounds and application of antiseptic probably also decrease the chance of infection. So far, S. pyogenes strains remain susceptible to penicillin. In patients allergic to penicillin, erythromycin can be substituted.

Table 22.6 summarizes the main features of impetigo.

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