Schaechter's Mechanisms of Microbial Disase-Chapter 13 (Strep and Entero)

Group A Streptococci (GAS)

• Can present itself as strep throat (Pharyngitis) and Pyoderma

• Cannot penetrate intact skin but can penetrate open wounds

• Releases M-Protein and Hyaluronic Acid in the body to evade phagocytosis and the Immune Response

Group B

• S. agalactiae

• Beta, Yamma hemolysis

• Can cause Neonatal Pneumonia, Meningitis, Sepsis

• Commonly lives in the lower gastrointestinal tract and the female genital tract

• Early onset occurs in the first 6 days of life as pneumonia, then later as sepsis

• Later onset from days 7-90 presents as bacteremia with high meningitis rates

• can cause UTIs, endometriosis, and amnionitis

Enterococcus

• E. faecalis, e.faecium

• Nosocomial infections, UTIs, Endocarditis

• alpha, yamma, and beta-hemolysis

Group A

• S. pyogenes

• Beta Hemolysis

• Can cause Pharyngitis, Pyoderma, Toxic Shock Syndrome, Necrotizing fasciitis, rheumatic fever, scarlet fever, cellulitis

Hyaluronic Acid Capsule

• Found in human connective tissue

• Streptococci can be enveloped in this and can successfully camouflage themselves in a host antigen that does not elicit a immune response.

Group A Streptococci Damage

• Evokes a strong inflammatory response in the tissue

• Streptococcal Pyogenic Exotoxins (SPE) A,B, and C can cause Rheumatic Fever

Acute Rheumatic Fever

• Appears 1-4 weeks following strep throat

• Includes carditis, polyarthritis, chorea, nodules, and erythema marginatum.

• Ongoing inflammation in the heart can contribute to mitral and aortic valvular stenosis, which can lead to rheumatic heart disease.

• A full penicillin course treatment for 9 days after the onset of a sore throat is the standard

Viridians Streptococci

• a-hemolytic species

• S.mutans and S.sobrinus (which can lead to endocarditis)

• produce lactic acid during sugar metabolism

• S.milleri (involved in polymicrobial diseases of the brain, liver, and abdominal cavity)