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18 Cards in this Set
- Front
- Back
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Streptococci and Enterococci- General Description
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Pyogenic, non-motile, catalase negative, gram positive in chains that cause a host of diseases, enterococci only recently distinguished
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Strep Species
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S. Pneumoniae
S. Pyogenes Enterococcal Non-enterococcal S. Agalacticae Viridians |
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Classification of Streptococci
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Hemolysis on agar plates, S. Pyogenes is completely hemolytic B, Viridians is partially hemolytic A, and Enterococci is not hemolytic Y
Lancefield goruping can also be used to identify A and B Also catalase tests, and facultative anaerobes |
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Identification of Streptococci
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First catalse test- identifies them as streptococci
Second Distinguishing test |
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Group A Streptococci Disease GAS- S. Pyogenes
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Greater than 18million cases with 517,000 deaths a year of GAS disease
15,6 Million Cases Rheumatic Heart Disease 600 million case of GAS pharyngitis 111 million cases of Pyoderma |
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Group A Streptococci Structure
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Has a cell membrane, peptidoglycan cell wall with M protein Pilli, and a capsule made from hyularonic acid
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Group A Streptococci Extracellular Substances
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Streptolysins, NADase, hyularonidase, streptokinase, streptodornases, and pryrogenic exotoxins
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M Protein in Disease
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M-protein is antiphagocytic and inhibits the activation of the alternative complement pathway. There are over 80 types and it used to subtype. Antibodies are type specific. Vaccines target variable and conserved regions. Strains lacking M protein are avirulent.
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Group A Streptococci Pharyngitis Clinical Features
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sore throat, sudden onset, fever, pain with swallowing, headache, lymphadenitis, tonsillar exudates, soft palate petechiae
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Group A Streptococci Pharyngitis Epidemiology
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Humans are the natural reservoir, common in 5-15 year olds, common in cold climates, different M strains possible and can change rapidly, and asymptomatic carriage is possible
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Group A Streptococci Pharyngitis Pathogenesis
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Bacteria spread by droplets or nasal secretion with increased risk in crowds, with those containing M protein or hyaluronate being more easily transmitted. Bacteria forms aggregates and adheres to epithelium using adhesins and lipoteichoic acid, infection depends on presence of M protein antibodies
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Nonsuppuartive Sequelae of Phayrngitis
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Rheumatic fever: molecular mimicry cross with myosin
Glomerulonephritis |
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Streptococcal Pyoderma Pathogenesis and Epidemiology
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Seen in 2-5 year olds and low income areas, starts with colonization on skin and then auto-innoculation when skin is damaged, straisn are different from those that carry pharyngitis.
Rare Complications: glomerunephritis and lymphadenitis |
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Streptococcal TSS
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Caused by super antigen, been increasing cases with exotoxin A-C, different from aureus due to presence of infection like fascitis.
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Treatment of S. Pyogenes
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Sensitive to penicillin, treatment with protein synthesis blockers, prophy antibiotics
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Streptococcus pneumoniae Description
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gram positive, lancelet shaped diplococci, encapsulated with techoic acid containing phosphophoryl choline, A-hemolytic, adhesins, 90 seerotypes and naturally competent
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Streptococcus pneumoniae epidemiology
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Causes disease at the extremes of age, colonizes nasopharny (5-10% Adults 20-40% in children), transmitted by extensive contact, mortality at 17% with 65% of deaths within 3 days
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Streptococcus pneumoniae Pathogenesis
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Capsules are anti-phagocytic, phasic with one phase being transparent and other phase opaque, thickened capsule wall, techoic acid can bind cells, nasopharynz dripings lead to invasion into lungs and bind type alverolar cells,
Released Pneumolysins that are lytic to host cells • Peptidoglycan is responsible for inflammatory • Antimicrobial resistance serious concern |
