Medically Important Gram-Positive Cocci Bacteria PDF
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Uploaded by GratefulRiemann6486
Arba Minch University
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This document provides information on medically important Gram-positive cocci bacteria, focusing on Staphylococcus and Streptococcus bacteria, their characteristics, and related infections. It includes details on identification tests, such as Gram staining and hemolysis pattern analysis, which are essential in microbiology. Key topics cover bacterial classification, pathogenesis, and laboratory diagnosis.
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Medically Important Gram-Positive Cocci Bacteria Course Objectives: - Describe common medically important Gram-positive bacteria. - Explain their general characteristics, classification, pathogenesis mechanisms & laboratory diagnosis. - Describe common Gram-positive cocci bacterial infections....
Medically Important Gram-Positive Cocci Bacteria Course Objectives: - Describe common medically important Gram-positive bacteria. - Explain their general characteristics, classification, pathogenesis mechanisms & laboratory diagnosis. - Describe common Gram-positive cocci bacterial infections. ### Gram-Positive Cocci: Streptococci vs. Staphylococci #### Staphylococcus: - Includes species like S. aureus, S. saprophyticus, and S. epidermidis. - Catalase-positive; S. aureus is coagulase-positive. - Ferments mannitol, forms golden yellow colonies on MSA agar. - Normal flora of nasal passages, skin, and mucous membranes. - Pathogenesis involves adhesion, immune system invasion, and toxin production. - Causes skin infections (impetigo, folliculitis), pneumonia, food poisoning, toxic shock syndrome, and metastatic infections. - Lab identification: Gram staining, culture on MSA, coagulase test. #### Streptococcus: - Gram-positive, catalase-negative, arranged in chains or pairs. - Classification based on hemolysis patterns (alpha, beta, gamma) and Lancefield grouping. - S. pyogenes (Group A) causes pharyngitis, skin infections, rheumatic fever, scarlet fever, and acute glomerulonephritis. - S. agalactiae (Group B) causes neonatal meningitis, pneumonia, and postpartum sepsis. - Enterococcus (Group D) includes E. faecalis and E. faecium, leading to UTIs and endocarditis. - S. pneumoniae causes pneumonia, meningitis, otitis media, and sinusitis. #### Identification Tests: - Gram staining, culture on blood agar. - Hemolysis patterns: Alpha (S. pneumoniae), Beta (S. pyogenes, S. agalactiae), Gamma (Enterococcus). - Optochin sensitivity test for S. pneumoniae. - ASO titer for post-infectious diagnosis of S. pyogenes.
