Streptococcus Overview PDF
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University of Houston-Downtown
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This document provides a comprehensive overview of Streptococcus and Enterococcus, two significant bacterial genera. It covers their classification, pathogenesis, epidemiology, and control measures. The information is useful for in-depth study of medical microbiology topics.
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Read Quiz Comprehensive Overview of Streptococcus and Enterococcus Introduction Streptococcus and Enterococcus are two significant genera of Gram-positive bacteria, frequently implicated in a variety of...
Read Quiz Comprehensive Overview of Streptococcus and Enterococcus Introduction Streptococcus and Enterococcus are two significant genera of Gram-positive bacteria, frequently implicated in a variety of human diseases. While belonging to different genera, both share certain characteristics, as well as unique attributes that influence their pathogenicity, clinical manifestations, and treatment approaches. This detailed content piece aims to synthesize the information on their classification, pathogenesis, epidemiology, clinical diseases, and control measures for in-depth study purposes. 1. Streptococcus 1.1 General Characteristics Gram-positive cocci arranged in pairs or chains Facultative anaerobes with complex nutritional needs Catalase negative and capable of fermenting carbohydrates 1.2 Classification Lancefield Grouping: Based on carbohydrate antigens (e.g., Group A includes Streptococcus pyogenes) Hemolytic Patterns: Beta (β) Hemolysis: Complete hemolysis (e.g., S. pyogenes) https://www.studocu.com/en-us/notes 12/4/24, 7 04 PM Page 1 of 6 : Alpha (α) Hemolysis: Incomplete hemolysis (e.g., S. pneumoniae) Gamma (γ) Hemolysis: No hemolysis Biochemical properties 1.3 Streptococcus pyogenes (Group A Streptococcus) 1.3.1 Pathogenesis and Immunity Avoidance of Opsonization and Phagocytosis: Hyaluronic acid capsule: Resembles host tissues, avoiding immune detection M protein: Prevents phagocytosis and aids in adhesion Other Proteins: F protein and lipoteichoic acids function as adhesins Toxins and Enzymes: Streptolysin O and S: Pore-forming toxins responsible for β-hemolysis and cell lysis Pyrogenic Exotoxins (SpeA, SpeB): Superantigens involved in severe immune responses 1.3.2 Clinical Diseases Pharyngitis: One of the most common bacterial causes Scarlet Fever: Characterized by a distinctive rash from pyrogenic toxins Skin Infections: Includes impetigo, erysipelas, and necrotizing fasciitis Streptococcal Toxic Shock Syndrome (STSS): Severe systemic disease with high mortality 1.3.3 Treatment and Control Penicillin remains highly effective, although diagnosis and prompt treatment are crucial to prevent complications like rheumatic fever and glomerulonephritis 1.4 Streptococcus pneumoniae https://www.studocu.com/en-us/notes 12/4/24, 7 04 PM Page 2 of 6 : 1.4.1 Pathogenesis and Immunity Attachment Mechanisms: Surface Protein Adhesins: Facilitate adherence to host cells Secretory IgA protease: Cleaves IgA in mucosal surfaces Pneumolysin: Contributes to tissue damage and immune evasion Capsule: Key virulence factor enabling phagocytic survival 1.4.2 Epidemiology Colonizes the nasopharynx of healthy individuals and can spread to the lungs, sinuses, and meninges Vaccine Introduction: Reduction in incidence due to effective vaccination strategies, including the 23-valent polysaccharide and conjugate vaccines 1.4.3 Clinical Diseases Pneumonia: Notable for its abrupt onset and localized infection Sinusitis and Otitis Media: Commonly follows viral infections Meningitis and Bacteremia: High morbidity and mortality rates, especially in vulnerable populations 1.4.4 Treatment and Control Penicillin Resistance: Increasing resistance necessitates use of alternatives like fluoroquinolones or vancomycin combined with ceftriaxone 1.5 Streptococcus agalactiae (Group B Streptococcus) 1.5.1 Pathogenesis and Immunity Capsule: Major virulence factor, particularly in neonates lacking maternal antibodies Surface Proteins: Such as C antigen playing roles in pathogenicity 1.5.2 Epidemiology Colonizes the lower gastrointestinal and genitourinary tracts https://www.studocu.com/en-us/notes 12/4/24, 7 04 PM Page 3 of 6 : Neonatal Transmission: High colonization rates in infants born to colonized mothers 1.5.3 Clinical Diseases Neonatal Diseases: Early-Onset Disease: Often manifests as bacteremia, pneumonia, or meningitis Late-Onset Disease: Primarily meningitis Adult Infections: Including bacteremia, endometritis in postpartum women, and urinary tract infections 1.5.4 Treatment and Control Penicillin Susceptibility: Screening of pregnant women and use of prophylactic antibiotics to prevent neonatal disease 1.6 Viridans Streptococci 1.6.1 Characteristics and Epidemiology Comprise more than 30 species and subspecies, often part of normal flora Subgroups: Include Anginosus, Mitis, Mutans, Salivarius, Bovis, and ungrouped 1.6.2 Pathogenic Potential Oral Cavity: Major role in dental caries (e.g., S. mutans) Systemic Infections: Can lead to endocarditis, especially in individuals with pre-existing heart conditions 2. Enterococcus 2.1 General Characteristics Gram-positive cocci arranged in pairs or chains Facultative anaerobes with complex nutritional requirements https://www.studocu.com/en-us/notes 12/4/24, 7 04 PM Page 4 of 6 : Resistant to many environmental conditions including high salt concentrations and bile acids 2.2 Classification Belong to group D in the Lancefield classification based on the presence of a unique antigen 2.3 Pathogenesis and Immunity Limited Virulence Factors: Does not produce potent toxins but can cause disease, particularly in compromised hosts Antibiotic Resistance: Known reservoirs for resistance genes, contributing to significant clinical challenges 2.4 Epidemiology Normal Enteric Flora: Found in the gastrointestinal and genitourinary tracts of humans and animals Nosocomial Infections: Frequently isolated from hospitalized patients' skin and respiratory tract 2.5 Clinical Diseases Urinary Tract Infections (UTIs): Especially in patients with catheterization Endocarditis: Particularly when involving intravascular catheters Wound Infections: Often polymicrobial and associated with other organisms 2.6 Treatment and Control High Antibiotic Resistance: Ample resistance to aminoglycosides, beta- lactams, and vancomycin Combination Therapy: Often necessary using aminoglycosides and cell- wall active agents https://www.studocu.com/en-us/notes 12/4/24, 7 04 PM Page 5 of 6 : Transference of Resistance: Plasmid-encoded resistance elements pose a risk of transferring to other pathogenic bacteria, including Staphylococcus aureus Summary Understanding the epidemiology, pathogenesis, clinical manifestations, and control measures for Streptococcus and Enterococcus is crucial for effective management of the infections caused by these bacteria. Their ability to cause a wide range of diseases coupled with increasing antibiotic resistance highlights the need for continued research and adaptation of clinical practices to mitigate their impact on public health. https://www.studocu.com/en-us/notes 12/4/24, 7 04 PM Page 6 of 6 :