Bacteria of dental interest Gram-positive cocci PDF

Unit 15 Bacteria of dental interest: Gram-positive cocci Microbiology Sara Mª Martínez Sánchez Ana Isabel Garcia Guillén Dentistry INDEX CONTENTS 1. Generalities 2. Classification 3. Oral streptococci 4.Streptococcus mutans Enterococcus 5. Staphylococci 6. Staphylococcus aureus 7. Micrococci 8...

Unit 15 Bacteria of dental interest: Gram-positive cocci Microbiology Sara Mª Martínez Sánchez Ana Isabel Garcia Guillén Dentistry INDEX CONTENTS 1. Generalities 2. Classification 3. Oral streptococci 4.Streptococcus mutans Enterococcus 5. Staphylococci 6. Staphylococcus aureus 7. Micrococci 8. Gemella 9. Parvimonas, Peptococcus and Peptostreptococcus 10. Atopobium 3 Overview Gram negative 4 Overview Gram positive 5 Gram positive cocci Streptococcus Domain: Bacteria Phylum: Firmicutes Class: Bacilli Order: Lactobacillales Family: Streptococcaceae Genus: Streptococcus Essentials of Microbiology, 6 Streptococci Generalities • Lactic acid bacteria • Gram-positive spherical or oval cocci in pairs and chains • 0.7-0.9 µm in diameter • Facultative anaerobe, capnophilic (CO2) • Catalase-negative • Grow well on blood agar (enrichment with glucose and serum) • Normal microbiota in humans and animals • Include the cariogenic S. mutans group 7 Streptococcus Classification: haemolytic reactions streptolysin, streptococcal hemolytic exotoxin α-haemolysis narrow zone of partial haemolysis and green discolouration β-haemolysis wide, clear, translucent zone of complete haemolysis γ-haemolysis no haemolysis 8 Streptococcus Classification: serogroups • Carbohydrate antigens on cell wall (virulence β-haemolytic) • Serogrouping, termed Lancefield grouping • 20 Lancefield groups are recognized (A–H and K–V) • groups A-C include human pathogens • group D includes Enterococci Antigenic structure of S. pyogenes 1. hyaluronic acid capsule; 2. Cell wall: 2A peptidoglycan, 2B group-specific carbohydrate, and 2C protein lipoteichoic acid fimbria; 3. Cytoplasmic membrane; 4. Cytoplasm; 5. Pili covered with lipoteichoic acid 10 Streptococci Classification • GROUP A S. pyogenes causes a number of infections: tonsillitis and pharyngitis, scarlet fever, otitis media, impetigo (β-haemolysis) • GROUP B S. agalactiae: neonatal meningitis and sepsis • GROUP D. Enterococcus faecalis • OTHER S. pneumoniae: pneumonia and meningitis in adults, otitis media and sinusitis in children 11 Oral Streptococci Groups Oral streptococci present different types of haemolysis • Live principally in the oropharynx (MICROBIOTA) • Mixed group of organisms with variable characteristics • Typing and molecular techniques revealed complex nature of this group • Nomenclature is in a constant state of flux • Typically show α-haemolysis on blood agar (not constant) • Divided into four main species groups. 12 Oral Streptococci Groups 13 Oral Streptococci Habitat and transmission • Large proportion of the resident oral flora microbiota • Subsequent to tooth eruption • Also predentate children • Transmitted via vertical transmission from mother to child 14 Oral Streptococci Cardiovascular disease • Pathogenesis of certain cardiovascular diseases • Most prevalent in extirpated heart valves and atheromatous plaques incidence of 68.6% and 74.1%, respectively • Entry into the blood stream during intraoral surgical procedures sometimes even during tooth-brushing 15 Oral Streptococci Streptococcus mutans • Notoriety in the 1960s • Caries experimentally induced transmitted by oral inoculation • "mutans" results from its frequent transition from coccal phase to coccobacillary phase • Seven distinct species and serotypes (a–h) are recognized • Limited to human isolates belonging to three serotypes (c, e and f) and eight 16 Oral Streptococci Metabolism of sucrose Streptococcus mutans Sucrose to lactic acid by glucansucrase Acidic environment causes vulnerability of enamel Sticky, extracellular, dextran-based polysaccharide to cohere (biofilm) Dextransucrase: Gelatinous colonies of mutans streptococci mainly comprising extracellular polysaccharides. n sucrose ⇒ (glucose)n + n fructose Other sugars to lactic acid 17 Enterococcus Generalities Normal constituents of microbiota. Main species: E. faecalis (most virulent). Form pulpal infection, associated with endodontic treatment failure E. faecium 19 Staphylococci Pathogeneicity Staphylococcus epidermidis -Skin surface and spreads by contact -Catheter related tract sepsis, artificial joints and urinary S. saprophyticus -urinary tract infections in women -sexual transmission colonize the periurethral skin and the mucosa -mannitol fermentation reaction 20 Staphylococcus aureus Typing hemolysin 21 Staphylococcus aureus Pathogenicity 22 Staphylococcus aureus Pathogenicity Staphylococcus aureus coagulates dilute human serum or rabbit plasma (i.e. it is coagulase-positive), whereas Staphylococcus epidermidis does not (coagulase-negative). 23 Staphylococcus aureus Multiresistance • Resistance to β-lactam drugs • Resistance to methicillin independent of β-lactamase • Resistance to vancomycin (alterations in the cell wall ’tolerance’)(MRSA) • Nosocomial infections • Active against Staphylococcus aureus include: • Penicillin for sensitive isolates flucloxacillin (stable against β-lactamase) Erythromycin Fusidic acid (useful for skin infections) Cephalosporins 24 https://www.youtube.com/watch?v=dRNYWX4v0VE 25 Micrococcus Generalities • • Catalase-positive similar to staphylococci Coagulase-negative • white colonies on blood agar (sometimes pink, orange or yellow) • Stomatococcus mucilagenosus • Is found in abundance on the lingual surface • Extracellular slime • Role in disease, if any, is unknown 26 Gemella Generalities: Habitat: Diseases: Species: Diplococcus, growth in high partial pressure of CO2 Oral mucosa, Dental plaque Endocarditis, Gingivitis, Periodontitis Gemella haemolysans, Gemella morbillorum 27 Parvimonas, Peptococcus and Peptostreptococcus Generalities: Habitat: Diseases: cocci-bacilli and cocci, strict anaerobe Oral mucosa, Digestive, Urinary, Skin Gingivitis, Periodontitis, 28 Atopobium Generalities: Habitat: Diseases: Species: Recently discovered genus, cocci in chains, facultative anaerobe Oral mucosa, Vagina Gingivitis, Periodontitis, A. parvulum, A. rimae (periodontitis) A. parvulum (vaginitis) 29 Key facts • Streptococci are Gram-positive bacteria and appear as spherical or oval cocci in chains and pairs. • Streptococci can be classified according to (1) the degree of haemolysis on blood agar (α, mild; β, complete; γ no haemolysis) and (2) the cell wall carbohydrate antigens into Lancefield groups . • Lancefield group A contains the important human pathogen Streptococcus pyogenes; the latter infection leads to rheumatic fever and rheumatic carditis, which makes the endocardium susceptible to future episodes of infection. • Oral streptococci are a mixed group of organisms and typically show αhaemolysis on blood agar. • Oral streptococci can be divided into four main ‘species groups’ and, of these, the mutans group bacteria are the major agents of dental caries. • Staphylococci resemble streptococci in appearance but are arranged in grape-like clusters and are all catalase-positive (all streptococci are catalasenegative). 30 Key facts • Staphylococcus aureus is a common pathogen causing localized skin and serious systemic infections; it produces numerous toxins and enzymes as virulence factors. • Antibiotic resistance in staphylococci, a problem of worldwide concern, has led to the emergence of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus (VRSA). 31 Summary 32 Questions 1. Select the correct answer. Which of the following options are catalase-negative Gram-positive spherical or oval cocci, that grow well on blood agar, and are lactic acid bacteria. A) Staphylococci B) Streptococci C) Lactobacilli D) None of them 33 Questions 1. Select the correct answer. Which of the following options are catalase-negative Gram-positive spherical or oval cocci, that grow well on blood agar, and are lactic acid bacteria. A) Staphylococci B) Streptococci C) Lactobacilli D) None of them 34 Questions 1. Staphylococcus aureus is: A) Catalase negative B) Coagulase negative C) Coagulase positive D) None of them 35 Questions 1. Staphylococcus aureus is: A) Catalase negative B) Coagulase negative C) Coagulase positive D) None of them 36 Questions The microorganism that causes tonsillitis and pharyngitis, scarlet fever, otitis media, and impetigo is: A) Streptococcus mutans B) Streptococcus pyogenes C) Streptococus piogenes D) S. agalactiae 37 Questions The microorganism that causes tonsillitis and pharyngitis, scarlet fever, otitis media, and impetigo is: A) Streptococcus mutans B) Streptococcus pyogenes C) Streptococus piogenes D) S. agalactiae 38 BIBLIOGRAPHIC REFERENCES Kumar , S. (2016). Essentials of Microbiology. Jaypee Brothers Medical Publishers (P) Ltd. Samaranayake, L. (2012)Essential Microbiology for dentistry .Fourth Edition. Elsevier Ltd. 39 Ana Isabel García Guillén [email protected] UCAM Universidad Católica de Murcia © © UCAM UCAM