9 - The Staphylococci Staphylococci Morphology &...

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Unformatted text preview: The Staphylococci Staphylococci Morphology & Identification (-) (+) Gram positive Facultative anaerobes Grape like-clusters Catalase positive Major components of Major normal flora skin nose Catalase test ((((((( Staphylococcus aureus Antigenic Structure Pathogenesis • • • • • • • • Fc receptor immunoglobulin PHAGOCYTE PHAGOCYTE Protein A BACTERIUM Catalase Coagulase Hyaluronidase and Lipase ipase Hemolysin or sphingomyelinase C sphingomyelinase Leukocidin Exfoliative Toxin Toxic Shock Syndrome Toxin (superantigen) Enterotoxins Pathogenesis of staphylococcal infections Stye: ((( Stye: Carbuncle: ( Impetigo (((( Suppurative • Skin Skin Furuncle; Protein A, Leukocidin, Hemolysin Furuncle; Stye; lipase Stye; Impetigo; contagious Impetigo; Epidermal necrolysis Epidermal Exfoliative Dermatitis (6,7,8); Exfoliative toxin Exfoliative Mastitis Mastitis Abscess (deep tissue); granulation; coagulase, hyaluronidase (burn, Abscess wound) • Systemic Systemic Bactermia (from abscess, wound, burn) , Osteomyelitis (tibia) ,Pneumonia Pneumonia • Food poisoning • • • • not a human infection food contaminated from humans food – growth – enterotoxin enterotoxin onset and recovery both occur within few hours Vomiting/ nausea/ diarrhea/ abdominal /pain nausea diarrhea • Toxic shock syndrome • babies – scalded skin syndrome * Exfoliatin • • • • • • fever scarlatiniform rash desquamation vomiting diarrhea myalgias Infections associated with indwelling devices Infections Laboratory • • • 1. 2. 3. • • A. Direct examination; Gram Stain B. Primary media; BAP C. Differential Tests. Mannitol Salts Coagulase DNase D. Phage typing E. Antibiotic Sensitivity (plasmid, B lactamase) : penicillin /methicillin/vancomycin API STAPH Kit Summary Figure (Identification Scheme) Note: S trep. viridans are alpha hemolytic and negative for all the tests below GRAM POSITIVE COCCI Catalase + Staphylococcus (Clusters) - (pairs & chains) Streptococcus Coagulase + S. aureus hemolytic mannitol yellow - Hemolysis • S. epidermidis nonhem olytic (usua lly) mannitol (2) white • BETA: B acitracin + S .pyogenes (group A) CAMP/Hippurate + S. agalactiae (group B) ALPHA: Optochin /Bile Solubility GAMMA: Bile Es culin + S. p neumoniae + 6.5% NaCl + Group D* Enterococcus Bile Esc ulin + 6.5% NaCl - Group D* N on-Enterococcus (*can also be beta or alpha hemolytic) Staphylococcus epidermidis Staphylococcus • • • • major component skin flora opportunistic infections – less common than S.aureus S.aureus nosocomial infections nosocomial – heart valves heart Identification – Non-hemolytic (sheep blood agar) – Does not ferment mannitol – Non-pigmented Non-pigmented – Coagulase-negative Staphylococcus saprophyticus • urinary tract infections urinary • coagulase-negative – not differentiated from S. epidermidis S. The Streptococcus Streptococcus Morphology & Identification • • • • facultative anaerobe Gram-positive Chains or pairs or Catalase negative negative (staphylococci are catalase positive) (staphylococci Cell surface structure of S pyogenes and extracellular substances •Lancefield groups *one or more species per group *surface antigens: M, T, R groupable streptococci streptococci •A, B and D –most important •C, G, F C, –Rare Non-groupable •S. pneumoniae –pneumonia pneumonia •viridans streptococci –e.g. S. mutans *dental dental caries caries Lipoteichoic Acid and F-protein Lipoteichoic lipoteichoic acid F-protein fibronectin fibronectin epithelial cells M protein protein • major target major – natural immunity • strain variation – antigenicity • re-infection – occurs with different strain M protein IMMUNE IMMUNE Complement Complement IgG r r M protein protein r NON-IMMUNE peptidoglycan fibrinogen r r r Toxins & Enzymes Hemolysis alpha beta gamma Classofication of Streptococci of Particular Medical Interest Pathogenesis of S pyogenes infections. S. pyogenes (Group A) -suppurative pyogenes Group -suppurative • affect all ages peak incidence at affect 5-15 years of age • non-invasive non-invasive – pharyngitis pharyngitis – skin infection, impetigo • invasive bacteremia invasive – toxic shock-like syndrome toxic – "flesh eating" bacteria – pyrogenic toxin • • • Rheumatic fever -etiology Scarlet fever Scarlet M protein protein rash rash – cross-reacts heart myosin cross-reacts – autoimmunity erythrogenic toxin cell wall antigens cell rheumatic fever rheumatic – poorly digested in vivo in inflammatory disease – persist indefinitely life threatening Post-infectious diagnosis (serology) chronic sequalae • antibodies to streptolysin O antibodies fever fever • important if delayed clinical sequelae Heart occur occur Joints rheumatic NOT rheumatoid arthritis • superantigen • T cell mitogen Acute glomerulonephritis Acute • activates immune activates immune complex disease of kidney immune system system Group B streptococcus identification identification • • • neonatal meningitis septicemia transmission transmission – vaginal flora vaginal hemolysis hemolysis • hippurate hydrolysis • CAMP reaction – increases hemolysis of S. aureus increases S. Group D streptococcus Group • Growth on bile esculin agar – black precipitate black • • 6.5% saline grow grow – enterococci enterococci • no growth no – non-enterococci non-enterococci Enterococci Enterococci • • • distantly related to other streptococci genus Enterococcus genus Enterococcus gut flora – urinary tract infection urinary • fecal contamination – opportunistic infections • particularly endocarditis • most common E. (S.) faecalis most E. • resistant to many antibiotics resistant – including vancomycin • terminal D-ala replaced by D-lactate terminal Viridans streptococci Viridans • • • • • diverse species diverse oral oral dental caries hemolytic and negative for other tests non-groupable. includes S. mutans includes S. – endocarditis endocarditis – tooth extraction Streptococcus pneumoniae S. pneumoniae - diplococci • capsule: capsule: • pneumolysin: pneumolysin: • Surface protein Surface adhesinand secretory IgA protease. • Teichoic acid and the Teichoic Peptidoglycan fragment, phosphorylchorine . phosphorylchorine • leading cause pneumonia – particularly young and old – after damage to upper after respiratory tract respiratory *e.g. following viral infection • bacteremia • meningitis • middle ear infections (otitis media) Summary Figure (Identification Scheme) Note: S trep. viridans are alpha hemolytic and negative for all the tests below GRAM POSITIVE COCCI Catalase + Staphylococcus (Clusters) - (pairs & chains) Streptococcus Coagulase + S. aureus hemolytic mannitol yellow - Hemolysis • S. epidermidis nonhem olytic (usua lly) mannitol (2) white • BETA: B acitracin + S .pyogenes (group A) CAMP/Hippurate + S. agalactiae (group B) ALPHA: Optochin /Bile Solubility GAMMA: Bile Es culin + S. p neumoniae + 6.5% NaCl + Group D* Enterococcus Bile Esc ulin + 6.5% NaCl - Group D* N on-Enterococcus (*can also be beta or alpha hemolytic) Bile solubility test Streptex antiserum optochin sensitive Not optochin sensitive Quellung reaction • • • using antisera using capsule "fixed" capsule visible microscopically Latex agglutination - streptococci Prevention and Treatment Prevention • Immunity ; 14 capsule types mixed vaccine vaccine • Most strains susceptible to ost penicillin , but resistance is common common Neisseria Neisseria • Gram negative • diplococci (pairs of cocci) cocci) • oxidase positive oxidase • Culture: 5-10% CO2 • Thayer Martin. – selective – chocolate agar chocolate * heated blood heated N. meningitidis N. gonorrhoeae Virulence Factors Similar, but – Differences in utilization LPS LPS Capsule IgA protease Hemolysin IgA protease PILI Opacity (OPA) proteins Outer Membrane Proteins PILI Opacity (OPA) proteins Outer Membrane Proteins X NO capsule NO hemolysin Neisseria gonorrhoeae • After 2-14 days After •Found only in man • Gonorrhea: second most common venereal disease disease Gram stain of pure culture Urethral exudate Using the Gram stain in patient specimens, the organisms are most often observed in polymorphonuclear leukocytes Neisseria gonorrhoeae Pili = key in anchorage of organisms to mucosal epithelium. Nonpiliated gonococci are avirulent OUTER MEMBRANE PROTEINS Porin proteins (Por) = prevent phagolysosome fusion & allow intracellular survival [ also called protein I] Opacity proteins (Opa) = binding of organisms to epithelium [also called protein II] Reduction-modifiable proteins (Rmp) = protection against bactericidal antibodies [ also called protein III] Urethritis Bartholin’s Duct Purulent conjunctivitis/Ophthalmia neonatorum Infection in newborns during vaginal delivery Disseminated gonococcal infection (DGI). Fever, polyarthritis (or monoarticular septic arthritis), and/or dermatitis (pustules on a hemorrhagic base). Smear Smear • polymorphonuclear cell • Gram negative cocci many in cells many • Culture Antibiotic therapy • lactamase-resistant cephalosporin lactamase-resistant – e.g. ceftriaxone e.g. • resistant strains – common – produce lactamases – destroy penicillin destroy N. meningitidis N. (the "meningococcus") Neisseria Neisseria meningitidis meningitidis • resides in man only resides in • usually sporadic cases – mostly young children children • outbreaks – adults – crowded conditions * e.g. army e.g. barracks barracks Upper respiratory tract infection tract – adhesion pili Meningococcal Meningococcal meninigitis meninigitis • 1-4 days • Second most common econd meningitis – pneumococcus, most common • Fatal if untreated atal • Responds well to esponds antibiotic therapy antibiotic – penicillin Bloodstream Bloodstream Brain Prevention Prevention Diagnosis Diagnosis • spinal fluid spinal – Gram negative diplococci within polymorphonuclear cells polymorphonuclear – meningococcal antigens • Culture Culture – Thayer Martin agar Thayer • capsule – inhibit phagocytosis inhibit • anti-capsular antibodies anti-capsular – stop infection stop • antigenic variation – serogroups serogroups • vaccine – multiple serogroups multiple ...
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