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Module 6a   cocci
 

Module 6a cocci

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    Module 6a   cocci Module 6a cocci Presentation Transcript

    • CocciGram Positive cocciGram Negative cocci Ver 2011-1
    • Gram Negative cocci:• Neisseriaceae - only • produces “cytochrome aerobic family oxidase” - Oxidase• Genus Neisseria, Test Kingella, Eikenella, • N. gonnorhea Simonsiella & (gonococcus ) - Allysiella venereal disease• diplococci • N. meningitidis• exhibits “twitching” (meningococcus) - type of movement meningitis
    • Antigenic Structure• Pili – fimbriae that enhance cell attachment• Por – protein that occurs in trimers thru which some nutrients enter the cell• Opa – proteins for adhesion of gonococci within colonies and expression of CD66• Rmp (Protein III) – antigenically conserved, associates with Por in formation of pores• LOS – Lipooligosaccharide –responsible for toxicity of gonococcal infections
    • • Neisseria gonorrhoeae is a fastidious organism requiring growth factors which are present in hemolyzed blood cells. Thayer-Martin chocolate agar plates have VCN antibiotics which prevent growth of most organisms while supporting N. gonorrhoeae growth
    • • As a group, the Neisseria species are non- sporulating, non-flagellated, gram negative diplococci (a distinct bean shape arranged in pairs) that may or may not have a capsule and/or pili that facilitate attachment to mucus membranes. They are sensitive to cold, desiccation, light, and acidity; most require complex enriched media (e.g., chocolate agar, or modified Thayer-Martin media) and high O2.
    • N. meningitidis (associated withcerebrospinal meningitis: inflammation ofthe meningeal layers of the brain promotedby the capsule, released endotoxin, and IgAprotease). N.lactimica is a weak nasopharyngealpathogen that is sometimes mistaken forN.meningitidis , lactose fermenter &usually found in children
    • Moraxella catarrhalis• Previously named Branhamella catarrhalis & before that Neisseria catarrhalis.• Found in 40-50% of normal school children• May cause bronchitis, pneumonia, sinusitis, otitis media and conjunctivitis• Concerned as a cause of infection for immunocompromised patients
    • Gram negative cocci :• Veillonellaceae - • found in the only anaerobic gastrointestinal tracts family of animals, but• genus Veillonella, Veillonella are found Acidaminococcus, in considerable Megasphaera numbers within the• forms pairs or short oral cavity chains but smaller • mostly non-pathogenic than Neisseria
    • Gram + cocci - Peptostreptococcus• Gram + coccus of variable size and shape found on the skin and as part of the normal flora of mucous membrane• Formerly called peptococcus• Frequently found in mixed infections due to normal flora• Occassionally, cultures from breast, brain, or pulmonary infections
    • Gram positive cocci :• Micrococcus- – obligate aerobes found in water & soil – pigmented types – morphologically similar to staphylococcus – unlike streptococcus acid is produced thru aerobic oxidation & not fermentation
    • Staphylococcus can be both aerobic & anaerobic found primarily in mammalian skin & anterior nares most important strain : S.aureus, epidermidis & saprophyticus S. aureus secretes enterotoxin which causes food poisoning
    • General Characteristics• Staph. are resistant to drying & high salt concentration (halophilic)• S. aureus also produces coagulase, an enzyme w/c clots plasma & distinguish it from S. epidermidis
    • Morphology & Identification:• Spherical about 1um in diameter arranged in irregular clusters• Can occur singly, pairs, tetrads and chains in liquid culture• Develop rapid resistance to many antimicrobial agents & present difficult therapeutic problems• Contains around 35 species
    • Culture• Grow readily on most medium• Young culture stain strongly gram +, on ageing become gram negative• Non-motile, non-spore forming• Lysed with penicillin• Grows in BAP with resistance to nafcillin• Exhibits “coagglutination” , some strains are encapsulated
    • Streptococcus - appear in chains of varying length - grow in the presence or absence of air - several species are indigenous in animals & man found in skin, oral cavity, respiratory tract
    • - some specie also found in plants & dairyproducts-classified by Lancefield from Group A to H,K-U based on a group specific carbohydrateknown as C substance in the cell envelopeand determined by an amino sugar
    • Classification of strep is based on• Colony morphology & reaction to blood agar• Serologic specificity of cell wall/antigens• Biochemical reactions & resistance to factors• Ecologic features
    • Typing usually done for Groups A, B, C, F & G• Strep A – rhamnose N-acetylglucosamine• Strep B – rhamnose glucosamine polysaccharide• Strep C – rhamnose N-acetylgalactosamine• Strep D – glycerol techoic acid
    • Characteristic of medically significant strep: Disease Name Group HemolysisS. Pyogenes A Beta PharyngitisS. Agalactiae B Beta MeningitisS. Dysgalactiae C,G Beta Similar to AE. Faecalis D Alpha UTI. EndocarditisS. Bovis D Gamma Endocardits, colonS. Anginosus F Alpha, beta Brain abscessViridans group NONE Alpha Dental cariesS. Pneumoniae NONE Alpha PneumoniaPeptostreptococcus NONE Alpha Abscesses
    • Antigenic structure & toxins:• M Protein – major virulence factor of Strep A• T substance – acid labile, heat labile• Nucleoproteins – P substance• Streptokinase – Fibrinolysin• Streptodornase – depolymerizes DNA• Hyaluronidase – splits hyaluronic acid• Pyrogenic Exotoxins – Exotoxins A, B, C• Hemolysins - Streptolysin O & S
    • Medically important gram + cocci• Staphylococcus aureus, (staphylococcal scalded skin syndrome, skin infections - e.g. boils etc., toxic shock syndrome, food poisoning, osteomyelitis, septic arthritis, pneumonia, and endocarditis)
    • • Staphylococcus epidermidis (artificial valve endocarditis, catheter and shunt infections, prosthetic infections)• Staphylococcus saprophyticus, (urinary tract infection in young sexually active females
    • • Streptococcus pyogenes (Lancefield group A) (pharyngitis, scarlet fever, toxic shock syndrome, skin infections, post infectious sequelae - rheumatic fever and glomerulonephritis
    • • Streptococcus agalactiae(meningitis, pneumonia and bacteremia in the newborn)• Group D streptococci including the enterococcus (the enterococci are responsible for nosocomial urinary tract infections, bacteremia)
    • • Streptococcus pneumoniae (pneumonia - community acquired, sinusitis, meningitis, bacteremia, otitis media)• Viridans streptococci – (dental caries - S. mutans, endocarditis, bacteremia)
    • Diseases attributable to invasion by S pyogenes, B-hemolytic Group A Streptococcus• Erypelas• Cellulitis• Necrotizing Fasciitis• Puerperal Fever• Bactermia/Sepsis
    • Properties that help distinquish between Staphylococcus and Streptococcus/Enterococcus• Catalase activity• Coagulase Activity• Novobiocin• Hemolysis – Alpha (Bile solubility & Optochin), Beta & Gamma• Bacitracin sensitivity– inhibits cell wall synthesis