Downloaded 11 times
Uploaded byEhsan Lee
Module 6a cocci
Gram positive cocci include medically important genera such as Staphylococcus, Streptococcus, and Enterococcus. Staphylococcus aureus can cause skin infections, food poisoning, and pneumonia. Streptococcus pyogenes (Group A Strep) is a cause of pharyngitis and Streptococcus agalactiae can cause neonatal meningitis. Viridans streptococci are associated with dental caries and endocarditis.
More Related Content
Module 6a cocci
- 1. Cocci Gram Positive cocci GramNegative cocci Ver 2011-1
- 2. 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
- 3. 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
- 4. • Neisseria gonorrhoeaeis 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
- 5. • As agroup, 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.
- 6. N. meningitidis (associatedwith cerebrospinal meningitis: inflammation of the meningeal layers of the brain promoted by the capsule, released endotoxin, and IgA protease). N.lactimica is a weak nasopharyngeal pathogen that is sometimes mistaken for N.meningitidis , lactose fermenter & usually found in children
- 7. Moraxella catarrhalis • Previouslynamed 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
- 9. 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
- 11. 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
- 12. 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
- 13. Staphylococcus canbe 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
- 14. 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
- 15. 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
- 16. Culture • Grow readilyon 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
- 17. 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
- 18. - some speciealso found in plants & dairy products -classified by Lancefield from Group A to H, K-U based on a group specific carbohydrate known as C substance in the cell envelope and determined by an amino sugar
- 19. Classification of strepis based on • Colony morphology & reaction to blood agar • Serologic specificity of cell wall/antigens • Biochemical reactions & resistance to factors • Ecologic features
- 20. Typing usually donefor 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
- 21. Characteristic of medically significant strep: Disease Name Group Hemolysis S. Pyogenes A Beta Pharyngitis S. Agalactiae B Beta Meningitis S. Dysgalactiae C,G Beta Similar to A E. Faecalis D Alpha UTI. Endocarditis S. Bovis D Gamma Endocardits, colon S. Anginosus F Alpha, beta Brain abscess Viridans group NONE Alpha Dental caries S. Pneumoniae NONE Alpha Pneumonia Peptostreptococcus NONE Alpha Abscesses
- 22. 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
- 23. 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)
- 24. • Staphylococcus epidermidis (artificial valve endocarditis, catheter and shunt infections, prosthetic infections) • Staphylococcus saprophyticus, (urinary tract infection in young sexually active females
- 25. • Streptococcus pyogenes (Lancefield group A) (pharyngitis, scarlet fever, toxic shock syndrome, skin infections, post infectious sequelae - rheumatic fever and glomerulonephritis
- 26. • 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)
- 27. • Streptococcus pneumoniae (pneumonia - community acquired, sinusitis, meningitis, bacteremia, otitis media) • Viridans streptococci – (dental caries - S. mutans, endocarditis, bacteremia)
- 28. Diseases attributable toinvasion by S pyogenes, B-hemolytic Group A Streptococcus • Erypelas • Cellulitis • Necrotizing Fasciitis • Puerperal Fever • Bactermia/Sepsis
- 29. Properties that helpdistinquish between Staphylococcus and Streptococcus/Enterococcus • Catalase activity • Coagulase Activity • Novobiocin • Hemolysis – Alpha (Bile solubility & Optochin), Beta & Gamma • Bacitracin sensitivity– inhibits cell wall synthesis