1 / 19

Virulence Factors & Features Important in Disease

Virulence Factors & Features Important in Disease. Surface adherence & colonization. Gram-positive teichoic acids M fimbriae of Streptococcus pyogenes Gram-negative pili IgA proteases: Streptococcus pneumoniae Neisseria spp. Haemophilus influenzae Biofilms

chavez
Download Presentation

Virulence Factors & Features Important in Disease

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Virulence Factors & Features Important in Disease

  2. Surface adherence & colonization • Gram-positive teichoic acids • M fimbriae of Streptococcus pyogenes • Gram-negative pili • IgA proteases: • Streptococcus pneumoniae • Neisseria spp. • Haemophilus influenzae • Biofilms • Staphylococcus epidermidis biofilms adhere to artificial body parts & catheters • Streptococcus mutans biofilms cause dental plaque

  3. Antiphagocytic structures • Capsules • Streptococcus pyogenes ] SOME • Klebsiella pneumoniae & ] KILLERS • K1 strains of Escherichia coli • Haemophilus influenzae ] HAVE • Pseudomonas aeruginosa ] PRETTY • Neisseria meningitidis ] NICE • Cryptococcus neoformans ] CAPSULES • Pili of Neisseria gonorrheae • M protein of Streptococcus pyogenes • A protein of Staphylococcus aureus

  4. Toxins Toxin with ADP-ribosyl transferase activity

  5. Heat stability of bacterial toxins • Heat stable at boiling point of water • Endotoxin • Heat stable at 60oC for 10 mins • S. aureus enterotoxin • Stable toxin (ST) of E. coli • Yersinia enterocolitica toxin • Denatured by moderate heat • All the rest of the bacterial toxins

  6. Toxins that cause membrane damage • Clostridium perfringens • Alpha toxin (lecithinase) • S. aureus • Alpha toxin (pore-forming toxin)

  7. Other virulence factors • Coagulase • Staphylococcus aureus • Yersinia pestis • Urease • Cryptococcus neoformans • Nocardia • Helicobacter pylori • Proteus ] increase urine pH in UTI • Ureaplasma urealyticum] causing kidney stones esp Proteus • Hyaluronidase • Group A streptococci • S. aureus

  8. Identifiers of microorganisms

  9. Stain Reactions Non-Gram staining or poorly seen on Gram stain • No cell wall Mycoplasmas, Ureaplasma • Too small  Chlamydia, Rickettsia • Too thin  spirochetes (Treponema, Borrelia, Leptospira) • Gram-neg stain seen only if counterstain time is increased

  10. Stain Reactions Acid-fast • Mycobacterium • Nocardia (partially) • Legionella micdadei • Cryptosporidium oocysts • Isospora oocysts

  11. Stain Reactions Silver staining • Fungi • Legionella Periodic acid-Schiff • Fungi stain red Calcofluor white • Fungi fluoresce blue-white on black India Ink wet mount • Cryptococcus – colorless cells with halos on black • Misses 50%

  12. Special culture limitations Intracellular pathogens • Obligate intracellular • ALL viruses • Chlamydia • aLL Rickettsias except Bartonella (Rochalimea) • Mycobacterium leprae • Plasmodia • Toxoplasma • Facultative intracellular • Listeria • Mycobacteria • Histoplasma • Brucella

  13. Special culture limitations Non-intracellular pathogens that can’t be cultured routinely • T. pallidum • Pneumocystis

  14. Anaerobes • Actinomyces • Bacteroides • Clostridium Microaerophilic • Campylobacter grows at 42oC • Helicobacter = 37oC Obligate aerobes • Mycobacterium tuberculosis • Pseudomonas • Mycoplasmapneumoniae

  15. Media or Growth Factors • Charcoal yeast extract agar → Legionella • Cholesterol → Mycoplasmas & Ureaplasma • Salt tolerant • Staphylococcus aureus • Enterococcus faecalis • Streptococcus bovis • Vibrio parahaemolyticus • V. vulnificus • X & V factors (hematin & NADH) • H. influenzae

  16. Media or Growth Factors • Chocolate agar • Haemophilus & Neisseria • Thayer Martin • Neisseria • Regan-Lowe • Bordetella pertussis • Lowenstein-Jensen • Mycobacteria

  17. Specific inhibitors • Bacitracin • “A” disk inhibits Streptococcus pyogenes (Grp A) • Optochin • “P” disk inhibits (& bile lyses) Pneumococcus

More Related