1 / 15

A. GRAM'S POSITIVE COCCI

A. GRAM'S POSITIVE COCCI. 2. STREPTOCOCCUS SPP. Microscopic examination. Microscopic examination. Morphological Description Type of stain : gram stain Gram reaction : gm +ve Color : violet Shape : cocci Size : small

hamlin
Télécharger la présentation

A. GRAM'S POSITIVE COCCI

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. A. GRAM'S POSITIVE COCCI 2. STREPTOCOCCUS SPP.

  2. Microscopic examination

  3. Microscopic examination Morphological Description • Type of stain: gram stain • Gram reaction: gm +ve • Color: violet • Shape: cocci • Size: small • Arrangment: chains or pairs

  4. Classification of streptococci *S. pyogenes *S. pneumonia *S. faecalis *Viridans streptococci

  5. Cultivation Culture Media 1. Blood agar 2. Chocolate agar

  6. Blood agar Type: enriched, differential medium Constituents: nutrient agar +5- 10% defibrinated blood Principle: species of strepto- cocci give various types of hemolysis on blood agar Use: * for isolation of pathogenic bacteria * differentiate Strepto- coccusspp. according to their hemolytic activity Chocolate agar Type: enriched Constituents: blood agar heated at 56oC Principle: hemoglobin releases hemin (X-factor), required by fastidious organisms Use: permits growth of fastidious bacteria & to help in the recovery of Streptococcus spp Culture Media

  7. Tests • Blood hemolysis:α, β, γ • Biochemical tests:1.Bile solubility 2. Bacitracin sensitivity 3. Optochin sensitivity • Serological test: Antistreptolysin O test (ASO)

  8. Blood hemolysis

  9. Bile solubility • Medium: Nutrient broth + bile salt. • Principle: Lysis of m.o. sensitive to bile salts as Streptococcus pneumoniae • Use: To differentiate betweenα-haemolytic streptococci S. pneumoniae +ve &S. viridans -ve

  10. Bacitracin sensitivity • Medium: Blood agar • Reagent: 0.04 unit bacitracin disc is applied to the surface of the agar plat • Principle: S. pyogenes (β-hemolytic) is sensitive to bacitracin α & γ hemolytic streptococci are resistant to bacitracin • Use: To differentiate betweenStrept. pyogenes (S) from other α & γ hemolytic streptococci (R) Bacitracin Test+ve

  11. Optochin sensitivity • Medium: Blood agar • Reagent: Optochin (ethyl hydrocuprein HCl) • Principle: Optochin inhibits the growth of some m. o. • Use: To differentiate betweenα-haemolytic streptococciS. pneumoniae +ve &S. viridans -ve -ve S. viridans +ve S. pneumoniae Optochin Sensitivity Test +ve -ve

  12. Antistreptolysin O test (ASO)Serologic Agglutination Test • Medium: Polystyrene latex particles coated with Streptolysin O Antigen • Reagent: Streptolysin O Antigen • Principle: Reagent + Serum → agglutination (+ ve Ag-Ab reaction) • Use: Detection of anti-streptolysin O in patient’s serum is an indication for streptococcal infection.

  13. ASO test +ve -ve

  14. Mixed cultureGram stain and streak for isolation MAcConkey Day 1 Day 2 TSA Gram stain and select a Gram negative colony Oxidase (-) Oxidase (+) Lac negative on MAC Lac positive on MAC Lac negative on MAC Day 3 Urea (+) Green sheen on EMB Dark purple on EMB Glucose fermentation (-) H2S (+)on TSI Citrate (-) Citrate (+) Lipase (+) on tributyrin Day 4 Proteus vulgaris Escherichia coli E. aerogenes Ps. aeruginosa

  15. Mixed cultureGram stain and streak for isolation MSA Day 1 Day 2 TSA Gram stain and select a Gram positive colony Catalase (+) Negative for mannitol on MSA Positive for mannitol on MSA Day 3 Nitrate (+) Nitrate (-) Trehalose(-) Novobiocin sensitive Novobiocin sensitive Novobiocin resistant Day 4 Staphylococcus epidermidis Staphylococcus aureus Staphylococcus saprophyticus

More Related