1 / 32

Streptococci

Streptococci. Gehan J. Panagoda Division of Microbiology. Morphology. Gram +ve, chains, diplo, initially from erysipelas, divisions one plane, mention about Staph, length of chains varies on culture conditions. No relationship between length and virulence.  haemolysis. Strep and pus.

brad
Download Presentation

Streptococci

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. Streptococci Gehan J. Panagoda Division of Microbiology

  2. Morphology • Gram +ve, chains, diplo, initially from erysipelas, divisions one plane, mention about Staph, length of chains varies on culture conditions. No relationship between length and virulence

  3.  haemolysis Strep and pus Cervical lymph adenitis Tonsilitis

  4. Culture • Aerobes, facultatively anerobic, pathgenic Strep require exacting nutrients. Therefore, grow well in BA. 10% CO2 promotes growth and haemolysis.

  5. HaemolysisAlpha, partial with greenish discolouration (unidentified reductant haemoglobin - viridans strep and pneumococcus (NO SUCH THING CALLED STREP. VIRIDANS). Beta, a wide clear zone, beta haemolysins - Streptolysin O and S - S. pyogenes. Gamma - non-haemolytic (commonly used term) - S. faecalis.

  6. Classification • For aerobic and facultative anaerobic • .Haemolytic classification • I have already mentioned about this. Most of the pathogenic Strep causing primary infections fall into beta. Alpha Strep is generally remains as commensals.

  7. .Serological classification - For beta haemolytic Strep • 1. Based on the group specific polysaccharide (c) antigen of the cell wall - Lancefield classification, 20 A-V, No I and J. THE MOST IMPORTANT GROUP IS A - S. pyogenes.

  8. 1.1 Based on the type specific antigen (M, T, R most important is A - Mass Transit Railway) - forS. pyogenes serotyping - Grifith classification - 80 serotypes. M is on the cell, resists phagocytosis, promotes adherence to the host. WITHOUT M IS AVIRULENT.

  9. .Classification based on Schleifer and Kilpper-Balz (1987) -Based on the structure of the cell wall and G + C composition (NOT IMPORTANT FOR YOU).

  10. S. pyogenes • PATHOGENIC FEATURES - 1. M that is the type specific antigen 2. Capsular hyaluronic acid - capsule also in gp C during the logrithmic phase. ANTIBODIES PRODUCED AGAINST THE CAPSULE IS NOT PROTECTICE.

  11. MEANS THE CAPSULE IS A VIRULENT FACTOR, SIMILAR TO THAT OF PNEUMOCOCCUS, INHIBITS PHAGOCYTOSIS

  12. 3. Toxins and enzymes Toxins - Streptolysin S and O - have already mentioned. Streptolysin O acts not only against red cells but also cytotoxic to neutrophils and platelets and cardiac tissue. An ASO titre of 160-200 units - suggests a recent infection. Erythrogenic toxin - the rash of scarlet fever.

  13. Enzymes • Streptokinase - lyse RBC, prevents a fibrin barrier around the leision thus spread • Nicotinamide adenine dinucleotidase (NADase)

  14. Hyaluronidase - acts on hyaluronic acid - antibodies against this is diagnostic. THEREFORE, ASO AND THIS IS IMPORTANT IN DIAGNOSIS OF S. PYOGENES INFECTIONS

  15. .Suppurative infections • Acute infections of the respiratory tract. Sore throat-(acute tosillitis/and or pharyngitis - organisms are at the site - can spread and cause cervical adenitis, otitis media, meningitis. Scarlet fever- a complication of sore throat, rash is due to erythrogenic toxin, organism is not at the site.

  16. Skin infections - Impetigo - among children, discrete infections, highly communicable, common in countries like Sri lanka (Why ? hot and humid). Organism is at the site. Can cause also by Staph. aureusErysipelas mainly among elderly - acutely spreading infection. Some time is associated with sore throat. Organism is present at the site. Believed to be a hypersensitivity reaction.

  17. Erysipelas - Butterfly-wing rash • Followed by upper • respiratory tract infection • On the face or leg • Transferred by fingers

  18. Scarlet fever Caused by an erythrogenuc strain Portal of entry is the throat May followed by infection of wound/burn

  19. Pathogenesis • (Immune mechanism) Ab produced against protein and polysaccharide of orga cross react with myocardial and heart valve tissue Not clear. • Immune response Marked ASO titre  200 Moderate to low • Course Progressive Spontaneous resolution • Penicillin • Prophylaxis Because of repeated attacks, Penicillin • Prophylaxis is Essential Not indicative

  20. .Laboratory diagnosis • .Acute suppurative infections • Smear - Strep and pus; Culture - in a transport medium, on BA 370C ,  haemolysis, overnight, better under anaerobic with 5-10% CO2, ELISA to detect Strep antigens, Serological tests - not useful

  21. .Non-suppurative complication • Culture - useful for the presence of Strep/ serological test to check the level of ASO titre  200 for rheumatic fever, DNAase-B test for acute nephritis

  22. .Other haemolytic Streptococci • Group B -S. agalactiae - bovine mastitis, neonatal septicaemia and meningitis • Group C and G • ENTEROCOCCI - Group D • STREPTOCOCCUS MILLERI (UK term) in USA (S. intermedius) (Group F) alpha, beta of gamma, present in the mouth, throat GI tract, infect internal organs, brain liver,

  23. Suacute bacterial endocarditis • Splinter haemorrhages • Lodging of emboli under finger nails • other than kidneys and brain

More Related