Microbiology 6th October 2016 Gram-Positive Cocci - Streptococci Discovery of Streptococci and Streptococcus pyogenes Hippocrates: 5th century BC - describes 'scarlet fever' as 'flesh-eating'. Theodor Billroth: 1874 - Erysipelas (wound infection); noticed inflammation in tissue. He designated 'strepto' chain like and 'coccus' round. Louis Pasteur: 1884 - Puerperal sepsis (childbed fever). He was the first to recover and grow Streptococcus pyogenes - septic shock after giving birth as clinicians where giving the women streptococcus. Anton Rosenbach: 1884 - Streptococcus pyogenes: caused pyrogenic inflammation in patients. Also gave Staphylococcus aureus and Staphylococcus epidermids. Streptococci Classification Kingdom: Bacteria Family: Streptococcaceae (streptos = twisted chains) Gram-positive cocci: 0.5-0.1um in diameter Facultative anaerobes - can grow with or without oxygen Some are capnophilic - only grow with enhanced CO2 (capnophilic growth). Grow at 18-40?, where 37? is optimum Catalase negative - don't break down hydrogen peroxide, as they don't have peroxidases. Nutritional requirments: - Blood or serum enriched media - Carbohydrate fermentation, producing lactic acid Approximately 40 species, where many cause disease: - Oral (viridans) streptococci (grow green colonies on agar): S. salivarius - causes dental caries, as they grow a biofilm on the tooth and break down the enamel (if we don't brush teeth). - S. pneumoniae - causes pneumonia - S. agalactiae - Neonatal meningitis - S. pyogenes - severe human disease e.g. tonsillitis, necrotizing fasciitis, scarlet fever Classification is based on serologic properties, haemolytic patterns, and biochemical properties. Serological properties are based on surface antigens, which was founded by Rebecca Lancefield, who developed the serologic classification scheme in 1933. The CHO surface antigens can be extracted. It classifies streps into groups (A to W) based on surface antigen. Streptococcus Haemolytic patterns (J.H. Brown, 1919): a-hemolytic B-hemolytic y-hemolytic clear. green, partial hemolysis no hemolysis complete hemolysis S prouroasice Niridens' Enterococcus apocies HD, production: sindlione hoemoglobin te grses mehemoglobin Simptolyan O and S
Microbiology - Complete (beta) haemolysis - Incomplete (alpha) haemolysis No (gamma) haemolysis Biochemical properties are based on fermentation of sugars. 6th October 2016 Streptococci are divided into two groups: 1. Beta-haemolytic streptococci, which are then classified by Lancefield grouping. 2. Alpha and gamma-haemolytic streptococci, which are then classified through biochemical tests. A B D F gop120 STREP VP HIP ESC PYRA &GAL AGUR ØGAL PAL LAP ADH Classification (A) - haemolytic properties Classification (B) - Surface Antigens Rebecca Lancefield - Group antigen: - M-proteins - Group A antigen binds to NAG in cell wall causing agglutination C Tests are done to see what m-protein the strep has. G Surface antigens are carbohydrate antigens surrounding the cell wall. Topl20 STREP RIB ARA MAN SOR LAC TRE NU RAF AMD GLYG VP HIP ESC PYRA &GAL AGUR AGAL PAL LAP ADH REB ARA MAN SOR LAC TRE INU BAF AMD OLYO Protein M antigen (1,2,3,4,5,6 etc) 0 Polysaccharide group antigen (A,B,C etc) serological assay to determine surface antigens Eg. Streptococcus group A Further typing Streptococcus group A, M12 Gp A antigen: NAG·rhamnose Full identification of Streptococci Analytical Profile Index (API) API uses