Streptococcus (gram positive coccus)

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1 #13 made by : aseel al-waked corrected by Shatha Khtoum date : 6/11/2016

2 Streptococcus (gram positive coccus) Slide 2 (56:00): Streptococci Facultative anaerobe Gram-positive usually chains (sometimes pairs) Catalase negative Non-motile Hemolysins Lancefield Groups (C-carbohydrate in cell wall) 18 antigens It causes dangerous diseases. Usually in chains (sometimes in pairs) like in St.pneumoniae ( pneumoniae coccus ). Why we need to make catalase? To differentiate between staphylococcus and streptococcus. Slide 3(57:12): The streptococci are gram-positive spherical bacteria that characteristically form pairs or chains during growth. some are members of the normal human microbiota; others are associated with important human diseases. No one system suffices to classify them. CLASSIFICATION A. Hemolysis Many streptococci are able to hemolyzed RBCs in vitro in varying degrees. Complete disruption of erythrocytes with clearing of the blood around the bacterial growth is called β - hemolysis. Incomplete lysis of erythrocytes with reduction of hemoglobin and the formation of green pigment is called α - hemolysis. Other streptococci are nonhemolytic (sometimes called γ- hemolysis). There are no one single system use to classify streptococcus not like staphylococcus which we can differentiate between pathogenic and non-pathogenic by coagulase. why there are no one single system used to classify streptococcus? Because there is variation of antigen (contain more than one) so it will depend on more than one system. Classification: 1-Hemolysis activity: Alpha partial hemolysis. Beta complete hemolysis.

3 Gamma no hemolysis. Most important and which are more pathogenic to human is beta hemolysis. That doesn t mean alpha and gamma are non-pathogenic, there are dangerous injuries of alpha (i.e. pneumonia). Complete hemolysis mean around bacteria there are clearing regions (don t contain blood) There are groups involved within group beta, we classify it depending on (c carbohydrate sugar on cell wall). Slide 4(59:18): b. Group-Specific Substance (Lancefield Classification) This carbohydrate is contained in the cell wall of many Streptococci and forms the basis of serologic grouping into lancefield groups: a h and k u. The system created by Rebecca Lancefield, she diagnosed streptococcus types in cell wall and noticed that there 18 types different from each other, also serologic by serum (antigen and antibody reaction) # a-g for human, others for animal. Steps of determining Lancefield serogroup: After we notice that the sample is beta hemolytic, we take a drop of anti a put it on the sample and mix it, if it becomes agglutinated then it is Lancefield serotype a but if it doesn t agglutinate we put anti B and so on. Beta hemolytic group a streptococcus is long so we call it streptococcus pyogenes (the scientific name). Note: we take the first letter of genus and follow it with species but if there are more than one genus starting with the same letter we take the first 2 letters (i.e. streptococcus pyogenes St.pyogenes to distinguish it from staphylococcus S. c. Capsular Polysaccharides The antigenic specificity of the capsular polysaccharides is used to classify Streptococcus pneumonia into more than 90 types. # a-g for human, others for animal. Steps of determining Lancefield serogroup: -groups with beta-hemolytic have strains we classify it by capsular polysaccharide We use capsular polysaccharide to classify (St.pneumoniae and St. agalactiae ) There are 90 types of St.pneumoniae, the most important one is B. (vaccine is made of B capsule) Strains (types) of capsular polysaccharide also have strains and we classify them by M protein. Streptococcus infections are recurrent infections (especially tonsillitis) If someone was injured from group a, would it give immunity from this type? No, because he might get injured from another strain of group a. Slide 5(1:05:39):

4 #Note: A, B, D and the last 3 one A it causes tonsillitis. B milk loving bacteria. The first isolation from breast of animals and it cause mastitis to animal. B: it is present as normal flora in the vagina, in some female that carry St. agalactiae and during delivery if the uterus is cut or damaged the uterus will cause its insinuation inside the uterus. حمى النفاس Puerperal fever: affect women after delivery if she carries St. agalactiae D Gama-hemolysis, it is divided into 3 groups: 1-enterococcus (E.faecalis): secreted from feces and it s responsible for UTI. 2-nonenterococcus (S bovis): use NaCl growth test for it. -viridans alpha-hemolytic. -anaerobic gamma hemolysis, cause dental caries and endocarditis. some female has anaerobic normal flora in their vagina. -S.pneumonia alpha-hemolytic,it s infection always in the lower respiratory tract. Slide 6(1:11:43): Strep Virulence Factors

5 -capsule mainly hyaluronic acid but it can have other components. -LTa linked with lipid. - group carbohydrate (c carbohydrate). if it doesn t classify on M protein it may be classified on a, r, t protein. Extracellular substance: 1-streptolysin: very important we have 2 types O, S. 2-N ADase: dissolve DNA. 3-streptokinase: like staphylokinase dissolve fibrin. 4-streptodornase: dissolve nucleic acid. 5-M protein: part of fimbria, it s an antigen and very important to bacteria because it work like capsule. Slide 7(1:13:53): M- PROTEIN - major target (hair like projection) - strain variation (antigenicity) - re-infection occurs with different strain (150, types of M protein, a person can have repeated infections with S pyogenes of different M types). lipoteichoic acid (attachment of streptococci to epithelial cells). Capsule (Anti-phagocytic) (mucoid strains) There is difference in antigenicity of bacteria. Slide 8(1:14:51):

6 1-scarlet fever (rash): rash and fever as a result of toxin. 2-strep TSS: toxins different but it has the same symptoms. 3-necrotizing fasciitis (flesh eating bacteria). 4-immune mediated: recurrent infection (i.e: tonsillitis, vaginitis) Rheumatic fever not rheumatology (autoimmune disease), also the examination in the lab is different. Rheumatic fever (ASO test) rheumatology (RF test). Slide 9(1:16:34): O: most important one. Antistreptolysin mean antistreptolysin antibody. When it occur infection in streptococcus, streptococcus produce St.O or St.S. Virulence factors of S. pyogene Streptolysin( O & S), Antistreptolysin O (ASO). ASO serum titer in excess of units is considered abnormally. ASO : use to diagnose streptococcus. Titar :concentration of antibodies, if its more than 160 considers as clinical sign of toxin ( reached high stage ) and therefore we give the patient the treatment. (S = O2 stable; O = O2 labile S= O2 is stable, when we culture it, on the surface it make hemolysis so it is present normally on the surface. O=O2 is labile also it makes hemolysis but inside the agar because it is sensitive to O2 (sensitive means tolerant O2 but in small amount) St.O is toxin. Streptokinase (Break down clots) DNase (depolymerize) Hyaluronidase Proteases C5a peptidase (Decrease chemotaxis C5a: C one of complement system, complement systems are 9 Complement factors: one activate the other. Bacteria produce C5a peptidase that dissolve C5a so decrease chemotactic factors Toxins (Exotoxins) Pyrogenic toxin (Erythrogenic toxin A, B, C), responsible for Streptococcal Toxic Shock Syndrome and Scarlet Fever (superantigens) Increase immune cytokines Promote fever Pyrogenic: fever forming. Pyogenic: pus forming. Erythrogenic: rash appear on the skin in the color of scarlet or red. Superantigen: stimulate all the T lymphocyte to produce non-specific. Slid 10 (1:22):

7 Streptococcal infections Streptococcus pyogenes (group A streptococcus) A. Diseases attributable to invasion by S. pyogenes (β-hemolytic group A- Streptococci) Puerperal Fever, Cellulitis, Erysipelas, Bacteremia or sepsis, Necrotizing fasciitis (Streptococcal Gangrene, flesh eating bacteria). We said that St.agalactiae is normal flora, some female carry St.A. St.A and St.B both cause puerperal fever, but the main cause of puerperal fever is St.B After delivery damage or cut to tissue of uterus. B. Diseases attributable to local infection with S. pyogenes and their byproducts Streptococcal Sore throat, Streptococcal infection of superficial layers of skin( Impetigo), C. Invasive Toxigenic group a Streptococcal infections, Streptococcal toxic shock syndrome, and Scarlet fever D. Poststreptococcal diseases (Rheumatic fever, Glomerulonephritis- SpeB) Slid 11 Slid 12 Streptococcus pyogenes Slid 13(1:25:13):

8 Streptococcus group A -Beta hemolysis -lancefield classified as group A When we put Anti group A serum agglutination occur Bacitracin: Antigen resistance to all groups except group A which is sensitive Diagnosis is by a swab of the affected area, then the organism is cultured on the blood agar with an added bacitracin antibiotic disk to show beta hemolytic for the antibiotic. Because we has an inhibition zone around the bacteria, which means that group A is sensitive. Slide 14(1:27:04): Streptococcus agalactiae (milk loving) Group B Streptococci are part of the normal vaginal flora and lower gastrointestinal tract in 5 30% of women. Infection during the first month of life may present as Fulminant sepsis, Meningitis, or Respiratory distress syndrome. First month of life after delivery St.agalactiae of the mother Important pathogens among pregnant women and their neonates. If Meningitis transfer to the baby, it may cause Meningitis, Respiratory disease or sepsis Slide 15(1:30:54):

9 Sepsis, Meningitis lead to 1. death of neonates 20% % nerve cell (it irreplaceable) it cause abnormality or mental retardation Slid 16 (1:33): CAMP test: to diagnose beta-hemolytic group B Protein agalactia enhance the active of the other hemolysis producing bacteria We use another type of bacteria (sometimes staphylococcus) that exertion hemolysis, cultivate group B to produce CAMP factors, which make with hemolysis synergistic effect Large zone of hemolysis appears like arrow Sorry in advance for any unarranged mistakes