1 Streptococci (Gram positive cocci) Lecture 37 Streptococci (Gram positive cocci) Lecture 37 Faculty: Dr. Alvin Fox

2 Key Words Lancefield groups Hemolysis (alpha, beta, gamma) Group A streptococcus (S. pyogenes) - Bacitracin susceptibility test - M, T, R proteins - Streptolysins O and S - F protein/lipoteichoic acid - Rheumatic fever/carditis/arthritis - Glomerulonephritis - Scarlet fever - Toxic shock-like syndrome - Bacteremia - Flesh-eating bacteria - Pyrogenic toxin - Erythrogenic toxin Group B streptococcus (S.agalactiae) - Neonatal septicemia/meningitis - CAMP test - Hippurate hydrolysis test Group D streptococcus - Urinary tract infection - Endocarditis - Bile-esculin test - Enterococci - Non-enterococci Large colony Minute colony Viridans streptococci Dental caries/endocarditis

3 Streptococci – facultative anaerobe – Gram-positive – usually chains (sometimes pairs) – catalase negative (staphylococci are catalase positive) (staphylococci are catalase positive)

4 Streptococcus in chains (Gram stain)

5 Streptococcus pneumoniae (diplococcus). Fluorescent stain

6 Identification : Lancefield groups - carbohydrate antigens

7 streptococci groupable streptococci A, B and DA, B and D –frequent C, G, FC, G, F –less frequent

8 Non-groupable S. pneumoniaeS. pneumoniae –pneumonia viridans streptococciviridans streptococci –e.g. S. mutans *dental caries

9 hemolysis reaction - sheep blood agar (alpha)α (alpha) –partial hemolysis –green color (beta)β (beta) –complete clearing (gamma)γ (gamma) - no lysis White colonies

10 Hemolysis Groups A an BGroups A an B –β Group DGroup D – or – α or γ S. pneumoniae and viridansS. pneumoniae and viridans –α

11 Identification: hemolysis reaction + one biochemical characteristic

12 Group A streptococcus (S. pyogenes)

13 Group A streptococcal infections affect all ages peak incidence at 5-15 years of age

14. pyogenes -suppurative S. pyogenes -suppurative non-invasivenon-invasive –pharyngitis –skin infection, impetigo invasive bacteremiainvasive bacteremia –toxic shock-like syndrome –"flesh eating" bacteria –pyrogenic toxin

15 Pyrogenic toxin SuperantigenSuperantigen Non-specific activation of T cellsNon-specific activation of T cells −Cross-link antigen presenting cells (MHC) and T cell receptor −Cytokine production

16 Scarlet fever rash rash “erythrogenic toxin” “erythrogenic toxin”

17 non-suppurative rheumatic fever –inflammatory disease –life threatening –chronic sequalae feverfever heartheart joints joints rheumatic NOT rheumatoid arthritisrheumatic NOT rheumatoid arthritis

18 Rheumatic fever -etiology M proteinM protein –cross-reacts heart myosin –autoimmunity Cell wall antigensCell wall antigens – poorly digested in vivo –persist indefinitely

19 Rheumatic fever penicillinpenicillin -terminates pharyngitis -decreases carditis

20 Acute glomerulonephritis immune complex disease of kidney immune complex disease of kidney

21 Major pathogenesis factors lipoteichoic acid/F proteinlipoteichoic acid/F protein –fimbriae –binds to epithelial cells M proteinM protein –anti-phagocytic

22 S. pyogenes fibronectin lipoteichoic acid F-protein epithelial cells

23 M protein fibrinogen rr r peptidoglycan rr r IgG Complement IMMUNE NON-IMMUNE

24 M protein major targetmajor target –natural immunity strain variationstrain variation –antigenicity re-infectionre-infection –occurs with different strain

25 Capsules Anti-phagocyticAnti-phagocytic –mucoid strains

26 Isolation and identification hemolytic colonies β hemolytic colonies – bacitracin inhibits growth hemolytic colonies β hemolytic colonies – group A antigen

27 hemolysis β hemolysis Hemolysin/streptolysin OHemolysin/streptolysin O –sensitive oxygen Hemolysin/streplysin SHemolysin/streplysin S –insensitive oxygen

28 Modern Rapid “Strep” Test Throat swab extract (+/- streptococcal antigen) Antibody Liposome + - Streptococcal antigen

29 Post-infectious diagnosis (serology) antibodies to streptolysin Oantibodies to streptolysin O important if delayed clinical sequelae occur important if delayed clinical sequelae occur

30 Traditional serotyping of proteins: - M - T - R Typing Current: - Sequencing of M protein gene

31 Group B streptococcus neonatal meningitisneonatal meningitis septicemiasepticemia transmissiontransmission – vaginal flora

32 Group B streptococcus - identification hemolysis β hemolysis hippurate hydrolysishippurate hydrolysis CAMP reactionCAMP reaction –increases hemolysis of S. aureus –increases β hemolysis of S. aureus

33 Group D streptococcus Growth on bile esculin agarGrowth on bile esculin agar –black precipitate 6.5% saline6.5% saline grow grow – enterococci no growthno growth – non-enterococci

34 Enterococci distantly related to other streptococcidistantly related to other streptococci genus Enterococcusgenus Enterococcus gut floragut flora –urinary tract infection fecal contaminationfecal contamination –opportunistic infections particularly endocarditisparticularly endocarditis most common E. (S.) faecalismost common E. (S.) faecalis

35 Enterococci resistant to many antibioticsresistant to many antibiotics –including vancomycin terminal D-ala replaced by D-lactateterminal D-ala replaced by D-lactate

36 Minute colony streptococci Various groups/hemolysis (e.g. group A) – genetically distinct from large colony (e.g. S. pyogenes) from large colony (e.g. S. pyogenes) – no rheumatic fever Large colony Minute colony

37 Viridans streptococci diverse speciesdiverse species oraloral dental cariesdental caries hemolytic and negative for other tests α hemolytic and negative for other tests non-groupable.non-groupable. includes S. mutansincludes S. mutans –occassional endocarditis after tooth extraction