Streptococcus

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Streptococcus

  1. 1. STREPTOCOCCUS Gram+ cocci twisted*/coiled
  2. 3. <ul><li>Arranged in chains or pairs </li></ul><ul><li>Part of nl flora in humans and animals,some human pathogens </li></ul><ul><li>Strept.pyogenes-pyogenic infections-tendency to spread-non suppurative lesions-Rheumatic fever—glomerulonephritis which occurs sequelae to infection </li></ul><ul><li>Billroth-first saw—cocci chains in erysipelas & wound infections,called them streptococci </li></ul><ul><li>Ogston- isolatd,describd pathogenicity,named as streptococcus pyogenes </li></ul>
  3. 4. <ul><li>Classification </li></ul>
  4. 5. <ul><li>Alpha </li></ul><ul><li>Produce greenish discolouration with partial hemolysis around the colonies. </li></ul><ul><li>Zone of lysis is small(1-2cmwide)with definite margins,unlysed rbc’scan b markd out microscopically within this zone-known as Viridians streptococci—viridis=green </li></ul><ul><li>Nl commensals in throat---oppertunistic inf. </li></ul><ul><li>Str.pneumoniae/pneumococcus is also an alpha hemolytic one </li></ul>
  5. 7. <ul><li>Beta-produce sharply defined ,clear colourless zone of hemolysis,2-4cm wide,within which red cells are completely lysed. </li></ul><ul><li>“ hemolytic Streptococci”=beta hemolytic </li></ul><ul><li>Gamma </li></ul><ul><li>Nonhemolytic streptococci-produce no change in medium-so called “indifferent streptococci”---includes faecal(enterococci,strept.faecalis) </li></ul><ul><li>And relatd species-called enterococcus group </li></ul><ul><li>Hemolytic classified on carbohydrate C antigen on the cellwall-Lancefields grp-20-A-V,without I&J </li></ul><ul><li>Grp A-Strpt.pyogenes-into types-based on proteins-M,T,R—Griffith typing </li></ul>
  6. 9. Streptococcus pyogenes <ul><li>Morphology </li></ul><ul><li>Individual cocci are spherical or oval-0.5-1microns d—anerobically grown---smwht small—arrangd in chains—longer in liquids than in solids </li></ul><ul><li>Chains -dividing in one plane—daughter cells failing to separate –often with an appearance of pairing within chain,once classified with length-no relevence(strp.longus and brevis) </li></ul><ul><li>Infact sm non pathogenic frm longest chains—Str.salivarius </li></ul><ul><li>NONMOTILE NONSPORING,sm hav capsules(strp.pyogenes,grpC strains-composed oh hyaluronic acid—while polysacharide capsules in B &D </li></ul><ul><li>Capsules are best seen in young cultures </li></ul>
  7. 10. <ul><li>Cultural characters </li></ul><ul><li>Aerobe &fac.anerobe-growing best at 37C—growth only in media with fermentable sugars,enrichd blood /serum </li></ul><ul><li>Blood agar—incub-24hrs—colonies r small-circula,semitransparent,low convex discswith an area of clear hemolysis around tham.Growth and hemolysis are promoted by10% co2. </li></ul><ul><li>Virulent starins—fresh isolation-matt colony/finely granular </li></ul><ul><li>Avirulent—glossy colonies </li></ul><ul><li>Capsulated—mucoid colonies </li></ul><ul><li>Rarely—non hemolytic grp A </li></ul><ul><li>In liquid medium(glucose/serum)—growth occurs as granular turbidity with a powdery deposit---no pellicle formed </li></ul>
  8. 11. <ul><li>Biochemical reactions </li></ul><ul><li>Ferments sug---acid ---no gas </li></ul><ul><li>Catalae- </li></ul><ul><li>Not soluble in 10% bile,unlike pneumococci </li></ul><ul><li>Hydrolysis of PYR,failure to ferment ribose----strpet.pyogenes from other streptococci </li></ul><ul><li>Resistance </li></ul><ul><li>Delicate-easily destroyd by heat,54C—30min—dies in cultures unless kept at low temp.pref.in Robertson’s cookd meat med.—survive in dust ---sev. Week---if protesctd from sunlight—rapidly inactivated by antiseptics </li></ul><ul><li>More resistant to crystal violet thatn any other bact,incl…staph.aureus </li></ul><ul><li>Selective medium—Crystal violet(1mg%)+Naldixic acid(15mg%)+Colistin sulphate(10mg%)+blood agar……isolation of streptococci…also pneumococci </li></ul><ul><li>Suscptble 2 sulphonamides…anti biotics…WONT DVLP RESITANCE </li></ul>
  9. 12. <ul><li>Sensitivity to BACITRACIN—pyogenes frm other hemolytics </li></ul><ul><li>Antigenic structure </li></ul>
  10. 13. <ul><li>Capsule-inhibits phagocytosis-not antigenic in humans </li></ul><ul><li>Peptidoglyacan—rigidity—pyogenic and thrombolytic activity </li></ul><ul><li>Grouping by pptn test—CHO—with grp antisera— </li></ul><ul><li>Test-streptcocci grown in—TODD-HEWITTbroth and extractd </li></ul><ul><li>with HCl-Lancefield’s Acid extraction method </li></ul><ul><li>,formamide(Fuller’s Method), </li></ul><ul><li>by an enzyme produced by Syreptmyces albus—Maxted’s method </li></ul><ul><li>by autoclaving(Randz &Randall’s method) </li></ul><ul><li>Extract+spacific antisera---in capillary tubes—pptn occurs within 5 min-at the interface between the extract & the homologous antiserum </li></ul><ul><li>Grouping also done by agar gel preperation </li></ul>
  11. 14. <ul><li>Sevral protein antigens r identified in the outr part of the cellwall.—pyogens—M,T,R </li></ul><ul><li>M-virulent-inhibits phagocytocis,antigenic-heat &acid stable---susp to tryptic digestion---can b extractd by Lancefield’s acid extraction method&typing is done wih type specific antisera---80 M antisera are identified </li></ul><ul><li>T-acid labile—Trypsin resistant,,but many M type posess same T antigen– demonstratd by Slide agglutination test,using trypsi treatd whole strptococci </li></ul><ul><li>R antigen-(B,C,G) </li></ul><ul><li>T&R---no virulence </li></ul><ul><li>Non-type protein associatd with M protein---MAP- M associatd protein </li></ul><ul><li>Pili consist –partly of M protein& coverd with lipoteichoicacid(imp in attachment to epithelial tissue </li></ul>
  12. 15. <ul><li>Antigenic cross reactions seen </li></ul><ul><li>*capsular hyaluronic acid----human synovial fluid </li></ul><ul><li>*cellwall protein---myocardium </li></ul><ul><li>*grp A carbohydrates---Cardiac valves </li></ul><ul><li>*Cytoplasmic membrane antigens---vascular intima </li></ul><ul><li>*Peptidoglycans----skin anigens </li></ul><ul><li>Toxins &other virulence factors </li></ul><ul><li>Several exotoxins—enzymes----M protein---C plysacharide </li></ul>
  13. 16. <ul><li>Hemolysins </li></ul><ul><li>O&S </li></ul><ul><li>O-oxygen labile-reactivated by reducing agents—in blood agar—O activity seen only in pour plates & not in surface cultures. </li></ul><ul><li>Obtaind in the active form-growing strept in broth containing reducing agents-sodium hydrosulphite </li></ul><ul><li>Heat labile too….virulent..cardiotoxic…leucotoxic…in biological action streptolysin O resembles—oxygen labile hemolysins of Cl perfingens,Cl.tetani &pneumococcus </li></ul><ul><li>Antistreptolysin appear---titre---infection(ASO titre) </li></ul><ul><li>Streptolysin is inhibited by cholesterol and not by nl sera,following certain chemical t/t or bacterial contamination sera may develop inhibitory sactivity due to some changes in lipoproteins </li></ul><ul><li>Such sera are unfit for ASOso </li></ul><ul><li>ASO test is nw done by serological method of latex agglutination.An ASO titre>200units----recent/reccurent infections with streptococci </li></ul><ul><li>S&O r produced by A,C & G also </li></ul>
  14. 17. <ul><li>Streptolysin S-oxygen stable-responsible for surface blood agar hemolysis </li></ul><ul><li>S-soluble in serum.protein-not antigenicConvalescent sera do not neutralise S activity…inhibited nonspecifically by serum lipoproteins </li></ul><ul><li>Pyrogenic Exotoxin(Erythrogenic,Dick,Scarlatinal toxin </li></ul><ul><li>Intraderamal inj---erythematous reaction(Dick’s test) </li></ul><ul><li>Used to identify children susceptble to scalet fever-a type of a/c pharyngitis with excessive erythematous rash,caused by strepto.pyogenes..producing this toxin….Blanching of the rash on local inj-of convalsent serum was used as d/g for scarlet fever(Schultz Charton reaction) </li></ul><ul><li>Primary effect of toxin…induction of fevr….renamd as Streptococcal pyrogenic exotoxin(SPE) </li></ul><ul><li>3 types—A,B,C </li></ul>
  15. 18. <ul><li>A&C-for bacteriophage….B-chromosoml </li></ul><ul><li>SPE-super atigens--- </li></ul><ul><li>Streptokinase(Fibrinolysin) </li></ul><ul><li>Activates plasminogen……lysis of fibrin </li></ul><ul><li>Antigenic protein,neutralising antibodies appear in convalescnt sera </li></ul><ul><li>Fibrin lysis---spread of infection… </li></ul><ul><li>Streptokinase given IV t/t of early MI,and other thromboembolic disorders </li></ul><ul><li>Deoxyribonucleases(Streptodornase/dnaSE) </li></ul><ul><li>Cause-depolymerisation of DNA---liquify thick pus—thin serous character of atreptococcal exudates </li></ul><ul><li>Empyema-DNAse is used therapeutically to liqufy localisd collections thick exudates-(Streptokinase+dornse used) </li></ul><ul><li>DNAse-A,B,C,D,Bis most antigenic </li></ul><ul><li>Demonstration of ANTiDNAse Ab---retrospective…inf. </li></ul><ul><li>Streptodornase B&D posessribonucelase activity </li></ul>
  16. 19. <ul><li>NADase-release Nicotinamide…leucotoxic </li></ul><ul><li>Hyaluronidase-favr spread of inf.strains that produce hyalorunidase in large amount are non capsultd----as H is presnt in capsulke </li></ul><ul><li>Antigenic----antibodies appear in sera </li></ul><ul><li>Serum opacity Factor-Sm M types—produce lipoproteinase…opacity whn applied to agar gelcontainig horse /swine serum.this is known as serum opacity factor(SOF) </li></ul><ul><li>Many strains produce---proteinase,Phosphatase,esterase,amylase… </li></ul>
  17. 20. <ul><li>Pathogenicity </li></ul><ul><li>Strept.pyogenes---pyogenic inf.—spread thru lymphatics & blood v </li></ul><ul><li>Respiaratory inf-----primry site of invasion is throat---sore throat(tonilitis---pharyngitis) </li></ul><ul><li>Astrepto--+2 Pharyngeal epithelum via pili.youngr children ---pharyngitis---older---tonsilitis </li></ul><ul><li>Locdalisation is beleivd to be hypersensitivity due to prior contactspread from throat ---otitis media,mastoiditis,quinsy,Ludwig’s Angina,suppurative adinitis---rarly lead to meningitis </li></ul><ul><li>Strept.pneumonia seldom follows throat infection---but complication of influenza/resp.viral ds. </li></ul>
  18. 21. <ul><li>Skin &soft tissue inf.—pyogene-variety of suppurative infections of skin,including inf. Of wounds or burns ---lead 2lymphangitis,cellulitis </li></ul><ul><li>Infection of minor abrasions led to fatal septicemia </li></ul>
  19. 22. <ul><li>Two types of strpt. Inf.skin—Erysipelas &Impetigo </li></ul><ul><li>Erysipelas-diffuse infection involving uperficial lymphatics—red,swolln, induratd skin,,sharply demarkatd frm surrounding healthy skin---seen only in older pts </li></ul><ul><li>Impetigo-strpt infection of scabies lesionsM Type strept.pyog—higher numberd M typesmay cause a/c glomerulonephritis in children </li></ul><ul><li>In Pyoderm- antibodies to DNAse B & Hyaluronidase is used---antecedent to GN,those to Streptolysin O not high ,ASO titre not useful </li></ul>
  20. 23. <ul><li>Streptococcal s/c inf….cellulitis---necrotising fascitis </li></ul><ul><li>NF-M types 1 and 3-which forms exotoxin A,esp. </li></ul><ul><li>“ flesh eating Bacteria” </li></ul><ul><li>Leads to DIC & Multiple systm failurestrep.pyogens can be isolatd from site---rise in titres of Antistreptolysin,&antiDNAse B can b demonstrated </li></ul><ul><li>Islotes r penicillin sensitive…but t/t not effective </li></ul><ul><li>Vancomysin ---DOC– in life threatning situations </li></ul>
  21. 24. <ul><li>Soft tissue infwith M,---TSS resembling staohs.—this ant NF occurs only in ones not immune to M types </li></ul><ul><li>Genital inf.-aer+aner-nl inhits female genitilia </li></ul><ul><li>Pyo—puerperla sepsis </li></ul><ul><li>Now mostly due to anerobic atrespto </li></ul><ul><li>Pyo-abcess in internal organ </li></ul><ul><li>Non suppurative complications-A/c Rheumatic fever& A/c Glomerulonephritis </li></ul><ul><li>1-3 wks aftr---then organism not detectable </li></ul>
  22. 25. <ul><li>Rheumatic fever—Carditis—connective tissue degeneration of heart valves,inflammatory miocardial lesions characterisd by Aschoff nodules </li></ul><ul><li>RF follows persistant /repeatd throt inf—with a strong antibod resp. </li></ul><ul><li>Lesions r due o hypewrsensitvity to streptococcol component </li></ul><ul><li>May b an element of autoimmunity </li></ul><ul><li>Antigenic croos reaction seen between heart asnd str.RF may follow infection with any serotype of Str.pyogenes </li></ul><ul><li>GN –only by a few types </li></ul><ul><li>Skin infections is more than throat inf.-------nephritis is a self limitd episode,& resides without permenent damage </li></ul><ul><li>Patho—cross reaction betwn glomerular memb & cell memb antign </li></ul><ul><li>Or due to immune complex ds. </li></ul>
  23. 26. <ul><li>Epidemiology </li></ul><ul><li>Major source—human URT </li></ul><ul><li>Symptomless infection is common.helps to maitain organism in the community </li></ul><ul><li>Transmission-contact ,contamination,dust fomites </li></ul><ul><li>Skin infections spresd by non-bitig insects-Eye gnat Hippelates </li></ul><ul><li>Str.inf of Respr.Tr.more in children T 5-8 yrs of age </li></ul><ul><li>Immunityn is type specific—ass. With antibody to M protein </li></ul><ul><li>Reinfection is due to multiplicity of serotypes </li></ul>
  24. 27. <ul><li>Lab dg </li></ul><ul><li>A/C---culture </li></ul><ul><li>Nonsuppurative—demonstration of antibodies </li></ul><ul><li>Gram staind films from pus and CCf-reliable if contaiuns gram+ cocci in chains </li></ul><ul><li>If from throat or genitilia—not useful ---as part of resident flora </li></ul><ul><li>Pike’s medium-transport medium </li></ul><ul><li>Specimen collectionswabs in Pike’s medium </li></ul><ul><li>Pike’s medium-1/10lakh crystal violet+1/16000 sodium azide in blood agar </li></ul><ul><li>37C anerobically..inc </li></ul><ul><li>/5-10% cdo2-hemolysis dvlps better </li></ul><ul><li>Prim.isol-sheep blood agr—it is inhibitory to HEMOPHILUS HEMOLYTICUS-confusd with hemolytic str. </li></ul>
  25. 28. <ul><li>Beta stp. Groupd by Lance Fields techniqufloursnt antibody tecniq for rapid identification of Grp A streptococci </li></ul><ul><li>Maxted’s observation-Pyogens r more sensitive to Bacitracin thn other streptococci </li></ul><ul><li>RF,GN-ASO titr >200---indicative of prior streptococcal infection </li></ul><ul><li>AntiDNAse B >300—sigfic </li></ul><ul><li>Streptozyme test-screening test -+ve for all streptococcal inf. Whthr from throat /skin </li></ul>
  26. 29. <ul><li>Prophylaxis </li></ul><ul><li>Indication is only to prevnt rheumatic fevr </li></ul><ul><li>Long term administration of penicillin in children who had early signs of RF </li></ul><ul><li>Prevents reinfection and furthe damage to heart </li></ul><ul><li>Not useful for GN- as it can follow a single infection and wont cause reinfection </li></ul><ul><li>Treatment </li></ul><ul><li>All Beta r sensitive to Penicilline G </li></ul><ul><li>Most r senstive to erythromycin </li></ul><ul><li>Penicilline allergy-erythromycin/cephalaxine </li></ul><ul><li>Tetracyclics and sulphonamides r not recommended </li></ul><ul><li>Antimicrobials have no effect on establishd GN/RF </li></ul>
  27. 30. Other hemolytic streptococci <ul><li>B,C,D,F,G-beta hemolytics also cause human inf. </li></ul><ul><li>Rarly H,K,O,R </li></ul>
  28. 31. Group B <ul><li>Cattle pathogen-Bovine mastitis </li></ul><ul><li>Strpt.agalactiae-singlemost common cause of neonatal meningiis </li></ul><ul><li>Also-arthritisosteomylitis,conjunctivitis,respiratory onfections,peritonitis,omphalitis,endocarditis. </li></ul><ul><li>Adult infections-puerperal sepsis and pneumonia </li></ul><ul><li>Ident.method-ability to hydrolyse Hippurate </li></ul><ul><li>CAMP reaction-accentuated zone of hemolysis,whn str.ag.straekd perpendicular to the strek of staph.aureus in blood agar </li></ul><ul><li>Occasionla strains Bacitracin sensitive </li></ul><ul><li>Human grp B-has virulence-polysacharide capsule </li></ul>
  29. 32. Group C <ul><li>Strept.equisimilis-URI,endocarditis,ostromylitis,brain abcess,pneumonia,puerperal sepsis </li></ul><ul><li>Tolernt to penicilline,esp.serious inf </li></ul><ul><li>Gentamicin+ </li></ul><ul><li>Trehalose f.like pyogenes,ferments ribose </li></ul><ul><li>Produces-streptolysin O,streptokinase(distinct from pyogens) </li></ul><ul><li>Strp.equisimilis-source of streptokinase for tthrombolytic therapy </li></ul>
  30. 33. Group F <ul><li>“ Minute Streptococci” </li></ul><ul><li>Grows poorly on blood agar unless incubatd with Co2 </li></ul><ul><li>Streptococcus MG-which is an alphalytic strain isolated from the case of primary atypical pneumonia </li></ul>
  31. 34. Group G <ul><li>Nl commensals in throat-cause tonilitis ,endocarditis,uribary infections in humans </li></ul><ul><li>Hand K-infective endocarditis </li></ul><ul><li>O-a/c tonsilitis,endocarditis </li></ul><ul><li>R-natural pathogens of pigs—meningitis,septicemia, respiratory inf. </li></ul>
  32. 35. Group D <ul><li>Two groups- </li></ul><ul><li>1.Enterococcus gp---separate genus-with-E.faecalis,faecium,durans </li></ul><ul><li>Non enterococcal gp-Str.bovis,st.equinus </li></ul><ul><li>Differntiating enterococci& streptococci </li></ul><ul><li>1.Mckonky tiny deep pink colonies </li></ul><ul><li>2.Relativly heat resistnt-60C for 30min </li></ul><ul><li>Appears as pairs of oval cocci,cells in a pair arranged at an angle to each other </li></ul><ul><li>3.Usually non hemolytic-sm strainsshow alpha/beta hemolysis </li></ul>
  33. 36. <ul><li>E.faecalis-Mannitol,sucrose,sorbitol,esculin---fermented& to grow on tellurite blood agar producing black colonies </li></ul><ul><li>Enterococci r presnt in intestine,genital tract and saliva </li></ul><ul><li>Uti,wound inf,ndocarditis,infection of biliary tract,septicemia,intra-abdominla abcess complicating diverticulitis,peritonitis </li></ul><ul><li>Non enterococci-gen susceptable to penicilline,inhibited by 6.5% NaCl/bile,cause UTI/endocarditis </li></ul>
  34. 37. The Viridans group <ul><li>Formerly called Str.viridans </li></ul><ul><li>Nl in mouth,URT,greenish/alpha lysis on blood agar </li></ul><ul><li>Sm nonlytic </li></ul><ul><li>They cannot be categorised undr Lancefield antigenic groups </li></ul><ul><li>But based on sugar fer.,cellwall comp.,production of dextrans and levans---str.mitis,salivarius,mutans,sanguis. </li></ul><ul><li>Sanguis-endocarditis in pre existing cardiac lesions </li></ul><ul><li>Following tooth extraction transient bacteremia---vegitates on implants,valves,diseasd heart </li></ul>
  35. 38. <ul><li>So prophylatic antibiotic cover is advised </li></ul><ul><li>Gen penicillin sensitive </li></ul><ul><li>Mutans-so called as it assumes a bacillary form in acid enironments </li></ul><ul><li>Imp in causation of dental caries </li></ul><ul><li>Breaks down dietery sucrose,producing acid and tough adhesive dextran </li></ul><ul><li>Acid damages dentine,dextrans bind together food debris,epithelial cells,mucus,bact---forms dental plaques—lead to caries </li></ul>

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