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Streptococcus
 

Streptococcus

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    Streptococcus Streptococcus Presentation Transcript

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