Streptococcus

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

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

Streptococcus

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Streptococcus