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  • 1. Enterobacteriaceae Coliforms-proteus Shigella Salmonella
  • 2.
    • Aerobic
    • Non- sporing,
    • Non-acid fast,
    • G-ve bacilli
    • Intestinal flora
  • 3. Old classification Salmonella, Shigeela Non lactose fermenters Shigella sonnei/Paracolons Late lactose fermenters Escheria,Klebsiella Lactose fermenters
  • 4. New classification Erwinia Erwinieae Tribe 4 Proteus,Morgenella.Providencia Proteeae Tribe 3 Klebsiella,Enterobacter,Hafnia,Serratia Klebsielleae Tribe 2 Escherichia,Edwardsiella,Citrobacter,Salmonella,Shigella Escherichiae Tribe 1
  • 5. E.coli
    • Motile-peritrichate flagella,aerobe & facultative anerobe
    • Good growth in ordinary media
    • Culture-fresh isolation-S/smooth form-easily emulsifiable in saline
    • Rough forms-/R forms-irregular,dull surface-autoagglutinable in saline
    • S-R variation occurs due to subculture-loss of surface antigens and virulence
  • 6.  
  • 7.
    • MacConkey’s agar- bright pink-
    • IMViC ++--(Indole ,Methyl red,Voges-Proskauer and citrate utilisation tests
  • 8.  
  • 9. Antigenic structure
  • 10.
    • Somatic antigen O,
    • capsular antigen K-1 and 2,(1resp for neonatal meningitis..)
    • Flagellar antigen H
    • Toxins-exo-hemolysisns and enterotoxins
    • Enterotoxins-heat labile(LT)—heat stable(ST)—verotoxin (VT)/Shiga like toxin/SLT
  • 11.  
  • 12.
    • ST- two types –A &B-
    • A-activate cGMP---fluid accumilation
    • B-activate cGMP/cAMP
    • VT-similar to Shigella dysenertae Type 1 toxin-
    • VT A & B subunits-phge encoded
    • Fimbrae-imp in UTI-P fimbriae binds specifically to the P blood group substance on RBC and uroepithelial cells
  • 13. Clinical infections
    • UTI
    • Diarrhea
    • Pyogenic infections
    • Septicemia
  • 14. Urinary Tract infection
    • Majority of naturally occuring UTI
    • By those found in feces-O grops-1,2,4,6,7.
    • Infection may be precipitated by obstruction,prostatic enlargement,calculi,pregnancy
    • Asyymptomatic bacteriuria-5-7% of pregnant-UTI without no symptoms----can lead to pyelonephritis,hypertension,premature births,death of fetus
  • 15.
    • Significant bacteriuria-collect mid tream sample of urine—sterile wide mouthed container---lab without delay
    • In presence of Active infection->= 1 lakh bacteria /ml----significant bacteriuria
    • Less than 10’000-not sig
    • Between equivocal
    • Semi quantitative-one loopful of urine in non-inhibitery medium & other in indicator medium
    • Former gives quantitative measurement of bacteriuria-later presumptive diagnosis
  • 16.
    • Antibiotics sensitivity is very imp-done using urine sample as inocula
    • Screening tests for presmptive d/g of significant bacteriuria
    • Griess Nitrate test-+ve –Nitrate reducing b.
    • Catalase test-+-bacteriuria and hematuria
    • Triphenyl Tetrazolium chloride test/TTC –
    • Microscopic demo
    • Glucose test paper
    • Dip slide culture methods
    • The antibody coated bacteria test-to find site of infection-specific antibodies are present in urine only whn the kidnes are affected,otherwise inf. In bladder
  • 17.
    • Diarrheagenic E coli
    • EP-pathogenic
    • ET-toxigenic
    • EH-haemorrhagic
    • EA-aggregative
    • EI-invasive
  • 18. EPEC
    • Infants
    • Do not produce enterotoxin,not invasive
    • Ininfantile enteritis-bacilli are seen adherent to the mucosa of SI,to cup like projections of enterocyte membrane---disruption of brush border microvilli
  • 19. ETEC
    • Endemic diarrhoea
    • Mild watery to fatal d/s
    • Traveller’s diarrhoea-
    • Entero toxins produced-LT/ST/both
    • First adhesion by fimbrial / Colonisation factor antigens(1,2,3,4,)
    • D/g- ligated rabbit ilial loop,LT(invitro methods-tissue culture)
  • 20. EIEC
    • Resembles shigella-nonmotile,O antigen cross reactivity
    • Enter invasive-capacity to invade interstitial epithelial cellsinvivo, penetrate HeLa cells
    • C/f-mild diarrhoea to frank dysentery(resmble shigellosis)
    • Children and adults
    • Lab dig- Sereny test-instillation of a suspension of freshly isolated EIEC /shigella—g.pig eyes-mucopurulent conjuntivitis
    • Cell penetration of HeLa/HEP2-d/gtic
    • Ability to penetrate-plasmid-
    • Plasmid codes for OM antigens called VMA(Virulence Marker Antigens) which can be detected by ELISA
  • 21. EHEC/Shigatoxigenic/Verotoxigenic
    • Producing VT—mild diarrhoea to fatal hemorrhagic colitis and hemorrhagic uraemic syndrome/HUS-young children and yelderly
    • Primary target of VT is vascular endothelial cells
    • In HUS_ch. Renal lesion-capillary micro angiopathy
    • Source –contaminated human/animal feces
    • Food poisoning in veg-salad vegetables
    • Lab d/g-demo.,VT—DNA probes for VT1 and VT2 genes –more sensitive-
  • 22. EAEC
    • Appear aggregated in stacked brick formaation on hep 2 cells
    • Persisitant diarr.
  • 23. Septicaemia
    • Blood stream invasion-shock
    • Systemic Inflammatory Response Syndrome(SIRS)
  • 24. Shigella
  • 25. Imp species
    • Shigella dysenteriae---Mannitol non fermenting
    • Shigella sonnei-mannitol fermenting
    • Shigella boydii---mannitol fermenting
    • Shigella flexneri---mannitol fermenting
  • 26.
    • Dysentery-frequent passage of blood stained mucopurulent stools
    • Bacillary and amoebic
    • MacConkey agar colourless-except shigella sonnei-pink
    • Deoxycholate citrate agar-selective medium
    • Growth is inhibited in Wilson –Blair Bismuth sulphite medium
    • Fermentation of mannitol is imp. In classification-by SH.flexneri,boydii,sonnei
    • Not by Sh.dysenteriae
  • 27.
    • Antigens-O,K,
    • Classification
    • Sh.dysenteriae-mannitol non fermenting-indole –ve,only member that is always catalase +ve
    • Toxin –Shiga toxin by Sh.dysenteriae type 1-earliest eg. Of an exotoxin produced by Gram –ve bacillus
    • Neuro,entero,cyto toxicity
    • Shiga toxin has A and B units
    • A-A1 & A2-A1 inactivates host cell 60S ribosomes
  • 28.
    • Sh.sonnei-catalase –ve,late lactose fermenters
    • Mildest of the bacillary dysentery
    • MC shigellosis in developed countries
  • 29. Pathogenicity
    • Shigella causes bacillary dysentery-infestion occurs by ingestion
    • Low minimal infective dose-10-100 bacilli only-as they survive gastric acidity than other enterobacteria
    • Pathogenic mech. Similar to EIEC
  • 30.  
  • 31.
    • Invasive property of bacillus can be demonstrated by its ability to penetrate cultured HeLa/Hep2 cells
    • Invasive property is related to the presence in the bacillus of large plasmids coding OMP responsible for cell penrtration—these proteins are called VMAL(Virulence Marker Antigens)
    • Detection of VMA by ELISA serves as a virulence test for Shigella,as for EIEC
  • 32. Bacillary dysentery
    • Ingestion----IP-1-7days,usually 48hrs
    • Frequent passage of loose,scanty feces containing blood and mucus,along with abdominal cramps and tenesmus
    • Cx-Sh.dysenteriae-type 1-arthritis,toxic neuritis,conjunctivitis,parotitis,intussusception
    • HUS
    • T/t- based on sensitivity