Salmonella
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Salmonella Salmonella Presentation Transcript

  • Salmonella Enterobacteriaceae 3
  •  
    • Salmonella can cause
    • Enteric fever
    • Gastroenteritis
    • Septicemia with or without focal suppuration
    • Carrier state
    • Salmonella typhi—typhoid fever
    • Eberth-Gaffky bacillus/Eberthella typhi
    • Practically salmonella has been divided into
    • The enteric fever group-typhoid,paratyphoid bacilli
    • The food poisoning group
    • Gram –ve,rods,motile except S gallinarum-pullorum which is always nonmotile
    • Aerobic and facultative anerobic
    • Grows readily on simple media
    • MacConkey and DCC media- colourless
    • Wilson and Blair bismuth sulphite medium-jet black colonies
    • Selenite F &tetrathionate broth are commnly employed as enrichment media
    • S typhi- anerogenic
    • MR+,VP-ve,C+
    • Typhi- donot grow in Simmon’s citrate medium as they need tryptophan as the gowth factor
    • Antigenic structure-
    • Flagellar antigen-H
    • Somatic antigen O
    • Surface antigen-Vi
  •  
    • H antigen- heat labile-strongly immunogenic,induces antibody formation in high titres
    • O antigen-phospholipid-Protein-Polysacharide complx—also called Boivin antigen---heat stable
    • Vi antigen- analogue to K antigen in the coliforms-surface Polysacharide antigen enveloping the o antigen—heat labile—tend to loss in serial subculture
    • Vi polysacharide acts as a virulence factor by inhibiting phogocytosis-resisting complement activation and bacterial lysis
    • Poorly immunogenic
    • Purified Vi vaccine
    • Total absence of vi antibody in a proven case of typhoid fever indicates poor Prgns
    • Antibody disappears early in convalescence
    • Its persistance indicates dvlpmnt of carrier state.
  • Antigenic variation
    • H-O
    • V-W-loss of Vi by sub culture-now agglutinable with O antiserum (W form)
    • S-R-by loss of O antigen & virulence
    • O antigen
  • H-O variation
    • Associated with loss of flagella
    • Phase Variation-flagellar antigens two types
    • Phase 1 –specific for species
    • Phase 2 –group specific
    • Diphasic-both-
    • S.typhi –monophasic
    • Phase 1 can b converted to 2 by Craigie’s method
  •  
  • Pathogenicity
    • Enteric Fever-
    • Typhoid fever- S. typhi
    • Paratyphoid fever – S.paratyphi A,B,C
  •  
  • D/s course
    • IP-7-14 days
    • Gradual onset-headache,malaise,anorexia-caoted tongue-abdominal discomfort-constipation/diarrhoea
    • Step ladder pyrexia-typical-
    • Hepato splenomegaly
    • Rose spots-in skin which blanch on pressure
    • Complications-perforation,he,circulatory collpase
    • Relapse may occur in convalescence-higher if treated early with chloramphenicol
    • Paratyphoid is milder form
    • Leads to frank septicemia with suppurative complications
    • Infection with Alkaligens faecalis- similar c/f
    • Epidemiology-
    • Carriers-3w-3m-Convalescent
    • 3m-1yr-temporary
    • More than 1yr-c/c
  • Lab d/g
    • Isolation and demonstration of antibodies
    • ,bacilli demonstration
    • Blood culture-diagnostic maximum at first week,rapidly –ve on treating with antibiotics
  •  
    • Cultures should be declared –ve only after incubation period of 10 days
    • May use Casteneda’s method-
    • Feces culture-salmonella are shed in the feces thruout the course of disease,even in carriers
    • Imp, if antibiotics hav started-as they r slowly eliminated from gut than from blood
    • Feces—MacConkey-/DCA/WB
    • Clot culture-blood- allowed to clot—serum is used for widal—clot to bile broth—high rate of isolation as bactericidal action of serum is less
    • Urine culture-,Bile culture,rose spots,csf,sputum –less imp
  • Widal reaction
    • In H- +ve –loose,cotton woolly clumps
    • O +ve –disc like pattern at the bottom of the tube
    • Result-
    • Ab appear by end of first week- ifearly –ve—titre inc steadly till 3/4 th week and it decline after
    • Test more samples
    • 1/100 or more for O & 1/200 or more for H is sigfig
    • Ab-may be due to proir d/s,immunisation,carriers
    • H agglutinins persist longer than O
    • If immunised with TAB, Ab against both ,in natural infection only causative org.
    • t/ted case –poor Ab titre
    • Other serological methods-ELISA,CIE
    • Staphylococcal co-agglutination test-in early phase of d/s-S.aureus-/Cowan 1 strain-which contains Protein A is stabilised by formaldehyde and coated with S typhi antibody---1%---with serum –visible agglutination in 2 min
    • Not paositive after first week
  • D/g of carriers
    • Islation from faeces,bile,urine cultures
    • Widal is no value in endemic states
    • Demo of Vi agglutinins is imp
    • Sewer-swab technique-Gauze pads in sewers and drains -cultured
  • Px
    • TAB vaccine-with S,typhi,S.paratyphi A & B
    • Typhi-1000 million
    • A & B- 750 million each/ml---killed by heating at 50-60C—preserved in phenol
    • In india- divalant Typhoid-paratyphoid A is given
    • Two doses—0.5ml s/c at an intervel of 4-6 weeks
    • 0.1ml I/D
    • Newer vaccines
    • Typhoral-live oral vaccine
    • Typhin-Vi---injectable
  • T/t
    • Chloramphenicol,tetracycline, streptomycin
    • Ampicilline, Aox,cotrimoxazole
  • Salmonella Gastroenteritis
    • Enterocolitis/food poisoning
    • -zoonotic-source of infection –animal products
    • Caused by any salmonella except typhi
    • Short IP-24 hrs-diarrhoea, vomiting, abdominal pain,fever---loose stools
    • Subsides in 2-4 days
    • T/t –if uncomplicated-symptomatic- antibiotics not neede