Pathogenesis
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PATHOGENESIS. Shigella cause bacillary dysentery There are two types of dysentery They are : a) Amoebic dysentery b) Bacillary dysentery. AMOEBIC DYSENTERY. BACILLARY DYSENTERY. Incubation period is long Insidious onset Local abdominal tenderness Moderate tenesmus

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  • Shigella cause bacillary dysentery

  • There are two types of dysentery

  • They are : a) Amoebic dysentery

  • b) Bacillary dysentery


AMOEBIC DYSENTERY

BACILLARY DYSENTERY

  • Incubation period is long

  • Insidious onset

  • Local abdominal tenderness

  • Moderate tenesmus

  • Fever absent

  • Short

  • Sudden onset

  • Generalised

  • severe

  • present


  • Blood,mucus,hardly any fecal matter

  • More

  • Small


Lab diagnosis
LAB DIAGNOSIS

AMOEBIC DYSENTERY

BACILLARY DYSENTERY

  • MICROSCOPY

  • Few pus cells

  • RBC agglutinated

  • Trophozoites present

  • Charcoatlayden crystals present

  • Numerous

  • Discrete not agglutinated

  • Absent

  • Absent


  • Can be demonstrated

  • Marked leukocytosis

  • positive




  • MECHANISM OF ACTION.

  • Bacilli infect the epithelial

    cells of villi in LI

    multiplication

    Inflammatory reaction with

    capillary thrombosis

    Necrosis of epithelial cells


  • Sh.dysenteriae type 1 forms an exotoxin.

  • CONGO RED BINDING TEST.

  • VIRULENCE MARKERS ANTIGENS

    • Virulence test.




  • In severe cases- bacteremia

  • COMPLICATIONS.

    • Arthritis

    • Toxic neuritis

    • Conjunctivitis

    • Parotitis

    • HUS


  • Severity ranges from mild diarrhoea to acute fulminating dysentery

  • The whole spectrum of infection is termed as SHIGELLOSIS.

  • Of 10,000 people ingested with Sh.flexneri

    • 25% asymptomatic

    • 25% transient fever

    • 25%fever with watery diarrhoea

    • 25% typical dysentery






  • In recent years,suddenly Sh. Dysentriae became virulent epidemic form.



Diagnosis depends on isolating bacilli from feaces.. 1.SPECIMENS.

-fresh stool

-rectal swab

-ideal specimen

-direct swab of an ulcer.


2.TRANSPORT.

  • Sach’s buffered glycerol saline.

    3.DIRECT MICROSCOPY.

  • Saline & Iodine preparations.

    4.CULTURE.

  • MacConkey’s agar

  • DCA


5.COLONY MORPHOLOGY&STAINING

  • NLF

  • Gram negative

  • Motility

    6.BIOCHEMICAL REACTIONS.

  • Urease,citrate,H2S,KCN-negative.

    7.SLIDE AGGLUTINATION



  • Uncomplicated shigellosis-self limiting.

  • Dehydration has to be corrected in infants and children

  • Antibacterial treatment not indicated

  • In severe cases-nalidixicacid,norfloxacin,otherflouroquinolones.


Prevention
PREVENTION

  • General prophylaxis.

  • Chemoprophylaxis.

  • Immunoprophylaxis.



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