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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PATHOGENESIS

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Pathogenesis

PATHOGENESIS


Pathogenesis

  • Shigella cause bacillary dysentery

  • There are two types of dysentery

  • They are : a) Amoebic dysentery

  • b) Bacillary dysentery


Pathogenesis

AMOEBIC DYSENTERY

BACILLARY DYSENTERY

  • Incubation period is long

  • Insidious onset

  • Local abdominal tenderness

  • Moderate tenesmus

  • Fever absent

  • Short

  • Sudden onset

  • Generalised

  • severe

  • present


Pathogenesis

  • Stool consists of blood,mucus,necroticcells&feacal matter

  • Frequency less

  • Volume copious

  • 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


Pathogenesis

  • Bacilli not demonstrated in stool culture

  • Mild leucocytosis in blood smear

  • Serum agglutination negative

  • Can be demonstrated

  • Marked leukocytosis

  • positive


Pathogenesis

  • Source-infected human beings

  • Mode of transmission

    • Direct

    • Fomites

    • Water

    • Contaminated food

    • Flies

    • In young male homosexuals


Pathogenesis

  • Minimum infective dose is low

  • Pathogenecity resemble that of EIEC


Pathogenesis

  • MECHANISM OF ACTION.

  • Bacilli infect the epithelial

    cells of villi in LI

    multiplication

    Inflammatory reaction with

    capillary thrombosis

    Necrosis of epithelial cells


Pathogenesis

  • Sh.dysenteriae type 1 forms an exotoxin.

  • CONGO RED BINDING TEST.

  • VIRULENCE MARKERS ANTIGENS

    • Virulence test.


Clinical manifestations

CLINICAL MANIFESTATIONS


Pathogenesis

  • Incubation period-1 to 7 days.

  • SYMPTOMS

    • Frequent passage of loose scanty stools containing blood & mucus

    • Abdominal cramps

    • Tenesmus

    • Fever & vomiting


Pathogenesis

  • In severe cases- bacteremia

  • COMPLICATIONS.

    • Arthritis

    • Toxic neuritis

    • Conjunctivitis

    • Parotitis

    • HUS


Pathogenesis

  • 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


Epidemiology

EPIDEMIOLOGY


Pathogenesis

  • Epidemics always accompanies wars,poverty,lack of sanitation.

  • Source-humans

    • Cases

    • Less often carriers


Pathogenesis

  • ASYLUM DYSENTERY.

  • In USA

    • North-Sh.sonnei

    • South-Sh.flexneri.


Pathogenesis

  • In INDIA ,all age groups

    • Flexneri 50-85%

    • Dysentriae 8-25%

    • Sonnei 2-24%

    • Boydii 0-8%


Pathogenesis

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


Lab diagnosis1

LAB DIAGNOSIS.


Pathogenesis

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

-fresh stool

-rectal swab

-ideal specimen

-direct swab of an ulcer.


Pathogenesis

2.TRANSPORT.

  • Sach’s buffered glycerol saline.

    3.DIRECT MICROSCOPY.

  • Saline & Iodine preparations.

    4.CULTURE.

  • MacConkey’s agar

  • DCA


Pathogenesis

5.COLONY MORPHOLOGY&STAINING

  • NLF

  • Gram negative

  • Motility

    6.BIOCHEMICAL REACTIONS.

  • Urease,citrate,H2S,KCN-negative.

    7.SLIDE AGGLUTINATION


Treatment

TREATMENT


Pathogenesis

  • 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.


Pathogenesis

Thank you


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