PATHOGENESIS

Shigella cause bacillary dysentery There are two types of dysentery They are : a) Amoebic dysentery b) Bacillary dysentery

Incubation period is long Insidious onset Local abdominal tenderness AMOEBIC DYSENTERY BACILLARY DYSENTERY Incubation period is long Insidious onset Local abdominal tenderness Moderate tenesmus Fever absent Short Sudden onset Generalised severe present

Stool consists of blood,mucus,necrotic cells&feacal matter Frequency less Volume copious Blood,mucus,hardly any fecal matter More Small

LAB DIAGNOSIS Numerous Discrete not agglutinated Absent Few pus cells AMOEBIC DYSENTERY BACILLARY DYSENTERY MICROSCOPY Few pus cells RBC agglutinated Trophozoites present Charcoat layden crystals present Numerous Discrete not agglutinated Absent

Bacilli not demonstrated in stool culture Mild leucocytosis in blood smear Serum agglutination negative Can be demonstrated Marked leukocytosis positive

Source-infected human beings Mode of transmission Direct Fomites Water Contaminated food Flies In young male homosexuals

Minimum infective dose is low Pathogenecity resemble that of EIEC

MECHANISM OF ACTION. Bacilli infect the epithelial cells of villi in LI multiplication Inflammatory reaction with capillary thrombosis Necrosis of epithelial cells

VIRULENCE MARKERS ANTIGENS Sh.dysenteriae type 1 forms an exotoxin. CONGO RED BINDING TEST. VIRULENCE MARKERS ANTIGENS Virulence test.

CLINICAL MANIFESTATIONS

Incubation period-1 to 7 days. SYMPTOMS Frequent passage of loose scanty stools containing blood & mucus Abdominal cramps Tenesmus Fever & vomiting

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

EPIDEMIOLOGY

Epidemics always accompanies wars,poverty,lack of sanitation. Source-humans Cases Less often carriers

ASYLUM DYSENTERY. In USA North-Sh.sonnei South-Sh.flexneri.

In INDIA ,all age groups Flexneri 50-85% Dysentriae 8-25% Sonnei 2-24% Boydii 0-8%

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

LAB DIAGNOSIS.

Diagnosis depends on isolating bacilli from feaces. 1. SPECIMENS 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

TREATMENT

Uncomplicated shigellosis-self limiting. Dehydration has to be corrected in infants and children Antibacterial treatment not indicated In severe cases-nalidixic acid,norfloxacin,other flouroquinolones.

PREVENTION General prophylaxis. Chemoprophylaxis. Immunoprophylaxis.

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