Post on 24-Feb-2016
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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 onsetLocal abdominal tenderness
Moderate tenesmus
Fever absent
Short
Sudden onsetGeneralised
severe
present
Stool consists of blood,mucus,necrotic cells&feacal matter
Frequency less
Volume copious
Blood,mucus,hardly any fecal matter
MoreSmall
LAB DIAGNOSISAMOEBIC DYSENTERY BACILLARY
DYSENTERYMICROSCOPYFew pus cellsRBC agglutinated
Trophozoites present
Charcoat layden crystals present
NumerousDiscrete not agglutinated
AbsentAbsent
Bacilli not demonstrated in stool culture
Mild leucocytosis in blood smear
Serum agglutination negative
Can be demonstrated
Marked leukocytosis
positive
Source-infected human beingsMode of transmission
DirectFomitesWaterContaminated foodFliesIn 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
Sh.dysenteriae type 1 forms an exotoxin.
CONGO RED BINDING TEST.
VIRULENCE MARKERS ANTIGENS
Virulence test.
CLINICAL MANIFESTATIONS
Incubation period-1 to 7 days.
SYMPTOMSFrequent passage of loose scanty stools containing blood & mucus
Abdominal crampsTenesmusFever & vomiting
In severe cases- bacteremiaCOMPLICATIONS.
ArthritisToxic neuritis ConjunctivitisParotitisHUS
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% asymptomatic25% transient fever25%fever with watery diarrhoea25% typical dysentery
EPIDEMIOLOGY
Epidemics always accompanies wars,poverty,lack of sanitation.
Source-humansCasesLess often carriers
ASYLUM DYSENTERY.In USA
North-Sh.sonneiSouth-Sh.flexneri.
In INDIA ,all age groupsFlexneri 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.
-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 agarDCA
5.COLONY MORPHOLOGY&STAINING
NLFGram negativeMotility6.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 indicatedIn severe cases-nalidixic acid,norfloxacin,other flouroquinolones.
PREVENTIONGeneral prophylaxis.Chemoprophylaxis. Immunoprophylaxis.
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