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Sharq Elneil CollegeSchool of Medical Laboratory Sciences    Department of Microbiology   Medical Bacteriology course     ...
Kiyoshi Shiga7 February 1871
Historical informationDiscovered over 100 years ago by a Japanese scientist named Kiyoshi Shiga,Since its discovery, the...
Reservoirs:Human intestines are the natural habitat and reservoir for Shigella ,thus the bacteria are present in the sto...
Morphology Shigellae are Gram negative, rods.Unlike salmonellae and many otherenterobacteria, shigellae are non-motile. ...
Medically Important sppSubgroup A: Shigella dysenteriaeContains 12 distinct serotypesSerotype 1 was formerly called S. shi...
Culture &chaacteristics:Shigellae are aerobes and facultativeanaerobes.They grow between 10–45 ºC with anoptimum tempera...
XLD agar: Shigellae produce red-pinkcolonies, 2–4 mm in diameter,without black centresDCA and MacConkey agar:Shigellaeprod...
.Salmonella-Shigella (SS) agar: Despite its name, this medium isnot suitable for isolating shigellae asit is inhibitory t...
Routes of transmissionFaecal-oral route with poor sanitation,unhygienic conditions, overcrowding,facilitating the rapid s...
Reactions of shigellae● Lactose negative (S. sonnei is a late lactose andsucrose fermenter)● H2S negative● Urease negative...
Colicins typingColicins are bactericidal macromoleculeswhich have narrow spectrum activity and theyare produced by Sh.sonn...
Virulence factorsseveral toxins (endotoxin, enterotoxin, andcytotoxin)its ability to induce endocytosis into host cells,...
Pathology: ShigellosisDeveloping countries:Sh. flexneri is endemic (always present) in mostcommunitiesSh. dysenteriae type...
Fecal-oral transmissionperson-to-person, fomites, food, water,Waterborne and water-washedInfectious dose: low; as few ...
Shigellosis - Complicationssevere anorexia (loss of appetite)hypoproteinaemia (a low concentration of blood protein)hyp...
Laboratory diagnosisSpecimens:Collection of SpacimenCultureIdentificaionSerologyMolecular characterization   -
Antimicrobial suseptibility testingAmpicillin,Septra,Nalidixic acidCiprofloxacin. Since manyShigella are becoming resi...
Prevention and Control: Handwashing, especially afterdefacationImproved sanitation and hygiene Improve water, wastetreat...
THANKYOU FOR ATTENTION
Shigella mahadi ppt
Shigella mahadi ppt
Shigella mahadi ppt
Shigella mahadi ppt
Shigella mahadi ppt
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  1. 1. Sharq Elneil CollegeSchool of Medical Laboratory Sciences Department of Microbiology Medical Bacteriology course shigella U.Mahadi Hassan Mahmoud mahadi2010sd@yahoo.com Bsc, Msc, MIBMS Microbiology
  2. 2. Kiyoshi Shiga7 February 1871
  3. 3. Historical informationDiscovered over 100 years ago by a Japanese scientist named Kiyoshi Shiga,Since its discovery, there have been several epidemics of shigellosis (caused by the S. dysenteriae bacteriumOutbreak in the Mexican-Guatemalan border caused the deaths of 20,000 people
  4. 4. Reservoirs:Human intestines are the natural habitat and reservoir for Shigella ,thus the bacteria are present in the stools of an infected person up to a week or two after the alleviation of symptoms
  5. 5. Morphology Shigellae are Gram negative, rods.Unlike salmonellae and many otherenterobacteria, shigellae are non-motile. Non-sporing Noncapsulate
  6. 6. Medically Important sppSubgroup A: Shigella dysenteriaeContains 12 distinct serotypesSerotype 1 was formerly called S. shigaSerotype 2 was formerly called S. schmitziiSubgroup B: Shigella flexneriContains 6 related serotypes and 4 serotypesdivided into subserotypes.Subgroup C: Shigella boydiiContains 18 distinct serotypesSubgroup D: Shigella sonneiContains one serotype
  7. 7. Culture &chaacteristics:Shigellae are aerobes and facultativeanaerobes.They grow between 10–45 ºC with anoptimum temperature of 37 ºC.Specimens must be cultured with theminimum of delay. A selective medium is required toisolate Shigella species from faeces.
  8. 8. XLD agar: Shigellae produce red-pinkcolonies, 2–4 mm in diameter,without black centresDCA and MacConkey agar:Shigellaeproduce non-lactose fermenting palecoloured 1–2 mm diameter colonies.On prolonged incubation, S. sonneiforms pink colonies
  9. 9. .Salmonella-Shigella (SS) agar: Despite its name, this medium isnot suitable for isolating shigellae asit is inhibitory to most strains
  10. 10. Routes of transmissionFaecal-oral route with poor sanitation,unhygienic conditions, overcrowding,facilitating the rapid spread of infection.Only a few organisms are required tocause disease.Houseflies help to transfer shigellaefrom faeces to food. The
  11. 11. Reactions of shigellae● Lactose negative (S. sonnei is a late lactose andsucrose fermenter)● H2S negative● Urease negative● Oxidase negative● Citrate negative● Lysine decarboxylase (LDC) negative● Ornithine decarboxylase (ODC) negative exceptS. sonnei which is ODC positive● Beta-galactosidase (ONPG) negative. S. sonneiand up to 15% of Sd 1 strains and minority ofS. boydii strains are ONPG positive
  12. 12. Colicins typingColicins are bactericidal macromoleculeswhich have narrow spectrum activity and theyare produced by Sh.sonneii (16)colicins kill sensitive bacteria in 3 definedsteps :1. Adsorption onto a specific receptor at the surface of the bacterium.2. Translocation across the outer membrane.3. Killing activity.
  13. 13. Virulence factorsseveral toxins (endotoxin, enterotoxin, andcytotoxin)its ability to induce endocytosis into host cells, andintracellular growth. Each variation of the bacteria is able to penetratelarge intestine epithelial cells and multiply within.S. dysenteriae, however, causes more severesymptoms due to the production of the Shiga toxin.This enables it to kill host cells by inhibiting proteinsynthesis
  14. 14. Pathology: ShigellosisDeveloping countries:Sh. flexneri is endemic (always present) in mostcommunitiesSh. dysenteriae type 1 often occurs in an epidemic patternThese two species of Shigella generally produce the mostsevere illness.Developed countries:Sh. sonnei is the most common and is the least virulentSh. boydii causes disease of intermediate severity is leastcommon, except in the Indian sub-continent.
  15. 15. Fecal-oral transmissionperson-to-person, fomites, food, water,Waterborne and water-washedInfectious dose: low; as few as 10 cells toinfectIncubation period: 1 to 7 days; typically,1-3 daysDuration of illness: untreated: severe symptoms for about two weeks Antibiotic treatment shortens illness and prevent spread to others
  16. 16. Shigellosis - Complicationssevere anorexia (loss of appetite)hypoproteinaemia (a low concentration of blood protein)hyponatraemia (a low concentration of blood sodium)dilation of the large intestineseizuresanaemiakidney damagepersistent diarrhoea
  17. 17. Laboratory diagnosisSpecimens:Collection of SpacimenCultureIdentificaionSerologyMolecular characterization -
  18. 18. Antimicrobial suseptibility testingAmpicillin,Septra,Nalidixic acidCiprofloxacin. Since manyShigella are becoming resistant to antibiotics, theyshould be avoided as a means of treatment for mildcases , as most will recover without help.
  19. 19. Prevention and Control: Handwashing, especially afterdefacationImproved sanitation and hygiene Improve water, wastetreatment/disposal and food sanitation Reduce overcrowding, etc. No effective vaccine
  20. 20. THANKYOU FOR ATTENTION
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