This document provides information about Shigella spp., including its general characteristics as a gram-negative, non-motile, non-encapsulated, facultative anaerobic rod. It describes specimens used for laboratory diagnosis and various tests run, including microscopy showing gram-negative bacilli, growth on culture media like MacConkey agar and EMB agar, biochemical tests for oxidase, catalase, urease and citrate, and API 20E testing. It also covers serologic diagnosis and serotyping of Shigella into four serogroups.

1. Shigella spp.
Lab 7
Prepared by
Samira Fattah
Assis. Lec.
College of health sciences-HMU

2. General character:
- Short rods
- Gram-negative
- Non-motile
- Non-encapsulated
- facultative anaerobic
- Non-lactose fermenting

3. Specimen:
• fresh stool.
• Rectal swab.
• Serum
Laboratory diagnosis

4. • Microscopy:
• Microscopic examination is a gram negative bacilli.

5. On culture media

6. On MacConkey agar
Shigellae form non-lactose
fermenting pale colored or
colorless and transparent
colonies

7. On EMB agar
• Surface of EMB agar plates illustrating a mixed culture of E.
coli (green sheen colonies) and Shigella species. Most Shigella
species do not ferment lactose and, thus produce
nonpigmented, semitranslucent colonies on EMB agar.

8. On SS agar
• Colonies are transparent,
translucent or opaque and
usually smooth (non lactose
fermenting).

9. On xylose lysine deoxycholate agar
Shigella growth on XLD is
transparent and the
same color as the
medium (red).

10. Motility test
• Shigella is non motile
• the growth of organism spreads
out in only one direction, and
there is a sharply differentiated
edge between this growth and
the agar.

11. Biochemical test
• Oxidase test
• Cytochrome oxidase negative.
• Catalase test
• positive reaction

12. Biochemical test
• Urease -ve
• H2S -ve.
• lactose -ve
• Citrate -ve

13. API Test
• API 20E result for shigella

14. Serologic diagnosis
• Serologic examination with
polyvalent and monovalent
anti-sera
• For serogrouping and
serotyping.
• It is not used to diagnose
shigella infection,it is for
conformation.

15. serotyping
Shigella species are classified to four serogroups:
• Serogroup A: Shigella dysenteriae (12 serotypes)
• Serogroup B: Shigella flexneri (6 serotypes)
• Serogroup C: Shigella boydii (23 serotypes)
• Serogroup D: Shigella sonnei (1 serotype)