1. GI Bacteriology

2. The first thing we do is macroscopic examination (by naked eyes): so we can check the color:
·        If it is yellow so it is normal.
It could be red: this means that there is bleeding or mucus

3. ·        Some times it has fresh red color: this is maybe due to injury in the opening of anus (out side the bowel).
·        If it is black this means there is hemorrhage in the stomach. (Very important).

4. Microscopic examination
It is simple way, you take glass slide, and put one drop of saline, with a stick we touch the stool and then we spread it on the slide, then we have to put a cover slip.
We can use the slide to look for RBCs, WBCs, or parasites (by adding Iodine or something else).

5. We check each field and if the number of WBCs more than 10/high power field that means there is an infection. (High power field = 40X).
We look for more than one field and take the average of them.

6. The bacteria that cause infections to GIT are:
1.  Salmonella
2.    Shigella
3.    Helicobacter pylori
4.    Campylobacter jejuni
All of them cause diarrhea, so we do the culture to know which one of them is the causative agent of the infection.
** E.coli is considered in adults as normal flora, but in children it is considered as pathogenic.

7. Salmonella spp.
Salmonella spp. Colonies on SS Agar Show Black Discoloration, Indicative of H2S Formation.
# G –ve , rod shape, facultative anaerobic.

8. Salmonella spp.
IMViC
KIA: K/A with H2S in between the slant and the butt.
Cause food poisoning
Diarrhea and typhoid fever.

9. Shigella spp. G –ve, rod shape, facultative anaerobic.
IMViC : (+) + - -
KIA : K/A
Cause shigellosis and dysentery.

10. Proteus spp. 1- Swarming:
Typical Appearance of Swarming Motion of
Proteus spp. on Agar Surface3 main characteristics of proteus:
1- Swarming:
2- Urease test +ve (the only one that has this feature)
3- KIA : K/A/ H2S,

11. Proteus spp.
3- KIA : K/A/ H2S,

12. Staining Clostridium spp. with Shaeffer-Fulton Method
Positively Stains the Endospores

13. Escherichia coli
E. coli Colonies on MacConkey Agar Show Pink Discoloration, Indicative of Lactose Fermentation.

14. Escherichia coli E. coli Gives an A/A Pattern when Grown in both
Kligler-Iron Agar (KIA) and Triple Sugar-Iron (TSI) Agar

15. E. coli Shows a + + - - IMViC Pattern
Escherichia coli
E. coli Shows a IMViC Pattern

16. Staphylococcus aureus
Typical Appearance of Gram-Positive Cocci in Clusters

17. Staphylococcus aureus
S. aureus Shows a Positive Coagulase Reaction

18. Vibrio cholerae
Late fermentation occurred on TCBS plate representing V. cholerae

19. Campylobacter jejuni
Campylobacter jejuni infection causes cramping, diarrhea, abdominal pain and fever within 2 to 5 days after a person has been exposed to the organism. Campylobacter jejuni is one of the most common bacterial causes of diarrhea.

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