1. GIT-block Microbiology Lab.
Dr./ Tamer Ata

2. Contents Bacterial enteritis Fungal intoxication
Parasitological slides
Blood culture

3. Bacterial enteritis

4. Bacterial enteritis Mostly Gram negative bacilli including Vibrio spp.
Shigella spp.
Salmonella spp. (food poisoning & enteritis)
E. coli (EHEC O157/H7 & EPEC & ETEC& EIEC)
Campylobacter SPP.

5. Lab. Diagnosis Specimen: stool
CULTURE of specimen for isolation of the pathogen:
On selective and differential media as
XLD= Xylose Lysine Deoxycolate Agar
Identification of the isolated organism
Serological
Typing in outbreaks to trace source of infection

6. Culture media XLD media
Selective media for enteric Gram negative bacilli
Also differential media as can differentiate lactose fermenters (LF) from non lactose fermenters (NLF)
LF → yellow colonies
NLF → pink colonies + black color (H2S production)

7. LF colonies on XLD media
Possibility of the organism?
E. coli
Other test to confirm diagnosis?
Biochemical reactions as API 20 E
Serological characterization? To differentiate it from flora

8. NLF colonies on XLD media
Possibility of the organism?
Shigella spp.
Further identification between the spp. by?
Biochemical reactions as API 20 E
Serological characterization
Disease caused: Bacillary dysentery

9. NLF colonies with H2S production on XLD media

10. Possibility of the organism?
Salmonella spp.
Further identification between the spp. by?
Biochemical reactions as API 20 E
Serological characterization.
Disease caused: infective enteritis or enteric fever

11. API 20 E
PRINCIPLE?
Bacteria suspension placed in the small tubules of the strip
Each one is a lyophilized biochemical reaction
After incubation it gives colors which converted into numbers
From index we can identify the spp. Bacteria by its number
Uses: identification of bacterial spp. Also used in typing

12. Vibrio colonies on TCBS media
Possible bacteria: V. cholera
Confirmatory tests:
Serological typing
PCR
Biochemical reaction as +ve cholera red reaction
Disease caused by the organism: cholera
Type of the media: selective media

13. Vibrio colonies on TCBS media

14. Fungal intoxication

15. Aspergillus spp. on Sabouraud’s dextrose agar (SDA)
Suspected toxin:
Ochratoxin
Pathological effect of the toxin: nephrotoxic, immunosuppressive, carcinogenic and neurotoxic

16. Aspergillus by lactophenol cotton blue

17. Parasitology

18. Head of Taenia worm

19. Classification: Cestodes
T. saginata (beef tape worm)
mode of infection: ingestion of larva in undercooked meat beef)
Disease : asymptomatic or diarrhea
diagnosis: detect egg in stool
treatment: praziquantel

20. Enterobius vermicularis (pin worm)

21. Enterobius vermicularis (pin worm)
Classification: Nematodes
Infective stage: D shaped egg
Diagnostic stage: egg
Sensitive method for diagnosis: adhesive anal tape technique.
Habitat: caecum or large intestine
Clinically: nocturnal anal itching
Treatment: Mebendazole

22. Ascaris larva

23. Ascaris larva Classification: NEMATODES
Habitat: small intestine and bile ducts
Clinically: intestinal obstruction, biliary obstruction
Infective stage: egg
Diagnostic stage: egg
Treatment: Mebendazole

24. Blood culture

25. Blood culture Uses: Diagnose of
enteric fever in the first week
Brucellosis or Malta fever
Bacteremia and septicemia
Infective endocarditis
specimen: 5-10 cc venous blood under aseptic technique (at least 2 or 3 specimen taken from different limb)

26. Blood culture Principle:
Blood added to 50 cc nutrient broth (ratio 1/10 or 1/5) then incubated at 37°C for 7 days
Each day the culture is examined for signs of bacterial growth
If signs of bacterial growth are detected sub-culture, (or daily subculture), on blood, chocolate and Mac-Conkey agar were done to isolate and identify the organism
If 7 days pass without isolation of any growth, reported as negative sample

27. Blood culture Signs of bacterial growth as Advantage of big volume
Hemolysis
Turbidity
Surface pellicle
More nutrition for the organism
Dilute antibiotic if the patient receiving antibiotic

28. THANKS