1. Enterobacteriaceae - Microscopic appearance - Cultural characteristics
- Biochemical Tests of Enterobacteriaceae
- Identification of Enterobacteriaceae using API 20E

2. Enterobacteriaceae - Gram negative rods
- Aerobes and facultative anaerobes
- Motile and non-motile
- Oxidase negative
- Reduce nitrate to nitrite
- Ferment glucose with acid production

3. Non-Lactose fermenting
Enterobacteriaceae
Lactose fermenting
Non-Lactose fermenting

4. Lactose fermenting
Escherichia
Klebsiella
Enterobacter
Citrobacter

5. Escherichia coli - Urinary tract infections. ( urine )*
- Infections of wounds, peritonitis, sepsis and toxic
shocks. ( pus )*
- Meningitis and bacteraemia in neonates. ( CSF & blood )*
- Diarrhoeal disease. ( faeces )*
* Specimens depending to site of infection.

6. Gram negative rod, motile. A minority of strains are capsulated.

7. On Blood agar E. coli produces 1–4 mm diameter mucoid colonies
On Blood agar E. coli produces 1–4 mm diameter mucoid colonies. Some strains are haemolytic.

8. On MacConkey agar E. coli ferments lactose, producing smooth pink colonies.

9. On KIA (Kligler iron agar) Most strains of E
On KIA (Kligler iron agar) Most strains of E. coli produce an acid deep and an acid slope with gas production.

10. Klebsiellae - chect infections. ( sputum )*
- Infections of wounds. ( pus )*
- Urinary tract infection. ( urine )*
- rhinoscleroma. ( infected tissues )*
* Specimens depending to site of infection.

11. Gram negative rod, non-motile.

12. Klebsiella is usually capsulated.

13. On Blood agar Klebsiellae produce large grey-white
usually mucoid colonies

14. On MacConkey agar Most klebsiellae are lactose-fermenting, producing mucoid pink colonies.

15. Citrobacter & Enterobacter
- Opportunistic pathogens occasionally isolated from urine, pus, blood and other specimens.

16. - C.freundii is Gram negative motile rod

17. On MacConkey agar C.freundii are lactose-fermenting, producing pink colonies.

18. - E.cloacae is Gram negative motile rod

19. On MacConkey agar Enterobacter are lactose-fermenting, producing shiny pink colonies.

20. Vogues Proskauer Test
used to detect acetoin in a bacterial broth culture
- The test is performed by adding alpha-naphthol and potassium hydroxide to the Voges-Proskauer broth which has been inoculated with bacteria. A cherry red color indicates a positive result, while a yellow-brown color indicates a negative result

21. Vogues Proskauer Test
- digestion of glucose to acetylmethylcarbinol. If glucose is being broken down, it will react with alpha-naphthol (VP reagent 1) and potassium hydroxide (VP reagent 2) to form a red color. Alpha-naphthol and potassium hydroxide are chemicals that detect acetoin.

22. Citrate Utilization Test
- The test is based on the ability of an organism to use citrate as its only source of carbon.
Bacteria that can grow on this medium turn the Bromothymol
blue indicator from green to blue.

23. Indole Production
When C.tetani is cultured in a medium which contains tryptophan. Indole production is detected by Kovac’s reagent which contains 4 (p)-dimethylaminobenzaldehyde which reacts with the indole to produce a red coloured compound.

24. Urease Test
The test organism is cultured in a medium which contains urea and the indicator phenol red.
When the strain is urease producing, the enzyme will break down the urea (by hydrolysis) to give ammonia and carbon dioxide. With the release of ammonia, the medium becomes alkaline as shown by a change
in colour of the indicator to pink-red.