selective &differenial media

2. selective &differenial media Supervisor: Ph. D Abdelraouf A. Elmanama Mohammed Mrwan laqqan Detect by: Zeinab H. Wahdan

3. Selective media Selective media are used for the growth of only select microorganisms. For example, if a microorganism is resistant to a certain antibiotic, such as ampcillin or tetracycline , then that antibiotic can be added to the medium in order to prevent other cells, which do not possess the resistance, from growing.

4. Media contains some dyes such as crystal violet , methylene blue and eosin Y. Other media contains bile salts which inhibits the growth of Gram positive bacteria

5. Thiosulfate citrate bile salt Agar (TCBS) Selective media for Vibrio Cholerae because the high pH which inhibit Gram +ve bacteria &most of Enter bacteria

6. Aspergillus Niger sabouraud dextrose agar Selective media for fungi because the pH5.6

7. Differential media • Differential media or indicator media distinguish one microorganism type from another growing on the same media.

8. This type of media uses the biochemical characteristics of a microorganism growing in the presence of specific nutrients or indicators (such asneutral red ,phenol red, methylene blue or eosin Y) added to the medium to visibly indicate the defining characteristics of a microorganism.

9. Blood agar plates are often used to diagnose infection. On the right is a positive Streptococcusculture; on the left a positive Staphylococcus culture

10. Examples for selective and differential media • Eosin methylene blue agar (EMB) • Mannitol Salt Agar (MSA) • MacConkey Agar (Mac) • SalmonellaShigella Agar(SSAgar

11. Eosin methylene blue agar (EMB) • Eosin methylene blue agar (EMB) is a selective and differential medium used to isolate fecal coliforms. • Selective because the contains of Eosin Y and methylene blue are inhibit growth of most gram positive bacteria

12. Differential because the contains of : 1-pH indicator are E & MB dyes which combine to form a dark purple precipitate at low pH 2-lactose carbohydrate sources which encourage the growth of fecal coli forms and provide a means of differentiating them as: • Lactose fermenter produced acid and gives pink colors. • Non-lactose fermenter normally-colored or colorless colonies

13. Eosin methylene blue agar (EMB)

14. E. coli results in a metallic green sheen on EMB .

15. Enterobacter aerogenes and Enterobacter cloacaeboth form pink colonies on EMB.

16. Salmonella typhimurium and Pseudomonas aeruginosa both form colorless colonies on EMB.

17. MacConkey Agar • MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. • Selective because the contains of Bile salts and crystal violet inhibit the growth of Gram positive organisms.

18. MacConkey Agar

19. Differential because the contains of : • Lactose as a source of fermentable carbohydrate, allowing for differentiation. • Lactose fermenter will gives red colors • lactose non- fermenter will give • normally- colored or colorless colonies. • Neutral red is a pH indicator that turns red at a pH below 6.8 and iscolorless at any pH greater than 6.8.

20. Non-fermenters will produce normally-colored or colorless colonies. • Lactose fermenters will produce pink colors colonies

21. Klebsiella pneumoniaeMicrococcus gluteus does not grow on Mac agar

22. Escherichia coli on Mac

23. E.Coli& Serratia marcesens on Mac agar

24. Mannitol Salt Agar (MSA) • Mannitol Salt Agar (MSA) is a selective and differential medium. • Selective because contain the high concentration of salt (7.5%) which selects for members of the genus Staphylococcus, since they can tolerate high saline levels. • Organisms from other genera may grow, but they typically grow very weakly.

25. MSA differential because the contains of : • pH indicator phenol red which gives yellow color at low pH. • Mannitol sugar as a carbon sources which encourage the growth Staphylococcus aureus and provide a means of differentiating them from the other Staphylococci which will not ferment mannitol.

26. Staphylococcus epidermidis Staphylococcus aureusyellow color

27. The Staphylococcus aureus will give yellow.  The Serratia marcesens does not grow on MSA

28. Streptococcus agalactiae does not grow on MSA. Staphylococcus epidermidis grows but does not ferment mannitol

29. SalmonellaShigella Agar (S.S Agar) • Salmonella Shigella Agar is a selective and differential medium. • Selective for Salmonella & Shigella because its containNa-citrate & bile salts which inhibit Gram +Ve & most of Gram - Ve bacteria . • Differential between Salmonella & Shigella because Salmonella can utilize the citrate a carbon source & give a black color as a result H2S produces . • But Shigella can notutilize the citrate a carbon source & give colorless

30. Salmonella on SS agar give a black color as a result H2S produces

31. Note Never Ever Trust The Selectivity Of The Selective Media

32. References:- http://en.wikipedia.org/wiki/Mannitol_Salt_Agar“ http://gateway.nlm.nih.gov/MeetingAbstracts/102265145.html 2003http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Media.html 2003http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Media.html#Bristol's_Medium http://books.google.com/books?id=AtjDUn5KfG0C&pg=PA172&ots=H0ClQyGxd4&dq=selective+and+differential+media&sig=6f8CshJIEPuoTNVVerDwYNttk_o#PPP15,M1 http://www.arabslab.com/vb/showthread.php?t=2415 http://en.wikipedia.org/wiki/Image:Proteus_McConkey.jpg#file http://www.biomedcentral.com/content/figures/1471-2180-4-6-4.jpg

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