Selective Media-1.pptx

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1. Selective & Deferential Media Presented to : Sir Rizwan sb P resented by : Hamza Khalid ( 224 300 ) Mateen Iqbal ( 224 335 ) Malik Atif ( 224 302 )

2. Selective Media Selective media are types of culture media used in microbiology that contain specific components designed to encourage the growth of certain microorganisms while inhibiting the growth of others. These media are selective because they create conditions that favor the growth of specific types of bacteria or fungi, making it easier to isolate and identify particular organisms from a mixed sample. The selectivity is achieved through the incorporation of various inhibitors, such as antibiotics, dyes, or specific nutrients that target certain groups of microorganisms.

3. Example 1) MacConkey Agar 2) Mannitol Salt Agar 3 ) Thayer-Martin Agar 4) Cetrimide Agar 5) Eosin Methylene Blue (EMB) Agar 6) LJ Agar

4. MacConkey Agar MacConkey Agar is a selective medium used in microbiology. It was developed by Alfred Theodore MacConkey , and it is commonly used to isolate and differentiate Gram-negative bacteria, particularly the members of the Enterobacteriaceae family. Composition: Peptone: Provides nitrogen and other nutrients for bacterial growth. Lactose: The fermentable carbohydrate that allows for the differentiation of lactose-fermenting and non-lactose-fermenting bacteria. Bile salts and crystal violet: Inhibit the growth of Gram-positive bacteria, allowing for the selective isolation of Gram-negative bacteria. Neutral red dye: Serves as a pH indicator. It turns red at acidic pH, which helps in distinguishing between lactose fermenters and non- fermenters .

5. Selective Properties: MacConkey Agar is selective because it contains bile salts and crystal violet, which inhibit the growth of Gram-positive bacteria. This allows for the preferential growth of Gram-negative bacteria. Appearance of Colonies: Lactose-fermenting colonies typically appear as pink to red. Non-lactose-fermenting colonies are usually colorless or pale. Common Uses: Isolation and differentiation of enteric bacteria, especially within the Enterobacteriaceae family. Identification of lactose fermenters , which include many clinically significant bacteria such as Escherichia coli.

6. Mannitol Salt Agar Mannitol Salt Agar (MSA) is a selective used in microbiology. It is particularly useful for the isolation and differentiation of Staphylococcus species, especially Staphylococcus aureus . Here are some key features of Mannitol Salt Agar: Selective Properties: MSA is selective because it contains a high concentration of salt (7.5% sodium chloride). This high salt concentration is inhibitory to many bacteria but allows for the growth of staphylococci, which are relatively salt-tolerant.

7. Composition: Peptone: Provides nitrogen and other nutrients for bacterial growth. Mannitol : The fermentable carbohydrate that allows for the differentiation of mannitol -fermenting and non-fermenting bacteria. Sodium chloride: The high salt concentration makes the medium selective for staphylococci. Phenol red: pH indicator that changes color from red to yellow under acidic conditions. Appearance of Colonies: Staphylococcus aureus colonies, which can ferment mannitol , appear yellow due to the acidic byproducts of fermentation. Other Staphylococcus species that do not ferment mannitol typically form pink to red colonies.

8. Common Uses: Isolation and differentiation of staphylococci, especially Staphylococcus aureus , from clinical specimens. Identification of potential pathogens in food samples. Interpretation: Yellow colonies indicate mannitol fermentation and are often associated with Staphylococcus aureus . Pink to red colonies suggest non-fermentation of mannitol and may indicate other staphylococci.

9. Thayer-Martin Agar Thayer-Martin Agar is a selective culture medium used for the isolation of Neisseria gonorrhoeae , the bacteria responsible for the sexually transmitted infection gonorrhea. It is named after the researchers who developed it: J.O. Thayer and M. Martin. Selective Properties: Thayer-Martin Agar is highly selective for Neisseria gonorrhoeae because it contains antibiotics that inhibit the growth of many other bacteria, particularly the normal flora of the genital tract. The antibiotics in the medium include vancomycin , colistin , and nystatin .

10. Composition: Vancomycin : Inhibits the growth of Gram-positive bacteria. Colistin : Inhibits the growth of Gram-negative bacteria other than Neisseria species. Nystatin : Inhibits the growth of fungi. Chocolate agar base: Provides nutrients for bacterial growth. Appearance of Colonies: Neisseria gonorrhoeae typically forms small, transparent, and grayish colonies on Thayer-Martin Agar.

11. Common Uses: Isolation of Neisseria gonorrhoeae from clinical specimens, particularly those obtained from genital sites. Screening for gonorrhea in diagnostic microbiology laboratories. Interpretation: Growth of colonies on Thayer-Martin Agar may indicate the presence of Neisseria gonorrhoeae . Inhibition of the growth of other bacteria and fungi allows for the selective isolation of Neisseria gonorrhoeae .

12. Cetrimide Agar Cetrimide Agar is a selective culture medium designed for the isolation and identification of Pseudomonas aeruginosa , a Gram-negative bacterium known for its opportunistic pathogenicity . The medium is named after the quaternary ammonium compound cetrimide , which is a key ingredient that imparts selectivity to the medium. Selective Properties: Cetrimide Agar is selective for Pseudomonas aeruginosa . The high concentration of cetrimide in the medium inhibits the growth of many other bacteria, allowing Pseudomonas aeruginosa to selectively grow.

13. Composition: Cetrimide : A quaternary ammonium compound that inhibits the growth of many bacteria but allows for the growth of Pseudomonas aeruginosa . Peptone and other nutrients: Provide essential nutrients for bacterial growth. Appearance of Colonies: Pseudomonas aeruginosa colonies on Cetrimide Agar typically appear as greenish or bluish-green, making them easily distinguishable from other bacterial colonies.

14. Common Uses: Isolation and identification of Pseudomonas aeruginosa from various clinical and environmental samples. Monitoring the presence of Pseudomonas aeruginosa in healthcare settings, especially in water sources. Interpretation: Growth of colonies on Cetrimide Agar may indicate the presence of Pseudomonas aeruginosa . The characteristic color of Pseudomonas aeruginosa colonies on this medium aids in the identification of this bacterium.

15. Löwenstein -Jensen (LJ) agar Löwenstein -Jensen (LJ) agar is a specialized culture medium used primarily for the isolation and cultivation of Mycobacterium species, especially Mycobacterium tuberculosis—the causative agent of tuberculosis (TB). The medium is named after its developers, Löwenstein and Jensen. Selective Properties: LJ agar is selective for the growth of mycobacteria , including the slow-growing Mycobacterium tuberculosis. It contains malachite green, an inhibitory dye that suppresses the growth of contaminants.

16. Composition: Egg-based medium: LJ agar is typically made using eggs, which provide essential nutrients for the growth of mycobacteria . Malachite green: Acts as a selective agent by inhibiting the growth of contaminants. Glycerol: Provides a carbon source for the metabolism of mycobacteria . Asparagine , citric acid, and potassium phosphate: Additional nutrients to support mycobacterial growth. Appearance of Colonies: Mycobacterial colonies on LJ agar are often rough, dry, and cream-colored. The characteristic appearance helps in the presumptive identification of Mycobacterium tuberculosis.

17. Common Uses: Isolation and cultivation of Mycobacterium tuberculosis and other mycobacterial species. Drug susceptibility testing for Mycobacterium tuberculosis. Incubation Conditions: LJ agar plates are incubated at a temperature of 37°C (98.6°F) for several weeks, as mycobacteria are slow-growing organisms.

18. Eosin Methylene Blue (EMB) Agar Eosin Methylene Blue (EMB) Agar is a selective and differential culture medium commonly used in microbiology for the isolation and differentiation of Gram-negative bacteria, particularly members of the Enterobacteriaceae family. The medium is named after the two dyes it contains: eosin Y and methylene blue. Selective Properties: EMB Agar is selective for Gram-negative bacteria. It contains eosin Y and methylene blue, which inhibit the growth of most Gram-positive bacteria.

19. Composition: Peptone: Provides nitrogen and other nutrients for bacterial growth. Lactose: The fermentable carbohydrate that allows for the differentiation of lactose-fermenting and non-lactose-fermenting bacteria. Eosin Y and Methylene Blue: Dyes that inhibit the growth of Gram-positive bacteria and differentiate lactose fermenters based on the color of the colonies. Appearance of Colonies: Lactose Fermenters (e.g., E. coli): Produce colonies with a dark center and a greenish metallic sheen. Non-lactose Fermenters (e.g., Salmonella): Form colorless colonies.

20. Common Uses: Isolation and differentiation of Gram-negative enteric bacteria, especially coliforms , from various samples, including fecal specimens and water samples. Interpretation: EMB Agar allows the differentiation of bacteria based on their ability to ferment lactose. The characteristic color of colonies helps in the identification of specific bacterial species.

21.  Differential media  Differential media are culture media designed to distinguish between different types of microorganisms based on their growth patterns, biochemical characteristics, or other identifiable traits. These media typically contain specific indicators, substrates, or chemicals that produce visible changes in the appearance of colonies or in the medium itself, allowing for the differentiation of microorganisms

22. Examples 1) MacConkey Agar 2) Blood Agar 3) Mannitol Salt Agar 4) Triple Sugar Iron (TSI) Agar 5) Hektoen Enteric Agar 6) CLED

23. MacConkey Agar MacConkey Agar is a selective and differential culture medium used in microbiology to isolate and identify Gram-negative bacteria, particularly those belonging to the Enterobacteriaceae family. Developed by Alfred Theodore MacConkey , this agar is widely employed in clinical laboratories for the detection of enteric pathogens, especially Escherichia coli and Salmonella species.

24. Composition: Peptone: Provides nitrogen and other nutrients for bacterial growth. Lactose: A fermentable carbohydrate used for differentiation. Bile salts and crystal violet: Selective agents inhibiting Gram-positive bacteria. Neutral red dye: pH indicator for differentiating lactose fermenters . Differential Properties: Differentiates between lactose-fermenting and non-lactose-fermenting bacteria. Lactose fermenters produce acid during fermentation, leading to a drop in pH. The neutral red pH indicator in the agar causes these colonies to appear pink or red. Non-lactose fermenters do not produce acid, and their colonies remain colorless or pale.

25. Appearance of Colonies: Lactose Fermenters (e.g., Escherichia coli): Appear pink to red. Non-lactose Fermenters (e.g., Salmonella): Appear colorless or pale. Interpretation: Pink/red colonies indicate lactose fermentation by Gram-negative bacteria. Colorless or pale colonies suggest non-lactose-fermenting Gram-negative bacteria.

26. Blood Agar Blood Agar is a general-purpose enriched culture medium used in microbiology for the isolation, cultivation, and identification of various microorganisms, especially fastidious bacteria that require extra nutrients. The medium contains blood, usually sheep or horse blood, which provides essential nutrients, and it allows for the observation of different hemolytic reactions.

27. Composition: Peptone and Yeast Extract: Provide nitrogen and other nutrients. Blood: Usually sheep or horse blood, which supplies additional nutrients and allows for the observation of hemolysis . Agar: Solidifying agent. Hemolysis : Blood Agar is often used to observe hemolytic reactions, where bacteria produce enzymes that lyse (break down) red blood cells. There are three main types of hemolysis : Alpha- hemolysis : Partial hemolysis , resulting in a greenish discoloration around the colonies. Beta- hemolysis : Complete hemolysis , leading to a clear zone around the colonies due to the complete breakdown of red blood cells. Gamma- hemolysis : No hemolysis , and there is no change in the appearance of the medium around the colonies.

28. Common Uses: Isolation and cultivation of a variety of bacteria, including pathogenic bacteria. Identification of hemolytic patterns for classification and differentiation of bacteria. Appearance of Colonies: Alpha-hemolytic Colonies: Greenish discoloration around colonies. Beta-hemolytic Colonies: Clear zones around colonies. Gamma-hemolytic Colonies: No change in the appearance of the medium around colonies.

29. Mannitol Salt Agar (MSA) Mannitol Salt Agar (MSA) is a selective and differential culture medium used in microbiology for the isolation and identification of Staphylococcus species, particularly Staphylococcus aureus . The medium is named for its two main components: mannitol , a sugar alcohol, and salt ( NaCl ). It was developed to inhibit the growth of most bacteria while promoting the growth of staphylococci.

30. Differential Properties: MSA is differential based on the ability of Staphylococcus species to ferment mannitol . Mannitol fermentation produces acid, causing a change in the color of the medium. Composition: Peptone: Provides nitrogen and other nutrients for bacterial growth. Mannitol : The fermentable carbohydrate that allows for the differentiation of mannitol -fermenting and non-fermenting bacteria. Sodium chloride ( NaCl ): The high salt concentration that makes the medium selective for staphylococci. Phenol red: pH indicator that changes color from red to yellow under acidic conditions.

31. Appearance of Colonies: Mannitol Fermenters (e.g., Staphylococcus aureus ): Produce yellow colonies due to the acid byproducts of mannitol fermentation. Non- fermenters (e.g., coagulase -negative staphylococci): Colonies remain red. Interpretation: Yellow colonies on MSA indicate mannitol fermentation and are often associated with Staphylococcus aureus . Red or pink colonies suggest non-fermentation of mannitol , which may indicate other staphylococci.

32. Triple Sugar Iron (TSI) Agar Triple Sugar Iron (TSI) Agar is a differential culture medium used in microbiology for the differentiation of enteric bacteria, especially those belonging to the Enterobacteriaceae family. The medium contains three sugars—glucose, lactose, and sucrose—along with iron salts and a pH indicator. TSI Agar is particularly useful for identifying bacteria based on their ability to ferment sugars, produce gas, and produce hydrogen sulfide.

33. Differential Properties: TSI Agar is differential based on several factors, including sugar fermentation, gas production, and hydrogen sulfide production. It helps distinguish between different genera and species of Enterobacteriaceae . Composition: Peptone: Provides nitrogen and other nutrients for bacterial growth. Glucose, Lactose, and Sucrose: Three sugars that serve as fermentation substrates. Phenol red: pH indicator that changes color based on the production of acids during sugar fermentation. Sodium thiosulfate and ferrous sulfate: Indicators of hydrogen sulfide production. Agar: Solidifying agent.

34. Common Uses: Identification of enteric bacteria, particularly within the Enterobacteriaceae family. Differentiation of bacteria based on their ability to ferment sugars and produce gas and hydrogen sulfide. Appearance of Tubes: The medium is usually dispensed in tubes with a slant and a butt. Slant: Contains the three sugars, and the pH indicator shows the fermentation of these sugars. Butt: Also contains the three sugars, but it provides an anaerobic environment to detect gas production.

35. CLED AGAR Cysteine -Lactose-Electrolyte-Deficient (CLED) Agar is a selective and differential culture medium used in microbiology for the isolation and differentiation of urinary tract pathogens. It is specifically designed for the cultivation of bacteria from urine samples and helps in the identification and quantification of bacterial growth.

36. Selective Properties: CLED Agar is selective for the growth of urinary tract pathogens and inhibits the swarming of Proteus species, which is important for the accurate interpretation of cultures. Differential Properties: Differentiates between lactose-fermenting and non-lactose-fermenting bacteria. Provides a visually distinguishable indicator for lactose fermentation. Composition: Peptone: Source of amino acids and nitrogen for bacterial growth. Lactose: A fermentable carbohydrate that aids in the differentiation of bacteria. Cysteine : An amino acid that helps in the reduction of sulfur compounds. Electrolytes: Balanced electrolytes support bacterial growth. Agar: Solidifying agent.

37. Indicator System: CLED Agar typically contains a pH indicator ( bromothymol blue or a similar dye) that changes color based on the acidity of the medium. Acid production during lactose fermentation leads to a change in color. Appearance of Colonies: Lactose Fermenters : Produce yellow colonies due to the acid byproducts of lactose fermentation. Non-lactose Fermenters : Colonies remain their natural color. Interpretation: Yellow colonies indicate lactose fermentation. Non-lactose fermenters may produce colonies with their natural color.

38. Hektoen Enteric Agar Hektoen Enteric Agar is a selective and differential culture medium used in microbiology for the isolation and differentiation of enteric bacteria, particularly those belonging to the family Enterobacteriaceae . The medium was developed to aid in the identification of Salmonella and Shigella species, which are significant causes of bacterial gastroenteritis.

39. Selective Properties: Hektoen Enteric Agar is selective, primarily inhibiting the growth of Gram-positive bacteria and certain Gram-negative bacteria, allowing for the isolation of enteric pathogens. Differential Properties: Differentiates between bacteria based on their ability to ferment carbohydrates, especially lactose and sucrose. Detects the production of hydrogen sulfide.

40. Composition: Peptone: Provides nitrogen and other nutrients for bacterial growth. Lactose and Sucrose: Fermentable carbohydrates that aid in differentiation. Bile Salts: Inhibit the growth of Gram-positive bacteria. Sodium Thiosulfate and Ferric Ammonium Citrate: Indicators of hydrogen sulfide production. Bromothymol Blue and Acid Fuchsin : pH indicators for detecting carbohydrate fermentation. Agar: Solidifying agent.

41. Appearance of Colonies: Lactose/Sucrose Fermenters : Produce yellow-orange colonies. Non-lactose/Sucrose Fermenters : Produce blue-green colonies. H2S Production: Indicates blackening of the medium. Common Uses: Isolation and identification of enteric bacteria, particularly Salmonella and Shigella species, from clinical specimens, food, and environmental samples. Differentiation of lactose and sucrose fermenters . Interpretation: Yellow-orange colonies indicate lactose/sucrose fermentation. Blue-green colonies indicate non-fermentation. Blackening of the medium indicates hydrogen sulfide production.