1 / 14

Microbial Control

Microbial Control. Lab 4. Selective and Differential Media. We have completed Isolation of bacteria using steak plate and spread plate This is a good beginning, but now we must determine more about the bacteria using: Selective Media and Differential Media. Selective and Differential Media.

euridice
Download Presentation

Microbial Control

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Microbial Control Lab 4

  2. Selective and Differential Media We have completed Isolation of bacteria using steak plate and spread plate This is a good beginning, but now we must determine more about the bacteria using: Selective Media and Differential Media

  3. Selective and Differential Media Selective Media – chemicals added that allow certain bacteria to grow and inhibit others. Differential Media – Allows all bacteria to grow but has chemicals to cause a change in appearance of certain bacteria.

  4. Selective and Differential Media Media can be selective, differential or both The 3 media we will use today in Exercises 1-3 are BOTH selective and differential

  5. Selective and Differential Media • Exercise 1 – Manitol Salt Agar (MSA) • Manitol – carbohydrate (differential) • Sodium Chloride – salt (selective) • Phenol Red – pH indicator Only pathogenic forms of S. aureus can ferment manitol which produces acid and therefore causes the pH indicator to turn yellow Only staphylococci bacteria can live in salt MSA is Selective for all staphylococci and differential for S. aureus

  6. Selective and Differential Media Exercise 2 - Eosin Methylene Blue Agar (EMB) • Lactose – carbohydrate (differential) • Sucrose – carbohydrate (differential) • Eosin Y – Dye (selective) • Methylene Blue – Dye (selective) Dye inhibits growth of Gram + Bacteria Selective for Gram – bacteria and is Differential for fecal coliform bacteria by how actively it ferments the carbohydrate (fecal coliform will have a green metalic sheen)

  7. Selective and Differential Media Exercise 3 – Mac Conkey Agar • Lactose – carbohydrate (differential) • Bile salts – salt (selective) • Neutral Red – pH indicator • Crystal Violet – Dye (selective) Bile salts and dye inhibit Gram + bacteria Selective for Gram – bacteria and Differential for gram – especially enterbacteriaceae because they can ferment lactose and create acid causeing pH indicator to turn red

  8. Microbial Control Exercise 4 – Kirby bauer Antibiotic Sensitivity • Sensitive – if a bacteria is sensitive to an antibiotic, the antibiotic will inhibit or slow growth of that bacteria and will have a “zone of inhibition” (an area of no bacteria growth) around the antibiotic.

  9. Microbial Control Exercise 4 – Kirby bauer Antibiotic Sensitivity – (cont) • Resistant – if a bacteria is resistant to an antibiotic, then the presence of the antibiotic will have no affect on the growth of the bacteria

  10. Microbial Control Exercise 5 - Effectiveness of Disinfectants We will use paper disks soaked in various disinfectants to determine the effectiveness of those products Make sure to use a disk soaked in sterile water placed in center of agar plate for our control group

  11. Microbial Control Exercise 6 – Effect of pH • pH scale ranges fro 0 – 14 • pH 7 is neutral • Below 7 is acidic • Above 7 is basic • Each number is 10 times more than the one before it

  12. Microbial Control Exercise 6 – Effect of pH (cont) We want to determine the optimum pH for each bacteria Below pH 5.5 – Acidophiles pH 5.5 – 8.5 – Neutrophiles Above pH 8.5 - Alkaphiles

  13. Microbial Control Exercise 7 – Effect of Temperature • We want to determine the optimum temperature for bacteria • Cardinal Temperatures for a bacteria are their optimum temperature, minimum temperature and maximum temperature

  14. Microbial Control Exercise 7 – Effect of Temperature (cont) • Below 20° C – psychorphiles • Freezing to 30 ° C - psychrotrophs • 15 ° - 45 ° C – mesophiles • Usually bacteria in human body are mesophiles • Above 40 ° C – thermophiles • 65 ° – 110 ° C – Extreme thermophiles

More Related