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LAB # 4 Selective & Differential Media

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by

Mariam Kaleem

on 1 October 2014

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Transcript of LAB # 4 Selective & Differential Media

Lab # 4: 1. Selective & Differential Media
2. Public Health Experiment

DIFFERENCE BETWEEN SELECTIVE & DIFFERENTIAL
Selective Media: Inhibit
Selective media are used for the growth of only select microorganisms.

Differential Media: Differentiate
Differential media or indicator media distinguish one microorganism type from another growing on the same media.

TYPES OF SELECTIVE AND DIFFERENTIAL MEDIUM
Eosin Methylene Blue (EMB)
Blood Agar ( BA)- Differential Media
Hektoen Enteric Agar (HE)
MacConkey Agar (MAC)
Mannitol Salt Agar (MSA)
Brilliant Green Agar (BGA)
Vogel-Johnson Agar (VJ)
EMB
Contains:
Dye
- Eosin & Methylene Blue = Selective
Gram "+" :no growth
Gram "- " :growth
Carbohydrates
- Lactose- acid production for fecal coliforms = Differential
Lactose Fermenters
: Purple black / Pink or Metallic green sheen (E.coli)
Non-Lactose Fermenters
: Colorless or translucent amber colonies
GRAM "+" vs Gram "-"
"+"
Retain Crystal Violet
Thick Peptidoglycan wall
Purple
No Outer Membrane
"-"
Does not retain Crystal Violet
Thin Peptidoglycan wall
Pink
Outer Membrane
Lactose: E. coli
Non-Lactose: S. enteritidis
Differential Plate: Blood Agar
Contains
5% Sheep blood
Differentiate Hemolytic types
Beta-Hemolysis
: Clear Zone
Alpha- Hemolysis
: Green to gray colonies
Gamma-Hemolysis
: No Hemolysis

S. aureus-Beta Hemolysis
B. meg- Alpha Hemolysis
Hektoen Enteric Agar
Contains:
Dyes :bromthymol blue and acid fuchsin & Bile Salts:
Gram "-" Enteric (growth)
Gram + (No growth)
Inhibits most non-pathogenic (G-) bacteria
Lactose
Lactose fermenter: Orange-yellow color (E.coli)
thiosulfate and ferric ammonium citrate
H2S producing bacteria- Black ppt production (Salmonella)
MacConkey
Contains
bile salts and the dye crystal violet
Gram "- "(growth)
gram "+" (no growth)
Lactose
Lactose fermenters
- Acid end products + Ph indicator
(red)
=
pink
Non-lactose Fermenters-
Translucent/ Colorless colonies
E.coli-Lactose
Salmonella-Non Lactose
MSA
Contains:
7.5% Sodium Chloride
- Halotolerant (G "+")
Mannitol
- Acid produce
pH Indicator
- Phenol red- Color Change Yellow

S. aureus: Opaque color-Yellow medium
S.epidemidis:Opaque color

Brilliant Green Agar
Contains
Brilliant Green Dye:
Gram "-" (Growth- Salmonella) & Gram "+" (NG)
Lactose & sucrose
: Fermentation-Acid
pH Indicator
- Red to yellow
E.coli-Yellow green colony surrounded by yellow-green zone
Salmonella-Slightly pink colony surrounded by brilliant red medium
Vogel Johnson Agar
Contains
Mannitol
Reduce Potassium Tellurite
: Inhibition nonstaphylococal organisms, some G+ & G-
lithium Chloride & High glycine
Phenol Red
Coagulase " + " Staphylococci (Gray-black colonies + Yellow medium)
others- Transluscent to black
TODAY'S LAB
Please streak bacteria
this order

1.S.aureus
2. S. pneumonia
3.M. Smegmatis
4.B. megaterium
5.E.coli
6. S. enteritidis
1
2
3
4
5
6
Antibiotics Resistance:
! Speed the growth of cattle, pigs and chickens, thus reducing costs for the producers (NY TIMES)

! at least 2 million Americans fall ill — and 23,000 die — from antibiotic-resistant infections (NY TIMES)

! Doctors contribution

FDA policy- Antibiotics labels- Agriculture

Link: http://www.nytimes.com/2013/12/22/opinion/sunday/the-peril-of-antibiotic-use-on-farms.html?_r=0

FDA, agriculture and antibiotics
FDA hopes to curb antibiotic use on farms
http://www.cnn.com/2013/12/11/health/fda-antibiotics-farms/
Streptococcus Pneumoiae
dissolves clotting
tonsilitis
Hemolysis-RUPTURE

RBC
"pathogenic"
(Hektoen Institute in Chicago)
Inhibit Major of b Gram -
Full transcript