Why is Baird Parker Agar considered a selective medium?
Baird-Parker agar is a type of agar used for the selective isolation of gram-positive Staphylococci species. It contains lithium chloride and tellurite to inhibit the growth of alternative microbial flora, while the included pyruvate and glycine promote the growth of Staphylococci.
What type of medium is Baird Parker Agar?
selective medium
Publisher Summary. Baird–parker agar is a selective medium for the enumeration of Staphylococcus aureus in foods and this was first reported by Baird–Parker. It is widely recommended by national and international bodies. Selectivity is attained with potassium tellurite and lithium chloride.
Is the Baird Parker Agar BPA test selective or differential?
Tellurite (TeO32−)-containing Baird-Parker agar (BPA) is used as a selective and differential medium for the isolation and enumeration of Staphylococcus aureus from foods (2).
What ingredient in the Baird Parker Agar is both selective and differential?
7,8 BD Baird-Parker Agar contains the carbon and nitrogen sources necessary for growth. Glycine, lithium chloride and potassium tellurite act as selective agents. Egg yolk is the substrate to detect lecithinase production, and, in addition, lipase activity.
Can E coli grow on Baird Parker Agar?
The medium allows the growth of Staphylococcus aureus and selectively inhibits the growth of most other bacteria….Result Interpretation of Baird Parker Agar.
| Organisms | Growth |
|---|---|
| Escherichia coli | Large brown-black, Negative for lecithinase |
What organisms can be differentiated on Baird Parker Agar?
Baird Parker Agar is used for the isolation and differentiation of coagulase-positive staphylococci in food and pharmaceuticals according to the Baird Parker method. As a nitrogen source for the organism, casein peptone and meat extract are added to the medium.
What is differential agar?
Differential media contain compounds that allow groups of microorganisms to be visually distinguished by the appearance of the colony or the surrounding media, usually on the basis of some biochemical difference between the two groups.
Does Staphylococcus aureus grow on blood agar?
On blood agar plates, colonies of Staphylococcus aureus are frequently surrounded by zones of clear beta-hemolysis. The golden appearance of colonies of some strains is the etymological root of the bacteria’s name; aureus meaning “golden” in Latin.
What does E coli look like on a MacConkey agar plate?
coli transformations create colored colonies on some media. For example, growth on a MacConkey agar plate shows that E. coli are not inhibited by bile salts and crystal violet. The pink color of the bacterial growth indicates E.
What is the role of Lecithinase?
Lecithinase is a type of phospholipase that acts upon lecithin. perfringens alpha toxin (lecithinase) causes myonecrosis and hemolysis. The lecithinase of S. aureus is used in detection of coagulase-positive strains, because of high link between lecithinase activity and coagulase activity.
Is an example of differential medium?
A differential medium support the growth of any microbe but distinguishes them based on how they metabolize or change the medium. One example of differential medium is blood agar. Blood agar distinguishes microbes based on their ability to lyse red blood cells (RBCs), a property known as hemolysis.
Why is blood agar differential?
Blood agar is differential media because 3 different types of hemolysis, or lysing of red blood cells, can be seen on this plate. Beta hemolytic organisms completely lyse red blood cells, leaving an area of total clearing underneath and around the colonies.
What does staph look like on blood agar?
STAPHYLOCOCCI – BLOOD AGAR CULTURE On blood agar, S. aureus usually displays a light to golden yellow pigment, whereas S. epidermidis has a white pigment and S. saprophyticus either a bright yellow or white pigment.
What type of bacteria grow on blood agar?
Blood Agar is used to grow a wide range of pathogens particularly those that are more difficult to grow such as Haemophilus influenzae, Streptococcus pneumoniae and Neisseria species. It is also required to detect and differentiate haemolytic bacteria, especially Streptococcus species.
What color is E. coli bacteria?
E. coli is Gram-negative because its cell wall is composed of a thin peptidoglycan layer and an outer membrane. During the staining process, E. coli picks up the color of the counterstain safranin and stains pink.
How do I know if I have E. coli colony?
coli colony is off-white or beige in color with a shiny texture. It often looks like mucus or a cloudy film over the whole surface of the plate. An E. coli colony is slightly raised and has an entire, fixed margin and a steady growth pattern, creating concentric growth rings in the colony.
Is lecithinase a toxin?
Lecithinase is a type of phospholipase that acts upon lecithin. It can be produced by Clostridium perfringens, Staphylococcus aureus, Pseudomonas aeruginosa or Listeria monocytogenes. C. perfringens alpha toxin (lecithinase) causes myonecrosis and hemolysis.
Where is lecithinase found?
Bacillus cereus, a strong lecithinase positive organism, can be identified using Mannitol-egg yolk-polymyxin (MYP) agar plates. It is an aerobic spore producing organism that is found commonly in soil, in many raw and processed foods,on vegetables, and often a causative agent of food poisoning.
Can a medium be both selective and differential?
Media can be DIFFERENTIAL; allowing different types of microorganisms to grow on it, but depending on the organism’s metabolism, different microorganisms may appear differently. A culture medium can be both selective and/or differential.
What makes a medium differential?
Such a medium normally consists of a mixture of protein digests (peptone, tryptone, etc.) and inorganic salts, hardened by the addition of 1.5% agar. Blood agar is one type of differential medium, allowing bacteria to be distinguished by the type of hemolysis produced (see below).
What is Baird Parker used for?
Baird- Parker Agar is widely used and is included in many standard procedures for testing foods, cosmetics, or swimming pool waters for the presence of Staphylococcus aureus. 2-6 It may also be used for the isolation of S. aureus from clinical specimens and is also called Egg- Tellurite-Glycine-Pyruvate Agar (ETGPA).
Which of the following components of Baird Parker Agar cause the observation of opaque zone around colonies?
The egg yolk emulsion contains lecithin and proteins that can be broken down by various bacterial enzymes. Lecithinase breaks down lecithin and produces an insoluble precipitate resulting in opaque zones in the medium surrounding the colonies.
Lithium chloride and potassium tellurite are selective agents which inhibit most bacteria other than S. aureus. Potassium tellurite is also a differential agent which is reduced to metallic tellurium by S. aureus resulting in black colonies.
Does E coli grow on Baird Parker Agar?
bacteria, and identifying pathogens amongst normal gastrointestinal flora can be challenging. Hektoen agar is a selective and differential medium that helps isolate and differentiate Salmonella and Shigella from normal enteric gram-negative organisms, while preventing the growth of most gram-positive organisms.
What bacteria does not grow on blood agar?
Fastidious organisms, such as streptococci, do not grow well on ordinary growth media but grow on blood agar.
What is the purpose of Baird Parker agar?
Baird–Parker agar is a selective medium for the enumeration of Staphylococcus aureus in foods and this was first reported by Baird–Parker. Baird-Parker Agar was developed by Baird Parker in 1962. It is a selective medium for the detection and enumeration of coagulase-positive staphylococci from food samples.
Where is Baird-Parker medium used in home economics?
1 Faculty of Home Economics and Department of Microbiology, The University of Alberta, Edmonton, Alberta, Canada T6G 2M8.
Is the tellurite additive in Baird Parker agar toxic?
The tellurite additive is toxic to egg yolk-clearing strains other than S. aureus and imparts a black color to the colonies. Egg yolk tellurite enrichment is added as supplement. Suspend desired quantity (as per manufacturers instruction) of the medium in 950 ml purified water.
How long does it take to dissolve Baird Parker agar?
Suspend desired quantity (as per manufacturers instruction) of the medium in 950 ml purified water. Heat with frequent agitation and boil for one minute to completely dissolve the medium. Autoclave at 121°C for 15 minutes.