NYC Agar Base medium was initially created by Fauer, Weisburd and Wilson at the New York City Department of Health to isolate the pathogenic Neisseria strains from human samples. NYC medium, designed primarily to isolate pathogenic Neisseria is also able to support the growth of mycoplasmas with large colonies or mycoplasmas T (Ureaplasma). It is a translucent medium, highly selective, allowing direct microscopic observations and presumed identification of mycoplasmas and Neisseria gonorrhoeae.
Principle of New York City Agar
NYC Agar is a clear medium, made up of corn starch, peptone and base buffered by phosphates, and supplemented with horse hemoglobin, horse plasma yeast autolysate, dextrose and certain antibiotics. Proteose peptone is a rich source of proteoses, peptones as well as amino acids, which are free and supply nutrients that aid in the development of the bacteria. The medium is buffered by phosphate. Starch neutralizes toxic chemical metabolites created by Neisseria. The sodium chloride is essential for to maintain equilibrium in osmotic conditions, thus preserving the cell’s integrity. The supplement that is selective has the antibiotic vancomycin that reduces the growth of gram-positive bacteria. Colistin which blocks gram-negative bacteria, such as Pseudomonas species. Nystatin reduces yeast growth, and trimethoprim lactate blocks Proteus species from swarming. Trimethoprim in combination with colistin work together to combat bacteria that are gram-negative. Lysed horse serum, horse blood and yeast dialysate are nutrients that enable a rapid healing of disease-causing Neisseria species. The autolysate supplement for yeast fulfills the CO2 needs required to boost Neisseria growth. It is a source of oxaloacetic acids that is transformed by gonococci to produce enough CO2 to support the growth of gonococci that are capnophilic. Furthermore, the presence yeast autolysate decreases the lag period of development of Neisseria and increases the size and the number of colonies.
Composition of New York City Agar
|Ingredients||Gms / L|
|Dipotassium hydrogen phosphate||4.0|
|Potassium dihydrogen phosphate||1.0|
Final pH ( at 25°C) 7.4±0.2
Preparation of New York City Agar
- Submerge 25.50 grams into 320 milliliters distillate water.
- Bring the temperature to a boil to completely dissolve the medium.
- Sterilize using autoclaving with 15 lbs in pressure (121degC) over 15 mins. Beware of overheating.
- Cool to 45-50°C and then add aseptically 100 ml blood cells from horses that have been sedimented and 60ml of citrated horse plasma. Add Rehydrated contents of 1 vial NYC Supplement as well as 1 vial yeast autolysate Supplement.
- Mix well, then pour into sterilized Petri plates.
Physical Properties of New York City Agar
- Appearance: Cream to yellow homogeneous free flowing powder
- Gelling: Firm, comparable with 2.0% agar gel.
- Colour and Clarity of Prepared medium: Clear yellow to slightly opaque gel forms inside Petri plates
- Reaction: Reaction of 5.1% w/v aqueous solution at 25°C. pH : 7.4±0.2
- pH: 7.20-7.60
M1348: Cultural traits observed following the presence of 5-10 percent CO2 and 70-80 percent humidity. This was done with horse blood cells that have been sucked out and citrated horse plasma as well as the rehydrated the contents from 1 vial NYC Supplement (FD150 along with 1 vial Yeast Autolysate Supplement(FD027) After an incubation time of 35 to 37 degrees Celsius for 40-48 hours.
Storage and Shelf Life
Keep below 30degC in a tightly sealed container. The prepared medium between 2 and 8 degC. The expiry date should be noted on the label
Result on New York City Agar
- Neisseria gonorrhoeae:tiny (0.5-1.0 millimeters) grayish-white, to colorless mucoid colonies.
- Neisseria meningitidis: large mucoid colonies, colorless or blueish-gray
Uses of New York City Agar
- New York City (NYC) medium is a highly selective medium for the cultivating and isolation of pathogenic Neisseria species.
- It is helpful in gonorrhea screening programs as well as in the detection of mycoplasmas that are active or not. infections.
- The medium is useful in determining the frequency mycoplasmas that are associated with urinary tract infection.
- It also aids in the development of mycoplasmas that are genital (Mycoplasma hominis as well as Ureaplasma urinarylyticum).
Limitations of New York City Agar
- It is suggested that immunological, biochemical, mass spectrometry and molecular testing be conducted on colonies of pure culture to ensure complete identification.
- Certain varieties of Neisseria gonorrhoeae can be affected by the presence of vancomycin within the media that is selective, therefore the addition of nonselective chocolate is recommended, particularly for cases of suspicion that are culture negative or sterilized specimens.