What is New York City Agar?

• New York City Agar (NYC Agar) is a selective and differential medium originally developed by Fauer, Weisburd, and Wilson at the New York City Department of Health. It was primarily designed for the selective isolation of pathogenic Neisseria species, particularly Neisseria gonorrhoeae, from clinical specimens.
• NYC Agar Base is composed of a peptone-corn starch-agar base that is buffered with phosphates. It is supplemented with horse plasma, horse hemoglobin, dextrose, yeast autolysate, and antibiotics. These components provide the necessary nutrients and selective properties for the growth and identification of pathogenic Neisseria species.
• The transparent nature of NYC medium allows for direct microscopic observation, aiding in the presumptive identification of mycoplasmas as well as Neisseria gonorrhoeae. In addition to Neisseria species, NYC medium also supports the growth of large-colony mycoplasmas (Mycoplasma hominis) and T-mycoplasmas (Ureaplasma urealyticum).
• The selective supplement added to NYC Agar contains antibiotics such as vancomycin, colistin, nystatin, and trimethoprim. These antibiotics help suppress the accompanying flora, inhibiting the growth of gram-positive bacteria (vancomycin), gram-negative bacteria (colistin), and certain other microorganisms. The starch in the medium neutralizes toxic metabolites produced by Neisseria species.
• Furthermore, NYC Agar contains yeast autolysate, which provides the necessary CO2 requirement for the enhanced growth of Neisseria. The presence of yeast autolysate reduces the lag phase of growth, leading to increased colony size and number.
• NYC Agar is useful for the diagnosis of gonorrhea and the recognition of active or asymptomatic mycoplasma infections. Its selective properties and transparent nature make it a valuable medium for the isolation and identification of pathogenic Neisseria species and mycoplasmas from clinical specimens.
• To use NYC Agar, the specimen can be directly streaked on the medium to obtain maximum isolation of the target microorganisms.

Principle of New York City Agar

The principle of New York City Agar (NYC Agar) is based on its composition and selective properties. NYC Agar is a transparent medium that contains a peptone-corn starch agar base buffered with phosphates and supplemented with various ingredients to support the growth and identification of pathogenic Neisseria species.

The key components and principles of NYC Agar are as follows:

1. Peptone and Corn Starch Agar Base: The peptone component in NYC Agar provides essential nutrients such as proteoses, peptones, and free amino acids that support the growth of pathogenic Neisseria species. The corn starch agar base acts as a solidifying agent for the medium.
2. Phosphate Buffer: Phosphate serves as a buffer in the medium, helping to maintain the pH and stabilize the growth environment.
3. Starch: Starch is included in NYC Agar to neutralize any toxic metabolites produced by Neisseria species, ensuring the viability and growth of the bacteria.
4. Sodium Chloride: Sodium chloride provides essential electrolytes that help maintain osmotic equilibrium in the medium, contributing to the integrity and function of bacterial cells.
5. Selective Supplement: The selective supplement added to NYC Agar contains specific antibiotics to inhibit the growth of unwanted microorganisms. Vancomycin inhibits the growth of gram-positive bacteria, colistin inhibits gram-negative bacilli (including Pseudomonas species), nystatin suppresses yeast growth, and trimethoprim lactate prevents swarming of Proteus species. The combination of trimethoprim and colistin acts synergistically against gram-negative bacilli.
6. Enrichments: NYC Agar is supplemented with lysed horse blood, horse serum, and yeast dialysate. These enrichments provide additional nutrients and growth factors to support the luxuriant recovery of pathogenic Neisseria species.
7. Yeast Autolysate: The presence of yeast autolysate in NYC Agar fulfills the CO2 requirements necessary for the enhanced growth of Neisseria. Yeast contains oxaloacetic acid, which is metabolized by gonococci to produce sufficient CO2 for the growth of capnophilic (CO2-requiring) Neisseria species. Additionally, the yeast autolysate reduces the lag phase of Neisseria growth, leading to increased colony size and number.

The combination of these components and principles in NYC Agar allows for the selective isolation and presumptive identification of pathogenic Neisseria species, including Neisseria gonorrhoeae. The transparent nature of the medium facilitates direct microscopic observation and aids in the identification of characteristic colony appearances.

Composition of New York City Agar

Ingredients	Gms / L
Proteose peptone	15.0
Corn starch	1.0
Glucose	5.0
Sodium chloride	5.0
Dipotassium hydrogen phosphate	4.0
Potassium dihydrogen phosphate	1.0
Agar	20.0

Final pH ( at 25°C) 7.4±0.2

Preparation of New York City Agar

The preparation of New York City Agar (NYC Agar) involves the following steps:

1. Suspend 25.50 grams of NYC Agar Base in 320 ml of distilled water.
2. Heat the suspension to boiling, ensuring complete dissolution of the medium.
3. Sterilize the medium by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Take care to avoid overheating, as excessive heat can be detrimental to the medium.
4. After autoclaving, cool the medium to a temperature of 45-50°C.
5. Aseptically add 100 ml of sedimented horse blood cells and 60 ml of citrated horse plasma to the cooled medium. These additions help provide essential nutrients and enrichments for the growth of pathogenic Neisseria species.
6. Rehydrate the contents of 1 vial of NYC Supplement and 1 vial of Yeast Autolysate Supplement according to the manufacturer’s instructions.
7. Aseptically add the rehydrated contents of the NYC Supplement and Yeast Autolysate Supplement to the medium, ensuring thorough mixing.
8. Pour the prepared NYC Agar into sterile Petri plates.

By following these steps, NYC Agar can be prepared and poured into Petri plates for subsequent use. It is important to maintain sterility throughout the preparation process to prevent contamination and ensure the integrity of the medium.

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

Cultural Response

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

On New York City Agar (NYC Agar), the growth of different Neisseria species can be observed and differentiated based on their colony characteristics. Here are the expected results for two important Neisseria species:

1. Neisseria gonorrhoeae:
   • Colony Appearance: Small colonies, ranging from 0.5-1.0 mm in size.
   • Color: Grayish-white to colorless.
   • Texture: Mucoid consistency.
2. Neisseria meningitidis:
   • Colony Appearance: Large colonies.
   • Color: Colorless to bluish-gray.
   • Texture: Mucoid consistency.

These colony appearances serve as presumptive identification of Neisseria gonorrhoeae and Neisseria meningitidis on NYC Agar. It is important to note that further confirmatory tests, such as biochemical testing or serological assays, are necessary to conclusively identify the specific Neisseria species.

By observing the colony characteristics on NYC Agar, particularly the size, color, and texture, it is possible to make an initial differentiation between Neisseria gonorrhoeae and Neisseria meningitidis. However, definitive identification requires additional confirmatory tests for accurate species identification.

Organism	Inoculum (CFU)	Growth	Recovery
Haemophilus influenzae	50-100	good-luxuriant	>=50%
ATCC 19418
Neisseria gonorrhoea	50-100	good-luxuriant	>=50%
ATCC 19424
Neisseria meningitidis	50-100	good-luxuriant	>=50%
ATCC 13090
Streptococcus pneumoniae	50-100	good-luxuriant	>=50%
ATCC 6303
Streptococcus pyogenes	50-100	good-luxuriant	>=50%
ATCC 19615
Pseudomonas aeruginosa	50-100	none-poor	<=10%
ATCC 27853
Proteus mirabilis	50-100	none-poor	<=10%
ATCC 13883

Uses of New York City Agar

New York City Agar (NYC Agar) has various uses in microbiology and diagnostic settings. Here are some important applications of NYC Agar:

1. Isolation and Cultivation of Pathogenic Neisseria Species: NYC Agar is primarily used as an enriched selective medium for the isolation and cultivation of pathogenic Neisseria species, including Neisseria gonorrhoeae and Neisseria meningitidis. It provides the necessary nutrients and selective properties to support the growth of these bacteria, aiding in their isolation and identification.
2. Gonorrhea Screening Programs: NYC Agar is particularly useful in screening programs for the detection of gonorrhea. It allows for the selective growth and identification of Neisseria gonorrhoeae from clinical specimens, aiding in the diagnosis and management of gonorrhea infections.
3. Recognition of Mycoplasma Infections: NYC Agar can also be used to recognize active or asymptomatic mycoplasma infections. In addition to supporting the growth of pathogenic Neisseria species, NYC Agar also facilitates the growth of genital mycoplasmas, such as Mycoplasma hominis and Ureaplasma urealyticum. This makes it valuable in establishing the frequency of association between mycoplasmas and urogenital tract infections.
4. Research and Diagnostic Studies: NYC Agar is utilized in research and diagnostic studies that involve the isolation, cultivation, and identification of pathogenic Neisseria species. It provides a reliable and selective medium for the study of these bacteria and their associated infections.

Overall, the uses of NYC Agar revolve around its ability to support the growth, isolation, and identification of pathogenic Neisseria species, aiding in the diagnosis and management of diseases such as gonorrhea. Additionally, it offers valuable insights into the association of mycoplasmas with urogenital tract infections.

Limitations of New York City Agar

New York City Agar (NYC Agar) has certain limitations that should be taken into consideration when using this medium. These limitations include:

1. Additional Testing for Complete Identification: While NYC Agar is selective for the isolation of pathogenic Neisseria species, further testing is required for complete identification. Biochemical, immunological, molecular, or mass spectrometry testing should be performed on colonies obtained from pure culture to achieve accurate and definitive identification of the Neisseria species.
2. Inhibition of Some Neisseria gonorrhoeae Strains: Certain strains of Neisseria gonorrhoeae may be inhibited by the concentration of vancomycin in selective media like NYC Agar. In cases where there is suspicion of gonorrhea, but the culture results are negative or for sterile specimens, it is recommended to add nonselective chocolate agar. The addition of chocolate agar provides a supportive environment for the growth of Neisseria gonorrhoeae strains that may be inhibited on selective media.

It is important to consider these limitations and follow appropriate protocols and guidelines when using NYC Agar. Supplemental testing and the inclusion of additional culture media may be necessary to ensure accurate identification, especially in cases where certain strains may be inhibited by the selective properties of the medium.

FAQ

References

• https://en.wikipedia.org/wiki/New_York_City_agar
• https://exodocientifica.com.br/_technical-data/M1348.pdf
• http://www.liofilchem.net/login/pd/ts/10040_TS.pdf
• https://microbeonline.com/new-york-city-medium-agar-introduction-principle-composition-uses/
• https://www.flickr.com/photos/nathanreading/6964972173
• https://stringfixer.com/nl/New_York_City_Agar
• https://www.microbiologiaitalia.it/terreni-di-coltura/new-york-city-agar/
• https://legacy.bd.com/ds/technicalCenter/inserts/L007377(06).pdf
• http://www.liofilchem.net/login/pd/ts/10040_TS.pdf
• http://www.oxoid.com/UK/blue/prod_detail/prod_detail.asp?pr=CM0367&c=UK&lang=EN&org=&minfo=Y&print=Y
• http://www.bacteriainphotos.com/n.%20gonorrhoeae.html