New York City Agar abbreviated NYC Agar is an enrichment culture media recommended for the selective isolation of gonococci species such as Neisseria species.It was originally developed by Fauer, Weisburd and Wilson at the New York City Department of Health for selective isolation of pathogenic Neisseria species from clinical specimens. It consists of primarily a peptone-corn starch agar-base buffered with phosphates and also supplemented with horse plasma, horse haemoglobin, dextrose sugar, yeast autolysate and some antibiotics (New York City Agar antibiotics).It very superior to other media generally employed for the isolation of Neisseria species and the transparent nature of the medium helps in studying the colonial growth types of bacteria colonies
Principle of New York City Agar
- It contains proteose peptone, horse plasma, haemoglobin which provide nutrients for the growth of Neisseria gonorrhoeae and Neisseria meningitidis
- The Phosphate buffers the medium.
- Other selective supplement added contains the antibiotics vancomycin, colistin, nystatin and trimethoprim which suppresses the accompanying flora.
- Vancomycin is inhibitory for gram-positive bacteria.
- Colistin inhibits gram negative bacteria, including Pseudomonas species
- trimethoprim inhibits Proteus species.
- The combination of trimethoprim and colistin acts synergistically against gram-negative bacilli
- Starch neutralizes the toxic metabolites produced by Neisseria .
- The yeast autolysate supplement fulfils the CO2 requirements needed to enhance Neisseria growth. Yeast also contains oxaloacetic acid which is metabolized by gonococci to produce sufficient CO2 for growth of capnophilic gonococci
- The presence of yeast autolysate also reduces the lag phase of growth of Neisseria , thus enhancing both size and number of colonies.
- The specimen can be directly streaked on the medium to obtain maximum isolation.
New York City Agar composition
The following are New York City Agar components
|Ingredients||Grams / Litre|
|Dipotassium hydrogen phosphate||4.000|
|Potassium dihydrogen phosphate||1.000|
|Final pH at temperature 25°C||7.4±0.2|
How to Prepare New York City Agar
- Starting by suspending 25.50 grams in 320 ml distilled water.
- Heat to boiling in order to completely dissolve the medium.
- Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Also avoid overheating and cool to temperature 45-50°C and aseptically add 100 ml of sedimented horse blood cells and 60 ml of citrated horse plasma along with rehydrated contents of 1 vial of NYC Supplement and 1 vial of Yeast Autolysate Supplement
- Mix well and pour into sterile Petri plates.
The preparation of New york city agar depends on each laboratory workload or the numbers of culture plates available. Anyway, note that a standard Petri dish is equivalent to 20 ml when completely poured.
NB: It is also advisable to incubate a petri dish for 24 hour for quality control in order to avoid wastage of resources and ease early determination of contamination after the preparation.
Appearance of Medium after preparation
NYC Agar appears yellow coloured clear to slightly opalescent gel forms in Petri dishes after preparation Depending on blood Supplement used,Colour change to reddish brown like chocolate agar
Type of Inoculums
- Urethral swab or Vaginal swab
How to inoculate on New york city Agar
- Streak the specimen or inoculum as soon as possible after it is received in the laboratory. If material is being cultured directly from a swab, proceed as follows
- Roll swab directly on the medium in a large “Z” to provide adequate exposure of swab to the medium for transfer of organisms.
- Cross-streak the “Z” pattern with a sterile wire loop
- Place the culture as soon as possible in an aerobic environment enriched with carbon dioxide(you can use an anaerobic jar with a candle)
- Incubate at 35 ± 2 °C and examine after overnight incubation and again after approximately 48 hours.
- Subculture for identification of N. gonorrhoeae should be made within 18–24 hours.
Plate reading and Colonies morphology
These cultural characteristics are observed after incubation at temperature 35-37°C for 40-48 hours in presence of 5-10% CO2 and 70% humidity with added sedimented horse blood cells and citrated horse plasma along with rehydrated contents of 1 vial of NYC Supplement and 1 vial of Yeast Autolysate Supplement
- Fauer, Weisburd, Wilson and May, 1973, Health Lab. Sci., 10: 44.
- Fauer, Weisburd and Wilson, 1973, Health Lab. Sci., 10: 55.
- Fauer Y. C., Weisburd M. H. and Wilson M. E., 1973, Health Lab Sci., 10(2), 61.
- Granato, Schneible-Smith and Weiner, 1981, J. Clin. Microbiol.13:963.
- Lawton and Koch, 1982, J. Clin. Microbiol., 20: 905.
- Simmons N. A., 1970, J. Clin. Pathol., 23, 757.