NNN medium:  Composition, Preparation, Results

By Acharya Tankeshwar •  Updated: 06/02/21 •  4 min read

The NNN (Novy-MacNeal-Nicolle), the medium is a common and world-known medium for isolation of the agent of the genus Leishmania, which causes leishmaniasis (cutaneous, mucocutaneous, or visceral). The culture of this organism in suitable media gives rise to a motile, extracellular form called, promastigote.

A variety of media has been used for the culture of Leishmanias. These can be divided into three main categories: semisolid, biphasic, and liquid. Other in vitro culture media include RPMI 1640, Evans, and Schneider.

NNN Medium was developed by Novy, McNeal and modified by Nicolle. NNN medium consists of two phases, blood agar base (part A) and Lockes solution (part B). This medium consists of blood agar and an overlay medium. The blood agar base is a highly nutritious medium that supports the growth of fastidious organisms like Leishmania and Trypanosoma. The specimens are inoculated into the liquid phase of the biphasic medium and incubated. The amastigotes transform into promastigotes in about 24 hours.

If you are in USA, CDC can provide ready to use NNN culture medium. You can inoculate the sample (keep it at room temperature) and mail them as soon as possible by overnight mail. CDC incubates the sample for 4 weeks, and if the culture becomes positive, it performs isoenzyme studies to identify the species of the parasites.

Amastigote form of Leishmania (LD Bodies)
Amastigote form of Leishmania (LD Bodies)

Uses of Culture:

Composition of Media:

Commercial suppliers supply the ready to use NNN medium which you have to purchase.  The constituents/ingredients of the media are:

Part A (ingredients  gms / litre)

Final pH ( at 25°C) 7.3 ± 0.2

Part B (ingredients  gms / litre)

Final pH ( at 25°C) 7.0 ± 0.2

Making of Culture Media/Tube

Commercial suppliers mostly supply dehydrated media (in the form of free-flowing powder). You can prepare ready-to-use culture media following the procedure mentioned below.

Part A:

  1. Suspend 31 grams in 1000 ml distilled water.
  2. Heat to boiling to dissolve the medium completely.
  3. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
  4. Cool to 45°C and aseptically add sterile defibrinated rabbit or human blood.
  5. Mix well and dispense in 5 ml amounts in test tubes or 25 ml amounts in flasks.
  6. Allow tubed media to cool in a slanted position.

Part B :

  1. Suspend 11.2 grams of Part B in 1000 ml distilled water.
  2. Heat to boiling to dissolve the medium completely.
  3. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
  4. Cool and add approximately 2 ml in tubes or 10-15 ml in flasks over solidified Part A medium.

Storage:

Keep the prepared media refrigerated until it is used (stable for 2-4 weeks) and bring it to room temperature right before inoculation.

Leishmania donovani Promastigotes in Culture
Leishmania donovani promastigotes in culture

Inoculation:

  1. Inoculate the specimen (spleen aspiration or bone marrow biopsy or lymph node aspiration) into the liquid phase of the biphasic medium.
  2. Incubate at 21-26°C for 4 weeks. Check for the growth of the organism and for possible fungal contamination after 4 days and continue by 4 days intervals for next 4 weeks.

Result:

If positive, luxuriant growth of the organism is seen in the media. Giemsa stains the culture filtrate and observes under a microscope; free, flagellated, Leishmania promastigote.

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please email at microbeonline@gmail.com