Levinthal’s Medium- Composition, Principle, Preparation, Results, Uses


Levinthal’s medium is a type of enriched culture medium that was developed by Samuel Levinthal in 1938. It is used for the isolation and identification of Haemophilus species, which are gram-negative bacteria that cause respiratory infections such as pneumonia, meningitis, and otitis media. Haemophilus species require certain growth factors that are not present in ordinary media, such as blood agar or chocolate agar. These growth factors are hemin (also known as factor X) and nicotinamide adenine dinucleotide (NAD) (also known as factor V). Levinthal’s medium contains these growth factors in the form of rabbit or human blood, which is added to a base medium consisting of peptone, beef extract, sodium chloride, and bacitracin. Bacitracin is an antibiotic that inhibits the growth of normal flora, such as staphylococci and streptococci, that may contaminate the specimens or interfere with the identification of Haemophilus species. By using Levinthal’s medium, Haemophilus species can be differentiated based on their ability to grow on the medium with or without added blood, and their hemolytic reactions on the agar surface. Levinthal’s medium is also useful for cultivating other fastidious organisms that require similar growth factors, such as Neisseria and Bordetella species. Levinthal’s medium is one of the classic media in microbiology that has contributed to the advancement of bacterial diagnosis and taxonomy.