Pyruvate Broth Test- Principle, Procedure, Results, Uses


The pyruvate broth test is a biochemical test that can serve two main objectives:

  • To assess the ability of bacteria to utilize pyruvate and produce metabolic acid.
  • To aid in the differentiation of Enterococcus faecalis from Enterococcus faecium.

Pyruvate is a key intermediate in several metabolic pathways, such as glycolysis, fermentation, and the citric acid cycle. Some bacteria can use pyruvate as a sole carbon and energy source and produce organic acids as the end products. These acids lower the pH of the medium and can be detected by a color indicator. Other bacteria cannot utilize pyruvate or produce neutral or alkaline compounds instead of acids.

Enterococcus faecalis and Enterococcus faecium are two closely related bacterial species that belong to the genus Enterococcus. They are gram-positive, catalase-negative, facultatively anaerobic cocci that are commonly found in the human gastrointestinal tract and can cause various infections, such as urinary tract infections, endocarditis, bacteremia, and wound infections. They are also resistant to many antibiotics and can pose a serious threat to public health.

The pyruvate broth test can help to distinguish between these two species based on their ability to utilize pyruvate and produce acid. Enterococcus faecalis can ferment pyruvate and produce lactic acid and oxaloacetic acid, which turn the medium yellow. Enterococcus faecium cannot ferment pyruvate and does not produce acid, so the medium remains greenish or slightly yellowish-green.

The pyruvate broth test is a simple, inexpensive, and reliable method to identify Enterococcus faecalis and differentiate it from Enterococcus faecium. It can also be used to test other bacteria that can utilize pyruvate and produce acid, such as Streptococcus bovis. However, it is not a definitive test and should be confirmed by other biochemical tests.