In this blog post, I am sharing information about the standard, conventional biochemical tests and their primary uses in the Microbiology laboratory for identifying pathogens of interest. Some of the biochemical tests mentioned here, for example, catalase test, and oxidase test, assist us in many ways apart from the primary purpose mentioned in this post;
MUG test is used to identify Escherichia coli. Escherichia coli produces the enzyme β-D-glucuronidase, which hydrolyzes β-D-glucopyranosid-uronic derivatives to aglycons and D-glucuronic acid.
Bacitracin sensitivity test differentiates Streptococcus pyogenes (positive) from other beta-hemolytic streptococci (resistant).
Bile solubility test is used to differentiate Streptococcus pneumoniae from other alpha-hemolytic streptococci. Bile or a solution of bile salt, such as sodium desoxycholate rapidly lyses pneumococcal colonies.
4. CAMP Test
Certain organisms such as Streptococcus agalactiae (Group B streptococci), produce a diffusible extracellular protein (CAMP) factor that acts synergistically with the beta-lysin of Staphylococcus aureus and causes enhanced lysis of RBCs.
Catalase test is used to differentiate Staphylococci (catalase-positive) from Streptococci (catalase test negative)
To differentiate members of the Enterobacteriaceae family.
Coagualse test is used to identify Staphylococcus aureus. Coagulase test differentiates Staphylococcus aureus (positive) from coagulase-negative staphylococci (CONS), such as S. epidermidis, S. saprophyticus.
8. DNase test
This test is used to determine the ability of an organism to hydrolyze DNA. It is primarily used to identify Staphylococcus aureus.
9. Indole test
This test is used to determine the ability of an organism to split tryptophan to form the compound indole. In a microbiology laboratory, it is used to differentiate gram-negative rods, particularly E. coli.
10. Litmus milk decolorization test
To help identify Enterococcus and some Clostridia, which have the ability to metabolize litmus milk.
12. Oxidase test
13. Urease test
Urease test is used to determine the ability of an organism to produce urease (an enzyme) that hydrolyzes urea. This test is done to help identify Proteus, Morganella, Yersinia enterocolitica, and Helicobacter pylori.