This is in contrast to Streptococcus species, whose growth is selected against ... crystal violet which inhibit the growth of Gram-positive bacteria. The differential ingredient is lactose.

Today you will finish up testing for both gram positive and gram negative organisms. There are few tests that can be read immediately that we call rapid tests. These are often useful initial steps to ...

"Normal flora" include Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, and anaerobes such as Bacteroides species, anaerobic gram-positive cocci, and Fusobacterium species.