I am working on a project of making a biofilm formation of Streptococcus uberis. One of the method I use is congo red agar. on trial level I've culture the bacteria on Congo red agar (CRA) and its grew as the literature said black dry some of them is red. and right now there is a little different of my culture on CRA the colony appearance mucoid with some tremendous slime on the surface of the colony. I thought my culture is contaminated but when I culture them again in blood agar it was the same bacteria Streptococcus uberis without slime (the same colony appearance).
My question is, is that normal ? or there is something wrong with my CRA? , or is that the appearance of positive biofilm formation of S uberis?
Any help, even general comments on false positives and CRA method, would be
Anim. Health Laboratory
PT. Greenfields Indonesia