Hi Sarah! Plate count agar (PCA) is a microbiological growth medium commonly used to assess or to monitor "total" or viable bacterial growth of a sample. PCA is not a selective medium. For LAB you have to use MRS, this medium was designed to favour the luxuriant growth of Lactobacilli for lab study.It contains sodium acetate, which suppresses the growth of many competing bacteria (although some other Lactobacillales, like Leuconostoc and Pediococcus, may grow).

Thank you for your answer Curiel. I was asking about PCA-BCP after I read this article, Lee & Lee (2008). It's explained that Korean FDA recommend to use this medium to enumerate the total number of LAB. Bromocresol purple is added as pH indicator to differentiate among LAB. So I was thingking, if it's a common medium for total bacteria and only gives color to LAB, I can distinguish and enumerate LAB and non-LAB in one medium. But I'm not very sure about it.

Hello Sarah! You should not use PCA to grow LAB because they are having complex nutritional requirement. Also, on PCA there are chances of growth of contaminates as it is a general purpose media. But MRS agar is selective as well as rich in nutrient which gives rise luxuriant growth of LAB. Just for a try, you can do plating on both the media and check the no. of colonies of LAB. If you feel there is no difference in cell count, then definitely you can grow for using PCA-BCP as colour change to acid production helps to differentiate colonies of LAB. But, upto my experience you will not get proper growth of LAB on this media.

@Nihir, thank you for your answer. I knew if we used PCA, the growth of LAB is not very good. I will try to use PCA-BCP, that's why I need more references. However, medium MRS is actually not selective for LAB, it gives luxurious growth for them but other bacteria could also grow, that's why I wanted to know if the addition of BCP could differ them to other bacteria