Can MacConkey agar develop gram-positive bacteria?

I was intrigued by your question, so I took google and found this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4316258/ In the article they claim that clinical streptococcus pneumonia was found in a 21 year old male. read more

Their inclusion makes MacConkey agar a selective medium suitable to isolate Gram negative bacteria. The cell wall of Gram positive bacteria does not prevent both of these two compounds from entering inside the cells. Both these two compounds are antibacterial, so in their presence Gram positive bacteria can not grow. read more

The MacConkey agar can only develop gram negative bacteria. The agar used in MacConkey test contains crystal violet colorant, which is the first colorant used in gram staining. What crystal violet does is it deeply penetrates the cell wall of gram positive bacteria. read more

MacConkey agar is an indicator, a selective and differential culture medium for bacteria designed to selectively isolate Gram-negative and enteric bacilli and differentiate them based on lactose fermentation. The crystal violet and bile salts inhibit the growth of gram-positive organisms which allows for the selection and isolation of gram-negative bacteria. Enteric bacteria that have the ability to ferment lactose can be detected using the carbohydrate lactose, and the pH indicator neutral red. read more