Growth Analysis of Escherichia coli and Salmonella typhi on MacConkey Agar Modification

MacConkey Agar (MCA) is a selective and differential media that is used to isolate and differentiate easily growing Gram-negative bacteria, especially members of the Enterobacteriaceae family. This study aims to obtain MCA modified media. Research has been conducted by inoculating Escherichia coli and Salmonella typhi on MCA media as control and modification of MCA from Nutrient Agar added by bile salts, violet crystals as inhibitors of Gram-positive bacteria, lactose addition to distinguish the properties of bacteria that can ferment lactose and bacteria that cannot ferment lactose, using phenol red as an indicator, the test bacteria were incubated for 24 hours at 37°C and then counted the number of CFU/mL colonies and their lactose fermentation properties were observed. Research results were calculated by the t-test. T-test results showed that there were no differences in the average number of colonies of Escherichia coli and Salmonella typhi in the two media. So it can be concluded that the modified MCA media can be used as a substitute for MCA and show the nature of Lactose Fermenter with a color change from orange to bright yellow because the indicator used is phenol red. So it can be concluded that the MCA modification media can be used as a substitute for MCA.