I am trying to better understand the interest in determining the MAR index. Why not limit ourself to the resistance profile? Does MAR have a particular importance?
MAR is important as the phenomena of multidrug resistance bacteria is increased in the world. It allows classification of bacteria according to their resistance to a certain number of antibiotic among all antibiotics tested. It gives information on contamination from high risk environment such as feaces, water...
To strenghten your knowledge on MAR, I invite you to have a look on the paper of KRUMPERMAN 1983
The MAR index is calculated as the ratio of 'the number of antibiotics to which the organism is resistant' to the 'total number of antibiotics to which the organism is exposed' and it has been shown to be a cost effective and valid method of bacteria source tracking.