Update README.md

README.md

@@ -103,9 +103,9 @@ of the abundance for resistant organisms over that of susceptible
 organisms.
 
 If the bacterial community is dominated by susceptible organisms, the
-index will be negative. Conversely, the index is positive if susceptible
+index will be positive. Conversely, the index is negative if susceptible
 organisms constitute a minority. If an antibiotic has the predicted
-effect on a bacterial community, the index should increase after the
+effect on a bacterial community, the index should decrease after the
 antibiotic is introduced.
 
 Let’s compute the vancomycin response index for each sample in the