Fig. 2

Isolate pairs with smaller SNP differences were more likely to come from the same hospital or hospitals with higher level of patient sharing. a Isolate pairs with smaller SNP differences were more likely to come from the same hospital (red line) than 100 permutations of random assignment of hospitals (gray lines). b In order to obtain the effect of different levels patient sharing, we calculated normalized proportion of pairs, which is the quantity (N _ki /N _i )/(N _k /N), where N is the total number of pairs of isolates, N _k is the number of pairs of isolates from hospitals with a particular amount of patient sharing k, N _i is the number of pairs of samples with less than i SNP differences, and N _ki is the number of pairs of samples coming from hospitals with a particular amount of patient sharing k differing by less than i SNPs. Samples collected from the hospitals with higher level of patient sharing were more likely to have smaller SNP difference. Even a very low level of patient sharing (0.1-0.2 %) shows higher normalized proportion of pairs with smaller SNP differences than no patient sharing