Resistance to macrolides is
usually mediated by genes on mobile elements. The
relationship between macrolide resistant isolates is not
clonal but depends on the movement of resistance genes
between isolates [36]. Penicillin resistance is not mediated
by mobile elements. Therefore, macrolide resistance
is spread by gene movement and penicillin resistance is
spread by isolate movement. Thus, as gene movement is
a more frequent event than isolate movement the ability
for macrolide resistance to spread is of higher concern
than penicillin resistance spread. We believe that the
increase in macrolide resistance as opposed to penicillin
resistance is associated with the ability of the macrolide
resistance genes to transfer more efficiently than the
penicillin resistant isolates to disseminate.