Streptococcus pneumoniae Transposon Tn1545/Tn6003Changes to Tn6002Due to Spontaneous Excision in Circular Form of theerm(B)- andaphA3-Containing Macrolide-Aminoglycoside-Streptothricin (MAS) Element

Abstract

ABSTRACTThe macrolide-aminoglycoside-streptothricin (MAS) element, an ∼4.2-kb insertion containingerm(B) andaphA3resistance determinants, distinguishesStreptococcus pneumoniaetransposon Tn1545/Tn6003from Tn6002. Here, it is shown to be an unstable genetic element that, although it lacks recombinase genes, can exploit long,erm(B)-containing direct repeats acting asattsites for spontaneous excision that may result in loss. Consequent to excision, which is RecA independent, Tn1545/Tn6003changes to Tn6002. In pneumococcal populations harboring Tn1545/Tn6003, the latter appears to coexist with Tn6002.