Resistance of Streptococcus pneumoniae to Deformylase Inhibitors Is Due to Mutations in defB

Resistance to peptide deformylase inhibitors in Escherichia coli or Staphylococcus aureus is due to inactivation of transformylase activity. Knockout experiments in Streptococcus pneumoniae R6x indicate that the transformylase (fmt) and deformylase (defB) genes are essential and that a def paralog (defA) is not. Actinonin-resistant mutants of S. pneumoniae ATCC 49619 harbor mutations in defB but not in fmt. Reintroduction of the mutated defB gene into wild-type S. pneumoniae R6x recreates the resistance phenotype. The altered enzyme displays decreased sensitivity to actinonin.