Fatal levofloxacin failure in treatment of a bacteremic patient infected with Streptococcus pneumoniae with a preexisting parC mutation.

The fatal outcome of levofloxacin treatment in a patient with bacteremic pneumonia caused by Streptococcus pneumoniae with a preexisting parC mutation is reported. Failure was due to the emergence of a gyrA mutation after 4 days of therapy. Problems encountered in detecting first-step mutation isolates are discussed.