Susceptibility of nongrowing uropathogenic Escherichia coli to fluoroquinolones: killing and induction of the SOS response

Abstract

Uropathogenic Escherichia coli (UPEC) is the primary cause of urinary tract infections. UPEC is capable of entering the host cells and adapting to an intracellular lifestyle. This provides bacteria protection against host defensive mechanisms and antibiotics, leading to chronic and recurrent infections. Due to the limited nutrients inside host cells, bacteria are nongrowing. Nongrowing bacteria are not killed by most bactericidal antibiotics. However, some antibiotics of the fluoroquinolone group - gatifloxacin and ofloxacin – are known to be effective. According to an unpublished study, it was suggested that fluoroquinolones do not kill nongrowing bacteria but poison them. This study investigated the killing efficiency and in-duction of SOS response by a set of different fluoroquinolones in various growth conditions. Specifically, bactericidal effect on stationary phase culture before and after 1M NaCl incubation and induction of SOS response for growing stationary phase and regrowing cultures. The results of this thesis have supported the hypothesis of delayed bacterial death after fluoroquinolone poisoning.