Objective To evaluate antibacterial activity of levofloxacin to
Helicobacter pylori ( H.pylori ) strains. Methods
The minimum inhibitory concentration (MIC) for 52 clinical isolates was detected by agar dilution method and compared with those of amoxicillin and
clarithromycin. To investigate the effects of pH variation on the susceptibility of H.pylori to levofloxacin, Mueller Hinton agar with 7% defibrinated sheep blood was adjusted to a pH range of 4 0 to 7 0 by adding hydrochloric acid. Results 1 9% of strains was resistant to levofloxacin, 25% was resistant to clarithromycin and 11 5% was resistant to amoxicillin. Dual resistance to amoxicillin and clarithromycin was demonstrated in five H.pylori strains, which were susceptible to levofloxacin. The prevalence of strains with resistance to clarithromycin was higher than that of strains with resistance to levofloxacin and amoxicillin ( P <0 05). The activity of levofloxacin was diminished under acidic environment ( P <0 01). Conclusions The study indicated a high rate of resistance of H.pylori to amoxicillin and clarithromycin in this area. Levofloxacin is an attractive candidate for the treatment of
Helicobacter pylori infection in case of combined resistance of the bacterium to the first line antimicrobial agents.