Resistance to fluoroquinolones has increased markedly since their introduction. Mechanisms of resistance to any antibiotic class might play a role in resistance to an unrelated antibiotic class. This study evaluated the relationship between extended-spectrum beta-lactamase (ESBL) production and ciprofloxacin resistance in Escherichia coli and Klebsiella pneumoniae strains isolated as causative agents of urinary tract infection. ESBL-producing strains were significantly more frequent among ciprofloxacin-resistant E. coli strains than among ciprofloxacin-susceptible E. coli strains (p = 0.015), but the difference was not significant among K. pneumoniae strains (p = 0.276).

The results suggest that the majority of S. typhimurium strains were closely related.