engleski

Low virulence associated with fluoroquinolone resistance of uropathogenic Escherichia coli strains

Escherichia coli is the most frequent cause of urinary tract infections (UTIs), and particular virulence characteristics are associated with ability of strain to cause uncomplicated UTI. The aim of this study was the characterization of virulence characteristics of E. coli strains isolated from urine of outpatients in Zagreb region, in dependence to flouroquinolone sensitivity. During the five-month study period a total of 2, 451 E. coli strains were isolated from urine of nonhospitalized patients with significant bacteriuria. A total of 60 fluoroquinolone-resistant (FR) and a total of 60 fluoroquinolone-sensitive (FS) E. coli strains were randomly collected and characterised. Susceptibility to antibiotics was determined by disk-diffusion and broth microdilution method according to NCCLS (National Committee for Clinical Laboratory Standards). For each strain O-serogroup, adhesion type, production of hemolysin, and the serum sensitivity were examined. Bacterial susceptibility to serum killing was measured by assessing regrowth after incubation in serum, the adhesins were determined by hemagglutination and inhibition of hemagglutination, and serotyping was performed on glass slides. The range of minimal inhibitory concentrations of ciprofloxacin was 8-64 mg/L in the resistant group of strains. All FR strains were co-resistant to amoxycillin, most (39) were co-resistant to trimethoprim/sulfametoxazole, and 20 out of 60 strains were co-resistant to aminoglycosides. Investigated virulence factors were significantly less frequent among resistant isolates. UTI-associated antigens were less prevalent in FR strains than in FS strains with a high frequency of strains with incomplete O-antigen in the resistant group in contrast to the sensitive group of strains (p<0.01). Hemolysin production and adhesins expression were less prevalent in FR strains than in FS strains as well (p<0.01), and in 38 (63.3%) and 39 (65%) of resistant strains adhesions and hemolysin were not detected, respectively. The prevalence of serum-resistant strains was significantly higher in FS group of strains, as compared to strains isolated in FR group (p<0.01), which is in accordance with higher virulence and invasive potential of these strains. These results suggest the association of fluoroquinolone resistance and a decrease in the expression of virulence factors in uropathogenic community-acquired E. coli

community-acquired urinary tract infections; fluoroquinolon-resistant Escherichia coli; virulence characteristics

DOI: 10.1111/j.1469-0691.2009.02858.x