RESUMO
Enterohemorrhagic escherichia coli (EHEC) has been recognized as the main etiologic agent of hemorrhagic colitis and hemolytic uremic syndrome (HUS). The usefulness of antibiotic treatment in patients with EHRC infections is a matter of current debate. Knowledge on EHEC antimicrobial susceptibility patterns in different geographic areas is important for both treatment considerations and for strain characterization. We studied by diffusion disk agar technique the antibiotic susceptibility of 83 EHEC strains obtained from stools of patients with HUS or diarrhea. Eleven antimicrobials were tested (ampicillin, cotrimoxazole, tetracycline, chloramphenicol, furazolidone, gentamycin, amikacin, ciprofloxacin, erythromycin, vancomycin and metronidazol). Resistant strains by disk diffusion were tested for MIC (mg/ml) by agar dilution. SLT-I and SLT-II were detected with specific biotinylated gene probes. All 83 strains were susceptible to furazolidone, ciprofloxacin, gentamycin and amikacin. Resistance was detected to tetracycline 4 percent, chloramphenicol 5 percent, cotrimoxazole 24 percent and ampicillin 25 percent. As expected for EHEC strains all were resistant to erythromycin, vancomycin and metronidazol. Resistant strains were significantly more common in non toxigenic and SLT-I producing strains (p=0.01). Resistant strains were similarly distributed among patients who had diarrhea only and those who developed HUS (p=0.3). In Chile, resistant EHEC strains seem to be more common and of different genotypes than those reported in more developed countries. Regional differences of EHEC antibiotic susceptibility patterns indicate a need for continious monitoring, specially if antibiotic prove to be useful in disease prevention