IN-VITRO SUSCEPTIBILITY OF ENTEROHEMORRHA GIC ESCHERICHIA-COLI TO ANTIMICROBIALS - RELATIONSHIP BETWEEN SUSCEPTIBILITY AND TOXIGENIC GENOTYPES

Enterohemorrhagic E coli (EHEC) has been recognized as the main etiolo gic agent of hemorrhagic colitis and hemolytic uremic syndrome (HUS). The usefulness of antibiotic treatment in patients with EHEC infection s is a matter of current debate. Knowledge on EHEC antimicrobial susce ptibility patterns in different geographic areas is important for both treatment considerations and for strain characterization We studied b y diffusion disk agar technique the antibiotic susceptibility of 83 EH EC strains obtained from stools of patients with HUS or diarrhea. Elev en antimicrobials were tested (ampicillin, cotrimoxazole, tetracycline , chloramphenicol, furazolidone, gentamycin, amikacin, ciprofloxacin, erythromycin, vancomycin, and metronidazol). Resistant strains by disk diffusion wets tested for MIC (mg/ml) by agar dilution. SLT-I and SLT -II were detected with specific biotinylated gene probes. All 83 strai ns were susceptible to furazolidone, ciprofloxacin, gentamycin and ami kacin. Resistance was detected to tetracycline 4% chloramphenicol 5%, cotrimoxazole 24% and ampicillin 25%. As expected for EHEC strains all were resistant to erythromycin, vancomycin, and metronidazol. Resista nt strains were significantly more common in non toxigenic and SLT-I p roducing strains (p = 0.01). Resistant strains were similarly distribu ted 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 that those reported in more developed countries . Regional differences of EHEC antibiotic susceptibility patterns indi cate a need for continuos monitoring,specially if antibiotics to be us eful in disease prevention.