In vitro antimicrobial susceptibility testing of bacterial enteropathogenscausing traveler's diarrhea in four geographic regions

The emergence of resistant enteropathogens has been reported worldwide. Few data are available on the contemporary in vitro activities of commonly use d antimicrobial agents against enteropathogens causing traveler's diarrhea (TD). The susceptibility patterns of antimicrobial agents currently availab le or under evaluation against pathogens causing TD in four different areas of the world were evaluated. Pathogens were identified in stool samples fr om U.S., Canadian, or European adults (18 years of age or older) with TD du ring 1997, visiting India, Mexico, Jamaica, or Kenya. MICs of 11different a ntimicrobials were determined against 284 bacterial enteropathogens by the agar dilution method. Ciprofloxacin, levofloxacin, ceftriaxone, and azithro mycin were highly active in vitro against the enteropathogens, while tradit ional antimicrobials such as ampicillin, trimethoprim, and trimethoprim/sul famethoxazole showed high levels and high frequencies of resistance. Rifaxi min, a promising and poorly absorbable drug, had an MIC at which 90% of the strains tested were inhibited of 32 mug/ml, 250 times lower than the conce ntration of this drug in the stools. Amdinocillin, nalidixic acid, and doxy cycline showed moderate activity. Fluoroquinolones are still the drugs of c hoice for TD in most regions of the world, although our study has a limitat ion due to the lack of Escherichia coli samples from Kenya and possible bia s in selection of the patients for evaluation. Azithromycin and rifaximin s hould be considered as promising new agents. The widespread in vitro resist ance of the traditional antimicrobial agents reported since the 1980s and t he new finding of resistance to fluoroquinolones in Southeast Asia are the main reasons for monitoring carefully the antimicrobial susceptibility patt erns worldwide and for developing and evaluating new antimicrobial agents f or the treatment of TD.