Laboratory Comparison of Rifaximin and Norfloxacin for the Control of Bacterial Diarrhea in a Region of Northern Iran

Abstract

Context: Traveler's diarrhea is a common gastrointestinal illness and the most frequently encountered travel-related health problem. Objectives: This study aimed to investigate the prevalence of bacterial traveler’s diarrhea, determine the frequency of bacterial isolates, and compare their antimicrobial resistance patterns, with a particular focus on resistance to norfloxacin and rifaximin. Methods: Standard biochemical and microbiological tests were performed on diarrheal stool samples from 143 hospitalized patients, followed by antibiotic susceptibility testing using the disk diffusion method in accordance with Clinical and Laboratory Standards Institute (CLSI) 2021 guidelines. The minimum inhibitory concentrations (MICs) of rifaximin and norfloxacin were determined using the broth microdilution method. Results: Among culture-positive samples (23.78% of all samples), Salmonella spp. was the most frequently isolated pathogen (13.29% of all samples), whereas Aeromonas spp. had the lowest isolation rate (2%). The highest levels of antibiotic resistance were observed to tetracycline and ampicillin. The rifaximin MIC that inhibited the growth of 90% of enterotoxigenic Escherichia coli isolates was 512 μg/mL, which was 2-fold lower than that of norfloxacin. The corresponding MIC values for Salmonella spp., Campylobacter spp., and Aeromonas spp. were also 2-fold lower with rifaximin. Conclusions: Salmonella was identified as the most common bacterial cause of travelers’ diarrhea in these patients. The in vitro findings suggest that rifaximin may offer an advantage over norfloxacin in the treatment of bacterial diarrhea.