Susceptibility to rifaximin and other antimicrobial agents of bacteria isolated from acute gastrointestinal infections in Mexico

Abstract

Background: Bacterial resistance may hamper the antimicrobial management of acute gastroenteritis. Bacterial susceptibility to rifaximin, an antibiotic that achieves high fecal concentrations (up to 8,000 μg/g), has not been evaluated in Mexico. Objective: To determine the susceptibility to rifaximin and other antimicrobial agents of enteropathogenic bacteria isolated from patients with acute gastroenteritis in Mexico. Material and methods: Bacterial strains were analyzed in stool samples from 1,000 patients with diagnosis of acute gastroenteritis. The susceptibility to rifaximin (RIF) was tested by microdilution (< 100, < 200, < 400 and < 800 μg/ml) and susceptibility to chloramphenicol (CHL), trimethoprim-sulfamethoxazole (T-S), neomycin (NEO), furazolidone (FUR), fosfomycin (FOS), ampicillin (AMP) and ciprofloxacin (CIP) was tested by agar diffusion at the concentrations recommended by the Clinical & Laboratory Standards Institute and the American Society for Microbiology. Results: Isolated bacteria were: enteropathogenic Escherichia coli (E. coli) (EPEC) 531, Shigella 120, non-Typhi Salmonella 117, Aeromonas spp. 80, enterotoxigenic E. coli (ETEC) 54, Yersinia enterocolitica 20, Campylobacter jejuni 20, Vibrio spp. 20, Plesiomonas shigelloides 20, and enterohemorrhagic E. coli (EHEC 0:157) 18. The overall cumulative susceptibility to RIF at <100, <200, <400, and <800 μg/ml was 70.6, 90.8, 99.3, and 100%, respectively. The overall susceptibility to each antibiotic was: AMP 32.2%, T-S 53.6%, NEO 54.1%, FUR 64.7%, CIP 67.3%, CLO 73%, and FOS 81.3%. The susceptibility to RIF <400 and RIF <800 μg/ml was significantly greater than with the other antibiotics (p < 0.001). Conclusions: Resistance of enteropathogenic bacteria to various antibiotics used in gastrointestinal infections is high. Rifaximin was active against 99-100% of these enteropathogens at reachable concentrations in the intestine with the recommended dose.

Keywords

• Rifaximin
• Bacterial resistance
• Bacterial susceptibility
• Antibiotics
• Gastroenteritis
• Small intestinal bacterial overgrowth