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

BackgroundBacterial 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.ObjectiveTo determine the susceptibility to rifaximin and other antimicrobial agents of enteropathogenic bacteria isolated from patients with acute gastroenteritis in Mexico.Material and methodsBacterial 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.ResultsIsolated 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).ConclusionsResistance 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.

ResumenAntecedentesLa resistencia bacteriana puede dificultar el tratamiento antimicrobiano de las gastroenteritis agudas. La susceptibilidad bacteriana de los enteropatógenos a la rifaximina, un antibiótico que alcanza altas concentraciones fecales (hasta 8,000 μg/g) no se ha evaluado en México.ObjetivosDeterminar la susceptibilidad a rifaximina y a otros antimicrobianos de bacterias enteropatógenas aisladas de pacientes con gastroenteritis aguda en México.Material y métodosSe analizaron las cepas bacterianas en las heces de 1,000 pacientes con diagnóstico de gastroenteritis aguda. Se probó la susceptibilidad a la rifaximina (RIF) con microdilución (< 100, < 200, < 400 y < 800 μg/ml), la susceptibilidad a cloranfenicol (CLO), trimetoprim-sulfametoxazol (T-S), neomicina (NEO), furazolidona (FUR), fosfomicina (FOS), ampicilina (AMP) y ciprofloxacino (CIP) se probó por difusión-agar a las concentraciones recomendadas por CLSI y ASM.ResultadosLas bacterias aisladas fueron: Escherichia coli (E. coli) enteropatógena (EPEC) 531, Shigella 120, Salmonella no-typhi 117, Aeromonas spp. 80, E. coli enterotoxigénica 54, Yersinia enterocolitica 20, Campylobacter jejuni 20, Vibrio spp. 20, Pleisiomonas shigelloides 20 y E. coli enterohemorrágica (EHEC 0:157) 18. La susceptibilidad global acumulada a RIF < 100, < 200, < 400, < 800 μg/ml fue del 70.6, el 90.8, el 99.3 y el 100%, respectivamente. La susceptibilidad global a cada antibiótico fue: AMP 32.2%, T-S 53.6%, NEO 54.1%, FUR 64.7%, CIP 67.3%, CLO 73%, FOS 81.3%. La susceptibilidad a RIF < 400 y < 800 μg/ml fue significativamente mayor que con los otros antimicrobianos (p < 0.001).ConclusionesLa resistencia de las bacterias enteropatógenas a antimicrobianos utilizados en gastroenteritis es alta. La rifaximina fue activa contra el 99-100% de las bacterias en concentraciones alcanzables en el contenido intestinal con las dosis recomendadas.