Susceptibility to rifaximin and other antimicrobials of bacteria isolated in patients with acute gastrointestinal infections in Southeast Mexico

Abstract

Introduction: Enteropathogenic bacteria isolated in Mexico City have shown a high rate of resistance to different antibiotics, with the exception of rifaximin (RIF). RIF is a nonabsorbable antibiotic that reaches high fecal concentrations (≈ 8,000 μg/g). Susceptibility to antimicrobials can vary in different geographic regions. Aim: To study the susceptibility to rifaximin and other antimicrobials of enteropathogenic bacteria isolated in patients with acute diarrhea in the southeastern region of Mexico. Material and methods: A total of 614 strains of bacteria isolated from patients with acute diarrhea from 4 cities in Southeast Mexico were analyzed. An antibiogram with the following antibiotics was created: ampicillin (AMP), trimethoprim/sulfamethoxazole (T-S), neomycin (NEO), furazolidone (FUR), ciprofloxacin (CIP), chloramphenicol (CHL), and fosfomycin (FOS), assessed through the agar diffusion method at the standard concentrations recommended by the Clinical and Laboratory Standards Institute (CLSI) and the American Society for Microbiology (ASM), and RIF, assessed through microdilution at 4 concentrations. Results: The bacteria were Escherichia coli (55%), as the majority, in all its pathogenic variants, Shigella (16.8%), Salmonella (15.3%), Aeromonas (7.8%), and less than 5% Campylobacter, Yersinia, Vibrio, and Plesiomonas. The accumulated overall susceptibility to RIF was 69.1, 90.8, 98.9, and 100% at concentrations of 100, 200, 400, and 800 μg/ml, respectively. Overall susceptibility to other antibiotics was FOS 82.8%, CHL 76.8%, CIP 73.9%, FUR 64%, T-S 58.7%, NEO 55.8%, and AMP 23.8%. Susceptibility to RIF at 400 and 800 μg was significantly greater than with the other antimicrobials (P 98% of the bacterial strains and a high frequency of resistance to several common antimicrobials. Resumen: Antecedentes: Bacterias enteropatógenas aisladas en la Ciudad de México han mostrado una alta tasa de resistencia a diversos antibióticos, con excepción de la rifaximina (RIF). La RIF es un antibiótico no absorbible que alcanza altas concentraciones fecales (≈ 8,000 μg/g). La susceptibilidad a los antimicrobianos puede variar en distintas regiones geográficas. Objetivo: Investigar la susceptibilidad a rifaximina y otros antimicrobianos de bacterias enteropatógenas aisladas de pacientes con diarrea aguda en el sureste de México. Material y métodos: Se analizaron 614 cepas de bacterias aisladas de pacientes con diarrea aguda de 4 ciudades del sureste del México. Se realizó antibiograma con: ampicilina (AMP), trimetoprim/sulfametoxazol (T-S), neomicina (NEO), furazolidona (FUR), ciprofloxacino (CIP), cloranfenicol (CLO) y fosfomicina (FOS) por difusión en agar a las concentraciones estándar recomendadas por CLSI y ASM y RIF en 4 concentraciones por microdilución. Resultados: La mayoría de las bacterias fueron Escherichia coli (55%) en todas sus variantes patógenas, Shigella (16.8%), Salmonella (15.3%), Aeromonas (7.8%) y menos de 5% Campylobacter, Yersinia, Vibrio y Plesiomonas. La susceptibilidad global acumulada a RIF fue del 69.1, el 90.8, el 98.9 y el 100% a las concentraciones de 100, 200, 400 y 800 μg/ml, respectivamente. La susceptibilidad global a los otros antibióticos fue: FOS 82.8%, CLO 76.8%, CIP 73.9%, FUR 64%, T-S 58.7%, NEO 55.8% y AMP 23.8%. La susceptibilidad a RIF 400 y 800 μg fue significativamente mayor que con los otros antimicrobianos (p  98% de las cepas bacterianas y alta frecuencia de resistencia a varios antimicrobianos comunes. Keywords: Rifaximin, Bacterial resistance, Bacterial susceptibility, Southeast Mexico, Gastroenteritis, Acute diarrhea, Palabras clave: Rifaximina, Resistencia bacteriana, Susceptibilidad bacteriana, Sureste mexicano, Gastroenteritis, Diarrea aguda