[1] Univ Autonoma Nuevo Leon, Hosp Univ Dr Jose Eleuterio Gonzalez, Serv Gastroenterol, Monterrey 64460, Nuevo Leon, Mexico
[2] Univ Autonoma Nuevo Leon, Fac Med, Dept Microbiol, Monterrey 64460, Nuevo Leon, Mexico
[3] Collaborat Grp Digest Dis Res, Mexico City, DF, Mexico