title: Low efficacy of metronidazole in the eradication of Blastocystis hominis in symptomatic patients: Case series and systematic literature review.
abstract: BACKGROUND
  Blastocystis hominis (B. hominis) is a protozoan commonly found in the gastrointestinal tract. There are doubts about its clinical significance. Metronidazole (MTZ) is the recommended first-line treatment.
  
  
  METHODS
  A retrospective review was carried out between 2011 and 2012. A total of 151 samples were randomly selected from 383 samples positive for B. hominis. Inclusion criteria were: suggestive symptoms, treatment indication and microbiological follow-up. A systematic review was performed of all studies that evaluated the effect of MTZ on B. hominis infection.
  
  
  RESULTS
  Forty-six patients met the inclusion criteria (64% women; age, 44.2±2 years). MTZ was used in 39 patients, 31 of whom obtained a clinical response (79.5%) but only 15 a microbiological response (48.4%). No dose-effect relationship was observed. Twenty patients with no initial microbiological response received a second round of treatment (MTZ, cotrimoxazole, paramomycin, others), with a microbiological response in 70%. Overall, B. hominis was cured in 72% (95% CI: 57%-83%). Of 54 treatments associated with a clinical response, a microbiological response occurred in 31 (57%), while in the remaining 12 with no clinical response, microbiological cure was observed in only 2 (17%) (P=.022). The eradication rate in the systematic review varied between 0% and 100%.
  
  
  CONCLUSIONS
  There seems to be a relationship between the clinical and microbiological response to B. hominis treatment. The microbiological response to MTZ treatment is insufficient in our geographical setting. The systematic review shows that the response to MTZ is very variable.
authors.affiliation: Servicio de Aparato Digestivo, Hospital Universitari Mutua Terrassa, Terrassa, Barcelona, España.
authors.forename: Lissette
authors.initials: L
authors.lastname: Batista
authors.affiliation: Servicio de Microbiología, CATLAB, Viladecavalls, Barcelona, España.
authors.forename: Josefa
authors.initials: J
authors.lastname: Pérez Jove
authors.affiliation: Servicio de Aparato Digestivo, Hospital Universitari Mutua Terrassa, Terrassa, Barcelona, España; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), España.
authors.forename: Mercè
authors.initials: M
authors.lastname: Rosinach
authors.affiliation: Servicio de Aparato Digestivo, Hospital Universitari Mutua Terrassa, Terrassa, Barcelona, España.
authors.forename: Victoria
authors.initials: V
authors.lastname: Gonzalo
authors.affiliation: Servicio de Aparato Digestivo, Hospital Universitari Mutua Terrassa, Terrassa, Barcelona, España.
authors.forename: Empar
authors.initials: E
authors.lastname: Sainz
authors.affiliation: Servicio de Aparato Digestivo, Hospital Universitari Mutua Terrassa, Terrassa, Barcelona, España; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), España.
authors.forename: Carme
authors.initials: C
authors.lastname: Loras
authors.affiliation: Servicio de Aparato Digestivo, Hospital Universitari Mutua Terrassa, Terrassa, Barcelona, España; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), España.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Forné
authors.affiliation: Servicio de Aparato Digestivo, Hospital Universitari Mutua Terrassa, Terrassa, Barcelona, España; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), España.
authors.forename: Maria
authors.initials: M
authors.lastname: Esteve
authors.affiliation: Servicio de Aparato Digestivo, Hospital Universitari Mutua Terrassa, Terrassa, Barcelona, España; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), España. Electronic address: ffbanares@mutuaterrasa.es.
authors.forename: Fernando
authors.initials: F
authors.lastname: Fernández-Bañares
mesh_terms: D000368:Aged; D000981:Antiprotozoal Agents / Q000494:pharmacology / Q000627:therapeutic use*; D016776:Blastocystis Infections / Q000188:drug therapy* / Q000469:parasitology; D016845:Blastocystis hominis / Q000187:drug effects* / Q000302:isolation & purification; D003967:Diarrhea / Q000188:drug therapy* / Q000469:parasitology; D004351:Drug Resistance; D057915:Drug Substitution; D004415:Dyspepsia / Q000188:drug therapy / Q000469:parasitology; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D008297:Male; D008795:Metronidazole / Q000494:pharmacology / Q000627:therapeutic use*; D008875:Middle Aged; D012189:Retrospective Studies; D012494:Sampling Studies; D016896:Treatment Outcome
chemical_list: D000981:Antiprotozoal Agents; D008795:Metronidazole
keywords: Blastocystis hominis; Clinical response; Metronidazol; Metronidazole; Microbiological response; Paramomicina; Paramomycin; Respuesta clínica; Respuesta microbiológica; Trimetropim-sulfamethoxazole; Trimetropim-sulfametoxazol