title: Refractory giardiasis: a molecular appraisal from a tertiary care centre in India.
abstract: OBJECTIVE
  The intestinal flagellate Giardia lamblia includes many genetically distinct assemblages, of which assemblage A and B, predominantly infect humans. Nitroimidazoles derivatives (metronidazole and tinidazole) and nitazoxanide are some of the therapeutic agents for treatment of giardiasis. Nevertheless, some individuals with giardiasis are non-responsive to standard therapy. The present study highlights cases of refractory giardiasis and attempts to elucidate if genetic heterogeneity in the parasite is associated with treatment failure.
  
  
  METHODS
  Three stool samples were obtained on three consecutive days from 4000 patients with diarrhoea and were microscopically examined for the detection of trophozoites, and/or cysts, using both normal saline and Lugol's iodine. A hemi-nested polymerase chain reaction (PCR) assay using triose phosphate isomerase (tpi) as the target gene was performed to determine the assemblages. Sequencing of the PCR products of the patients showing failure to treatment of giardiasis was also performed.
  
  
  RESULTS
  Two per cent (82/4000) of the total patients were microscopically positive for Giardia lamblia in the stool samples. All these patients were treated with metronidazole/tinidazole as per the standard regimens. However, eight patients showed treatment failure to giardiasis as stool examinations were repeatedly positive even after treatment with multiple courses of anti-giardial therapy. Genetic characterisation of all eight Giardia isolates showed that they belonged to Assemblage B and had homogeneous sequences. These patients were either treated with extended regimens or with combination therapy of anti-giardials.
  
  
  CONCLUSIONS
  In our experience, combination of two or more drugs for a longer duration is the treatment modality to treat refractory giardiasis.
authors.forename: P
authors.initials: P
authors.lastname: Yadav
authors.affiliation: Department of Microbiology, Department of Gastroenterology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: V
authors.initials: V
authors.lastname: Tak
authors.forename: B R
authors.initials: BR
authors.lastname: Mirdha
authors.forename: G K
authors.initials: GK
authors.lastname: Makharia
mesh_terms: D000293:Adolescent; D000328:Adult; D000981:Antiprotozoal Agents / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D004359:Drug Therapy, Combination / Q000379:methods; D016829:Giardia lamblia / Q000302:isolation & purification*; D005873:Giardiasis / Q000175:diagnosis* / Q000469:parasitology / Q000473:pathology*; D006801:Humans; D007194:India; D008297:Male; D062606:Tertiary Care Centers; D017211:Treatment Failure; D055815:Young Adult
chemical_list: D000981:Antiprotozoal Agents