Blastocystis Isolates from Patients with Irritable Bowel Syndrome and from Asymptomatic Carriers Exhibit Similar Parasitological Loads, but Significantly Different Generation Times and Genetic Variability across Multiple Subtypes.
Blastocystis spp is a common intestinal parasite of humans and animals that has been associated to the etiology of irritable bowel syndrome (IBS); however, some studies have not found this association. Furthermore, many biological features of Blastocystis are little known. The objective of present study was to assess the generation times of Blastocystis cultures, from IBS patients and from asymptomatic carriers. A total of 100 isolates were obtained from 50 IBS patients and from 50 asymptomatic carriers. Up to 50 mg of feces from each participant were cultured in Barret's and in Pavlova's media during 48 h. Initial and final parasitological load were measured by microscopy and by quantitative PCR. Amplicons were purified, sequenced and submitted to GenBank; sequences were analysed for genetic diversity and a Bayesian inference allowed identifying genetic subtypes (ST). Generation times for Blastocystis isolates in both media, based on microscopic measures and molecular assays, were calculated. The clinical symptoms of IBS patients and distribution of Blastocystis ST 1, 2 and 3 in both groups was comparable to previous reports. Interestingly, the group of cases showed scarce mean nucleotide diversity (π) as compared to the control group (0.011±0.016 and 0.118±0.177, respectively), whilst high gene flow and small genetic differentiation indexes between different ST were found. Besides, Tajima's D test showed negative values for ST1-ST3. No statistical differences regarding parasitological load between cases and controls in both media, as searched by microscopy and by qPCR, were detected except that parasites grew faster in Barret's than in Pavlova's medium. Interestingly, slow growth of isolates recovered from cases in comparison to those of controls was observed (p<0.05). We propose that generation times of Blastocystis might be easily affected by intestinal environmental changes due to IBS probably because virulent strains with slow growth may be selected, reducing their genetic variability.
Escuela Superior de Medicina, Instituto Politecnico Nacional, Plan de San Luis y Diaz Mirón s/n, Casco de Santo Tomas, 11340, Mexico City, DF, Mexico.
Gie-Bele
GB
Vargas-Sanchez
Hospital General "Dr. Manuel Gea Gonzalez", Calzada de Tlalpan 4800, Seccion XVI, 14080, Mexico City, DF, Mexico.
Mirza
M
Romero-Valdovinos
Hospital Infantil de Mexico Federico Gomez, Dr. Marquez 162, Doctores, 06720, Mexico City, DF, Mexico.
Celedonio
C
Ramirez-Guerrero
Centro Especializado de Atención Primaria "Melchor-Ocampo, Bicentenario", Secretaria de Salud del Estado Mexico, Estado de Mexico, 54880, Mexico.
Ines
I
Vargas-Hernandez
Hospital General "Dr. Manuel Gea Gonzalez", Calzada de Tlalpan 4800, Seccion XVI, 14080, Mexico City, DF, Mexico.
Maria Elena
ME
Ramirez-Miranda
Hospital General "Dr. Manuel Gea Gonzalez", Calzada de Tlalpan 4800, Seccion XVI, 14080, Mexico City, DF, Mexico.
Joel
J
Martinez-Ocaña
Departamento de Medicina Experimental, Facultad de Medicina, Universidad Nacional Autonoma de Mexico, 04510, Mexico City, DF, Mexico.
Alicia
A
Valadez
Departamento de Medicina Experimental, Facultad de Medicina, Universidad Nacional Autonoma de Mexico, 04510, Mexico City, DF, Mexico.
Cecilia
C
Ximenez
Hospital General "Dr. Manuel Gea Gonzalez", Calzada de Tlalpan 4800, Seccion XVI, 14080, Mexico City, DF, Mexico.
Eduardo
E
Lopez-Escamilla
Escuela Superior de Medicina, Instituto Politecnico Nacional, Plan de San Luis y Diaz Mirón s/n, Casco de Santo Tomas, 11340, Mexico City, DF, Mexico.
Maria Elena
ME
Hernandez-Campos
Departamento de Ecologia Evolutiva, Instituto de Ecologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad 3000, 04510, Mexico City, DF, Mexico.
Guiehdani
G
Villalobos
Hospital General "Dr. Manuel Gea Gonzalez", Calzada de Tlalpan 4800, Seccion XVI, 14080, Mexico City, DF, Mexico.
Fernando
F
Martinez-Hernandez
Hospital General "Dr. Manuel Gea Gonzalez", Calzada de Tlalpan 4800, Seccion XVI, 14080, Mexico City, DF, Mexico.
Pablo
P
Maravilla
D000328:Adult; D001499:Bayes Theorem; D016844:Blastocystis / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D016776:Blastocystis Infections / Q000469:parasitology*; D016022:Case-Control Studies; D016054:DNA, Protozoan / Q000032:analysis; D005243:Feces / Q000469:parasitology; D005260:Female; D014644:Genetic Variation; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000175:diagnosis / Q000469:parasitology*; D008297:Male; D008875:Middle Aged; D010361:Patients; D010802:Phylogeny; D060888:Real-Time Polymerase Chain Reaction; D016415:Sequence Alignment
D016054:DNA, Protozoan