Restriction-fragment-length polymorphism analysis of small-subunit rRNA genes of Blastocystis hominis isolates from geographically diverse human hosts

Hoevers, Jacquelien; Holman, Patricia J.; Logan, Kathleen; Hommel, M.; Ashford, R. W.; Snowden, Karen F.

doi:10.1007/s004360050010

Cited by 51 publications

(32 citation statements)

References 28 publications

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“…Many epidemiologic studies reported only further use of molecular analysis if there are samples positive by culture. 4,17,24,[28][29][30] An obvious conclusion is that these studies did not provide a true representation of the prevalence of Blastocystis infections in human population studies where some culture systems used may not enable certain strains of Blastocystis to grow.…”

Section: Discussionmentioning

confidence: 99%

Comparison of Microscopy, Culture, and Conventional Polymerase Chain Reaction for Detection of Blastocystis sp. in Clinical Stool Samples

Roberts¹,

Barratt²,

Harkness³

et al. 2011

The American Society of Tropical Medicine and Hygiene

113

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Abstract. We tested 513 stool samples from patients in Sydney, Australia for Blastocystis by using five diagnostic techniques: microscopy of a permanently stained smear using a modified iron-hematoxylin stain, two xenic culture systems (a modified Boeck and Drbohlav's medium and tryptone, yeast extract, glucose, methionine-9 medium), and two published conventional polymerase chain reaction methods specific for the small subunit ribosomal DNA. Ninety-eight (19%) samples were positive for Blastocystis in one or more of the diagnostic techniques. The PCR 2 method was the most sensitive at detecting Blastocystis with a sensitivity of 94%, and the least sensitive was microscopy of the permanent stain (48%). Subtype 3 was the most predominant subtype (present in 43% of samples assigned to this group). This study highlights the low sensitivity of microscopy when used as the sole diagnostic modality for detection of Blastocystis sp.

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Section: Discussionmentioning

confidence: 99%

Comparison of Microscopy, Culture, and Conventional Polymerase Chain Reaction for Detection of Blastocystis sp. in Clinical Stool Samples

Roberts¹,

Barratt²,

Harkness³

et al. 2011

The American Society of Tropical Medicine and Hygiene

113

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“…Genotypic characterization of Blastocystis from humans and animals was determined by an RFLP analysis of partial ssu rDNA (4). Although a few different primer pairs were used for the PCR-RFLP analysis of this gene in recent reports (3,7,12,19), we chose a primer pair specific to partial ssu rDNA of B. hominis (3) since mixed infection with intestinal protozoa might be found in some specimens. Genomic DNA and a primer pair (forward, 5Ј-G GAGGTAGTGACAATAAATC-3Ј; reverse, 5Ј-CGTTCATGATGAACAATT-3Ј) were used in PCR with conditions as described by .…”

Section: Methodsmentioning

confidence: 99%

Blastocystis Isolates from a Pig and a Horse Are Closely Related to Blastocystis hominis

Thathaisong¹,

Worapong

Mungthin³

et al. 2003

J Clin Microbiol

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Blastocystis has a widespread distribution in a variety of animals, which is a potential source of infection for humans. However, the contribution of zoonotic transmission remains unclear due to the absence of molecular proof of these organisms being identical to those found in humans. We report herein the similar subgroup of Blastocystis isolates from humans, pigs, and a horse using a restriction fragment length polymorphism (RFLP) analysis of partial small-subunit ribosomal DNA (ssu rDNA). Additionally, sequence and phylogenic analysis of partial ssu rDNA of Blastocystis from a human, a pig, and a horse sharing a common subgroup shows that Blastocystis isolates from a pig and a horse were monophyletic and closely related to B. hominis, with 92 to 94% identity. These results suggest the possibility of zoonotic potential of Blastocystis.Blastocystis hominis is one of the most common intestinal protozoa found in humans. This organism has been recognized as a causative agent of diarrhea both in immunocompromised and immunocompetent hosts in several studies (6,8). However, its role in human disease is still intensely debated since most cases are asymptomatic (2,18,21,23). It has been reported from both developed and developing countries, with a high prevalence in tropical areas, ranging between 30 and 50% (2, 15, 21). Our knowledge of this organism in several aspects, including its transmission, is still unclear. Zoonotic transmission of B. hominis has been speculated since epidemiological studies suggested a linkage between close contact with animals and blastocystosis in humans (8,17). In addition, Blastocystislike organisms were detected in a wide range of animals (1, 4, 9, 16). However, there was no conclusive evidence demonstrating animal-to-human transmission and zoonotic potential of B. hominis. One of the difficulties is the identification of these organisms since infection with Blastocystis has been diagnosed on the basis of morphology, host of origin, and in vitro culture characteristics (4). Although the morphology of Blastocystis detected in some animals was similar to those found in humans, only few animal isolates of Blastocystis were genetically proven to be identical to human isolates (7,25). Using a restriction fragment length polymorphism (RFLP) analysis of small-subunit ribosomal DNA (ssu rDNA), Clark identified a ribodeme of Blastocystis isolated from guinea pigs similar to that found in B. hominis (7). Yoshikawa et al. also showed that the pattern of random amplified polymorphic DNA in Blastocystis isolated from a chicken was similar to that displayed by B. hominis isolate HE87-1 (25). These observations, however, were limited and lack epidemiological data to support the association. Therefore, to determine the zoonotic potential of B. hominis, we conducted a study of genotypic characterization using RFLP analysis of partial ssu rDNAs of Blastocystis isolated from humans compared to those isolated from animals. ssu rDNAs of Blastocystis isolated from a human, a pig, and a horse were also partia...

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“…possible coinfection with other microbes, and the possibility that what is now called B. hominis includes both pathogenic and nonpathogenic species or strains (9,14). Although we could not resolve the long-standing controversy about the pathogenicity of B. hominis, we urge caution in attributing symptomatology to B. hominis infection.…”

Section: Discussionmentioning

confidence: 88%

“…Although we did not design our study to address the controversial question of whether B. hominis is a pathogen (9,14,15,17,20,26,27,31,32), we took advantage of the high incidence of B. hominis infection by comparing the patterns of acquisition and excretion of B. hominis with those of the known pathogens and nonpathogens. We were intrigued to note that, in several respects, B. hominis behaved more like a nonpathogen than a pathogen.…”

Section: Discussionmentioning

confidence: 99%

Multiyear Prospective Study of Intestinal Parasitism in a Cohort of Peace Corps Volunteers in Guatemala

et al. 2001

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We conducted a prospective, longitudinal study in a cohort of 36 Peace Corps volunteers (PCVs) in Guatemala to study the incidence and natural history of intestinal parasitic infections during the PCVs' >2-year overseas stay. PCVs collected stool specimens at least monthly and when ill with gastrointestinal symptoms. Of the 1,168 specimens tested, 453 (38.8%) were positive for at least one parasite and 48 (4.1%) were positive for a pathogenic parasite. A median interval of 187 days (range, 14 to 752 days) elapsed before the first documented parasitic infection, and the median intervals from arrival until subsequent infections (e.g., second or third) were >300 days. The PCVs had 116 episodes of infection with 11 parasites, including up to 4 episodes per PCV with specific nonpathogens and Blastocystis hominis. The incidence, in episodes per 100 person-years, was highest for B. hominis (65), followed by Entamoeba coli (31), Cryptosporidium parvum (17), and Entamoeba hartmanni (17). The PCVs' B. hominis episodes lasted 6,809 person-days (28.7% of the 23,689 person-days in the study), the E. coli episodes lasted 2,055 person-days (8.7%), and each of the other types of episodes lasted <2% of the person-days in the study. Gastrointestinal symptoms were somewhat more common and more persistent, but not significantly so, in association with pathogen episodes than with B. hominis and nonpathogen episodes. Although infections with pathogenic parasites could account for only a minority of the PCVs' diarrheal episodes, the continued acquisition of parasitic infections throughout the PCVs' >2-year stay in Guatemala suggests that PCVs repeatedly had fecal exposures and thus were at risk for infections with both parasitic and nonparasitic pathogens throughout their overseas service.The most common medical disorder among travelers from developed countries to developing countries is diarrheal illness (28, 29), which also is the most common reason that Peace Corps volunteers (PCVs) seek medical care (4, 7). Various bacterial enteropathogens, such as enterotoxigenic Escherichia coli, are the most commonly identified etiologic agents of travelers' diarrhea (5, 18, 21). However, surveillance data from 1990 suggested that intestinal parasitism was prevalent among PCVs and that infection with Entamoeba histolytica was particularly common among PCVs in Guatemala (7,10). In that context, we conducted studies among PCVs in Guatemala to identify risk factors for diarrheal illness in general and to determine how common various parasitic infections are in this setting. We first conducted a clinic-based, case-control study, which included 48 case (diarrheal) episodes, 26 control episodes, and 115 stool specimens obtained during these episodes (10). Six (12.5%) of the case episodes could be accounted for by protozoal pathogens, specifically, Cyclospora cayetanensis (three episodes), Cryptosporidium parvum (one), Giardia lamblia (one), and E. histolytica-Entamoeba dispar (one). Infection with Blastocystis hominis was equally prevalent among cas...

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Restriction-fragment-length polymorphism analysis of small-subunit rRNA genes of Blastocystis hominis isolates from geographically diverse human hosts

Cited by 51 publications

References 28 publications

Comparison of Microscopy, Culture, and Conventional Polymerase Chain Reaction for Detection of Blastocystis sp. in Clinical Stool Samples

Comparison of Microscopy, Culture, and Conventional Polymerase Chain Reaction for Detection of Blastocystis sp. in Clinical Stool Samples

Blastocystis Isolates from a Pig and a Horse Are Closely Related to Blastocystis hominis

Multiyear Prospective Study of Intestinal Parasitism in a Cohort of Peace Corps Volunteers in Guatemala

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