Pragmatic Combination of Available Diagnostic Tools for Optimal Detection of Intestinal Microsporidia

Microsporidia in HIV-Positive and HIV-Negative Pediatric Patients with Diarrhea at a Tertiary Care Hospital

Background  Human microsporidiosis presents as an important and rapidly emerging opportunistic infection. However, the exact burden of this infection especially in the pediatric population of Northern India remains unknown. In this study, we investigated the prevalence of microsporidia among human immunodeficiency virus (HIV)-positive and HIV-negative pediatric patients who presented with diarrhea. Methods  A total of 263 children were recruited consisting of 98 HIV seropositive with diarrhea and 165 HIV seronegative but with diarrhea. Morning stool samples were collected and both direct and formol ether concentrated samples were examined for the presence of intestinal parasites. The modified acid-fast staining was done for coccidian parasites and trichrome stain for microsporidia detection. Further, the species were detected using a real-time polymerase chain reaction (PCR) targeting a conserved region of the small ribosomal subunit rRNA gene of Enterocytozoon bieneusi , Encephalitozoon hellem , Encephalitozoon intestinalis , and Encephalitozoon cuniculi . Results  Overall, one or more parasites were detected in 52.04% (51/98) of HIV seropositive and 53.33% (88/165) of seronegative children ( p  = 0.8391). However, coccidian parasites were detected in a significantly huge number of HIV seropositive children (21.43% [21/98]) as compared with HIV seronegative children (4.24% [7/165]). Microsporidial DNA could be detected in HIV seropositive with diarrhea children (17.35% [17/98]) by PCR. A significant correlation between low CD4 count (≤ 200/μL) and intestinal parasite positivity could be established. Conclusion  Microsporidia is a significant cause of diarrhea in HIV seropositive pediatric patients and should be kept in mind as one of the differential diagnoses in such patients.

Intestinal Microsporidia Infection in Leukemic Children: Microscopic and Molecular Detection

BACKGROUND

Microsporidia infection was originally described as an immunocompromised associated pathogen. Limitations to correct microscopic diagnosis of microsporidia include size of the organism presenting a challenge even to a highly competent laboratory expert.

OBJECTIVE

The present study aimed to detect microsporidia infection among leukemic children. The performance of modified trichrome stain and PCR in the diagnosis of microsporidia was evaluated with further speciation.

METHODS

Stool samples of 100 leukemic children on chemotherapy were examined microscopically for microsporidia. DNA was extracted from all samples. Amplification was performed by conventional and nested PCR. Sequencing of amplified products was performed on unspeciated samples.

RESULTS

Microsporidia were detected in 23% of the children by MTS and 29% by PCR. The 29 positive samples were subjected to PCR for speciation. Enterocytozoon bieneusi was found to predominate in 20 cases, Encephalitozoon intestinalis in three cases, two cases had co-infection, and the remaining four samples were not amplified with either E. bieneusi or E. intestinalis specific primers. By DNA sequencing of the unspeciated samples, three samples shared high homology with Encephalitozoon hellem and one sample with Encephalitozoon cuniculi. Referring to PCR as a gold standard, MTS exhibited 72.4% sensitivity and 97.2% specificity with 90% accuracy. Among a number of studied variables, diarrhea and colic were significantly associated with microsporidia infection when diagnosed by either technique.

CONCLUSION

The use of sensitive and discriminative molecular tools will contribute to determining the true prevalence of microsporidiosis and possibly their potential transmission source depending on species identification.

Evidence for Zoonotic Potential of Enterocytozoon bieneusi in Its First Molecular Characterization in Captive Mammals at Bangladesh National Zoo

To determine the occurrence and genotypes of Enterocytozoon bieneusi in captive mammals at Bangladesh National Zoo and to assess their zoonotic significance, 200 fecal samples from 32 mammalian species were examined using a nested PCR and sequencing of internal transcribed spacer (ITS) gene. Enterocytozoon bieneusi was detected in 16.5% (33/200) of the samples. Seven different ITS genotypes were identified, including two known genotypes (D and J) and five new ones (BAN4 to BAN8). Genotype D was the most common genotype being observed in 19 isolates. In phylogenetic analysis, four genotypes (D, BAN4, BAN5, and BAN6), detected in 30 isolates (90.9%), belonged to Group 1 having zoonotic potential. The sequence of genotype J found in a Malayan pangolin was clustered in so-called ruminant-specific Group 2. The other two genotypes BAN7 and BAN8 were clustered in primate-specific Group 5. To our knowledge, this is the first report of molecular characterization of E. bieneusi in Bangladesh, particularly in captive-bred wildlife in this country. The potentially zoonotic genotypes of E. bieneusi are maintained in zoo mammals that may transmit among these animals and to the humans through environmental contamination or contact.

First identification and genotyping of Enterocytozoon bieneusi in humans in Myanmar

Background

Intestinal pathogen infections are widespread among impoverished populations. Enterocytozoon bieneusi is the most common pathogen of intestinal microsporidian species in humans worldwide. However, no epidemiological information is available on E. bieneusi infection in humans in Myanmar. The present study comprised the first identification and genotyping of E. bieneusi in humans conducted in Myanmar.

Results

A total of 172 fecal specimens were collected from the Wa people (one each) in four villages of Pangsang Township of the Matman District of Shan State, Myanmar, and each participant completed a questionnaire. E. bieneusi was identified and genotyped using polymerase chain reaction (PCR) and sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal RNA (rRNA) gene. The average prevalence of E. bieneusi was 8.72% (15/172), ranging from 3.85 to 13.89% by village. E. bieneusi infection was not related to any of the risk factors studied. Six genotypes were identified, comprising two known genotypes Peru6 (n = 10) and D (n = 1) and four novel genotypes (MMR23, MMR25, MMR86, and MMR87) (one each), and two people infected with genotype Peru6 were from the same family. A phylogenetic analysis based on a neighbor-joining tree of the ITS sequences of E. bieneusi indicated that all the six genotypes were clustered into group 1.

Conclusions

This is the first identification and genotyping of E. bieneusi in humans in Myanmar. The observations that the two people infected with genotype Peru6 were from the same family, and that all six genotypes obtained in the present study fell into zoonotic group 1, showed the potential for anthropogenic and zoonotic transmissions. The present data argue for the importance of epidemiological control and prevention from medical sectors.

Potential impacts of host specificity on zoonotic or interspecies transmission of Enterocytozoon bieneusi

Microsporidia are composed of a highly diverse group of single-celled, obligate intracellular fungi that colonize an extremely wide range of other eukaryotes, among which Enterocytozoon bieneusi is the most common species responsible for human microsporidiasis. Genotyping of E. bieneusi based on sequence analysis of the ribosomal internal transcribed spacer (ITS) has recognized ~500 genotypes in humans and a great variety of other mammals and birds. Those genotypes vary in genetic or hereditary characteristics and form 11 genetic groups in phylogenetic analysis of the ITS nucleotide sequences. Some of genotypes in Group 1 (e.g., D, EbpC, and type IV) and Group 2 (e.g., BEB4, BEB6, I, and J) have broad host and geographic ranges, constituting a major risk for zoonotic or cross-species transmission. By contrast, host specificity seems common in Group 3 to Group 11 whose members appear well adapted to specific hosts and thus would have minimal or unknown effects on public health. Multilocus sequence typing using the ITS, three microsatellites MS1, MS3, and MS7, and one minisatellite MS4, and population genetic analysis of Group 1 isolates reveal the occurrence of clonality, potential host adaptation, and population differentiation of E. bieneusi in various hosts. Nonetheless, it is still highly desirable to explore novel genetic markers with enough polymorphisms, to type complex or unstructured E. bieneusi populations of various host species and geographic origins, notably those belonging to Group 2 to Group 11. Additional population genetic and comparative genomic data are needed to elucidate the actual extent of host specificity in E. bieneusi and its potential impacts on zoonotic or interspecies transmission of microsporidiasis.