Blastocystis is a genus of common single-celled intestinal parasitic protists with an unsettled role in human health and disease. Being a stable component of intestinal microbiota, once established, ...the Blastocystis parasite appears more common in healthy individuals than in patients with infectious, functional, or inflammatory bowel disease. Recent data suggest that the parasite is associated with certain gut microbiota profiles and health indices. Convincing data and tools differentiating asymptomatic colonization from infection are yet to be demonstrated. Although the parasite may elicit disease under certain circumstances, the focus on Blastocystis may be shifting from a clinical to a public health perspective.
The development and integration of DNA-based methods in research and clinical microbiology laboratories have enabled standardised and comprehensive detection and differentiation of the microbes ...colonising our guts. For instance, the single-celled parasites Blastocystis and Dientamoeba appear to be much more common than previously thought, especially so in healthy individuals. While increasing evidence appears to suggest limited pathogenicity of these parasites, next-generation-sequencing-based studies have helped us to appreciate links between parasite colonisation and certain host phenotypical characteristics and gut microbial profiles. The fundamental question remains as to whether such parasites are merely indicators or active manipulators of gut microbiota structure and function. In this article, we collate existing evidence that these parasites are, at minimum, indicators of intestinal microbiota structure.
The development and implementation of DNA-based technologies in microbiology laboratories have helped us to understand that single-celled parasites such as Blastocystis and Dientamoeba are far more common than previously anticipated.
Colonisation by these parasites appears to be negatively associated with symptoms of severe gastrointestinal disease and high body mass index. Hence, these parasites are most common in individuals with a healthy gut, while less prevalent in patients with irritable bowel syndrome, and even less common in patients with inflammatory bowel disease. Moreover, Blastocystis is more common among normal-weight individuals than among overweight and obese individuals.
Several recent studies suggest that certain microbial communities are linked to the presence of parasites such as Blastocystis and Entamoeba. Indeed, the gut microbiota of a given person can, to some extent, be predicted by parasite colonization status – and vice versa.
We hypothesise that colonization by parasites such as Blastocystis is dependent on gut physiological conditions such as hypoxia, and that colonization is seen only in individuals with eubiosis rather than dysbiosis, that is, a predominance of anaerobic bacteria of high diversity rather than facultative anaerobic bacteria such as, for example, Enterobacteriaceae.
Interestingly, several recent studies have found Blastocystis frequently in healthy individuals 7, sometimes at higher prevalence than in those with gastrointestinal disease 8. ...available data ...suggest that another protist, Dientamoeba fragilis (Fig 1E), has a similarly variable ecological role in the human intestinal ecosystem, occasionally associated with disease 9 but also highly prevalent in healthy individuals 7,8. ...a commensal relationship is more likely for those organisms confined to the lumen of the gut, as exemplified by Escherichia coli, Blastocystis, Dientamoeba, Enteromonas hominis (Fig 1B), and Retortamonas intestinalis (Fig 1C). ...the nature of the host-eukaryote relationship will change depending on the context of the host and the gut ecosystem, so that the same organism may be parasitic in some cases and commensal in others.
Blastocystis is the most common intestinal parasite found in epidemiological studies in Iran. The genus Blastocystis comprises multiple subtypes (ST), evincing the existence of extensive intrageneric ...diversity. Meanwhile, information on Blastocystis STs in domestic animals in Iran is limited. This study was designed to identify the prevalence and subtype distribution of Blastocystis in domestic animals and to evaluate the extent of zoonotic origin of human Blastocystis carriage. A total of 395 faecal samples from farm animals (220 from poultry, 100 from sheep and 75 from cattle) and 23 Blastocystis positive samples from humans (available from the previous report of this study and included for reference) from the Khuzestan province, southwestern Iran, were analysed. Standard parasitological methods and PCR‐based analysis of the SSU‐rRNA gene were used. Overall, 115 (29.1%; 95% CI, 26.5%–31.6%) of the animals were positive for Blastocystis sp. by parasitological methods. The highest colonization rate was found in cattle (50.6%, 38/75), followed by sheep (32.0%, 32/100) and poultry (20.4%, 45/220). Eight Blastocystis STs were identified among 55 sequenced isolates from animals (n = 32) and humans (n = 23): ST3 (27.3%), ST14 (25.4%), ST1 (12.7%), ST7 (12.7%), ST2 (9.1%), ST6 (7.3%), ST5 (3.6%) and ST10 (1.8%). Blastocystis ST1 and ST3 were found in both human and non‐human hosts, and examples of shared alleles (strains) were observed. Meanwhile, ST2 was observed only in humans, ST5 only in sheep, ST6 only in poultry and ST10 in only cattle. This is the most comprehensive report of Blastocystis STs in farm animals in Iran.
Blastocystis is a common single-celled intestinal parasitic genus, comprising several subtypes. Here, we screened data obtained by metagenomic analysis of faecal DNA for Blastocystis by searching for ...subtype-specific genes in coabundance gene groups, which are groups of genes that covary across a selection of 316 human faecal samples, hence representing genes originating from a single subtype. The 316 faecal samples were from 236 healthy individuals, 13 patients with Crohn's disease (CD) and 67 patients with ulcerative colitis (UC). The prevalence of Blastocystis was 20.3% in the healthy individuals and 14.9% in patients with UC. Meanwhile, Blastocystis was absent in patients with CD. Individuals with intestinal microbiota dominated by Bacteroides were much less prone to having Blastocystis-positive stool (Matthew's correlation coefficient = −0.25, P < 0.0001) than individuals with Ruminococcus- and Prevotella-driven enterotypes. This is the first study to investigate the relationship between Blastocystis and communities of gut bacteria using a metagenomics approach. The study serves as an example of how it is possible to retrospectively investigate microbial eukaryotic communities in the gut using metagenomic datasets targeting the bacterial component of the intestinal microbiome and the interplay between these microbial communities.
Analysis of metagenomics data obtained from 316 faecal genomic DNAs revealed significant differences in microbiota patterns of Blastocystis carriers and non-carriers.
Cryptosporidium meleagridis is a common cause of cryptosporidiosis in avian hosts and the third most common species involved in human cryptosporidiosis. Sequencing of the highly polymorphic 60-kDa ...glycoprotein (gp60) gene is a frequently used tool for investigation of the genetic diversity and transmission dynamics of Cryptosporidium. However, few studies have included gp60 sequencing of C. meleagridis. One explanation may be that the gp60 primers currently in use are based on Cryptosporidium hominis and Cryptosporidium parvum sequence data, potentially limiting successful amplification of the C. meleagridis gp60 gene. We therefore aimed to design primers for better gp60 subtyping of C. meleagridis. Initially, ∼1,440 bp of the gp60 locus of seven C. meleagridis isolates were amplified using primers flanking the open reading frame. The obtained sequence data (∼1,250 bp) were used to design primers for a nested PCR targeting C. meleagridis. Twenty isolates (16 from human and 4 from poultry) previously identified as C. meleagridis by analysis of small subunit (SSU) rRNA genes were investigated. Amplicons of the expected size (∼900 bp) were obtained from all 20 isolates. The subsequent sequence analysis identified 3 subtype families and 10 different subtypes. The most common subtype family, IIIb, was identified in 12 isolates, represented by 6 subtypes, 4 new and 2 previously reported. Subtype family IIIe was found in 3 isolates represented by 3 novel, distinct subtypes. Finally, IIIgA31G3R1 was found in 1 human isolate and 4 poultry isolates, all originating from a previously reported C. meleagridis outbreak at a Swedish organic farm.
The intestinal protozoan parasite
is an important cause of diarrheal disease worldwide. The aim of this study was to expand the knowledge on the molecular epidemiology of human cryptosporidiosis in ...Sweden to better understand transmission patterns and potential zoonotic sources.
-positive fecal samples were collected between January 2013 and December 2014 from 12 regional clinical microbiology laboratories in Sweden. Species and subtype determination was achieved using small subunit ribosomal RNA and 60 kDa glycoprotein gene analysis. Samples were available for 398 patients, of whom 250 (63%) and 138 (35%) had acquired the infection in Sweden and abroad, respectively. Species identification was successful for 95% (379/398) of the samples, revealing 12 species/genotypes:
(
= 299),
(
= 49),
(
= 8),
(
= 5),
chipmunk genotype I (
= 5),
(
= 4),
(
= 2),
(
= 2), and one each of
,
,
, and
horse genotype. One patient was co-infected with
and
. Subtyping was successful for all species/genotypes, except for
, and revealed large diversity, with 29 subtype families (including 4 novel ones:
IIr, IIs, IIt, and
horse genotype Vic) and 81 different subtypes. The most common subtype families were IIa (
= 164) and IId (
= 118) for
and Ib (
= 26) and Ia (
= 12) for
. Infections caused by the zoonotic
subtype families IIa and IId dominated both in patients infected in Sweden and abroad, while most
cases were travel-related. Infections caused by non-
and non-
species were quite common (8%) and equally represented in cases infected in Sweden and abroad.
Strongyloidiasis is a disease caused by the intestinal helminth Strongyloides stercoralis . When the immune system of infected individuals is compromised, larvae may migrate from the gastrointestinal ...tract to other tissues, causing S. stercoralis hyperinfection syndrome, which has a reported mortality of 71%. In this case, we report a patient with S. stercoralis hyperinfection syndrome with central nervous system (CNS) involvement. An elderly South East Asian male tourist presented with pulmonary symptoms, fever and infiltrates on chest X-ray. He later developed symptoms of CNS infection. S. stercoralis larvae were found in a stool sample. Microbiological examination of cerebrospinal fluid revealed S. stercoralis- specific DNA. The patient was treated with oral and rectal ivermectin and albendazole. The condition was complicated by sepsis, bacteraemia and hypereosinophilia. Unfortunately, the patient eventually died from pulmonary oedema and insufficiency. This case highlights the global importance of Strongyloides CNS infection in endemic and non-endemic regions.
Background
Neoehrlichia mikurensis (N. mikurensis) is a newly discovered tick‐borne pathogen that can inflict life‐threatening illness in immunocompromised patients. N. mikurensis infection is only ...detectable by polymerase chain reaction (PCR)‐based methodologies. We describe three distinct clinical manifestations of N. mikurensis infection (neoehrlichiosis) in Danish patients receiving B‐lymphocyte‐depleting therapy, rituximab, for underlying hematological, rheumatological, or neurological disorders. All three patients went through a protracted pre‐diagnostic period.
Methods
N. mikurensis DNA was detected and confirmed using two methods. Blood was tested by specific real‐time PCR targeting the groEL gene and by 16S and 18S profiling followed by sequencing. Bone marrow was analyzed by 16S and 18S profiling.
Results
N. mikurensis was detected in blood samples in all three cases and in bone marrow from one of the three. The severity of the symptoms ranged from prolonged fever lasting more than 6 months to life‐threatening hyperinflammation in the form of hemophagocytic lymphohistiocytosis (HLH). Interestingly, all patients presented with splenomegaly and two with hepatomegaly. After starting doxycycline therapy, symptoms were relieved within a few days, and biochemistry and organomegaly quickly normalized.
Conclusion
We present three Danish patients recognized by the same clinician over a period of 6 months, strongly suggesting that many cases are going unrecognized. Second, we describe the first case of N. mikurensis‐induced HLH and emphasize the potential severity of undetected neoehrlichiosis.
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