Your doctor will take your medical history, ask you about recent activities, such as traveling, and perform a physical exam. A number of lab tests help diagnose parasitic diseases and other noninfectious causes of gastrointestinal symptoms:. If you have a blastocystis infection without signs or symptoms, then you don't need treatment. Mild signs and symptoms might improve on their own within a few days. Responses to these medications vary greatly.
Also, because the organism might not be the cause of your symptoms, improvement might be due to the medication's effect on another organism.
You'll likely see your primary care doctor. However, in some cases, you might be referred to someone who specializes in either infectious disease or in digestive system disorders gastroenterologist. Be aware of pre-appointment restrictions. Researchers have cited the stress of city living [ 21 ] and the stress of international travel [ ] as factors in development of such illness so it is possible that increased urbanization and travel has lead to greater morbidity.
Serious gastrointestinal illness has been attributed to various viral and bacterial causes [ ] and the hygiene hypothesis, which suggests that lack of gastrointestinal infection in childhood leads to chronic gastrointestinal illness [ ]. Additional research may be valuable in understanding the relationship between trends in the prevalence of unexplained chronic gastrointestinal illness and poorly understood protozoal infections. Studies of the pathogenesis of Blastocystis have focused on immunological reactions of epithelial cells to proteases secreted by Blastocystis.
Co-culture studies of Blastocystis have shown Blastocystis initially down-regulates and then up-regulates production of the inflammatory cytokine IL-8 in epithelial cells [ ]. Specific in vitro co-culture studies have indicated that Blastocystis possesses pathogenicity mechanisms [ 83 , ]. Pathogenesis was reported to result from interaction between parasite products e.
Blastocystis also induced cell apoptosis, possibly in a subtype-dependent manner. The pathogenesis of Blastocystis has been problematic, since the infection presents with abdominal pain in the absence of endoscopic findings [ ].
Recent research into the etiology of abdominal pain, constipation and diarrhea in patients with symptoms attributed to IBS has suggested that the these symptoms are produced by high levels of serine protease produced in the gastrointestinal tract which are capable of exciting neurons directly through the protease-activated receptor-2 PAR2 pathway [ 84 , 89 ].
This may offer an explanation for the conundrum of patients who experience pain in gastrointestinal illness in the absence of endoscopic findings [ ]. While Blastocystis infection may be more serious in immunocompromised patients [ ], studies have found that the majority of patients with symptomatic Blastocystis infection are immunocompetent, a pattern that is also present in infection with Giardia and Entamoeba histolytica.
A Canadian study found that of symptomatic patients with findings of only Blastocystis infection, only 3 were immunocompromised. Outbreaks of symptomatic Blastocystis infection have occurred in demographic groups not traditionally associated with immunocompromised status, such as groups of schoolchildren in the Middle East [ 58 ] and parents and children from the same families [ , ].
To better understand conflicting findings concerning Blastocystis pathogenicity, we surveyed studies in the US National Institutes of Health Pubmed Database see additional file 1. Many researchers identified a specific finding which they felt would be inconsistent with the behavior of a pathogen, such as a lack of correlation between the quantity of Blastocystis in stool samples and the patient's symptoms [ ] or the absence of endoscopic findings in symptomatic infection [ ].
Appendix B additional file 2 summarizes characteristics of known gastrointestinal pathogens which may be of value. Additional observations follow, with details in additional file 3 :. Studies conducted on the more insular population of a health maintenance organization found Blastocystis to be non-pathogenic [ 5 , 9 , — ]. The variable sensitivity of diagnostic techniques discussed earlier may be responsible for some of the disagreement. Additional causes may include:. The description of Blastocystis as a co-infection in symptomatic patients from Californian physicians in the 's [ ] is consistent with the behavior of Blastocystis sp.
Blastocystis acquired overseas was associated with symptomatic infection, while US-acquired blastocystosis was asymptomatic [ 6 ]. Following an increase in detection rates of Blastocystis in the 's see Appendix A in additional file 1 , US studies now show Blastocystis appearing frequently as a symptomatic mono-infection [ 14 ] with characteristics similar to Cryptosporidium parvum and Entamoeba histolytica.
Figure 8. The characteristics of common enteric protozoa reported in study of specimens from US patients collected in [ 14 ]. Studies from the 's reported Blastocystis was usually found as a co-infection with Giardia or Entamoeba histolytica in symptomatic patients [ , ], which was not the case in [ 14 ].
In , the number of symptomatic patients who were found to be singly infected with Blastocystis exceeded the number of samples found positive for Cryptosporidium , Giardia , and Entamoeba histolytica combined. Symptomatic carriage of enteric protozoa may be mediated by host genetics see Appendix B in additional file 2 :In affluent countries, if symptomatic carriers can seek and receive treatment, they may leave a population of asymptomatic carriers to be studied by epidemiologists.
Studies may have fulfilled many criteria listed in a communication as necessary to establish the pathogenicity of Blastocystis [ ]: fulfillment of Koch's postulates [ 48 , , ]; identification of an immune response [ 82 , 85 , 86 ]; definition of the pathogenesis [ 83 , , , ]; identification of treatments [ 94 , , ]; and description of point source outbreak of diarrhea where Blastocystis was the cause [ 57 , , ]. Blastocystis comprises a group of genetically diverse organisms, some of which will cause chronic or acute infection in some immunocompetent humans.
The behavior of Blastocystis in humans is consistent with that of Giardia and Entamoeba histolytica — expression of symptoms depends on parasite genotype, host genotype, host immunity, and age. Parasite genotype may vary geographically along with other factors. Most diagnostics and treatments in clinical use for blastocystosis have been shown to have low sensitivity.
Stool culture may provide the best short-term option for improving sensitivity, with serum antibody testing being a better option if it becomes available. PCR testing is currently the only way to identify the genotype of Blastocystis isolates. Researchers from less affluent countries consistently report that Blastocystis is pathogenic, while some researchers in more affluent countries have authored contradictory studies.
The outcome has been that little clinical research is performed or supported by affluent countries, while less affluent countries now publish sophisticated studies into Blastocystis infection [ 43 , 51 , 53 , 75 , 94 , , ]. Blastocystis has met all criteria for pathogenicity that are met by Giardia and Entamoeba histolytica , such as fulfillment Koch's Postulates [ 48 , , , ], demonstration of a treatment that eliminates the organism and the symptoms, an immune response that is elevated in symptomatic individuals [ 36 ], and a positive association with symptoms in most studies.
Blastocystis fails to meet criteria which Giardia and Entamoeba histolytica fail to meet. For example, all persons infected are not symptomatic; all researchers in all geographies have not shown an association between infection and symptoms; and the use of inadequate methods in some historical studies has produced the appearance of non-pathogenicity [ , ]. The lack of reliable diagnostics and the development of metronidazole resistance in Blastocystis may lead to many undiagnosed infections.
Blastocystis may play a significant role in several chronic gastrointestinal illnesses of unknown etiology which can be expensive to manage and debilitating to patients. J Clin Microbiol. Zierdt CH: Blastocystis hominis—past and future. Clin Microbiol Rev. Clin Pediatr Phila. Article Google Scholar. J Trop Med Hyg. J Pediatr Surg.
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Brumpt E: Blastocystis hominis N. Et formes voisines. Bull Soc Pathol Exot. Belova LM: [The ultrastructure of Blastocystis galli from chickens]. Trends Parasitol. Perez-Brocal V, Clark CG: Analysis of two genomes from the mitochondrion-like organelle of the intestinal parasite Blastocystis: Complete sequences, gene content and genome organization. Mol Biol Evol.
Diagn Microbiol Infect Dis. Mol Cell Probes. Parasitol Int. J Parasitol. BMC Gastroenterol. Nimri LF: Evidence of an epidemic of Blastocystis hominis infections in preschool children in northern Jordan.
Nimri L, Batchoun R: Intestinal colonization of symptomatic and asymptomatic schoolchildren with Blastocystis hominis. Successful treatment with paromomycin. Allergol Immunopathol Madr. CAS Google Scholar. Biedermann T, Hartmann K, Sing A, Przybilla B: Hypersensitivity to non-steroidal anti-inflammatory drugs and chronic urticaria cured by treatment of Blastocystis hominis infection.
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When and how to wash your hands. Food and water safety. For example, one study found levels of immunoglobulin G2 directed against Blastocystis in IBS patients when compared with asymptomatic controls [ 48 ].
Other researchers have speculated that the increased incidence of Blastocystis is not a cause of IBS but is rather an indicator of intestinal dysfunction [ 18 ]. Thus, current studies do not suggest a clear role for Blastocystis as an etiologic agent of IBS, and controlled trials demonstrating a resolution of symptoms in Blastocystis -infected IBS patients with eradication of the organisms are needed [ 2 ].
Blastocystis is a polymorphic organism, and 4 major morphologic forms—vacuolar, cyst, granular, and amoeboid—can be seen in stool and axenic cultures.
Blastocystis is detected using standard clinical parasitologic techniques that are used to detect other enteric parasites, including direct smears stained with trichrome Figure 1 [ 49 ]; various concentration techniques, such as formol-ether ethyl acetate concentration technique [ 32 ]; and in vitro culture [ 50 ] Culture techniques are, most likely, more sensitive than direct smears.
Amplification of Blastocystis -specific DNA by polymerase chain reaction directly from stool has been reported and permits identification of the Blastocystis subtypes [ 2 , 9 ]. In comparative studies of diagnosis, polymerase chain reaction—based methods coupled with short-term axenic in vitro culture had the highest diagnostic utility in characterizing stool specimens [ 1 , 32 ]. As with other enteric pathogens, the examination of multiple stool specimens increases the diagnostic yield.
Blastocystis infection results in a serologic response, which can be detected by enzyme-linked immunosorbent assay or other assays; however, serologic testing is not currently used for diagnosis of this infection [ 51 ]. Fecal immunoassays are under development but have not been commercialized.
Remarkably, many laboratories do not report Blastocystis because of the long-held view by some in the medical community that it is always nonpathogenic. Treatment of Blastocystis infection remains a complicated issue. Because there is still a great deal of debate about the true pathogenicity of Blastocystis , there is still much debate about the need for treatment. Further knowledge about the genotyping and subtyping of Blastocystis and the impact that various subtypes may have on pathogenicity and antimicrobial efficacy is still being sought [ 22 ].
Patients with Blastocystis isolated in the stool can be coinfected with other pathogens, such as G. It is quite possible that patients who respond to treatment for Blastocystis with metronidazole or trimethoprim-sulfamethoxazole TMP-SMX may actually have clinical improvement owing to treatment of a secondary pathogen. To date, a number of antimicrobial agents have been used for treatment of Blastocystis infection Table 1 ; however, randomized, controlled trials are limited.
There have been 2 published placebo-controlled studies, and both concluded that resolution of symptoms was associated with eradication of the organism. It is not clear whether any of these patients harbored resistant subtypes or were reinfected [ 54 ].
In a study by Mogaddham et al [ 55 ], 28 of Blastocystis -infected patients were classified as having severe infection.
Twelve of these patients were treated with metronidazole, with infection eradicated in only 4. It is possible that metronidazole is effective for certain patients but does not provide complete eradication, particularly in those with severe infection, or that patients who did not respond may have been infected with resistant subtypes. Given the variable agreement regarding the pathogenicity of Blastocystis , there is no consensus as to which patients, if any, should undergo treatment for Blastocystis infection.
Trichrome stain showing a cyst of Blastocystis in stool. From the collection of Herman Zaiman, a collection of pictorial parasites. American Society of Tropical Medicine and Hygiene.
TMP-SMX has been used as a second-line agent in patients who may not be able to tolerate or do not respond to treatment with metronidazole. Ok et al [ 56 ] examined 38 children and 15 adults with symptomatic infection with Blastocystis stool specimens were negative for other parasitic or bacterial infections treated with TMP-SMX for 7 days.
Blastocystis was eradicated from stool in 36 Clinical symptoms resolved in 39 Similar outcomes were observed in a study using nitazoxanide, but this study did not follow patients over a long period, so the effect may have been short-lived.
Although these studies provide the best evidence to date for the pathogenic potential of this parasite, both studies used broad-spectrum antiparasitic agents, and thus the response to treatment could be attributed to the clearance of another possible enteric pathogen [ 2 ]. Additional agents, such as iodoquinol, tinidazole, nitazoxanide, emetine, pentamidine, iodochlorhydroxyquin, and furazolidone, have been used and have shown variable efficacy in eradicating Blastocystis infection [ 55 , 57 ].
One of the difficulties in assessing therapeutic efficacy is the tremendous variability in posttreatment follow-up of patients treated for Blastocystis infection [ 22 ]. Posttreatment microbiologic analysis showing Blastocystis- positive stools may not reflect treatment failure or resistance but could represent reinfection.
Patients may also have a secondary process that responded initially to treatment with subsequent treatment failure. There have been several studies examining the use of alternative agents in the treatment of Blastocystis infection. For example, Yakoob et al [ 58 ] studied the in vitro efficacy of garlic and other dietary herbs, compared with that of metronidazole, in the treatment of Blastocystis infection in both control subjects and patients with IBS.
The authors evaluated the efficacy of garlic and metronidazole at concentrations of 0. They found that garlic and metronidazole were equally effective at both concentrations. The isolates of Blastocystis were not as sensitive to the other herbs tested, which included ginger, black pepper, and white cumin.
Saccharomyces boulardii a probiotic has also been studied for Blastocystis treatment [ 59 ]. In a study by Dinleyici et al [ 59 ], children with a 2-week history of gastrointestinal symptoms and isolation of Blastocystis from the stool were randomized to treatment with Saccharomyces , metronidazole, or placebo for 10 days. Patients were evaluated for clinical and microbiologic cure at days 15 and 30 after initiation of treatment.
Clinical cure was found in Thirty days after initiation of treatment, clinical cure was found in Resolution of cysts in the stool was found in Given the variable agreement regarding the pathogenicity of Blastocystis , there is no consensus as to which patients should undergo treatment for Blastocystis infection.
In the asymptomatic individual, treatment is not necessarily indicated. Isolation of Blastocystis in stool from a symptomatic individual should lead to a thorough investigation for other causes of the gastrointestinal complaints. It is reasonable to initiate a trial of antimicrobial therapy in patients who have persistent diarrhea or who have undergone an extensive work-up without any other pathogen or gastrointestinal source identified.
Additional randomized, controlled trials are needed to better assess the therapeutic efficacy of the additional antiparasitic drugs and their use in this infection.
The relation of Blastocystis to human disease remains unclear, and many of the drugs used in the treatment of Blastocystis infection have significant side effects. A minimum of 3 stool examinations separated in time and performed in a reliable parasitology laboratory constitute an adequate examination.
If the individual is asymptomatic, we do not recommend specific antiparasitic therapy. However, we understand that a counterargument to this recommendation may be made, because most experts recommend treatment of asymptomatic individuals who pass cysts, such as those with E.
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