Blastocystis hominis chronic diarrhoea in AIDS patients

Diagnostic Features of Blastocystis Life Cycle Forms in the Small Intestine in an HIV-Infected Patient

PURPOSE

Blastocystis spp. are parasites of the intestinal tract found in many hosts including humans. This pathogen is commonly found in immunocompetent in asymptomatic individuals and in patients with gastrointestinal and extra-intestinal symptoms. Recently, it has been implicated as an important cause of diarrheal illness in immunocompromised individuals, including HIV-infected patients. At least six life cycle stages have been described in faeces and cultures, namely vacuolar, granular, multi-vacuolar, avacuolar, ameboid and cyst forms. The aim of the present study was to describe the histological findings of Blastocystis infection in an adult HIV-infected patient with gastrointestinal symptoms.

METHODS

Parasitological techniques and PCR were applied to stool samples. Histological analysis was performed on duodenal biopsy specimens.

RESULTS

Standard parasitological methods revealed vacuolar, granular, cyst and multi-vacuolar forms of Blastocystis in faecal samples with the presence of Blastocystis DNA being confirmed by PCR. DNA sequencing revealed Blastocystis subtype ST1. Histological findings in duodenal samples showed an inflammatory infiltrate with plasma cells and lymphocytes. We identified cyst, granular, ameboid and multi-vacuolar forms in the lumen.

CONCLUSION

To our knowledge, there are no previous peer review reports describing these four different forms of Blastocystis in histological sections from the lumen and the brush border of the enterocytes.

Is "dried stool spots on filter paper method (DSSFP)" more sensitive and effective for detecting Blastocystis spp. and their subtypes by PCR and sequencing?

PCR and DNA sequencing are currently the diagnostic methods of choice for detection of Blastocystis spp. and their suptypes. Fresh or frozen stool samples have disadvantages in terms of several aspects such as transportation, storage, and existence of PCR inhibitors. Filter paper technology may provide a solution to these issues. The aim of the present study was to detect Blastocystis spp. and their subtypes by employing two different preservation methods: conventional frozen stool (FS) and dried stool spots on filter paper (DSSFP). Concentration and purity of DNA, sensitivity of PCR, and DNA sequencing results obtained from the two methods were also compared. A total of 230 fecal samples were included and separated into two parts: one part of the fecal samples were directly frozen and stored at -20 °C. The remaining portion of the specimens were homogenized with saline and spread onto the filter papers as thin layer with a diameter of approximately 3 cm. After air-dried, the filter papers were stored at room temperature. DSSFP samples were collected by scraping from the filter papers. DNA were extracted by EURx Stool DNA Extraction Kit from both samples. Concentration and purity were measured with Nano-Drop, then PCR and sequencing were conducted for detection of Blastocystis spp. and its genotypes. Pure DNA was obtained with a A260/A280 ratio of 1.7-2.2 in both methods. DNA yield from FS was 25-405 ng/μl and average DNA concentration was 151 ng/μl, while these were 7-339 and 122 ng/μl for DSSFP, respectively. No PCR inhibition was observed in two methods. DNA from DSSFP were found to be stable and PCR were reproducible for at least 1 year. FS-PCR- and DSSFP-PCR-positive samples were 49 (21.3 %) and 58 (25.3 %), respectively (p = 0.078). The 43 specimens were concordantly positive by both FS-PCR and DSSFP-PCR. When the microscopy was taken as the gold standard, sensitivity of DSSFP-PCR and FS-PCR was 95.5 and 86.4 %, while specificity of both tests was 99.4 and 98.3 %, respectively. DNA sequencing results of 19 microscopically confirmed cases were strictly identical (concordance 100 %) in both methods, and ST2:6, ST3:8, ST4:3, and ST6:2 were the detected subtypes. Among the 230 fecal samples, the most predominant subtypes were ST3, ST2, ST4, and ST1 by both FS and DSSFP methods. Concordance of DNA sequencing results obtained from the two methods was noted to be 90.7 %. To our knowledge, this is the first study that demonstrates DNA extraction from DSSFP is more sensitive and effective than the FS method for diagnosis of Blastocystis spp. and their subtypes by PCR and DNA sequencing.

Blastocystosis in post-traumatic splenectomized patients

BACKGROUND/AIMS

The aim of this study was to determine the prevalence and significance of intestinal protozoa, specially Blastocystis spp., and to perform PCR-based subtype classification for understanding the importance of Blastocystis spp. in the pathogenesis of gastrointestinal disorders in post-traumatic splenectomized patients.

MATERIALS AND METHODS

A total of 60 stool samples were obtained from 30 post-traumatic splenectomized patients and 30 healthy controls. Wet mounts, trichrome and Kinyoun acid-fast stained slides were prepared from the stool specimens. PCR was used for detecting the presence of Giardia spp., Entamoeba spp., Dientamoeba fragilis, Cryptosporidium spp., Blastocystis spp. Genotyping was realized by using Blastocystis hominis STS primers.

RESULTS

In both study groups, any helminth eggs and other protozoa except Blastocystis spp. were not detected by microscopy and PCR, and also bacterial cultures were negative. Only stool microscopy was positive for Blastocystis spp. in 30% (9 of 30) of splenectomized patients and in 13% (4/30) of healthy controls. PCR for Blastocystis spp. was positive in 40% (12 of 30), B. hominis genotypes were 20% (6/30): STS1 in 10% (3/30) and STS3 in 10% (3/30) of splenectomized patients. In healthy controls Blastocystis spp. was 13% (4/30) by PCR and genotypes of B. hominis was not detected. The difference between the prevalence of Blastocystis spp. infection in splenectomized patients and control groups was statistically significant (p=0.020). Abdominal pain was the most frequent gastrointestinal symptom (p=0.019) among splenectomized patients positive for Blastocystis spp.

CONCLUSION

In post-traumatic healthy splenectomized patients, Blastocystis spp. were found to be the most prevalent protozoa and may be responsible for the gastrointestinal disorders.

High lipid storage in vacoular forms of subtype 6 Blastocystis sp. in ostrich

Background

Blastocystis sp., a widely prevalent intestinal protozoan parasite is found in a wide range of animals, including humans. The possibility of zoonotic transmission to human from birds especially ostriches led us to investigate on the cross infectivity of Blastocystis sp. isolated from the ostrich feces as well as the phenotypic and subtype characteristics. There is a need to investigate this especially with the rising number of ostrich farms due to the growing global ostrich industry.

Findings

100% of the ostriches were found to be positive for Blastocystis sp. using the in-vitro cultivation method. Transmission electron microscopy revealed high electron dense material in the central body of the vacoular forms. The membrane layer of the ostrich isolate was significantly (p = 0.003) thicker as compared to human isolate. Sudan staining revealed that this was lipid accumulation. We provide evidence for the first time, the existence of subtype 6 which has been previously reported only in pigs and cattle. Cysts, ranging from 3.0 to 7.0 μm in diameter caused experimental infection in Sprague Dawley rats implicating that Blastocystis sp. isolated from ostriches exhibits low host specificity.

Conclusion

The study for the first time demonstrates that Blastocystis sp. subtype 6 do exist in ostriches and show high lipid storage in the vacuoles of the parasites. The study further provides evidence for potential zoonotic transmission in ostrich farms as Blastocystis subtype 6 can infect rats and the same subtype have been previously reported in humans.

Higher Caspase-like activity in symptomatic isolates of Blastocystis spp

Background

Biochemical evidence of a caspase-like execution pathway has been demonstrated in a variety of protozoan parasites, including Blastocystis spp. The distinct differences in the phenotypic characterization reported previously have prompted us to compare the rate of apoptosis in Blastocystis spp. isolated from individuals who were symptomatic and asymptomatic. In the current study, we analysed the caspase activation involved in PCD mediated by a cytotoxic drug, (metronidazole) in both symptomatic & asymptomatic isolates.

Methods

Apoptosis was induced in Blastocystis spp. by treating cultures of symptomatic and asymptomatic isolates of 3 sub-types namely 1, 3 and 5 with two different concentrations, 0.1 and 0.0001 mg/ml of metronidazole (with and without pre-treatment with a pan-caspase inhibitor, zVAD.fmk). The experiment was repeated to assess the number of apoptotic cells in all the isolates of both conditions.

Results

Symptomatic isolates of subtype 3 (without pre-treatment with a pan-caspase inhibitor, zVAD.fmk) showed high fluorescence intensity for active caspase-like proteases [0.0001 mg/ml, 88% (p < 0.001) at 0.1 mg/ml, 70% (p < 0.001)] at the 72^nd hour in vitro culture in comparison with asymptomatic isolates [0.0001 mg/ml, 65%, at 0.1 mg/ml, 55%]. The number of apoptotic cells was higher [0.0001 mg/ml, 89% (p < 0.001) and at 0.1 mg/ml, 70% (p < 0.001)] at the 72^nd hour of in vitro culture in comparison with asymptomatic isolates [0.0001 mg/ml, 66% (p < 0.001) and at 0.1 mg/ml, 45% (p < 0.01)]. Cells treated with metronidazole in the presence of zVAD.fmk showed less than 10% caspase activation.

Conclusion

The high number of symptomatic cells expressing active caspase-like proteases and becoming apoptotic compared to asymptomatic cells clearly demonstrates that the response to metronidazole treatment is isolate dependent. Hence this justifies the conflicting reports on the curative success rates when treated with this drug. The study has also created a need to identify apoptosis effectors in Blastocystis spp of different isolates especially as it was shown that apoptosis was sub-typed related. These findings can be exploited for the development of diagnostic markers and novel therapeutic drugs to enhance the effectiveness of the diagnosis and treatment of the patients infected with Blastocystis spp.

Intra-subtype variation in enteroadhesion accounts for differences in epithelial barrier disruption and is associated with metronidazole resistance in Blastocystis subtype-7

Blastocystis is an extracellular, enteric pathogen that induces intestinal disorders in a range of hosts including humans. Recent studies have identified potential parasite virulence factors in and host responses to this parasite; however, little is known about Blastocystis-host attachment, which is crucial for colonization and virulence of luminal stages. By utilizing 7 different strains of the parasite belonging to two clinically relevant subtypes ST-4 and ST-7, we investigated Blastocystis-enterocyte adhesion and its association with parasite-induced epithelial barrier disruption. We also suggest that drug resistance in ST-7 strains might result in fitness cost that manifested as impairment of parasite adhesion and, consequently, virulence. ST-7 parasites were generally highly adhesive to Caco-2 cells and preferred binding to intercellular junctions. These strains also induced disruption of ZO-1 and occludin tight junction proteins as well as increased dextran-FITC flux across epithelial monolayers. Interestingly, their adhesion was correlated with metronidazole (Mz) susceptibility. Mz resistant (Mzr) strains were found to be less pathogenic, owing to compromised adhesion. Moreover, tolerance of nitrosative stress was also reduced in the Mzr strains. In conclusion, the findings indicate that Blastocystis attaches to intestinal epithelium and leads to epithelial barrier dysfunction and that drug resistance might entail a fitness cost in parasite virulence by limiting entero-adhesiveness. This is the first study of the cellular basis for strain-to-strain variation in parasite pathogenicity. Intra- and inter-subtype variability in cytopathogenicity provides a possible explanation for the diverse clinical outcomes of Blastocystis infections.

Apoptosis in Blastocystis spp. is related to subtype

Previous studies have shown that apoptosis-like features are observed in Blastocystis spp., an intestinal protozoan parasite, when exposed to the cytotoxic drug metronidazole (MTZ). This study reports that among the four subtypes of Blastocystis spp. investigated for rate of apoptosis when treated with MTZ, subtype 3 showed the highest significant increase after 72h of in vitro culture when treated with MTZ at 0.1mg/ml (79%; p<0.01) and 0.0001mg/ml (89%; p<0.001). The close correlation between viable cells and apoptotic cells for both dosages implies that the pathogenic potential of these isolates has been enhanced when treated with MTZ. This suggests that there is a mechanism in Blastocystis spp. that actually regulates the apoptotic process to produce higher number of viable cells when treated. Apoptosis may not just be programmed cell death but instead a mechanism to increase the number of viable cells to ensure survival during stressed conditions. The findings of the present study have an important contribution to influence chemotherapeutic approaches when developing drugs against the emerging Blastocystis spp. infections.

Antioxidant, antibacterial and antigiardial activities of Walsura robusta Roxb

Walsura robusta Roxb. (Family: Meliaceae) is a well-known multi-purpose medicinal plant, and has been employed for a wide range of disease conditions without documented scientific data. In the current study, four pure isolated compounds, 3,4,5-trimethoxyphenyl beta-D-glucopyranoside (1), turpinionoside A (2), (+)-lyoniresinol 3alpha-O-beta-D-glucopyranoside (3) and (-)-lyoniresinol 3alpha-O-beta-D-glucopyranoside (4), were isolated from the leaves and twigs of W. robusta. Biological evaluation for free radical scavenging, antibacterial and antigiardial activities was performed. We investigated antioxidant effects of the crude extracts as well as the isolated compounds using 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), hydroxyl radical (OH), and superoxide anion (O(2)) scavenging assays. Three phenolic glucosides (1, 3 and 4) were found to possess strong antioxidant activity. They scavenged DPPH(*) with IC(50) values in the range of 51.5-86.6 microM. We also detected the superoxide dismutase-like activities in compounds 3 and 4 which are lignan glucosides, demonstrating potent superoxide scavenging activity with IC(50) values in the range of 0.8 and 0.7 microM, respectively. Other biological activities including antibacterial and antigiardial assays were carried out. Preliminary results demonstrated that most extracts, except the diethyl ether extract, exhibited inhibition zones against all Gram-positive bacteria including Bacillus cereus, Staphylococcus aureus, Streptococcus mutans, and S. pyogenes. Aqueous extracts of this plant species could inhibit Gram-positive and some Gram-negative bacteria such as Escherichia coli, Salmonella typhi and Shigella sonnei. However, the determination of minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of W. robusta on all tested bacterial strains showed only weak activity, and their MBCs were greater than 25 mg mL(-1). For antigiardial activity, incubation with 2 x 10(5) trophozoites mL(-1) of the culture medium with the crude extracts at concentration ranged from 31.25 to 1000 microg mL(-1) demonstrated no activity (MIC > 1000 microg mL(-1)).

Blastocystis hominis infection in long-term care facilities in Taiwan: prevalence and associated clinical factors

Blastocystis hominis is probably the most common protozoan found in the human gut worldwide. In Taiwan, the prevalence of B. hominis infection is yet to be determined but is expected to be relatively higher among foreign workers. No data is available on the prevalence of B. hominis infection in long-term care facilities in Taiwan. This study included 713 subjects (552 residents and 161 care workers) from ten long-term care facilities in Taiwan who completed stool microscopic examinations with Merthiolate-iodine-formalin stain technique. The prevalence rate of blastocystosis was the highest among foreign and domestic care workers followed by residents (12.2%, 4.6%, and 2.7%, respectively). Older age (p = 0.04) and lower educational level (p = 0.008) were significantly associated with blastocystosis among care workers. Among residents, B. hominis infection was negatively associated with prolonged use of antibiotics within 3 months prior to examination (p = 0.05) and positively associated with tracheostomy in-place (p = 0.028). In conclusion, B. hominis infection was the most prevalent intestinal parasitic infection among both care workers and residents of long-term care facilities in Taiwan. Use of antibiotics was negatively associated with B. hominis infection among residents. Additionally, appropriate preventive measures should be implemented to older care workers with lesser educational attainment in order to reduce the risk of blastocystosis infection.

The anti-amoebic activity of some medicinal plants used by AIDS patients in southern Thailand

The anti-amoebic activities of chloroform, methanol and water extracts from 12 Thai medicinal plants (39 extracts) commonly used by AIDS patients in southern Thailand were screened, at a concentration of 1,000 microg/ml, against Entamoeba histolytica strain HTH-56:MUTM and strain HM1:IMSS growing in vitro. The extracts were incubated with 2x10(5) E. histolytica trophozoites/ml of medium at 37 degrees C under anaerobic conditions for 24 h. The cultures were examined with an inverted microscope and scored (1-4) according to the appearance and numbers of the trophozoites. The extracts that caused inhibition were selected and retested using the same conditions but with concentrations that ranged from 31.25 to 1,000 microg/ml using E. histolytica strain HM1:IMSS, and the IC(50) values for each extract were calculated. The chloroform extracts from Alpinia galanga (IC(50) 55.2 microg/ml), Barleria lupulina (IC(50) 78.5 microg/ml), Boesenbergia pandurata (IC(50) 45.8 microg/ml), Piper betle (IC(50) 91.1 microg/ml) and Piper chaba (IC(50) 71.4 microg/ml) and the methanol extract from B. pandurata (IC(50) 57.6 microg/ml) were all classified as "active", i.e. with an IC(50) of less than 100 microg/ml, whereas those from Murraya paniculata (IC(50) 116.5 microg/ml) and Zingiber zerumbet (IC(50) 196.9 microg/ml) were classified as being "moderately active". The IC(50) of a standard drug, metronidazole, was 1.1 microg/ml.

The effects of extracts from anti-diarrheic Thai medicinal plants on the in vitro growth of the intestinal protozoa parasite: Blastocystis hominis

The activities of n-hexane, dichloromethane and methanol extracts from five anti-diarrheic Thai medicinal plants, Acacia catechu (Fabaceae) resin, Amaranthus spinosus (Amaranthaceae) whole plant, Brucea javanica (Simaroubaceae) seed, Piper longum (Piperaceae) fruit and Quercus infectoria (Fagaceae) nut gall were tested against the in vitro growth of fresh isolates of the intestinal protozoan parasite, Blastocystis hominis. The extracts at concentrations that ranged from 62.5 to 2000 microg/mL, were incubated with several isolates of Blastocystis hominis for 48 h. The activities were classified as killed, inhibited, moderately inhibited and not-inhibited. Dichloromethane and methanol extracts from the Brucea javanica seed and a methanol extract from Quercus infectoria nut gall showed the highest activity. At a concentration of 2000 microg/mL, the three extracts killed 82, 75 and 67% of the Blastocystis hominis samples tested and inhibited 94, 100 and 76% of them, respectively. Metronidazole, used as a reference antiprotozoan drug, at a concentration of 40 microg/mL, killed 97% of the Blastocystis hominis isolates and inhibited all samples tested at concentrations that ranged from 1.25 to 20 microg/mL.

The in vitro anti-giardial activity of extracts from plants that are used for self-medication by AIDS patients in southern Thailand

This study evaluated the anti-giardial activity of chloroform, methanol and water extracts of 12 medicinal plants (39 extracts), commonly used as self medication by AIDS patients in southern Thailand. The plant extracts and a standard drug, metronidazole, were incubated with 2x10(5) trophozoites of Giardia intestinalis per millilitre of growth medium in 96-well tissue culture plates under anaerobic conditions for 24 h. The cultures were examined with an inverted microscope and the minimum inhibitory concentration and the IC50 value for each extract was determined. The chloroform extracts from Alpinia galanga, Boesenbergia pandurata, Eclipta prostrata, Piper betle, Piper chaba, Zingiber zerumbet, and the methanol extracts from B. pandurata and E. prostrata were classified as "active", i.e. with an IC50 of <100 microg/ml, whereas the chloroform extract from Murraya paniculata was classified as being "moderately active". This study shows that extracts from some medicinal plants have potential for use as therapeutic agents against G. intestinalis infections.

Metronidazole induces programmed cell death in the protozoan parasite Blastocystis hominis

Previous studies by the authors have shown that the protozoan parasite Blastocystis hominis succumbed to a cytotoxic monoclonal antibody with a number of cellular and biochemical features characteristic of apoptosis in higher eukaryotes. The present study reports that apoptosis-like features are also observed in growing cultures of axenic B. hominis upon exposure to metronidazole, a drug commonly used for the treatment of blastocystosis. Upon treatment with the drug, B. hominis cells displayed key morphological and biochemical features of programmed cell death (PCD), viz. nuclear condensation and nicked DNA in nucleus, reduced cytoplasmic volume, externalization of phosphatidylserine and maintenance of plasma membrane integrity with increasing permeability. This present study also supports the authors' previously postulated novel function for the B. hominis central vacuole in PCD; it acts as a repository where apoptotic bodies are stored before being released into the extracellular space. The implications and possible roles of PCD in B. hominis are discussed.

[Prevalence of Blastocystis hominis among food handlers from Caroni municipality, Bolivar State, Venezuela]

A cross-sectional survey was conducted to determine the prevalence of Blastocystis hominis infection in a random sample of apparently healthy food handlers. A total of 415 individuals attending the Manoa Urban Outpatient Clinic (Caroní Municipality, Bolívar State, Venezuela) in the Adult Hygiene Program and who requested health certification to work as food handlers were studied. Stool samples obtained by spontaneous evacuation were examined by direct microscopy and the Willis concentration method. A total of 150 individuals were infected (36.14%), 107 (25.78%) of whom with B. hominis. There was no difference between males and females (p > 0.05), but there was a significant difference between ages (chi(2) = 12.17; g.l. = 4), with infection more frequent between 18 and 27 years. In 71.02% of the cases, B. hominis was the only parasite. Giardia lamblia was the parasite most frequently associated with B. hominis (2.41%). In the majority (85%) of infected individuals, less than five microorganisms per microscopic field were observed. We conclude that B. hominis is a frequent intestinal parasite among food handlers in Caroní Municipality, Bolivar State, Venezuela.

Diarrhoea following renal transplantation

In this study, we retrospectively evaluated all attacks of diarrhoea in our renal transplant recipients that came to our medical attention between 1985 and 2000. Also, the clinical features of patients with diarrhoea were compared with the features of recipients without diarrhoea. We diagnosed 41 attacks of diarrhoea in 39 (12.6%) of 308 renal transplant recipients during this time period. An aetiology was detected in 33 (80.5%) of all diarrhoeal episodes and in seven (17.1%) of those the specific agent was diagnosed with the help of stool microscopy. The most frequent causes of diarrhoeal attacks were infectious agents (41.5%) and drugs (34%). Six (14.6%) episodes of diarrhoea were chronic and six were nosocomial. About two-thirds of diarrhoea developed within the late post-transplant period (>6 months). When recipients with diarrhoea were compared with those without diarrhoea, it was seen that diarrhoeal patients had significantly higher creatinine and significantly lower albumin levels when compared with the latter group (p < 0.05). Also, the frequency of antibiotic usage was significantly higher in diarrhoeal patients than in the control group (p < 0.05). Four (10.2%) patients with diarrhoea died despite institution of the appropriate therapy. Two of these deaths were primarily related to diarrhoea and the aetiological agent was Clostridium difficile in both these cases. During the 15-yr study period, 3.6% of all deaths and 5.1% of infection-related deaths in transplant recipients were secondary to diarrhoea. As a result, we observed that infections and drugs were the most frequent causes for diarrhoea in our series of renal transplant recipients. Also, diarrhoea was an important cause of mortality in this patient population.

Cryptosporidiosis in Kuwaiti children: seasonality and endemicity

OBJECTIVE

To detect the incidence of cryptosporidial infection in children presenting with gastrointestinal symptoms at the local hospital in Kuwait.

METHODS

Over a period of 3 years, September 1995 to August 1997, a single fecal sample from 3549 children was analyzed by modified saframin-methylene blue (SM-B) staining and a direct immunofluorescence test for the presence of Cryptosporidium oocysts.

RESULTS

Cryptosporidium oocysts were detected in 51 (10%) children with diarrhea. Prevalence was highest (73%) in children > 2 years of age compared with children < 2 years of age. The maximum number of cases, 38 of 51 (75%), was seen during the months January to April, indicating a marked seasonal variation. Polyparasitism was common in children with diarrhea; however, 43 of the 51 (84%) children with cryptosporidiosis had cryptosporidium infection only. Blastocystis hominis and Endolimax nana were the most common parasites detected (38% and 15%, respectively). Forty-seven of the 51 (90%) children with cryptosporidiosis were Kuwaiti and gave no history of travel abroad, suggesting that the infection was acquired indigenously. Sociodemographic information on children with cryptosporidiosis suggests three possible modes of transmission of infection: drinking contaminated water stored in overhead water tanks, person to person, or contact with infected animals.

CONCLUSION

In this study, we observed water-borne transmission of cryptosporidium infection in children with diarrhea. The infection is seasonal and endemic.

Effect of trimethoprim-sulfamethaxazole in Blastocystis hominis infection

OBJECTIVE

Blastocystis hominis (B. hominis) is a common intestinal parasite that has long been considered nonpathogenic. Recently there have been many reports supporting a role for the organism as a potential pathogen. We performed a study to examine the pathogenicity of B. hominis and the effect of trimethoprim-sulfamethaxazole (TMP-SMX) on this organism.

METHODS

Stool samples of patients, who came to the Department of Parasitology, Faculty of Medicine, Celal Bayar University, were examined by direct wet-mount, trichrome staining, formalin-ethyl acetate concentration, and Kinyoun acid fast techniques for intestinal parasites, and bacteriological stool cultures were performed. Fifty-three symptomatic patients (38 children and 15 adults) with two consequent stool samples positive for abundant B. hominis (five or more organisms per x400 field) and negative for other parasitic and bacterial pathogens were treated with TMP-SMX for 7 days, children 6 mg/kg TMP, 30 mg/kg SMX, and adults 320 mg TMP, 1600 mg SMX, daily. On the seventh day, at the end of treatment, stool samples of all patients were examined by same methods, and clinical symptoms were again evaluated.

RESULTS

B. hominis was eradicated in 36 of 38 (94.7%) children, and 14 of 15 (93.3%) adults. Clinical symptoms disappeared in 39 (73.6%), decreased in 10 (18.9%), and no change was observed in one (1.9%) patient, whereas symptoms persisted in all three (5.7%) patients in whom B. hominis could not be eradicated. Mean number of stools per day was significantly decreased from 4.3 to 1.2 in the 33 children (p < 0.001), and decreased from 3.5 to 1.0 in the four adults (p = 0.06) with diarrhea.

CONCLUSIONS

These results suggested that B. hominis may be pathogenic, especially when it is present in large numbers, and TMP-SMX is highly effective against this organism. Although there are some anecdotal reports, to our knowledge this is the first study examining the effect of TMP-SMX on B. hominis in humans.

Intestinal protozoa in HIV-infected patients: effect of rifaximin in Cryptosporidium parvum and Blastocystis hominis infections

In HIV-1 infected patients severe enteritis and chronic diarrhea are often documented as a consequence of multiple opportunistic infections. We analyzed 48 HIV-1 positive patients for the presence of intestinal pathogenic protozoa. Patients with CD4 > or = 200/mm3 showed a higher prevalence of a single pathogenic protozoa than patients with CD4 < or =200/mm3, who showed the presence of multiple protozoal infections. Patients who proved positive for only a single protozoa, Cryptosporidium or Blastocystis, were also positive, by stool culture, for the presence of Proteus mirabilis (3 samples), Citrobacter freundii (3 samples), Escherichia coli (one sample) or Enterobacter cloacae (one sample). Treatment with rifaximin (600 mg, 3 times a day, for 14 days) was efficacious in resolving the clinical symptoms and clearing protozoan infections in HIV-1 infected patients with CD4 > or = 200/mm3, who presented enteric and systemic symptoms due to Criptosporidium or Blastocystis associated with enteropathogenic bacteria.

Isolate resistance of Blastocystis hominis to metronidazole

Isolates of Blastocystis hominis from infected immigrant workers from Indonesia, Bangladesh and infected individuals from Singapore and Malaysia were assessed for growth pattern and degree of resistance to different concentrations of metronidazole. Viability of the cells was assessed using eosin-brillian cresyl blue which stained viable cells green and nonviable cells red. The Bangladeshi and Singaporean isolates were nonviable even at the lowest concentration of 0.01 mg/ml, whereas 40% of the initial inoculum of parasites from the Indonesian isolate at day one were still viable in cultures with 1.0 mg/ml metronidazole. The study shows that isolates of B. hominis of different geographical origin have different levels of resistance to metronidazole. The search for more effective drugs to eliminate th parasite appears inevitable, especially since surviving parasites from metronidazole cultures show greater ability to multiply in subcultures than controls.

In vitro response of Blastocystis hominis against traditional Chinese medicine

This is the first inn vitro study on the activity of 20 kinds of crude extracts of traditional Chinese medicine (TCM) on the intestinal parasite, Blastocystis hominis using the criteria of living cell count (LCC) and living cell rate (LCR). LCC and LCR were applied as observation indicators, the former as a fixed-quantity and the latter as a fixed-quality method. LCR calculated percentage rate of living cells using eosin-brilliant cresyl blue staining which could differentiate between living cells and dying or dead cells. There were five extracts with no inhibitory activity, thirteen with moderate inhibition and two with high inhibition. The crude extracts of Coptis chinensis (CC) and Brucea javanica (BJ) were found to be most active against B. hominis. The active concentration of CC was 100 micrograms/ml. The active concentration of BJ was 500 micrograms/ml. The active concentration of metronidazole (MD) was 10 micrograms/ml and this was taken as an active standard drug for B. hominis.

Blastocystis hominis revisited

Blastocystis hominis is a unicellular organism found commonly in the intestinal tract of humans and many other animals. Very little is known of the basic biology of the organism, and controversy surrounds its taxonomy and pathogenicity. There morphological forms (vacuolar, granular, and ameboid) have been recognized, but recent studies have revealed several additional forms (cyst, avacuolar, and multivacuolar). The biochemistry of the organism has not been studied to any extent, and organelles and structures of unknown function and composition are present in the cells. Several life cycles have been proposed but not experimentally validated. The form used for transmission has not been defined. Infections with the organism are worldwide and appear in both immunocompetent and immunodeficient individuals. Symptoms generally attributed to B. hominis infection are nonspecific, and the need for treatment is debated. If treatment appears warranted, metronidazole is suggested as the drug of choice, although failures of this drug in eradicating the organism have been reported. Infection is diagnosed by light microscopic examination of stained smears or wet mounts of fecal material. Most laboratories identify B. hominis by observing the vacuolar form, although morphological studies indicate that other forms, such as the cyst form and multivacuolar form, also should be sought for diagnosis.

Intestinal colonization of symptomatic and asymptomatic schoolchildren with Blastocystis hominis

A study of single stool specimens was done to determine the prevalence of intestinal parasites among 1,000 primary school children. A questionnaire was completed by each child's parents. Specimens were examined by using wet-mount preparation, formaline-ether concentration, and Sheather's flotation technique. Trichrome and acid-fast stains were done. Blastocystis hominis was observed in 203 (20.3%) of the specimens examined, and 175 specimens contained this organism in the absence of other pathogenic parasites. Older children had fewer B. hominis infections (6 to 7 years old, 50% infection rate; 8 to 9 years, 27.5%; 10 to 12 years, 9.5%). The most common complaints reported by 75 children harboring the parasite were a mild recurrent diarrhea, abdominal pain, nausea, anorexia, and fatigue. Blastocystosis is quite common among schoolchildren. Contaminated drinking water is suspected to be the source of infection.

Incidence of Blastocystis hominis in patients with diarrhoea

We studied the occurrence of the parasite Blastocystis hominis in 1066 stool specimens from patients with diarrhoea, and investigated the relationship between the presence of B. hominis in the faeces and the age of patients. The parasite was recovered from 3.7% samples, but as the sole species of micro-organism in the stool it was recovered from 1% samples. There was no statistically significant difference in the number of B. hominis-positive stools between the younger and the older patients (P < 0.25), yet in the latter, B. hominis was more frequently identified as the only species of micro-organism as compared with the younger group (P < 0.005). The presence of B. hominis in faecal samples of patients with diarrhoea harbouring no other intestinal pathogens suggests an aetiology that should receive more attention in Slovenia.

Evidence of an epidemic of Blastocystis hominis infections in preschool children in northern Jordan

Blastocystis hominis is now gaining acceptance as an agent of human intestinal disease. A case-control study of the cause of gastroenteritis in children less than 6 years old was conducted. A total of 500 stool specimens were examined by wet mount preparation, formalin-ether concentration, Sheather's sugar flotation technique, and permanent stains when necessary. B. hominis was found in 63 (25%) of 250 stool specimens of the cases examined; 38 (15%) of these specimens contained this parasite alone. The appearance of severe symptoms was associated with increased numbers of the parasite in the diarrheic specimens (more than five parasites per field at a magnification of x 400). The most common symptoms were abdominal pain, recurrent diarrhea, cramps, anorexia, and fatigue. Contaminated water was suspected to be the major source of infection, since several cases were associated with Giardia infection. These findings support the concept of B. hominis pathogenicity in children with gastroenteritis.

Varying incidence of Blastocystis hominis in cultures from faeces of patients with diarrhoea and from healthy persons

A study was performed on the frequency of Blastocystis hominis in the faeces from 100 patients suffering from diarrhoea and from 100 healthy persons. Surprisingly, an increased detection rate was observed in samples from healthy persons after anaerobic cultivation. This increased frequency is obviously not dependent on the kind of serum used as a culture supplement and raises the question whether the protozoa morphologically described as B. hominis represent a homogenous species. When rabbit and horse sera were used instead of human serum for cultivation, in both groups the share of positive cultures increased and more large forms of B. hominis cells were observed. Biological implications are being discussed.

Blastocystis hominis--past and future

The history of B. hominis is unique. Few infectious agents have provoked the many misconceptions that plague this enigmatic parasitic ameba. Conflicting descriptions of its nature and pathogenesis have continued throughout the 20th century. As seen by the greatly expanded number of reports in recent years, B. hominis is now a major subject of study, particularly for evidence of disease causation. Physicians are treating patients with intestinal disease caused by B. hominis. Many mild cases resolve in about 3 days without treatment, but others are acute and chronic disease is common. As with E. histolytica, the carrier state is often seen without symptoms. Treatment is usually with metronidazole, but emetine (for refractory infections), trimethoprim-sulfamethoxazole, and pentamidine are also effective. In fecal samples, this complex protozoan appears in a variety of cell forms which makes microscopic diagnosis difficult. As yet, no specific fluorescent-antibody test is available for diagnosis. A culture method to demonstrate the more easily recognized CB form is available, but probably not feasible for most diagnostic laboratories. The common cell forms are the CB form, the granular (mitochondria) form, and the ameba form. The unexpected size range of these forms in clinical material, from yeast size (ca. 7 microns) to giant cells of 20 to 40 microns, makes diagnosis difficult Pseudopodia may be demonstrated by the ameba form in heated microscope stage culture chambers. The anaerobic B. hominis has no cyst form. Its mitochondria are uniquely anaerobic and have no cytochrome protein or oxidative mitochondrial enzymes. Because of its many cell forms and anaerobic mitochondria, B. hominis is an organism of great interest for morphologic and biochemical study. Reproduction is asexual, usually by binary fission. Shizogony occurs in cultured cells. The CB appears to be an organelle whose specific purpose is for reproduction by shizogony. From 2 to 30 progeny are derived from schizogony. The ameba form reproduces by plasmotomy; it has no CB. The pathology of B. hominis infections has been studied in gnotobiotic guinea pigs in which inflammation of the intestinal mucosa and invasion of the superficial layers were seen. Only limited studies of human pathology are available. Those who have studied mucosal histopathology report inflammation and cellular changes that resolve after treatment. More study in this area is strongly indicated (32, 44, 57, 62, 67, 75). Ultrastructural details of B. hominis major forms, except for the schizont, are complete. The organism has no cell wall. The concentric CB takes up as much as 95% of the cell. The major organelles, which include multiple nuclei, Golgi apparatus, mitochondria, endoplasmic reticulum, fat, and other inclusions, are confined in two or four opposed pods in a thin band of peripheral cytoplasm between the spherical entire plasma membrane and the CB membrane. The pods buldge the CB membrane inward. There is evidence of a bacteroid endosymbiont. Education about B. hominis is needed. Entry of recent findings into new textbooks is imperative for its understanding among medical practitioners. Laboratory workers need to be aware of it for many reasons. The College of American Pathologists includes B. hominis in its proficiency testing samples and requires that it be reported from clinical samples.

Blastocystosis: a new disease in the acquired immunodeficiency syndrome?

The protozoon Blastocystis hominis may cause episodes of diarrhoea with abdominal pain, tenesmus, fever and eosinophilia. We have observed 5 cases of blastocystosis in male subjects with symptomatic HIV infection. All patients had a complete response to metronidazole. This report confirms that Blastocystis hominis may be responsible for HIV-related diarrhoea.