In vitro Effect of Silver Nanoparticles on Blastocystis hominis

INTRODUCTION

This study aims to assess the efficacy of silver nanoparticles (Ag Nps) alone and combined with metronidazole (Ag Nps + MTZ) as potential alternative therapeutic agents for Blastocystis hominis.

METHODS

The parasites were challenged with Ag Nps, Ag Nps + MTZ and MTZ. To assess the efficacy of drugs, counting of viable parasites was done after 1, 2, and 3 hours of adding the drugs.

RESULTS

Blastocystis hominis count was reduced by 20.72%, 28.23%, and 18.92% after one hour of adding Ag Nps, Ag Nps + MTZ, and MTZ, respectively. Cysts count was further reduced by 51.49%, 61.61%, and 40.78% after 2 hours and by 71.69%, 79.67%, and 62.65% after 3 hours of adding the drugs in the same order, respectively.

CONCLUSION

There was a statistically significant difference (P<0.05) in the in vitro growth inhibition of the parasite over the different time intervals when using the tested drugs against the control drug.

[Observation on growth status of Blastocystis hominis in three media]

OBJECTIVE

To observe the growth situation of Blastocystis hominis in vitro and select the optimal method for cultivation of B. hominis in different media.

METHODS

Ten positive stools with B. hominis were inoculated in three different media for cultivating, namely 1640, Jone's medium and vitro medium. And the stools with good growth status and high quantities of B. hominis were chosen to inoculate in the three media with equal amount after subcultivation, and the number of B. hominis was counted every 24 h for ten days, and the morphological changes and growth status were also observed.

RESULTS

The densities of B. hominis in the 1640 and Jone's medium were higher than that in the vitro medium 48 h after the inoculation. The same stool sample was inoculated to the three different media and observed for ten days, and the results indicated that the growth of B. hominis presented regular changes in the three media, the growth peaks were on the third, sixth and ninth day post inoculation; and the density of B. hominis was the highest in the Jone's medium. The morphology of B. hominis was the clearest and most dynamic in the vitro medium, while various reproductive forms were observed in the Jone's medium.

CONCLUSION

Jone's medium is suitable for the growth of B. hominis and can be the first choice for the cultivation of B. hominis in vitro, and vitro medium is the best medium for observing the growth situation of B. hominis.

In vitro sensitivity of Blastocystis hominis to garlic, ginger, white cumin, and black pepper used in diet

To determine the growth pattern and in vitro susceptibility of Blastocystis hominis to metronidazole (MTZ), garlic, ginger, white cumin, and black pepper. Stool specimens were collected from 16 irritable bowel syndrome (IBS) and 10 controls between July-November 2010. Stool microscopy and culture for B. hominis was performed. Drug susceptibility assays was done using 0.01 and 0.1 mg/ml of MTZ, garlic, ginger, white cumin, and black pepper. Effect was assessed on B. hominis culture after 48 h. Stool DNA was extracted using stool DNA extraction kit (Qiagen) and polymerase chain reaction (PCR) done using subtype-specific sequence-tagged-site primers. B. hominis genotype 3 and coinfection of 1 and 3 tended to grow well in culture compared to isolated type 1 infection. Exposed to MTZ at a concentration of 0.01 mg/ml, 38% (6/16) B. hominis from IBS did not grow in culture compared to 100% (10/10) of B. hominis from control (p = 0.001). When they were exposed to MTZ at 0.1 mg/ml, 56% (9/16) B. hominis from IBS did not grow in cultures compared to 100% (10/10) from control (p = 0.01). Forty-four percent (7/16) B. hominis from IBS did not grow in culture compared to 100% (10/10) B. hominis from control when exposed to garlic at a concentration of 0.01 mg/ml (p = 0.003) and following exposure to garlic at 0.1 mg/ml, 38% (6/16) B. hominis from IBS did not grow in cultures compared to 100% (10/10) from control (p = 0.001). B. hominis isolates from IBS had a cell count of 6,625 at a MTZ concentration of 0.01 mg/ml that reduced to 1,250 as MTZ concentration was increased to 0.1 mg/ml (p = 0.08). B. hominis from IBS with a mean cell count of 3 × 10(5) at baseline decreased to 1 × 10(4) when exposed to garlic at 0.01 mg/ml (p < 0.001) and to 1 × 10(3) (p < 0.001) when garlic was 0.1 mg/ml. B. hominis from IBS cell count decreased to 1 × 10(5) when exposed to white cumin at 0.01 mg/ml (p = 0.01) and to 1 × 10(5) (p < 0.001) when white cumin was 0.1 mg/ml. Exposed to black pepper at 0.1 mg/ml, cell count of B. hominis from IBS decreased to 1 × 10(5) (p = 0.01). B. hominis from IBS decreased to 1.3 × 10(5) exposed to ginger at 0.01 mg/ml (p = 0.001). B. hominis isolates were mostly genotypes 3, type 1 and 3 coinfection, and non-typeable B. hominis isolates. B. hominis isolates from IBS mostly genotype 1 demonstrated an increased sensitivity to garlic at 0.01 mg/ml with a B. hominis cell count of 3,714 compared to 6,142 when exposed to 0.01 mg/ml of MTZ. However, this sensitivity did not increase as garlic concentration was increased to 0.1 mg/ml, for B. hominis cell count was 6,000 compared to 1,428 as MTZ was increased to 0.1 mg/ml.

Evaluation of the in vitro effect of Nigella sativa aqueous extract on Blastocystis hominis isolates

The effect of Nigella sativa aqueous extract was evaluated against the in vitro growth of 2 different isolates of the intestinal protozoan parasite Blastocystis hominis. Different concentrations (10, 100, 500 microg/ml) of Nigella aqueous extract and metronidazole, an active standard drug for B. hominis, were incubated with B. hominis isolates in culture media at 37 degrees C. Their possible effect on B. hominnis living cell count (LCC) was assessed on Day 1, 3 & 6. The aqueous extract of N. sativa at concentrations of 100 and 500 microg/ml showed a potent lethal effect on both B. homninis isolates, but with different extent. There is no significant difference between the inhibitory effect of N. sativa and metronidazole on the LCC on the 6th day. On assessment of living cell rate (LCR) which calculate percentage rate of living cell, N. sativa at 500 microg/ml concentration has a significant inhibitory effect on both isolates. So, it is considered as the most active concentration of Nigella aqueous extract. These results prove that N. sativa aqueous extract could be useful in the treatment of B. hominis.

[Vitro culture of blastocystis hominis in medium DMEM]

OBJECTIVE

To establish the vitro culture of Blastocystis hominis (B. h) in medium DMEM for the further research on diagnosis, life cycle and pathogenicity of this intestinal protoza.

METHODS

The growth, reproduction and relevant factors of B . h under different culture conditions including sorts and concentrations of serum, pHs and number of inoculation were compared.

RESULTS

Conditions for the continuously anaerobic culture of B. h in medium DMEM were as follows: the number of inoculation were no less than 10(5) cells per tube, pHs ranged 7.0 - 8.0, concentrations of calf serum (or human serum and horse serum) ranged 10% - 30% , antibiotics and Amphotericin B should be added, subculturing could be choose at the each peaking-day 3,6 or 5 at 37 degrees C.

CONCLUSION

The medium DMEM could be used in diagnosis and continuously vitro culture for B. h.

Degradation of human secretory immunoglobulin A by Blastocystis

Microbial immunoglobulin A (IgA) proteases cleave human secretory IgA, promoting the mucosal adhesion of pathogens. To investigate if the enteric protozoan Blastocystis degrades human secretory IgA, cell lysate and conditioned medium from two species were exposed to immunoglobulin A. Secretory IgA was cleaved by both cell lysate and conditioned medium with mainly cysteine proteinase activity in B. hominis B isolate and aspartic proteinase activity in B. ratii WR1 isolate. These findings suggest that Blastocystis proteases may play a role in parasite survival in vivo.

In vitro susceptibility of Blastocystis hominis isolated from patients with irritable bowel syndrome

This study aims to determine the growth pattern and in vitro susceptibility of clinical isolates of Blastocystis hominis to different concentrations of metronidazole, furazolidone and ciprofloxacin. Stool specimens from 25 consecutive patients with irritable bowel syndrome presenting to the gastroenterology department of Aga Khan University Hospital between January and May 2003 are examined by microscopy and cultured for B. hominis. Drug susceptibility assays are performed for metronidazole, furazolidone, and ciprofloxacin using final concentrations of 0.01 mg/mL and 0.1 mg/mL. The effect of the drugs is assessed after B. hominis culture for 48 h. With furazolidone and metronidazole, 68% (17/25) and 60% (15/25) of B. hominis isolates, respectively, failed to grow at drug concentrations of both 0.01 mg/mL and 0.1 mg/mL. However, ciprofloxacin failed to suppress growth completely at both concentrations. B. hominis resistance to furazolidone, metronidazole and ciprofloxacin at 0.01 mg/mL was 32% (8/25), 40% (10/25) and 100% (25/25), respectively. B. hominis isolates varied in their degree of susceptibility to the three drugs studied, being greater with furazolidone than with metronidazole, and complete resistance with ciprofloxacin.

Fecal-oral transmission of the cyst form of Blastocystis hominis in rats

The infectivity of two Blastocystis hominis strains, RN94-9 and NIH:1295:1, was examined in 3-week-old SPF Wistar rats. The NIH:1295:1 strain, originally isolated from a guinea pig, was only able to infect rats via intracecal inoculation of the cultured organisms, while the RN94-9 strain, originally isolated from a laboratory rat, was able to infect rats by oral inoculation of the cultures due to the presence of a cystic form in the in vitro culture. Since many cysts were discharged in the feces of the infected rats, the infectivity of the concentrated cysts was compared between the two strains. Successful oral infection was observed in rats inoculated with 1 x 10(2)-1 x 10(6) cysts of the RN94-9 and NIH:1295:1 strains. The infectivity of the ten cysts varied in the three experiments of ten rats, being 20-100% and 30-100% in the RN94-9 and NIH:1295:1 strains, respectively. When an uninfected normal rat was housed with five experimentally inoculated rats, the normal rat became infected, demonstrating the fecal-oral transmission of the cyst form of this parasite. These results show that the Wistar rat is an ideal host for the propagation of strains RN94-9 and NIH:1295:1 of B. hominis, and demonstrate that the cyst form is the only transmissible form of this parasite.

The usefulness of short-term in vitro cultivation for the detection and molecular study of Blastocystis hominis in stool specimens

When in vitro cultivation was used as the 'gold standard' for the detection of Blastocystis hominis in stool specimens, simple smear and trichrome staining showed sensitivities of 16.7% and 40.2% and specificities of 94% and 80.4%, respectively. In vitro cultivation also enhanced PCR amplification for the detection of B. hominis in stool specimens. Our data show the usefulness of in vitro cultivation for the detection and molecular study of B. hominis in stool specimens.

Comparison of methods for detecting Blastocystis hominis

In order to determine the comparative sensitivity of two methods of detecting Blastocystis hominis and to investigate the seasonality of infection with this enteric protozoan parasite, the present study was conducted. In each of two 3-month periods representing winter, spring (February-April) and summer (July-September), 500 routine stool submissions were examined for B. hominis using microscopy following either formol-ether concentration or in vitro culture using Jones' medium. The organism was detected in 39 of the 1,000 samples investigated using the in vitro culture technique and in none of the samples using the formol-ether concentration technique. In 82% of the B. hominis-positive samples, no concurrent bacterial or parasitic pathogens were found, and diarrhoea was the most commonly recorded symptom among patients. Infection was more prevalent in summer than in winter/spring, occurring primarily in the 71-80-year age group. Cysts were detected in 20.5% of positive samples, but only following Ficoll-Paque concentration of formol-ether concentrates. Cyst excretion was more prevalent in summer than in winter/spring.

Irritable bowel syndrome: in search of an etiology: role of Blastocystis hominis

This study was designed to examine stool specimens of irritable bowel syndrome (IBS) patients for Blastocystis hominis, a common intestinal parasite. One hundred fifty patients were enrolled, 95 IBS cases and 55 controls. These patients provided a medical history, and underwent physical and laboratory evaluations that included stool microscopy and culture for B. hominis and colonoscopy. The 95 cases (51 males and 44 females) had a mean +/- SD age of 37.8 +/- 13.2 years. Stool microscopy was positive for B. hominis in 32% (30 of 95) of the cases and 7% (4 of 55) of the controls (P = 0.001). Stool culture was positive in 46% (44 of 95) of the cases and 7% (4 of 55) of the controls (P < 0.001). Stool culture for B. hominis in IBS was more sensitive than microscopy (P < 0.001). Blastocystis hominis was frequently demonstrated in the stool samples of IBS patients; however, its significance in IBS still needs to be investigated. Stool culture has a higher positive yield for B. hominis than stool microscopy.

[Emphasizing of Blastocystis hominis on culture media]

The aim of our study was to determine the frequency of Blastocystis hominis in the stool specimens sent to the Parasitological Laboratory of the Mureş County Hospital between October 2003 and May 2004. The 124 inoculated specimens showed positive values in 41.93%. After an incubation in anaerobic conditions at 37 degrees C for 24, 72 and 96 hours in liquid and biphasic media, the last proved to be better (69,24%) at an incubation time of 72 hours.

Diagnosis of Blastocystis hominis by different staining techniques

One hundred and fifty stool samples were collected from diarrheic patients of different ages, and examined for Blastocystis hominis by direct smears and concentrated by Sheather's sugar flotation. Staining was done by: Giemsa, two modifications of trichrome stain, modified Ziehl-Neelsen, safranin-methylene blue and two-auramine stains. Out of the 150 cases nine were positive for blastocystosis. The best stains were safranin-methylene blue and modified Ziehl-Neelsen stains. They had the advantage of staining cysts and amoeboid forms besides being rapid and easy to perform. The modified trichrome stains identified 8 ie, less specific and were time consuming. The auramine dyes stained the cyst, both the wall and internal body fluoresced brightly. Giemsa stain was not an efficient stain. Scanning and transmission electron microscopy (SEM, TEM) were performed to study the fine ultrastructure.

In-vitro cultivation: a sensitive method for detecting Blastocystis hominis

Currently, the detection of human infection with Blastocystis hominis is usually based on the examination under a light microscope of faecal samples, either directly, as 'simple smears', or after some form of concentration. Whether short-term, in-vitro cultivation would increase the sensitivity of such detection remains a matter of controversy. Over 900 fresh stool specimens, from soldiers in the Royal Thai Army, were each checked for the parasite using three methods: simple smears; formalin-ethyl-acetate concentration; and cultivation in Jones' medium. Although 334 of the samples were found to be culture-positive, the parasites were only detected in 142 of the simple smears, and faecal concentration led to an even lower sensitivity (64 positive samples). In-vitro cultivation does seem worthwhile in the detection of B. hominis carriage in field studies.

Blastocystis hominis: A simplified, high-efficiency method for clonal growth on solid agar

Colony growth of protozoan parasites in agar can be useful for axenization, cloning, and viability studies. This is usually achieved with the pour plate method, for which the parasite colonies are situated within the agar. This technique has been described for Giardia intestinalis, Trichomonas vaginalis, and Entamoeba and Blastocystis species. Extracting such colonies can be laborious. It would be especially useful if parasites could be grown on agar as colonies. These colonies, being exposed on the agar surface, could be conveniently isolated for further investigation. In this study, we report the successful culture of B. hominis cells as colonies on solid agar. Colonies were enumerated and the efficiency of plating was determined. It was observed that B. hominis could be easily cultured on agar as clones. The colonies were dome-shaped and mucoid and could grow to 3 mm in diameter. Flow cytometric analyses revealed that parasite colonies remained viable for up to 2 weeks. Viable colonies were conveniently expanded in liquid or solid media. Scanning electron microscopy revealed that each colony consists of two regions; a dome-shaped, central core region and a flattened, peripheral region. Older colonies possessed numerous strand-like surface coat projections. This study provides the first report of clonal growth of B. hominis on agar and a simple, effective method for cloning and expansion of B. hominis cells.

Blastocystis hominis: neutral red supravital staining and its application to in vitro drug sensitivity testing

A simple in vitro drug sensitivity testing system for Blastocystis hominis clinical isolates was developed. Application of supravital staining by neutral red allowed quantitative viability assessment. Four xenic cultures, isolated from human sources, were grown in modified monophasic Robinson's medium and tested for sensitivities to nine available drugs. Assessment was done using the cell-count method from air-dried preparations after supravital staining with neutral red. Also, the light absorbence method was evaluated. Trimethoprim, metronidazole, quinacrine, tetracycline, paromomycin, and two new antiprotozoal drugs, nitazoxanide and deacetyl-nitazoxanide, showed cytostatic or cytocidal effects on all or some Blastocystis isolates. Chloroquine and sulphamethoxazole did not demonstrate any effect at the concentrations studied.

Blastocystis hominis: origin and significance of vacuolar and granular forms

Using supravital neutral red staining and light microscopy, individual Blastocystis organisms, subcultured from clinical isolates in modified monophasic Robinson's medium, were followed over various periods on glass slides. A rapid transition from uniformly stained to granular and vacuolated forms preceded the organism's death as evidenced by pale staining and Brownian motion in the cell's interior. Granular and vacuolar forms of Blastocystis may indicate degenerative changes in individual cells, fixation artifact, or both.

Intestinal amebae

Although the intestinal amebae that infect humans are not thought of as classic agents of food-borne disease, food plays an important role in the transmission of these protozoa. This is particularly true for areas of the world where the organisms are endemic. Transmission of most intestinal protozoa occurs by the fecal-oral route via contaminated food or water. Among the four genera of amebae that infect man, only Entamoeba histolytica and Blastocystis hominis are causes of disease. This article focuses on E. histolytica because of the organism's medical and economic impact on humans. In addition, the epidemiology, control, and laboratory diagnosis of these protozoa are addressed.

Postcystic development of Blastocystis hominis

A concentrated suspension of Blastocystis hominis cysts was inoculated into Jones' medium and removed after 24 h for study of their development at the ultrastructural level. The parasite divides in the cyst, and up to three daughter cells can be seen. During this process the cyst wall dissolves, leaving behind thin membranous remnants. Excystation occurs mostly by the emergence of the daughter cells through an aperture in the outer fibrillar coat. Before excystation the vacuolar and the granular stages form and the daughter cells develop their own fibrillar layer.

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.

Development of Blastocystis hominis cysts into vacuolar forms in vitro

The development of cysts of Blastocystis hominis isolated from human feces by the Ficoll-Paque concentration method and cultured in Jones' medium containing 10% horse serum is described. The morphological changes were studied by light and transmission electron microscopy at different intervals for up to 48 h. The cysts developed into a large number of vacuolar forms within 24 h, and binary fission was the only mode of reproduction observed.

Scanning electron microscopy of Blastocystis hominis cysts

Scanning electron microscopy of Blastocystis hominis cysts reveals that some cysts have an outer coat, whereas others are naked. If intact, the outer coat forms a fan-like structure around the cyst and its surface is granular. The fragmented outer coat adheres to other cysts and bacteria, forming irregular clumps.

Cytopathic effects of Blastocystis hominis on Chinese hamster ovary (CHO) and adeno carcinoma HT29 cell cultures

Blastocystis hominis isolates from asymptomatic carriers and symptomatic patients were cultured in vitro, purified from the co-cultivated bacterial flora and tested for cytopathic effects on monolayers of Chinese Hamster Ovary (CHO) cells and Adeno Carcinoma HT29 cells. In the case of the CHO cells, living B. hominis cells and B. hominis cell lysates were able to cause significant cytopathic effects, which were dependent on the concentration of cells employed. Destruction of the cell monolayers was observed to the same extent with patient isolates derived from healthy or symptomatic B. hominis carriers. HT29 cells were less susceptible: B. hominis cells and cell lysates caused only minor effects which were not statistically significant. Culture filtrates of B. hominis exhibited cytopathic potential on CHO and HT29 cells; however, the control which consisted of filtrates from Robinson's cultures in which B. hominis failed to grow showed similar effects, too. Therefore the culture supernatants could not be proven to produce a specific cytopathic effect on CHO and HT29 cells.

Blastocystis hominis in animals: incidence of four serogroups

In toto, 520 faecal samples from mammals, birds, reptiles, amphibians, fish, and snails were investigated (see Table 1). 91 strains of Blastocystis hominis could be isolated by culture. However, only 48 of them were suitable for axenisation. 96 percent of samples belonged to four serogroups detected in humans but two strains, one from a pig and another from a duck, could not be classified, suggesting the existence of one or two further serogroups. While humans showed mainly serogroups I and II, pigs harboured serogroups III and IV. Four serogroups were isolated from monkeys. The question whether the genus Blastocystis consists of one or more species is discussed.

Description of an improved method for Blastocystis hominis culture and axenization

An improved method for Blastocystis hominis culture and axenization was developed in the present study. Stool samples were cultured in prereduced Boeck-Drbohlav NHI modified medium (with several modifications) supplemented with antibiotics (0.4% ampicillin, 0.1% streptomycin, 0.0006% amphotericin B). Axenization was performed by the combination of partial purification of B. hominis by Ficoll-metrizoic acid gradient and inoculation in fresh medium containing active antibiotics against remaining bacteria. A total of 25 strains were obtained by this procedure. The time required for axenization ranged between 3 and 5 weeks. The generation time of axenic strains ranged from 6.6 to 12.1 h (mean +/- SD 110.0 +/- 1.8 h) and the mean number of generations was 2.5 +/- 0.6 h per 24 h. The size of vacuolar and ameboid forms found in stools and in culture was similar. The special formulation of the medium used reduced the generation time and did not modify the cellular size as compared with fecal forms.

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.

Clonal growth of Blastocystis hominis in soft agar with sodium thioglycollate

The present report describes a method for establishment of colonies of Blastocystis hominis from single cells in soft agar. The percentage of colony-forming efficiency (% CFE = number of colonies grown/number of cells inoculated x 100) for the cultures was greatly improved by the addition of sodium thioglycollate. Five human Blastocystis isolates chosen for this study showed no apparent variation in colonial morphology. Isolated colonies were also successfully grown in liquid medium, providing a means of obtaining large numbers of B. hominis cells that had arisen from a single clone.

Observations on the ultrastructure and viability of the cystic stage of Blastocystis hominis from human feces

This report describes the ultrastructure and viability of cysts of Blastocystis hominis from feces of infected patients. The cysts were round to ovoid, measured 2-5 microns in size, and contained a condensed cytoplasm that had vacuoles of varying sizes, four nuclei, and as many as six cristate mitochondria. The cell wall was rather electron-lucent. Surprisingly, chromatoid-like structures were found in the cytoplasm and nucleus of some of the cysts. These have not previously been reported in Blastocystis. The cysts can survive in water for up to 19 days at normal temperatures but are fragile at extreme temperatures and in common disinfectants.

Colony formation of Blastocystis hominis in soft agar

This is the first description of a method for growing axenized Blastocystis hominis as colonies in petri dishes containing soft agar. Blastocystis cells cultured in two types of agar appeared to show different colonial morphologies as well as differing colony yields. Microscopic examination of the colonies revealed many amoeboid and giant cells. Many cells were also shown to possess thin filament-like structures that appeared to stretch across the central vacuole.

Ultrastructure of Blastocystis hominis cysts

Blastocystis hominis cysts were concentrated from human faeces by repeated washing in distilled water and centrifugation on Ficoll-Paque. This procedure gave a concentrated suspension of cysts without yielding any non-cystic forms. The cysts were examined by both transmission (TEM) and scanning electron microscopy (SEM). Cysts were surrounded by a fibrillar layer that appeared porous in SEM. Many naked cysts without the fibrillar layer were also visible in SEM. They were variable in shape but mostly circular to oval. The diameter of the cyst without the fibrillar layer was 3.5 microns in both TEM and SEM. The nuclear structure was typical of Blastocystis and exhibited multiple mitochondria with poorly developed cristae. Glycogen was present in small to large clumps in the cytoplasm. The cyst wall was 5-100 nm thick and was bounded internally by an electron-dense plasmalemma.

Elucidation of the life cycle of the intestinal protozoan Blastocystis hominis

This paper elucidates the status of the different morphological forms of Blastocystis and reports the existence of thin- and thick-walled cysts in B. hominis on the basis of current experimental evidence. It is suggested that the thin-walled cysts are autoinfectious, leading to multiplication of the organism in the intestinal tract. The thick-walled cysts are responsible for external transmission via the faecal-oral route. A life cycle for B. hominis is postulated on the basis of these findings.

Differentiation of the various stages of Blastocystis hominis by acridine orange staining

Acridine orange staining differentiates the cystic and the central body forms of Blastocystis hominis and offers a very convenient and easy method to observe the internal structure of the parasite. Acridine orange stains the nuclei and the central body of the rounded vacuolar forms of the parasite bright and dull green, respectively. The colour changes to yellow and then to flaming red-orange when the rounded central body forms of the parasite become cystic.

Lipid biosynthesis by axenic strains of Blastocystis hominis

Axenic strains of Blastocystis hominis incorporated 32P, added to the medium as orthophosphate, into a number of phospholipids, including sphingomyelin, cardiolipin, phosphatidic acid, the phosphoglycerides of choline, ethanolamine, serine, and inositol and some other minor phospholipids. Radioactive palmitate and glycerol provided in the growth medium introduced radiolabel into diacylglycerols, triacylglycerols, and all major phosphoglycerides found in the organism. Palmitate is a major fatty acid of cholesterol esters in B. hominis, but radioactive palmitate did not enter the cholesterol ester pool. Radioactive acetate was not incorporated into any lipids. Cholesterol and cholesterol esters of the organism were not labeled when cells were grown in the presence of radioactive glucose, mevalonic acid, or mevalonolactone. Radioactive cholesterol added to the medium became stably associated with B. hominis cells, but none of the radioactive cholesterol entered the cholesterol ester pool. Cholesterol-[3H]-palmitate added to the medium became stably associated with the organism, and most of the radioactivity associated with the cells remained in the cholesterol ester fraction on extended incubation. These results show that this parasitic protozoan has the capacity to synthesize most cellular lipids de novo, but suggest that it acquires free cholesterol and intact cholesterol esters directly from growth medium.

A multiple fission-like mode of asexual reproduction in Blastocystis hominis

A non-axenic and an axenic isolate of Blastocystis hominis have been induced to form cysts in vitro using an encystation medium. The morphology of the parasite at different time points was observed by scanning electron microscopy. In day-2 cultures the cysts were spherical and had a non-uniform, coarse outer surface around the body. A deep, pore-like opening was seen in some of the parasites. Most of the cysts from day-4 and day-6 cultures ruptured, revealing small, uniformly sized spherical bodies occurring in grape-like clusters. Acridine orange staining confirmed that these bodies were the progeny of Blastocystis hominis. A multiple fission-like reproduction process giving rise to many daughter Blastocystis occurs within the cyst.

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.

A cyst-like stage of Blastocystis hominis

A cyst-like form of Blastocystis hominis is described in stools and in culture. This form is more common in stored stools than fresh material. A cyst wall is secreted under the surface coat of the cell, and the surface coat and cell debris subsequently separate from the cyst. Whether this stage can withstand adverse environmental conditions and is infective to a new host remain to be determined.

Ultrastructural evidence for a possible differentiation way in the life-cycle of Blastocystis hominis

The present paper is reporting the characteristic ultrastructural aspects of an amoeboid B. hominis population obtained from a child having giardiasis and dysentery in history. The particular features of smooth endothelial reticulum are postulated as being the expression of functional changes of this organelle in the differentiation process, the protozoon passing from the amoeba to the vacuolar form.