609
LETTERS to the EDITOR
Clinical
significance of Blastocystis hominis
SiR,—One of the latest organisms to attract gastroenterological attention is Blastocystis hominis, and the debate about its clinical significance is heating Up.1 This protozoon is thought by many to be a human pathogen,2-4 but others argue that the case is far from proven.L5 Most studies so far have come from North America. We report here the prevalence of B hominis in faecal specimens sent to a UK district hospital and an attempt to assess clinical significance.
During the six months November, 1989, to May, 1990, 3317 faecal samples from 2596 patients were examined for enteric pathogens. All were tested for sahnonella, shigella, campylobacter, aeromonasplesiomonas, and cryptosporidium. Where relevant, additional investigations were done for Yersinia spp, Escherichia coli (0157, enterotoxigenic strains), Clostridium difficile, Clperfringens, Vibrio spp, and rotavirus. Where indicated, a formalin-ether concentration was done for parasites. For B hominis all faeces were examined under direct microscopy (high-power field x 400) in both physiological saline and 5% aqueous nigrosin (a counterstain, that proved superior for detection of scanty organisms). Positive specimens were cultured for viruses. Clinical details were sought and follow-up faecal specimens were asked for. B hominis was detected in 75 patients (3% total), coming second
changing colonic environment brought about by a separate disease process. Others talk of "symptomatic blastocystosis", representing undetected parasite infection or a functional bowel condition.9 The debate continues. to a
Department of Microbiology, Wycombe General Hospital, High Wycombe HP11 2TT, UK
D. J. WAGHORN P. HANCOCK
1. Rosenblatt JE. Blastocystis hominis. J Clin Microbiol 1990; 28: 2379-80. 2. Sheehan DJ, Raucher BG, McKitrick JC. Association of Blastocystis homims with signs and symptoms of human disease. J Clin Microbiol 1986; 24: 548-50. 3. Qadri SM, Al-Okaili GA, Al-Dayel F. Clinical significance of Blastocystis hominis. J Clin Microbiol 1989; 27: 2407-09. 4. Kain K, Noble M. Blastocystis homims infection in humans. Rev Infect Dis 1989; 11: 508-09. 5. Miller RA, Minshew BH. Blastocystis hominis: an organism in search of a disease. Rev Infect Dis 1988; 10: 930-38. 6. Garcia LS, Bruckner DA, Clancy MN. Clinical relevance of Blastocystis hominis. Lancet 1984; i: 1233-34. 7. Doyle PW, Helgason MM, Mathias RG, Proctor EM. Epidemiology and pathogenicity of Blastocystis hominis. J Clin Microbiol 1990; 28: 116-21. 8. Zuckerman MJ, Watts MT, Bhatt, BD, Meriano FV, Ho H, Polly SM. Intestinal permeability in patients with Blastocystis hominis infection. Gastroenterology 1990; 96: A568 (abstr). 9. Markell EK, Udkow MP. Blastocystis hominis: pathogen or fellow traveller? Am J Trop Med Hyg 1986; 35: 1023-26.
in frequency to Salmonella spp:
Pathogen
No
Pathogen
Salmonella spp B hominis
120 75 69 52 42 41 26
Miscellaneous parasites Entamoeba histolytica E coli’(enterotoxigenic
Campylobacter spp Rotavirus Cl difficile (cytotoxin positive) G lamblia
Cryptospondium sp Cl perfringens (enterotoxin positive)
17
strains) Shzgella spp E coli (0157:H7) Aeromonas spp Plesiomonas sp Yersinia spp
No 16 12 9 7 2 2 1 1
The clinical details of 9 of the 75 patients could not be assessed; of the remaining 66,14 had one or more other pathogens. Of the other 52,13 had a known underlying gastrointestinal disease and 15 were symptom-free (follow-up after illness). This left 24 patients whose clinical findings suggested a pathogenic role for B hominis, disappearance of symptoms coinciding with loss of the organism from faeces. The ages of those affected ranged from 4 to 60 years. Diarrhoea was the predominant symptom (23 out of 24 patients) but the clinical picture resembled that of giardial infection. 7 patients reported recent travel to Asia and Africa. The decision to prescribe oral metronidazole (7-day course) was taken on an individual patient basis but the course of illness did not appear to be much altered since 10 patients recovered without specific therapy and within a time to recovery similar to that in those treated. In contrast to series where only high concentrations of B hominis have been considered clinically significant/,310 of our cases had counts below 5 per high-power field but only 1 of 15 symptomless patients carried more than 5 per high-power field. None of our 24 patients had a raised eosinophil county Other countries have reported higher prevalence rates than the frequency we found but the symptoms were similar, diarrhoea, abdominal pain, and flatus predominating.6,7 Whether the role of B hominis in gastrointestinal disturbance is one of association or causation has not yet been established. Animal models suggesting a causative role have not been wholly convincing,s and there seems to be no change in intestinal permeability or evidence of intestinal inflammation.8One view is that B hominis overgrowth is a response
Outbreak of blastocystosis in institution for the mentally retarded SiR; Blastocystis hominis is an enteric protozoon associated with of gastrointestinal disease, but the route of transmission is not well established.l In 1989 Guglielmetti et al reported a family outbreak of blastocystosis in Siena.2 We report here a second outbreak of B hominis infection in Italy, this time in an institution for the mentally retarded, suggesting faecal-oral transmission of the some cases
disease.
During December, 1990, four men and two women from the institution were admitted to department of infectious diseases, St Anna Hospital, Ferrara, with diarrhoea and other symptoms of gastrointestinal disease (table). Stool specimens were examined same
fresh and after formalin/ethylacetate concentration and iodine and trichrome permanent stained smear procedures, and were cultured for bacterial pathogens (salmonella, shigella, campylobacter, Yersinia enterocolitica, vibrios, aeromonas); rotavirus antibodies were sought by ELISA test; and adenoviruses were looked for by a latex agglutination test. All patients’ stools contained large numbers of B hominis (5 or more cells at x 40 magnification) in absence of other parasites, CLINICAL DETAILS ON SIX CASES OF BLASTOCYSTOSIS FROM SAME INSTITUTION IN DECEMBER, 1990
LETTERS to the EDITOR
Clinical
significance of Blastocystis hominis
SiR,—One of the latest organisms to attract gastroenterological attention is Blastocystis hominis, and the debate about its clinical significance is heating Up.1 This protozoon is thought by many to be a human pathogen,2-4 but others argue that the case is far from proven.L5 Most studies so far have come from North America. We report here the prevalence of B hominis in faecal specimens sent to a UK district hospital and an attempt to assess clinical significance.
During the six months November, 1989, to May, 1990, 3317 faecal samples from 2596 patients were examined for enteric pathogens. All were tested for sahnonella, shigella, campylobacter, aeromonasplesiomonas, and cryptosporidium. Where relevant, additional investigations were done for Yersinia spp, Escherichia coli (0157, enterotoxigenic strains), Clostridium difficile, Clperfringens, Vibrio spp, and rotavirus. Where indicated, a formalin-ether concentration was done for parasites. For B hominis all faeces were examined under direct microscopy (high-power field x 400) in both physiological saline and 5% aqueous nigrosin (a counterstain, that proved superior for detection of scanty organisms). Positive specimens were cultured for viruses. Clinical details were sought and follow-up faecal specimens were asked for. B hominis was detected in 75 patients (3% total), coming second
changing colonic environment brought about by a separate disease process. Others talk of "symptomatic blastocystosis", representing undetected parasite infection or a functional bowel condition.9 The debate continues. to a
Department of Microbiology, Wycombe General Hospital, High Wycombe HP11 2TT, UK
D. J. WAGHORN P. HANCOCK
1. Rosenblatt JE. Blastocystis hominis. J Clin Microbiol 1990; 28: 2379-80. 2. Sheehan DJ, Raucher BG, McKitrick JC. Association of Blastocystis homims with signs and symptoms of human disease. J Clin Microbiol 1986; 24: 548-50. 3. Qadri SM, Al-Okaili GA, Al-Dayel F. Clinical significance of Blastocystis hominis. J Clin Microbiol 1989; 27: 2407-09. 4. Kain K, Noble M. Blastocystis homims infection in humans. Rev Infect Dis 1989; 11: 508-09. 5. Miller RA, Minshew BH. Blastocystis hominis: an organism in search of a disease. Rev Infect Dis 1988; 10: 930-38. 6. Garcia LS, Bruckner DA, Clancy MN. Clinical relevance of Blastocystis hominis. Lancet 1984; i: 1233-34. 7. Doyle PW, Helgason MM, Mathias RG, Proctor EM. Epidemiology and pathogenicity of Blastocystis hominis. J Clin Microbiol 1990; 28: 116-21. 8. Zuckerman MJ, Watts MT, Bhatt, BD, Meriano FV, Ho H, Polly SM. Intestinal permeability in patients with Blastocystis hominis infection. Gastroenterology 1990; 96: A568 (abstr). 9. Markell EK, Udkow MP. Blastocystis hominis: pathogen or fellow traveller? Am J Trop Med Hyg 1986; 35: 1023-26.
in frequency to Salmonella spp:
Pathogen
No
Pathogen
Salmonella spp B hominis
120 75 69 52 42 41 26
Miscellaneous parasites Entamoeba histolytica E coli’(enterotoxigenic
Campylobacter spp Rotavirus Cl difficile (cytotoxin positive) G lamblia
Cryptospondium sp Cl perfringens (enterotoxin positive)
17
strains) Shzgella spp E coli (0157:H7) Aeromonas spp Plesiomonas sp Yersinia spp
No 16 12 9 7 2 2 1 1
The clinical details of 9 of the 75 patients could not be assessed; of the remaining 66,14 had one or more other pathogens. Of the other 52,13 had a known underlying gastrointestinal disease and 15 were symptom-free (follow-up after illness). This left 24 patients whose clinical findings suggested a pathogenic role for B hominis, disappearance of symptoms coinciding with loss of the organism from faeces. The ages of those affected ranged from 4 to 60 years. Diarrhoea was the predominant symptom (23 out of 24 patients) but the clinical picture resembled that of giardial infection. 7 patients reported recent travel to Asia and Africa. The decision to prescribe oral metronidazole (7-day course) was taken on an individual patient basis but the course of illness did not appear to be much altered since 10 patients recovered without specific therapy and within a time to recovery similar to that in those treated. In contrast to series where only high concentrations of B hominis have been considered clinically significant/,310 of our cases had counts below 5 per high-power field but only 1 of 15 symptomless patients carried more than 5 per high-power field. None of our 24 patients had a raised eosinophil county Other countries have reported higher prevalence rates than the frequency we found but the symptoms were similar, diarrhoea, abdominal pain, and flatus predominating.6,7 Whether the role of B hominis in gastrointestinal disturbance is one of association or causation has not yet been established. Animal models suggesting a causative role have not been wholly convincing,s and there seems to be no change in intestinal permeability or evidence of intestinal inflammation.8One view is that B hominis overgrowth is a response
Outbreak of blastocystosis in institution for the mentally retarded SiR; Blastocystis hominis is an enteric protozoon associated with of gastrointestinal disease, but the route of transmission is not well established.l In 1989 Guglielmetti et al reported a family outbreak of blastocystosis in Siena.2 We report here a second outbreak of B hominis infection in Italy, this time in an institution for the mentally retarded, suggesting faecal-oral transmission of the some cases
disease.
During December, 1990, four men and two women from the institution were admitted to department of infectious diseases, St Anna Hospital, Ferrara, with diarrhoea and other symptoms of gastrointestinal disease (table). Stool specimens were examined same
fresh and after formalin/ethylacetate concentration and iodine and trichrome permanent stained smear procedures, and were cultured for bacterial pathogens (salmonella, shigella, campylobacter, Yersinia enterocolitica, vibrios, aeromonas); rotavirus antibodies were sought by ELISA test; and adenoviruses were looked for by a latex agglutination test. All patients’ stools contained large numbers of B hominis (5 or more cells at x 40 magnification) in absence of other parasites, CLINICAL DETAILS ON SIX CASES OF BLASTOCYSTOSIS FROM SAME INSTITUTION IN DECEMBER, 1990
