Comparison of direct fecal smear microscopy, culture, and polymerase chain reaction for the detection of Blastocystis sp. in human stool samples

OBJECTIVE@#To compare the sensitivity and specificity of direct fecal smear microscopy, culture, and polymerase chain reaction in the detection of Blastocystis sp. in human stool.@*METHODS@#Human stool samples were collected from a community in San Isidro, Rodriguez, Rizal, Philippines. These samples were subjected to direct fecal smear microscopy, culture and polymerase chain reaction to detect the presence of Blastocystis sp.@*RESULTS@#Of the 110 stool samples collected, 28 (25%) were detected positive for the presence of Blastocystis sp. by two or more tests. Culture method detected the highest number of Blastocystis-positive stool samples (n=36), followed by PCR of DNA extracted from culture (n=26), PCR of DNA extracted from stool (n=10), and direct fecal smear (n=9). Compared to culture, the sensitivity of the other detection methods were 66.7% for PCR from culture and 19.4% for both PCR from stool and direct fecal smear. Specificity of the methods was high, with PCR from culture and direct fecal smear having 97.3%, while PCR from stool at 95.9%.@*CONCLUSIONS@#In this study, in vitro culture is the best method for detecting Blastocystis sp. in human stool samples.

Perfil de parásitos y comensales entéricos de comunidades del cantón de Barva, Heredia, Costa Rica / Profile diners enteric parasites and communities in the canton of Barva, Heredia, Costa Rica

Se analizó la frecuencia de los protozoarios y helmintos observados en las muestras fecales de los pacientes que consultaron el laboratorio del Área de Salud de Barva, Coopesiba R.L., durante enero a noviembre del 2004. La presencia de organismos parásitos y comensales fue evidenciada en las muestras procedentes de todas las comunidades, mostrando una prevalencia global del 41.2 por ciento. Las comunidades de San Roque y Barva Distrito Central fueron las que presentaron, en los análisis efectuados, las prevalencias más alta, 45,4 por ciento, y más baja, 35,0 por ciento, respectivamente. Los organismos más frecuentes fueron Blastocystis hominis, con una prevalencia global del 27,4 por ciento, Endolimaz nana, 16,5 por ciento, y Entamoeba coli, 7,4 por ciento. Los únicos helmintos observados fueron Trichuris trichiura, 0,03 por ciento, e Hymenolepis nana, 0,1 por ciento. La distribución de los parásitos en las localidades del Cantón de Barva no fue homogénea. Los resultados mostraron prevalencias de organismos relativamente bajas pero sugieren la ocurrencia de condiciones permisivas para la transmisión de enteropatógenos que hacen su diseminación por fecalismo, lo cual conlleva la necesidad de insistir en medidas preventivas.

The frequency of protozoa and helminths observed in the fecal samples of the patients who consulted in the laboratory of the Barva Health Area (also known as Coopesiba, R.L.), during the months of January to November of 2004 was analyzed. The presence of parasitic as well as commensal organisms was evidenced in the samples coming from all the differentcommunities, showing a global prevalence of 41.2%. Thecommunities of San Roque as well as the Central District of Barva were the ones which showed, in the analysescarried out, the highest (45.4%) and the lowest (35.0%) prevalences, respectively. The most frequent organisms were Blastocystis hominis with a global prevalence of 27.4%, Endolimax nana (16.5%) and Entamoeba coli (7.4%). The only helminthic organisms observed wereTrichuris trichiura (0.03%) and Hymenolepis nana (0.1%). The parasite distribution in the communities of Barvawas not homogeneous. The results showed relatively low prevalences of the organisms but suggest the existenceof permissive conditions for transmission of enteric pathogens disseminated via the fecal route all of which emphasizes the need to stress preventive measures.

Diagnosis of intestinal infections by cultivation

An evaluation of the efficiency of fecal cultivation in modified Boeck and Drbohlav diphasic medium for the diagnosis of intestinal protozoan infections in comparison with 4 coverslip preparations of direct fecal smears and formalin-ether concentration technic was undertaken Of the three technics, cultivation has the highest percentage recovery efficiency for E. histolytica and T. hominis. Of 24 specimens positive for E. histolytica, cultivation detected 23 or 95.8 in contrast to 9 or 69.2 positive by combination of direct fecal smear and formalin-ether concentration. Forty-four specimens were positive by cultivation for T. hominis while only 16 of these or 37.2 were positive by direct fecal smear. Formalin-ether concentration is not suitable for the detection of T. hominis since the organisms are caught in the ether-debris layer In view of our experience, cultivation is recommended to be used routinely in the diagnosis of intestinal amoebiasis. (Summary)

Comparative evaluation of the merthiolate-iodine-formaldehyde concentration technique and the Kato-Katz technique in the quantitative diagnosis of schistosomiasis japonica

A total of 384 stool specimens found to be positive for schistosoma eggs using the Direct Fecal Smear were further examined quantitatively by the MIFC and the Kato-Katz techniques. MIFC has a higher efficiency rate (95.57%) as compared to Kato-Katz technique (73.43%). Kato-Katz yields a higher percentage of false negatives (26.56%). These found to be statistically significant. With regards to quantification, Kato-Katz has a higher mean egg difference (245.69%) but this was found to be statistically significant. Thus, MIFC technique is more reliable and efficient than Kato-Katz in the quantitative diagnosis of Schistosomiasis japonica. (Auth. Sum.)