Tear IgA-ELISA: a novel and sensitive method for diagnosis of ophthalmic cysticercosis.

For the first time, presence of locally secreted specific IgA antibodies in tear specimen from human with ophthalmic cysticercosis is documented in the present study. The ELISA using Taenia solium metacestode excretory secretory (ES) antigen demonstrated a diagnostic level of IgA antibodies in tears with 100% sensitivity (6 out of 6 confirmed cases of ophthalmic cysticercosis) whereas, 25 of 34 (73.52%) clinically suspected cases were diagnosed positive. The ELISA using T. solium metacestode somatic antigen detected a diagnostic titre of IgA antibody in tears with a sensitivity of 50% (3 out of 6 confirmed cases). The specificity of the tear IgAELISA using T. solium metacestode somatic and ES antigens is observed to be 94.87% and 92.3%, respectively. Overall in tears, the ELISA using T. solium metacestode ES antigens for detection of IgA antibodies shows a higher diagnostic efficiency (93.33%) compared to that using T. solium metacestode somatic antigen (88.88%). The sensitivities of the ELISA for detection of IgA antibodies in tears is observed to be higher than that for detection of IgG antibodies in serum using either somatic or ES antigens of the parasite.

A novel nested multiplex polymerase chain reaction (PCR) assay for differential detection of Entamoeba histolytica, E. moshkovskii and E. dispar DNA in stool samples.

BACKGROUND: E. histolytica, a pathogenic amoeba, is indistinguishable in its cyst and trophozoite stages from those of non-pathogenic E. moshkovskii and E. dispar by light microscopy. We have developed a nested multiplex PCR targeting a 16S-like rRNA gene for differential detection of all the three morphologically similar forms of E. histolytica, E. moshkovskii and E. dispar simultaneously in stool samples. RESULTS: The species specific product size for E. histolytica, E. moshkovskii and E. dispar was 439, 553 and 174 bp respectively, which was clearly different for all the three Entamoeba species. The nested multiplex PCR showed a sensitivity of 94% and specificity of 100% for the demonstration of E. histolytica, E. moshkovskii and E. dispar DNA in stool samples. The PCR was positive for E. histolytica, E. moshkovskii and E. dispar in a total of 190 out of 202 stool specimens (94% sensitive) that were positive for E. histolytica/E. dispar/E. moshkovskii by examination of stool by microscopy and/or culture. All the 35 negative control stool samples that were negative for E. histolytica/E. dispar/E. moshkovskii by microscopy and culture were also found negative by the nested multiplex PCR (100% specific). The result from the study shows that only 34.6% of the patient stool samples that were positive for E. histolytica/E. dispar/E. moshkovskii by examination of stool by microscopy and/or culture, were actually positive for pathogenic E. histolytica and the remaining majority of the stool samples were positive for non-pathogenic E. dispar or E. moshkovskii as demonstrated by the use of nested multiplex PCR. CONCLUSION: The present study reports a new nested multiplex PCR strategy for species specific detection and differentiation of E. histolytica, E. dispar and E. moshkovskii DNA in stool specimens. The test is highly specific, sensitive and also rapid, providing the results within 12 hours of receiving stool specimens.

A new serum hydatid antigen detection test for diagnosis of cystic echinococcosis.

Cystic echinococcosis (CE) is a major public health problem with a worldwide distribution in both humans and animals. Diagnosis of this disease by simple and rapid immunoassays is a priority. The objective of the present study was to standardize and evaluate the latex agglutination test (LAT) as a simple test for the detection of circulating hydatid antigen in serum. The subjects in this study included 141 patients in the following groups: surgically confirmed CE cases (18), ultrasound-proven cases (26), presumptive CE cases (47), controls with other parasitic disease (25), and healthy controls (25). A polystyrene latex (0.81 microm) suspension was used as a carrier particle for hydatid antibodies in the test. The latex particles were sensitized with hyperimmune hydatid antiserum raised in rabbits. The hydatid antibody-sensitized latex particles were used for the detection of hydatid antigens in serum. The results of the study showed that the LAT could detect the circulating hydatid antigen in 13 (72%) of 18 patients with surgically confirmed CE, 17 (65%) of 26 patients with ultrasound-proven CE, and 19 (40%) of 47 presumptive cases of CE. The test detected antigen in 1 (4%) of 25 controls with other parasitic disease, and no antigen was detected in the serum of 25 healthy controls. The LAT showed a sensitivity of 72%, a specificity of 98%, a positive predictive value of 93%, and a negative predictive value of 91%. The present study is the first report of the LAT for the detection of hydatid antigen in serum in the diagnosis of CE.