[Performance of Cholera-SMART and Pathogen-Detection-Kit in the quick diagnosis of cholera]. / Desempeño de los sistemas Cholera-SMART y Pathogen-Detection-Kit en el diagnóstico rápido del cólera.

OBJECTIVES: To compare the performance of two rapid systems for the diagnosis of cholera with the culture method, and to propose a strategy for improving the specificity and sensitivity of these systems and reducing the costs involved in making a diagnosis. METHODS: The following institutions participated in the study: the National Bacteriology Referral Center (Centro Nacional de Referencia en Bacteriologia, CNRB) of the Costa Rican Institute for Research and Teaching in Nutrition and Health (Instituto Costarricense de Investigacion y Ensenanza en Nutricion y Salud, INCIENSA) and various hospitals in the provinces of Alajuela, Guanacaste and San Jose, in Costa Rica. A total of 237 feces samples were used to asses the performance of two tests for the rapid detection of Vibrio cholerae 01: the Pathogen Detection Kit (PDK, Intelligent Monitoring Systems, Gainesville, Florida, USA) and Cholera-SMART (New Horizons Diagnostics Corp., Columbia, Maryland, USA), both when applied directly (direct SMART and direct PDK) and when applied to specimens cultured in broth-enriched medium for 6 hours (SMART-6 and CPK-6) and for 18 hours (SMART-18 and PDK-18) at 37 degrees C in alkaline peptone water. Liquid and partially formed stools were cultured and examined by means of the rapid direct test; when the initial result was negative, the tests were repeated after culture for periods of 6 and 18 hours. Rectal and fecal swabs were obtained from feces cultured in enriched-broth medium for 6 and 18 hours. In addition, we studied the sensitivity of the rapid testing systems by using pure cultures of V. cholerae 01 (strain SOS-833, CNRB, Costa Rica) that were incubated for 18 to 24 hours, and we assessed the usefulness of observing motility under the microscope in order to rationalize the use of rapid methods. RESULTS: The sensitivity of the direct SMART test and of the direct PDK test was 100% when samples obtained from liquid and partially formed stools and from the intestinal contents of dead bodies were used. With these samples, the direct SMART procedure showed a specificity of 100%, whereas the direct PDK procedure showed a specificity that ranged from 85.7% to 77.4%, depending on the type of sample. False positives obtained with the direct PDK method turned out to be negative with PDK-6 and PDK-18. Among the rectal and fecal swabs of persons with and without diarrhea or who had received prior treatment with antibiotics, three results that were negative with the SMART-6 procedure and two that were negative with the PDK-6 procedure turned out to be positive with the SMART-18 and PDK-18 procedures, respectively. Both systems showed excellent concordance (kappa index above 0.9) throughout. Both systems were sensitive to 6 x 10(7) colony-forming units per milliliter (cfu/mL), which was concordant with the microscopic observation of 10 microorganisms or more per field with the type of motility that characterizes vibrios (at 1000 x magnification). Samples having fewer than 10 microorganisms with the motility that characterizes vibrios had concentrations between 6 x 10(3) and 6 x 10(6) cfu/mL and became positive only after incubation in enriched-broth medium for 6 to 18 hours. We propose a strategy for diagnosing the presence of V. cholerae 01 infection in less time than it takes with traditional methods, with positive and negative predictive values of 100%. CONCLUSIONS: The SMART and PDK systems make it possible to accurately diagnose cholera quickly, don't require sophisticated equipment or highly qualified technical personnel, and perform satisfactorily in field conditions. Through the proposed strategy, it becomes possible to improve the specificity and sensitivity of these systems and to reduce the cost of making a diagnosis, thus making them suitable for use in cholera surveillance in low-income settings where this disease is a serious public health problem.

Macroscopic agglutination test for rapid diagnosis of human leptospirosis.

A commercially available slide agglutination test (SAT) for the diagnosis of human leptospirosis was evaluated by comparing it to an immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) and to the microscopic agglutination test (MAT). For all 108 patients, leptospirosis was diagnosed on the basis of a fourfold or greater increase in titer by MAT (seroconversion), and all but 1 of 245 controls were MAT negative (titers, <1:100). Both SAT and the IgM ELISA failed to detect one case of infection (sensitivity, 99%). Only 3 of 145 blood donors and none of the 100 patients with other illnesses were SAT positive (specificity, 99%). The overall results were similar for the three tests; however, SAT and ELISA were statistically more sensitive as initial screening tests. For 22% of the patients, the diagnosis of leptospirosis was made earlier by SAT than by MAT. SAT detected 27 (44%) of 62 MAT-negative patients with the first serum sample. ELISA and SAT had very similar results. Follow-up of patients for 1 year after the onset of symptoms showed a decreasing rate of positivity by SAT from the third month on. The rate of positivity by ELISA decreased more slowly, to about 67% by the end of the study. By MAT all patients were persistently reactive. SAT and ELISA seem to be convenient methods for the rapid and early screening for leptospirosis and could replace the less sensitive MAT. ELISA gives less subjective results than SAT and provides information on IgM kinetics, but it can be performed only by the more sophisticated laboratories. SAT is inexpensive, can be performed more quickly and more easily than ELISA, and could be used by the less well equipped laboratories.

Evaluación de una técnica ELISA para el despistaje de enfermedad de chagas: datos de seroprevalencia en la ciudad de Rosario / Evaluation of an ELISA for chagas disease screening: seroprevalence data in the city of Rosario

Se evaluó la performance de un ELISA para la detección de anticuerpos anti Trypanosoma cruzi, en comparación con las técnicas habitualmente usadas en este laboratorio (aglutinación de látex, aglutinación directa de parásitos coloreados, hemaglutinación indirecta e inmunofluorescencia indirecta). La comparación se realizó en forma simultánea y a doble ciego sobre 690 dadores voluntarios de sangre y 244 pacientes que asistían a consulta médica entre los meses de diciembre de 1992 y enero-febrero de 1993. La técnica en estudio resultó confiable tanto para el despistaje de dadores de sangre como para el diagnóstico de laboratorio. La seroprevalencia de la infección fue 8,1 por ciento entre los dadores de sangre y 12,3 por ciento entre los pacientes (AU)

Rapid detection of Vibrio cholerae O1 in stools of Peruvian cholera patients by using monoclonal immunodiagnostic kits. Loyaza Cholera Working Group in Peru.

We compared stool culture with two commercial Vibrio cholerae O1 rapid diagnostic kits which detect antigen in 100 adults with cholera in Peru. Serum vibriocidal-antibody titer was used as an external reference. Both rapid diagnostic kits appeared to detect cholera more frequently than did culture and were highly specific.

Relación entre anticuerpos circulantes y cantidad de Candida albicans en materia fecal / Relation betwen circulatory antibodies and quality of candida albicans in faecal materia

Se estudió la presencia de anticuerpos contra Candida albicans, en 42 pacientes a los cuales se solicitaba cultivo micológico y recuento de levaduras en materia fecal. Por métodos estandarizados se procesaron las muestras, se cuantificó la presencia de levadura por gramo de materia fecal y se identificó a Candida albicans. Se obtuvo suero de los pacientes en el momento de llevar las muestras de heces al laboratorio. La presencia de anticuerpos se determinó por tres técnicas serológicas: aglutinación en tubo, inmunodifusión en gel de agar e inmunofluorescencia indirecta frente a levaduras y a tubos germinativos. La correlación de las tres pruebas con los resultados de los cultivos y recuento de colonias fue determinada sólo después que todos los datos fueron acumulados. Los resultados muestran que no existe correlación entre la cantidad de levaduras presentes y los anticuerpos circulantes. Ninguno de los pacientes presentaba infección diseminada o superficial evidente; se tuvo como referencia, la colonización del hongo en intestino

Relación entre anticuerpos circulantes y cantidad de Candida albicans en materia fecal / Relation betwen circulatory antibodies and quality of candida albicans in faecal materia

Se estudió la presencia de anticuerpos contra Candida albicans, en 42 pacientes a los cuales se solicitaba cultivo micológico y recuento de levaduras en materia fecal. Por métodos estandarizados se procesaron las muestras, se cuantificó la presencia de levadura por gramo de materia fecal y se identificó a Candida albicans. Se obtuvo suero de los pacientes en el momento de llevar las muestras de heces al laboratorio. La presencia de anticuerpos se determinó por tres técnicas serológicas: aglutinación en tubo, inmunodifusión en gel de agar e inmunofluorescencia indirecta frente a levaduras y a tubos germinativos. La correlación de las tres pruebas con los resultados de los cultivos y recuento de colonias fue determinada sólo después que todos los datos fueron acumulados. Los resultados muestran que no existe correlación entre la cantidad de levaduras presentes y los anticuerpos circulantes. Ninguno de los pacientes presentaba infección diseminada o superficial evidente; se tuvo como referencia, la colonización del hongo en intestino (AU)