Rapid serodiagnosis of leptospirosis by latex agglutination test and flow-through assay.

PURPOSE: Diagnosis of leptospirosis facilitates patient management and initiation of therapy. The microscopic agglutination test (MAT) is the serological test used in reference laboratories because of its high degree of sensitivity and specificity. But the results are not available quickly for patient management. In the present study, in order to develop a simple, rapid immunodiagnostic assay, one of the outer membrane proteins (OMPs), recombinant LipL41 (rLipL41) has been utilised in latex agglutination test (LAT) and flow-through assay. METHODS: Part of LipL41 gene was expressed in Escherichia coli system and purified. The rLipL41 antigen of pathogenic Leptospira interrogans serovar Icterohaemorrhagiae, which is conserved in all pathogenic Leptospira spp. was used as capture antigen in the LAT and flow-through test. Both tests are very rapid and could be completed within 5 minutes. The sensitivity and specificity of rLipL41 was assessed and evaluated in LAT and flow-through assay in comparison with standard MAT. RESULTS: The sensitivity and specificity of the LAT were 89.70 and 90.45% and flow-through assay were 89.09 and 77.70%, respectively. CONCLUSIONS: The developed LAT and flow-through assays were simple, rapid and economical for the detection of leptospira infection and suitable for large-scale screening of samples in endemic areas without any sophisticated equipment.

Evaluation of methods and costs for detecting methicillin-resistant Staphylococcus aureus isolates from clinical specimens at regional hospitals in Trinidad and Tobago / Evaluación de métodos y costos para la detección de aislados de Staphylococcus aureus resistentes a la meticilina a partir de especímenes clínicos en los hospitales regionales de Trinidad y Tobago

OBJECTIVES: To evaluate and determine the most cost effective, rapid and specific method for detection of methicillin resistance in clinical isolates of S aureus in a setting with limited personnel and resources. METHODS: Standard laboratory methods were used to identify S aureus isolates. The conventional Methicillin Resistance Staphylococcus aureus (MRSA) detection methods used included, 1 µg oxacillin disk diffusion, oxacillin salt agar screen (CLSI), penicillin binding protein (PBP 2') latex agglutination test and E-tests oxacillin. Results of conventional tests were compared with a polymerase chain reaction (PCR) method for detecting MRSA isolates. Polymerase chain reaction detection of the mecA gene in S aureus was used as the " gold standard" for MRSA identification. RESULTS: All methods had 100% sensitivity except for oxacillin disk diffusion and oxacillin-salt agar screening with 98% and 99%, respectively. Specificity was also 100% for all methods except for oxacillin-disk diffusion (99%). Turn around time (TAT) for detection of MRSA was calculated to be within six hours for PCR. The fastest TAT of 1.25 hours was obtained for PBP 2' latex agglutination. Total cost for labour and materials to perform each method was highest for E-test, US$13.76/isolate. The cost for PCR when compared to that of latex agglutination was not statistically significant (US$3.74 vs US5.91, p = 0.4). CONCLUSIONS: All methods presented high sensitivity and specificity, but the latex agglutination test had the advantage of giving a reliable, rapid and most cost effective result that compares well to PCR in this environment.

OBJETIVOS: Evaluar y determinar el método más específico, rápido y costo-efectivo para la detección de la resistencia a la meticilina en aislados clínicos de S aureus en un lugar con personal y recursos limitados. MÉTODOS: A fin de identificar los aislados de S aureus, se utilizaron métodos estándar de laboratorio. Los métodos convencionales de detección de SARM usados incluyeron difusión por disco de oxacilina de 1 µg, prueba de tamizaje (" screening" ) de oxacilina en agar-sal (CLSI), test de aglutinación en látex para la detección de la proteína 2 fijadora de la penicilina (PBP 2'), y la prueba E-Test de oxacilina. Los resultados de las pruebas convencionales fueron comparados con un método de PCR para la detección de aislados SARM. La detección por PCR del gene mecA en S aureus fue usada como " estándar de oro" para la identificación de SARM. RESULTADOS: Todos los métodos tuvieron 100% de sensibilidad excepto la difusión por disco de oxacilina y el tamizaje de oxacilina en agar-sal, con 98% y 99% respectivamente. La especificad también fue de 100% para todos los métodos, con excepción de la difusión por disco de oxacilina (99%). El tiempo de respuesta (TAT, del inglés turn around time) para la detección de SARM se halla, según los cálculos, dentro de las seis horas para PCR. El TAT más rápido, 1.25 hrs, se obtuvo en la aglutinación en látex de PBP 2'. El costo total del trabajo y los materiales en la ejecución de cada método fue más alto en la prueba de E-Test, aislado/$13.76 USD. El costo de PCR en comparación con el de la aglutinación látex no fue estadísticamente significativo ($3.74 USD vs $5.91USD, p = 0.4). CONCLUSIONES: Todos los métodos presentaron alta sensibilidad y especificidad, pero el test de aglutinación en látex tuvo como ventaja el ofrecer un resultado confiable, rápido y altamente costo-efectivo, no muy diferente del PCR en este ambiente.

Comparison between RT-PCR and rapid agglutination test for diagnosis of human rotavirus infection.

Rotavirus represents the major cause of dehydrating diarrhea among infants and young children on worldwide scale and has recently become the target of research aimed at developing a vaccine. To that end, screening tests of clinical specimens ought to provide high sensitivity and specificity. Hence, in order to achieve that aim we compared a commercially available latex agglutination (LA) kit with reverse transcription polymerase chain reaction (RT-PCR) using primers amplifying the gene for the major neutralization antigen in 71 stool samples of children with acute gastroenteritis during November 1998-April 1999. Based on accuracy (76.05%), specificity (86.8%) and sensitivity (63.6%) determined for LA with RT-PCR serving as the gold standard, we recommend LA for field studies where speed and simplicity are crucial. Yet, for the purpose of further studies as to epidemiology and vaccine trials RT-PCR with its higher specificity and sensitivity will be required.