Capture immunoassay for LT detection produced by enterotoxigenic Escherichia coli in bacterial isolates

A capture enzyme-linked immunosorbent assay (ELISA), which detects LT-I toxin produced by enterotoxigenic Escherichia coli strains, has beendeveloped. This capture assay was performed using the IgG enriched fraction of anti-LT-I antiserum and IgG2b anti-LT-I monoclonal antibody and allowed a clear distinction between E. coli LT-I - producing and non-producing strains. The estimated accuracy of the assay is 78% for sensitivity, 94% for specificity and 92% for efficiency. Thus, the capture immunoassayis a sensitive tool for detection of E. coli, which produces heat-labile enterotoxin, and is suitable for use in clinical laboratories and epidemiological surveys in developing world.

O objetivo do presente trabalho foi a padronização de um imunoensaio de captura para detecção de amostras de E. coli produtoras da toxina LT-I. Este ensaio de captura foi desenvolvido utilizando-se a fração enriquecida em IgG do anticorpo policlonal anti-LT e um anticorpo monoclonal caracterizado como IgG2b. Através deste método verificou-se uma clara distinção entre cepas de E. coli produtoras e não produtoras da toxina (p 0,0001), sendo a sensibilidade do método de 78%, a especificidade de 94% e a eficiência de 92%. Assim, o imunoensaio de captura mostrou-se como uma ferramenta sensível para a detecção de amostras de E. coli que produzem a enterotoxina termo-lábil, podendo ser aplicado em laboratórios clínicos e inquéritos epidemiológicos em paises em desenvolvimento.

Urinary tract infection: detection of Escherichia coli antigens in human urine with an ELIEDA immunoenzymatic assay

Escherichia coli is the most common causative agent of urinary tract infection (UTI), and diagnosing this infection usually relies on bacteriologic methods. Nevertheless, screening methods can be useful for a rapid presumptive diagnosis even though some of these screening methods have low sensitivity or are expensive. To investigate a possible new alternativa approach, an antigen-based immunoassay-enzyme-linked immunoelectrodiffusion assay (ELIEDA)- was standardized for screening for this bacterial infection. Combining counter-immunoelectrophoresis with an immunoenzymatic assay, the ELIEDA requires concentrated urine specimens, a cellulose acetate membrane, polyclonal antibodies to E. coli raised in rabbits, and peroxidase-labeled sheep antibodies to rabbit immunoglobulin G (IgG). This ELIEDA technique was evaluated using 244 urine specimens, 76 of them with E.coli, 47 with heterologous bacteria, and 121 without bacteria. In comparison to bacteriologic methods, the sensitivity, specificity, and positive and negative predictive values for the ELIEDA were 93.4 por ciento, 98.2 por ciento, 95.9 por ciento, and 97.1, respectively. The data obtained suggest that this assay is useful for routine diagnostic screening for UTI caused by E.coli. In addition, since the ELIEDA stained membranes can be stored, this assay makes retrospective studies possible