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Development of a rapid latex agglutination test for the diagnosis of enteropathogenic Escherichia coli and Shiga toxin-producing Escherichia coli

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Anna Raquel Ribeiro dos Santos
Total Authors: 1
Document type: Master's Dissertation
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
Defense date:
Examining board members:
Roxane Maria Fontes Piazza; Elizabeth Natal de Gaspari; Beatriz Ernestina Cabilio Guth
Advisor: Roxane Maria Fontes Piazza

There are 800,000 deaths associated with diarrhea worldwide in children under five, and these are mainly in sub-Saharan Africa, Southeast Asia and Latin America. Among the causative pathogens of diarrhea, diarrheagenic Escherichia coli (DEC) is the most common bacterial etiological agent, including enteropathogenic E. coli (EPEC) and Shiga toxin-producing E. coli and its subgroup enterohemorrhagic E. coli (STEC/EHEC). Epidemiological data indicate the importance of early diagnosis and its realization in places with limited resources. Therefore, the objective of this work was to develop a rapid, sensitive and specific test for the diagnosis of EPEC and STEC/EHEC. First, different bacterial growth conditions were evaluated: Dulbecco\'s modified Eagle\'s medium (DMEM) or DMEM containing 1% tryptone, and DMEM pre-conditioned with EPEC/EHEC isolates. The production/secretion of the secreted proteins EspA and EspB was determined by indirect ELISA utilizing anti-EspA or anti-EspB monoclonal (MAb) and polyclonal (PAb) antibodies. Different treatments were tested for their effect on the release of Shiga toxins into the medium of STEC/EHEC bacterial cultures. The bacterial culture supernatant was treated with Triton X-100, and the sediment was treated with B-PER lysis buffer. The toxins release was determined by capture ELISA using anti-Stx1 or anti-Stx2 MAb and PAb. Subsequently, a latex agglutination test was developed and evaluated for the detection of EspB in EPEC/EHEC isolates and of Stx1 and Stx2 in STEC/EHEC isolates. EspB was defined as the biomarker and anti-EspB MAb as the tool for the diagnosis of EPEC/EHEC. The ideal conditions for the production/secretion of EspB were cultivation in DMEM. For the diagnosis of STEC/EHEC, the ideal conditions for the release of Stx were Triton X-100 treatment. ELISA as well as latex agglutination showed the sensitivities and specificities required for diagnostic tests of neglected diseases in developing countries. The latex agglutination test for the detection of these pathogens was precise, rapid and easy to perform, thereby being promising for their utilization in laboratories with limited resources. (AU)

FAPESP's process: 12/02618-9 - Validation of an immunochromatographic assay for the diagnosis of diarrheagenic Escherichia coli
Grantee:Anna Raquel Ribeiro dos Santos
Support Opportunities: Scholarships in Brazil - Master