Anti-amebic antibody activity in patients, determined with antigens prepared from virulent parasites (indirect hemagglutination assay and enzyme-linked immunosorbent assay).

BACKGROUND The serology of amebiasis is affected by low sensitivity and specificity. OBJECTIVES To evaluate the advantage of the indirect hemagglutination assay and enzyme-linked immunosorbent assay in the diagnosis of amebiasis, using Entamoeba histolytica soluble antigen (macerated amebic antigens) prepared from four different virulent isolates, continuously cultivated in the presence of the original enteric bacteria. METHODS Using IHA and ELISA with MAA antigen we examined 147 sera samples from patients with gastrointestinal symptoms, and 11 sera from amebiasis cases (confirmed by microscopy and copro-antigen ELISA). RESULTS Of 104 of the 147 (70.7%) symptomatic cases that were amebiasis positive by IHA, 81 (55.1%) were positive by MAA-ELISA. In addition, of 11 amebiasis cases confirmed by microscopy and copro-antigen ELISA, 7 (64%) were amebiasis positive by both tests. Four species of bacteria were isolated from the ameba cultures: Escherichia coli, Morganella morganii, Proteus mirabilis, and Streptococcus lactis. Elimination of the bacteria from the cultures by an antibiotics cocktail containing gentamicin, imipenem, piperacillin-tazobactam and vancomycin was the preferred method. Absorption of patients' sera to bacterial antigen prior to serological analysis had only a marginal effect. CONCLUSIONS These results indicate a correlation of 61% between the ELISA developed in this study and the IHA tests in the diagnosis of amebiasis.