Pathogenic and non-pathogenic zymodemes of Entamoeba histolytica in a rural area of Mexico. Concordance with serology.

OBJECTIVES: a) to describe the frequency of pathogenic and nonpathogenic zymodemes of E. histolytica in asymptomatic carriers in rural Mexico, b) to identify the isoenzymatic pattern of the zymodemes and c) to measure the concordance of pathogenic zymodemes and positive serology. DESIGN: Descriptive cross-sectional survey. Reference population: rural communities of the mexican highlands. STUDY UNITS: 2048 individuals from 341 families of 5 rural communities. METHODS: From the local census of each community, 70 to 100 families were selected by random sampling. All members of each family were studied. After obtaining the consent the following activities were done: a) filling of a questionnaire about housing and sanitary condition and structure of the family; age, sex, literacy and digestive symptoms and illness during the previous 4 weeks, in each individual; b) a blood sample for serology (CEIP and IHA) and c) a stool sample for coproparasitoscopic analysis (CPS) and zymodemes identification, in each individual. Statistical evaluation was done by kappa index and receiving operating curves (ROC). MAIN RESULTS: there were 122/1730 (7.1%) CPS studies positive to E histolytica cysts, 100/1730 (5.8%) zymodemes isolated and 137/1886 (7.3%) positive serologic studies. Of the 100 zymodemes 30 had a pathogenic pattern, three had a mixture (pathogenic/nonpathogenic) and 67 had a non-pathogenic patterns. There were two (XVII, XVIII) patterns described for the first time in Mexico. Concordance between pathogenic zymodemes and positive serology (IHA greater than 1:128) was very low, Kappa = 0.05. ROC curves for IHA in pathogenic and non-pathogenic zymodemes showed little relationship between positive serology and pathogenic pattern. CONCLUSIONS: Although the frequency of positive serology, coproparasitoscopic studies and zymodemes identification was similar, the concordance between serology and the coprologic studies was very low. This disagrees with other reports, and deserves further investigation using methodologic standards in design.

Efficacy of zymodemes of E. histolytica technique in an epidemiologic study and report of new zymodemes in Mexico.

OBJECTIVES: To determine the efficacy of zymodemes of E. histolytica technique in an epidemiologic study. To report the zymodemes for the first time described in Mexico. To report the main difficulties in the correct classification of zymodemes in this study. To describe the zymodemes identified in two evaluations done in 100 healthy individuals. DESIGN: A cross-sectional survey and a cohort of healthy persons. METHODS: We analyze the results of 1730 Robinson cultures performed in a cross-sectional survey done in the Municipality of Cadereyta, Queretaro, Mexico from October 1986 to August 1987. From positive cultures properly growth a Iysate was done and preserved in liquid nitrogen until the electrophoretic determination of 4 isoenzymes was done: EC 5.3.1.9. glucophosphate isomerase (GPI); EC 1.1.1.40 L-malate: NADP oxidoreductase (oxaloacetate decarboxylating) (ME); Ec 2.7.5.1 phosphoglucomutase (PGM); and EC 2.7.1.1 hexokinase (HK). RESULTS: Of 1730 cultures 289 (16.7%) developed trophozoites, in 100 (34.6%) was possible to make lysate and zymodeme. There were 67 ZNP, 3 mixtures (ZP and ZNP) and 30 ZP. There were two patterns for the first time described in Mexico (XVII and XVIII) and 30 strains had a pattern different from the 20 already described by Sargeaunt. Results observed in 100 individuals measured twice. [table: see text] There were 9 subjects in which zymodemes were isolated twice: at the first time 5 PZ and 4 NPZ, at the second time 1 PZ and 8 NPZ. At first time all 9 had negative serology and the second time one carrier of NPZ became positive. COMMENTS: In our study one tirth of Robinson cultures positive to trophozoites reached lysate. Efficacy of zymodemes and CPS is similar. We report for the first time in Mexico two non-pathogenic zymodemes (XVII and XVIII). We also report 30 zymodemes non-classified according to the standard proposed by Sargeaunt, one explanation for this feature is the possibility of zymodemes variability or new patterns. In endemic populations zymodeme pattern varies with time in asymptomatic carriers.