Volume 48, Issue 1
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



We used the polymerase chain reaction (PCR) to study the epidemiology of pathogenic and nonpathogenic in a rural community in Mexico. Formalin-fixed stool samples were used for extraction of DNA. The PCR amplifications were performed using two sets of primers that discriminate between pathogenic or nonpathogenic . A total of 201 randomly selected individuals were studied. Among them, 25 (12%) were diagnosed to be infected with by microscopy; PCR identified 24 of these as positive (sensitivity = 0.96) and of 176 negative individuals, only three were identified as positive (specificity = 0.98). The PCR analysis defined three populations: 14 cases were positive for both pathogenic and nonpathogenic , nine cases were positive for pathogenic and negative for nonpathogenic , and only one case was negative for pathogenic and positive for nonpathogenic . Infection by was strongly associated to infection with (odds ratio [OR] = 9.41, 95% confidence interval [CI] = 3.09, 28.65, < 0.0004) and (OR = 6.15, 95% CI = 2.03, 18.17, < 0.0004). This new technique has high specificity and sensitivity; it is simple, reproducible, fast, avoids the need to culture trophozoites, and can be applied in the field for epidemiologic studies.


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