For over 30 years it has been established that the Entamoeba histolytica protozoan included two biologically and genetically different species, one with a pathogenic phenotype called E. histolytica and the other with a non-pathogenic phenotype called Entamoeba dispar. Both of these amoebae species can infect humans. E. histolytica has been considered as a potential pathogen that can cause serious damage to the large intestine (colitis, dysentery) and other extraintestinal organs, mainly the liver (amebic liver abscess), whereas E. dispar is a species that interacts with humans in a commensal relationship, causing no symptoms or any tissue damage. This paradigm, however, should be reconsidered or re-evaluated. In the present work, we report the detection and genotyping of E. dispar sequences of DNA obtained from patients with amebic liver abscesses, including the genotyping of an isolate obtained from a Brazilian patient with a clinical diagnosis of intestinal amebiasis that was previously characterized as an E. dispar species. The genetic diversity and phylogenetic analysis performed by our group has shown the existence of several different genotypes of E. dispar that can be associated to, or be potentiality responsible for intestinal or liver tissue damage, similar to that observed with E. histolytica.

Cryptosporidiosis is a parasitic disease caused by Cryptosporidium spp. In immunocompetent individuals, it usually causes an acute and self-limited diarrhea; in infants, infection with Cryptosporidium spp. can cause malnutrition and growth retardation, and declined cognitive ability. In this study, we described for the first time the distribution of C. parvum and C. hominis subtypes in 12 children in Mexico by sequence characterization of the 60-kDa glycoprotein (GP60) gene of Cryptosporidium. Altogether, 7 subtypes belonging to 4 subtype families of C. hominis (Ia, Ib, Id and Ie) and 1 subtype family of C. parvum (IIa) were detected, including IaA14R3, IaA15R3, IbA10G2, IdA17, IeA11G3T3, IIaA15G2R1 and IIaA16G1R1. The frequency of the subtype families and subtypes in the samples analyzed in this study differed from what was observed in other countries.

The cellular immune response plays a critical role in the containment of persistent Mycobacterium tuberculosis infection; however, the immunological mechanisms that lead to its control are not completely identified. The goal of this study was to evaluate B (CD19+) and T (CD3+) peripheral blood lymphocyte profiles and T-cell subsets (CD4+ and CD8+) in patients with pulmonary tuberculosis (TB). Percentages (p = 0.02) and absolute numbers (p = 0.005) of B cells were significantly lower in patients with pulmonary TB than in healthy donors. In contrast, percentages (p = 0.12) and absolute numbers (p = 0.14) of T cells were similar in TB patients and healthy donors. No significant differences in percentages of CD4+ (p = 0.19) or CD8+ (p = 0.85) T cells between patients and healthy donors were observed. In summary, patients with pulmonary tuberculosis had a lower number of peripheral blood B lymphocytes than healthy controls.