The incidence and prevalence of intestinal parasites in children is most likely due to lack of natural or acquired resistance and differences in behavior and habits closely related to environmental and socioeconomic determinants. The most important protozoa that parasitize humans are Giardia, Entamoeba, Blastocystis, and Cryptosporidium. These parasites present wide intraspecific genetic diversity and subsequently classified into assemblages and subtypes. The Amazon basin is the largest in the world and is the fifth freshwater reserve on the planet. Contradictorily, people living in these areas (Indigenous populations) have poor quality of life, which favors the infection of diseases of fecal-oral transmission. The aim of this work was to unravel the molecular epidemiology of Giardia, Blastocystis and Cryptosporidium across four communities (Puerto Nariño, San Juan del Soco, Villa Andrea and Nuevo Paraíso). We obtained 284 fecal samples from children under 15 years old that were analyzed by direct microscopy (261 samples) and Real Time PCR (qPCR) (284 samples). The positive samples for these protozoa were further characterized by several molecular markers to depict assemblages and subtypes. We observed a frequency of Giardia infection by microscopy of 23.7% (62 samples) and by qPCR of 64.8% (184 samples); for Blastocystis by microscopy of 35.2% (92 samples) and by qPCR of 88.7% (252 samples) and for Cryptosporidium only 1.9% (5 samples) were positive by microscopy and qPCR 1.8% (5 samples). Regarding the Giardia assemblages, using the glutamate dehydrogenase (gdh) marker we observed AI, BIII and BIV assemblages and when using triose phosphate isomerase (tpi) we observed assemblages AI, AII, BIII and BIV. In contrast, Blastocystis STs detected were 1, 2, 3, 4, and 6. Lastly, the species C. viatorum, C. hominis (with the subtypes IdA19 and IaA12R8) and C. parvum (with the subtype IIcA5G3c) were identified. We observed a high profile of zoonotic transmission regarding the Giardia assemblages and Blastocystis STs/alleles. Also, we highlight the elevated frequency of infection by these two protozoans suggesting an active transmission in the area. Our findings reinforces the need to deploy better epidemiological surveillance systems for enteric pathogens in the area.

Cryptococcus neoformans melanizes in the environment and in mammalian tissues, but the process of melanization in either venue is mysterious given that this microbe produces melanin only from exogenous substrates. Understanding the process of melanization is important because melanization is believed to protect against various stresses in the environment, including UV radiation, and pigment production is associated with virulence. Melanization in C. neoformans requires the availability of diphenolic precursors. In contrast, many bacteria synthesize melanin from homogentisic acid (HGA). We report that C. neoformans strains representing all four serotypes can produce a brown pigment from HGA. The brown pigment was acid resistant and had the electron paramagnetic resonance spectrum of a stable free radical, qualities that identified it as a melanin. Melanin "ghost"-like particles obtained from pigmented C. neoformans cells were hydrophobic, fluorescent under a variety of irradiation wavelengths, negatively charged, insoluble in organic solvents and alcohols, resistant to degradation by strong acids, and vulnerable to bleaching. HGA melanization was laccase dependent and repressed by high concentrations of glucose. The ability of C. neoformans to utilize a bacterial melanin precursor compound suggests a new substrate source for melanization in the environment.

Several intestinal polyparasitism profiles were found, although in most cases fewer than six parasites were involved. Better prevalence estimations and identification of determinant factors will allow to priorize and direct resources to control these infections.

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La combinación de la actividad metabólica de cepas bacterianas potencializa la actividad antimicrobiana contra microorganismos patógenos, en comparación con la actividad que pueden presentar las cepas microbianas en forma individual. La formulación mixta de bacterias acido lácticas ha sido estudiada para la producción de preparados probióticos con actividad antimicrobiana contra patógenos. Listeria monocytogenes es considerado un microorganismo patógeno para el hombre y animales, causando principalmente, la enfermedad conocida como listeriosis. Se evaluó la actividad antimicrobiana de una formulación mixta de Lactobacillus brevis y Weisella cibaria frente a Listeria monocytogenes. L. brevis y W. cibaria se reprodujeron por fermentaciones en discontinuo durante 48 horas. Se midió la cinética de la actividad antimicrobiana contra L. monocytogenes en los siguientes tiempos de fermentación, 0, 1, 2, 6, 12, 24 y 48 horas. En cada tiempo, la actividad antimicrobiana de la mezcla de cepas se comparó con la actividad antimicrobiana de las cepas en forma individual. La actividad antimicrobiana se midió mediante el diámetro de Feret, utilizando un software de evaluación de imágenes. Se encontró que la actividad antimicrobiana de la mezcla de cepas contra L. monocytogenes fue estable desde la segunda hora de fermentación hasta las 48 horas. A partir de 18 horas de fermentación la mezcla de cepas presentó actividad antimicrobiana superior, comparada con las cepas individuales. Los resultados indican que la formulación mixta de L. brevis y W. cibaria podría ser una opción biotecnológica para el desarrollo de antimicrobianos naturales para el control y prevención de L. monocytogenes.