Leishmania metacyclogenesis is promoted in the absence of purines.

Leishmania parasites, the causative agent of leishmaniasis, are transmitted through the bite of an infected sand fly. Leishmania parasites present two basic forms known as promastigote and amastigote which, respectively, parasitizes the vector and the mammalian hosts. Infection of the vertebrate host is dependent on the development, in the vector, of metacyclic promastigotes, however, little is known about the factors that trigger metacyclogenesis in Leishmania parasites. It has been generally stated that "stressful conditions" will lead to development of metacyclic forms, and with the exception of a few studies no detailed analysis of the molecular nature of the stress factor has been performed. Here we show that presence/absence of nucleosides, especially adenosine, controls metacyclogenesis both in vitro and in vivo. We found that addition of an adenosine-receptor antagonist to in vitro cultures of Leishmania amazonensis significantly increases metacyclogenesis, an effect that can be reversed by the presence of specific purine nucleosides or nucleobases. Furthermore, our results show that proliferation and metacyclogenesis are independently regulated and that addition of adenosine to culture medium is sufficient to recover proliferative characteristics for purified metacyclic promastigotes. More importantly, we show that metacyclogenesis was inhibited in sand flies infected with Leishmania infantum chagasi that were fed a mixture of sucrose and adenosine. Our results fill a gap in the life cycle of Leishmania parasites by demonstrating how metacyclogenesis, a key point in the propagation of the parasite to the mammalian host, can be controlled by the presence of specific purines.

Qualidade higiênico-sanitária de formulações ministradas a neonatos / Hygienic-sanitary quality of infant formulas given to neonates

Premature babies hospitalized at the Neonatal Intensive Care Units,particularly those with low weight and that are not allowed to be normallyfed, often need nutritional support of Infant Formulas (IF). These formulas,when contaminated, can be the source of nosocomial infections, the mostprobable way of contamination being the inadequate handling andstorage of these formulas. Evaluate the Hygienic-Sanitary quality and thesusceptibility profi le of the bacteria isolated from Ifs prepared in the lactary in the city of Rio Grande-RS to antimicrobial agents. IF samples were collected during 6 months by hospital employees working in the morning (Group A) and afternoon (group B) shifts, totalizing 72 analyzed samples. The Most Probable Number method (MPN/ml) was utilized to measure the amount of thermo-resistant and total coliforms. For mesophilic microorganisms the number of Colony-forming Units (CFU/ml) was counted. Also, samples were cultured in Blood and MacConkey Agar media and the isolates were identifi ed by 16S rRNA sequencing and submitted to antibiogram by the Kirby-Bauer method. The samples from groups A and B presented, respectively, 88.9% and 55.5% of contamination by total coliforms and 61.1% e 38.8% by thermo-resistant coliforms. Concerning the count of mesophilic microorganisms, groups A and B presented, respectively, 69.4% and 52.7% of the samples with results above the allowed limit. The identified microorganisms were Escherichia coli, Acinetobacter spp., Pseudomonas spp. and Enterobacter spp. The antimicrobial susceptibility test showed that all isolates presented resistance to at least three tested antimicrobials and that all of the isolates were resistant to tetracycline and one of them was also resistant to a carbapenem (imipinem).

Los recién nacidos prematuros hospitalizados en Unidades de Cuidados Intensivos, principalmente aquellos con bajo peso y poca habilidad para alimentarse naturalmente, necesitan el soporte nutricional de preparadospara lactantes (PL). Los PL, cuando contaminados, son fuente de infecciones hospitalaria, siendo la manipulación y el almacenamiento inadecuados las causas más frecuentes de los brotes de infección. Evaluar la calidad higiénico-sanitaria y el perfi l de susceptibilidad a los antimicrobianos de bacterias aisladas en PL. Las muestras se recogieron durante el período de 6 meses con dos grupos de trabajo: matutino (Grupo A) y vespertino (grupo B) del lactario del hospital, totalizando 72 muestras analizadas. Se realizó el recuento de número más probable (NMP / ml)de termotolerantes y coliformes totales y el recuento de unidades formadoras de colonias (UFC / ml) de los microorganismos mesófi los. Lasmuestras fueron cultivadas en Agar Sangre y MacConkey Agar y los aislados fueron identifi cados por la secuenciación del 16S rRNAy sometidos al antibiograma por el método Kirby-Bauer. Las muestras de los grupos A y B, presentaron, 88,9 y 55,5% y 61,1 y 38,8% decontaminación por coliformes totales y coliformes termotolerantes respectivamente. En cuanto a los mesófi los el recuento de microorganismos de los grupos A y B, presento, respectivamente,69,4 y 52,7% de las muestras con valores arriba del límite permitido. Los microorganismos identificados fueron Escher ichia coli , Acinetobacter spp., Pseudomonas spp. y Enterobacter spp. El antibiograma mostró quelos aislados presentaban resistencia por lo menos a tres de los antimicrobianos, todos fueron resistentes a tetraciclina y uno de ellos también fue resistente a un carbapenem (imipinem).

Prematuros que se encontram em Unidades de Tratamento Intensivo Neonatal, particularmente aqueles com baixo peso e com difi culdades parareceber a alimentação natural, necessitam frequentemente de suporte nutricional por meio de fórmulas infantis (FI). As FI, quando contaminadas, podem ser fontes de infecção hospitalar, sendo a manipulação e oarmazenamento inadequados os prováveis meios de contaminação. O estudo objetivou avaliar a qualidade higiênico-sanitária e o perfilde suscetibilidade aos antimicrobianos das bactérias isoladas em FI preparadas no lactário de um hospital da cidade de Rio Grande-RS.Amostras de FI reconstituídas por lactaristas do turno da manhã (grupo A) e da tarde (grupo B) foram coletadas durante 6 meses, totalizando72 amostras analisadas. Foi realizada a contagem do Número Mais Provável (NMP/ml) de coliformes totais e termotolerantes e a contagem das Unidades Formadoras de Colônias (UFC/ml) de microrganismos mesófi los. Além disso, amostras foram semeadas em Ágar Sangue e MacConkey e os isolados foram identificados por meio de sequenciamento do 16S rRNA e submetidos ao antibiograma através de método de Kirby-Bauer. As amostras dos grupos A e B apresentaram, respectivamente, 88,9 e 55,5% de contaminação por coliformes totais e 61,1 e 38,8% por coliformes termotolerantes. Na contagem de microrganismos mesófilos, os grupos A e B apresentaram, respectivamente, 69,4 e 52,7% das amostras com contagem acima do limite permitido. Os microrganismos identificadosforam Escherichia coli, Acinetobacter spp., Pseudomonas spp. e Enterobacter spp. O teste de suscetibilidade antimicrobiana mostrou quetodos os isolados apresentavam resistência a pelo menos três antimicrobianos testados e que todos foram resistentes à tetraciclina e um também foi resistente a um carbapenem (imipinem).