Differential roles for pathogenicity islands SPI-13 and SPI-8 in the interaction of Salmonella Enteritidis and Salmonella Typhi with murine and human macrophages

BACKGROUND: Salmonella pathogenicity island (SPI)-13 is conserved in many serovars of S. enterica, including S. Enteritidis, S. Typhimurium and S. Gallinarum. However, it is absent in typhoid serovars such as S. Typhi and Paratyphi A, which carry SPI-8 at the same genomic location. Because the interaction with macrophages is a critical step in Salmonella pathogenicity, in this study we investigated the role played by SPI-13 and SPI-8 in the interaction of S. Enteritidis and S. Typhi with cultured murine (RAW264.7) and human (THP-1) macrophages. RESULTS: Our results showed that SPI-13 was required for internalization of S. Enteritidis in murine but not human macrophages. On the other hand, SPI-8 was not required for the interaction of S. Typhi with human or murine macrophages. Of note, the presence of an intact copy of SPI-13 in a S. Typhi mutant carrying a deletion of SPI-8 did not improve its ability to be internalized by, or survive in human or murine macrophages. CONCLUSIONS: Altogether, our results point out to different roles for SPI-13 and SPI-8 during Salmonella infection. While SPI-13 contributes to the interaction of S. Enteritidis with murine macrophages, SPI-8 is not required in the interaction of S. Typhi with murine or human macrophages. We hypothesized that typhoid serovars have lost SPI-13 and maintained SPI-8 to improve their fitness during another phase of human infection.

The normal chain length distribution of the O antigen is required for the interaction of Shigella flexneri 2a with polarized Caco-2 cells

Shigella flexneri causes bacillary dysentery in humans. Essential to the establishment of the disease is the invasion of the colonic epithelial cells. Here we investigated the role of the lipopolysaccharide (LPS) O antigen in the ability of S. flexneri to adhere to and invade polarized Caco-2 cells. The S. flexneri 2a O antigen has two preferred chain lengths: a short O antigen (S-OAg) regulated by the WzzB protein and a very long O antigen (VL-OAg) regulated by Wzz pHS2. Mutants with defined deletions of the genes required for O-antigen assembly and polymerization were constructed and assayed for their abilities to adhere to and enter cultured epithelial cells. The results show that both VL- and S-OAg are required for invasion through the basolateral cell membrane. In contrast, the absence of O antigen does not impair adhesion. Purified LPS does not act as a competitor for the invasion of Caco-2 cells by the wild-type strain, suggesting that LPS is not directly involved in the internalization process by epithelial cells.

Ethanol fermentation of enzymatically hydrolysed leached beet cosette using Trichoderma harzian um cellulases and Saccharomyces cerevisiae

Se hidrolizó coseta agotada de remolacha utilizando celulasas provenientes de una especie nativa de Trichoderma hazianum. Se obtuvo un 52% de conversión de los carbohidratos presentes en la coseta a azúcares reductores. La fermentación de los azúcares liberados a etanol mediante un proceso de hidrólisis y fermentación combinadas dio como resultado un 66% de conversión del component celulósico de la coseta en eatanol, con un rendimiento de 4,4 g/L de etanol. Al realizar la hidrólisis y fermentación en forma simultánea los rendimientos fueron similares, lográndose un 62% de conversión del componente celulósico de la coseta en etanol. Estos resultados se comparan con los obtenidos utilizando celulosa microcristalina como sustrato

Radioinmunodetección tumoral en un paciente portador de una neoplasia colorrectal: descripción del método / Tumoral radioimmunodetection in a patient with a colorectal neoplasm: description of the method

Se presentan los resultados de la aplicación de un método de detección de tumores "in vivo" mediante anticuerpos marcados con radioisótopos, en un paciente portador de un tumor colorrectal. Para ello se utilizan anticuerpos anti-CEA-I131. Se describe la técnica del procedimiento y se efectúa una revisión de la literatura pertinente. Se señala que el caso comunicado es el primero en el que se aplica la radioinmunodetección en nuestro medio