Distribution of additional virulence factors related to adhesion and toxicity in Shiga toxin‐producing Escherichia coli isolated from raw products in Argentina

A total of 73 Shiga toxin‐producing Escherichia coli (STEC) isolates, belonging to 25 serotypes and isolated from raw products in Argentina, were examined for the occurrence of genes responsible for bacterial adhesions to intestine, ehaA (EHEC autotransporter), lpfAO113 (long polar fimbriae), sab (STEC autotransporter [AT] contributing to biofilm formation), ecpA (E. coli common pilus), hcpA (haemorrhagic coli pilus), elfA (E. coli laminin‐binding fimbriae), sfpA (sorbitol‐fermenting EHEC O157 fimbriae plasmid‐encoded) and of the toxigenic gene cdt‐V (cytolethal distending toxin). Our study showed different adhesin profiles that are not linked to one specific serotype and that all analysed isolates possess, besides stx genes, some adherence genes. Several of the isolates contained also multiple toxin genes. The results of the present work alert the presence of genes coding for additional adhesins and cdt‐V toxin in LEE‐negative STEC strains that occur in foods, and this traits could increase their pathogenic potential.

Significance and Impact of the Study

Meat products are one of the main vehicles of Shiga toxin‐producing E. coli, and the presence of genes coding for additional adhesins and toxins could increase their pathogenic potential. There is a need for a more detailed characterization of the strains in regard to these extra virulence factors.     

Foliar anatomy and micromorphology of southern South American Alstroemeriaceae: Alstroemerieae,and its systematic implications in Alstroemeria

Alstroemerieae is an exclusively Central and South American tribe belonging to Alstroemeriaceae, which comprises two large genera, Alstroemeria and Bomarea. Alstroemeria has two areas of distribution, mediterranean Chile and central southeastern Brazil. Most Bomarea species grow in forests and hedges in moist areas, however, some species are adapted to dry Andean valleys and high altitudes. Previous leaf anatomical data were obtained from a limited group of species. To assess the value of the anatomical characters for the systematics and their importance as adaptations to different environments, we compared representative species from different geographical areas and habitats. Data regarding leaf anatomy and micromorphology were obtained from light microscopy and scanning electron microscopy and were combined with macromorphology for 27 Alstroemerieae species. In accordance with earlier studies, our results show variation in relation to several leaf morpho‐anatomical characters. Based on these we define seven types. We furthermore analyzed the morpho‐anatomical characters in a phylogenetic context. Morpho‐anatomical characters are highly homoplastic within the family. Leaf anatomy may support monophyly of Baker's informal grouping of Alstroemeria Brazilian species with rigid leaves, however, a more thorough study of Brazilian Alstroemeria species are needed to confirm this.     

Multiplex PCR Assay for the Detection of Five Putative Virulence Genes Encoded in Verotoxigenic <Emphasis Type="Italic">Escherichia coli</Emphasis> Plasmids

The aim was to perform a pentavalent PCR assay for the detection of putative virulence genes encoded in VTEC plasmids, katP, espP, subA, stcE, and ehxA. The five-specific primer pairs used in the assay do not interfere with each other and generate amplification products of 914, 774, 556, 399, and 262 bp. It was selected at random 39 strains belonged to 20 serotypes in order to evaluate the multiplex in a wide variety of strains. The results of this study indicate that it is possible to perform simultaneous amplification and search for recognized plasmid-encoded virulence markers from different E. coli serotypes and apply this technique to the genetic characterization of E. coli strains isolated from reservoirs, foods or patients. This complementary technique is a useful tool to detect interstrain differences for epidemiological studies and to provide information that could be related to the risk of human infection.