Genotypic and phenotypic diversity in Enterococcus faecalis: is agar invasion a pathogenicity score?

OBJECTIVES

The main objective of the present study is to analyze different genotypic and phenotypic traits related to virulence in Enterococcus faecalis, as well as evaluated the agar invasion phenotype in a collection of isolates with different clinical origins.

MATERIAL AND METHODS

Seventy-nine E. faecalis isolates, with invasive and non-invasive clinical origins, have been used in this work. Presence of cytolysin activator (cylA), gelatinase (gelE), surface protein (esp), aggregation substance (asa1), endocarditis antigen (efaA), and collagen-binding protein (ace) have been analyzed by PCR. Phenotypic characterization included gelatinase activity, haemolysin production, biofilm formation and agar invasion.

RESULTS

All the isolates tested harboured at least one of the virulence determinants. The 95.5% of isolates from haematologic samples were positive for agar invasion test, significantly higher than isolates from non-invasive diseases. A significant reduction in relative invasion area was observed in three selected agar-invasive strains after 15 serial passages.

CONCLUSIONS

It has been observed a significant high prevalence of agar-invasion positive isolates among strains belonged to haematological samples. Agar invasiveness is reduced after adaptation of clinical isolates to laboratory conditions, showing that agar invasion phenotype can be modulate by culture conditions as other virulence factors observed in different bacterial species.

Evolving architectural patterns in microbial colonies development

Semithin sections of colonies of three ATCC strains (Staphylococcus aureus, Escherichia coli, and Candida albicans) showed that their internal structure had specific patterns that evolved over the time. These patterns generally were defined by the presence of different layers composed of microorganisms with variable population densities and dead cells. The observed structures in this study could be explained as a particular form of biofilm with an air-semisolid interface.

Ultrastructural localization of Ani s 1, a major allergen from the fish parasite Anisakis simplex

No data about the nature or function of the first major Anisakis simplex allergen, named Ani s 1, is available. The aim of this study was to investigate the ultrastructural localization of this protein, to obtain further information about it. Ani s 1 was detected in secretory granules of the excretory gland and occasionally lining the main excretory canal. Our results suggest that Ani s 1 could be a secretory product and could have an enzymatic function related to mechanisms of infection.

Synaptic immunolocalization of glyoxylate-complex molecules in the striate areas of the rat cerebral cortex: light and electron microscopic studies

The location of glyoxylate-complex molecules has been investigated in several areas of the rat cerebral cortex using the immunohistochemical peroxidase-antiperoxidase (PAP) method. Antibodies against glyoxylate-complex molecules have been developed in the rabbit after immunization with a glyoxylate-bovine serum albumin conjugate. Observations carried out with the light microscope demonstrated positive immunostaining at the membrane level of scattered neurons located in all cortical areas, mainly in cortical layer IV. The striate areas (17, 18, 18a) had both the greatest number of immunopositive neurons and the most intense ones. At the electron microscopic level, it was observed that in the striate areas an immunopositive reaction was located mainly in the periphery of synaptic vesicles of some nerve endings, and in both pre- and postsynaptic membranes of these synaptic structures. The presence of glyoxylic acid and glyoxylate-complex molecules in such areas leads us to suggest that these substances could play an important role in selected synaptic contacts in which some pyramidal and non-pyramidal neurons are involved.