Enterococcus faecalis: specific and non-specific interactions with human polymorphonuclear leukocytes

Enterococcus faecalis: an overlooked cell invader

SUMMARYEnterococcus faecalis and Enterococcus faecium are human pathobionts that exhibit a dual lifestyle as commensal and pathogenic bacteria. The pathogenic lifestyle is associated with specific conditions involving host susceptibility and intestinal overgrowth or the use of a medical device. Although the virulence of E. faecium appears to benefit from its antimicrobial resistance, E. faecalis is recognized for its higher pathogenic potential. E. faecalis has long been considered a predominantly extracellular pathogen; it adheres to and is taken up by a wide range of mammalian cells, albeit with less efficiency than classical intracellular enteropathogens. Carbohydrate structures, rather than proteinaceous moieties, are likely to be primarily involved in the adhesion of E. faecalis to epithelial cells. Consistently, few adhesins have been implicated in the adhesion of E. faecalis to epithelial cells. On the host side, very little is known about cognate receptors, except for the role of glycosaminoglycans during macrophage infection. Several lines of evidence indicate that E. faecalis internalization may involve a zipper-like mechanism as well as a macropinocytosis pathway. Conversely, E. faecalis can use several strategies to prevent engulfment in phagocytes. However, the bacterial and host mechanisms underlying cell infection by E. faecalis are still in their infancy. The most recent striking finding is the existence of an intracellular lifestyle where E. faecalis can replicate within a variety of host cells. In this review, we summarize and discuss the current knowledge of E. faecalis-host cell interactions and argue on the need for further mechanistic studies to prevent or reduce infections.

Comparison of Therapeutic Efficacy Between Isolated Encephaloduroarteriosynangiosis and Medical Treatment in Patients with Atherosclerotic Middle Cerebral Artery Occlusion

BACKGROUND

Encephaloduroarteriosynangiosis (EDAS) as a form of indirect revascularization has been recently proposed as a potentially promising alternative for patients with intracranial atherosclerotic disease (ICAD). The object of this study was to compare the prognostic roles between isolated EDAS and medical therapy in patients with atherosclerotic middle cerebral artery occlusion (MCAO).

METHODS

From January 2014 to June 2017, 125 patients with atherosclerotic MCAO were enrolled in this prospective nonrandomized controlled cohort study. Patients who underwent EDAS (n = 60) were compared with those treated medically (n = 65). Early and late adverse events and functional outcomes including memory ability were compared between groups.

RESULTS

During 23.7 months of mean follow-up, rates of adverse events, including ischemic events in the territory of the qualifying middle cerebral artery, and death from any causes, were not significantly different in patients treated with EDAS and with medical therapy (6.7% vs. 12.3%; P = 0.285). Landmark analyses showed that at initial 6-month follow-up, there was no significant difference for adverse event rates, whereas the opposite finding was shown for the subsequent period (EDAS 1/57 [1.7%] vs. medical management 7/64 [10.9%]; P = 0.024). The P value for the interaction between time (first 6 months vs. subsequent period) was 0.044. No significant differences were found with respect to neural function status and cognitive ability.

CONCLUSIONS

In the long-term, isolated EDAS can be considered effective and safe for patients with atherosclerotic MCAO, whereas it may need additional medical therapy support in the short-term.

Hemagglutination properties of Enterococcus

In total, 86 enterococcal strains including representatives of most of the described species were tested for the ability to agglutinate human, sheep, and rabbit erythrocytes. Five strains did not react with any of the erythrocytes tested, and 81 (94.2%) strains agglutinated only rabbit erythrocytes. The hemagglutination titers ranged from 2 to 64. Loss of the hemagglutination activity was observed when rabbit erythrocytes were treated with trypsin or neuraminidase. Trypsin treatment of the bacterial suspensions also caused loss of the agglutination ability. On the other hand, heat treatment of bacterial suspensions increased the efficiency of the interactions, and higher titers were obtained. Assays for inhibition of hemagglutination were performed with alpha-D-fucose, alpha-D-galactose, beta-D-galactose, D-glucose, N-acetyl-galactosamine, N-acetyl-glucosamine, N-acetylneuraminic acid, N-acetylneuraminic acid-lactose, and fetuin. Only fetuin was able to inhibit the hemagglutination reactions. The results showed that hemagglutination properties are common to the different enterococcal species tested. They also suggest that enterococci possess hemagglutinins of proteic and non-proteic nature that are involved in the attachment to sialic acid-containing receptors on the surface of rabbit erythrocytes.