Arias and Murray discuss the factors that may have contributed to the rise of enterococci as nosocomial pathogens, with an emphasis on the epidemiology and pathogenesis of these species and their mechanisms of resistance to the most relevant anti-enterococcal agents used in clinical practice.

The rise of the Enterococcus : beyond vancomycin resistance

Enterococci are commensal organisms well suited to survival in intestinal and vaginal tracts and the oral cavity. However, as for most bacteria described as causing human disease, enterococci also possess properties that can be ascribed roles in pathogenesis. The natural ability of enterococci to readily acquire, accumulate, and share extrachromosomal elements encoding virulence traits or antibiotic resistance genes lends advantages to their survival under unusual environmental stresses and in part explains their increasing importance as nosocomial pathogens. This review discusses the current understanding of enterococcal virulence relating to (i) adherence to host tissues, (ii) invasion and abscess formation, (iii) factors potentially relevant to modulation of host inflammatory responses, and (iv) potentially toxic secreted products. Aggregation substance, surface carbohydrates, or fibronectin-binding moieties may facilitate adherence to host tissues. Enterococcus faecalis appears to have the capacity to translocate across intact intestinal mucosa in models of antibiotic-induced superinfection. Extracellular toxins such as cytolysin can induce tissue damage as shown in an endophthalmitis model, increase mortality in combination with aggregation substance in an endocarditis model, and cause systemic toxicity in a murine peritonitis model. Finally, lipoteichoic acid, superoxide production, or pheromones and corresponding peptide inhibitors each may modulate local inflammatory reactions. Images

Virulence of enterococci.

Enterococci, leading causes of nosocomial bacteremia, surgical wound infection, and urinary tract infection, are becoming resistant to many and sometimes all standard therapies. New rapid surveillance methods are highlighting the importance of examining enterococcal isolates at the species level. Most enterococcal infections are caused by Enterococcus faecalis, which are more likely to express traits related to overt virulence but--for the moment--also more likely to retain sensitivity to at least one effective antibiotic. The remaining infections are mostly caused by E. faecium, a species virtually devoid of known overt pathogenic traits but more likely to be resistant to even antibiotics of last resort. Effective control of multiple-drug resistant enterococci will require 1) better understanding of the interaction between enterococci, the hospital environment, and humans, 2) prudent antibiotic use, 3) better contact isolation in hospitals and other patient care environments, and 4) improved surveillance. Equally important is renewed vigor in the search for additional drugs, accompanied by the evolution of new therapeutic paradigms less vulnerable to the cycle of drug introduction and drug resistance.

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Multiple-drug resistant enterococci: the nature of the problem and an agenda for the future.

The microbial challenge in periodontitis

It is increasingly evident that human diseases are most often related to lifestyle, and should in theory be preventable. The stress of modern life, our reduced physical activity, and our consumption of manipulated and processed foods, and of chemicals—including pharmaceuticals—all contribute to our decreasing resistance to disease. Much evidence supports the fact that our genes, adapted during millions of years to the lifestyle of our prehistoric ancestors, tolerate poorly the dramatic changes in lifestyle that have occurred, especially in food habits during the past 100 years.1Changes in food habits in Western countries that no doubt constitute stresses to the human body and that may predispose to inflammatory, infectious, ulcerative, degenerative, and neoplastic diseases include the following: the consumption of 100 lb refined sugar per individual per year; the 10-fold increase in sodium consumption; the fourfold increase in consumption of saturated fat; the doubled consumption of cholesterol; a much reduced consumption of vegetable fibres, and of minerals such as potassium, magnesium, calcium, and chromium; and a considerable reduction in consumption of n-3 fats, membrane lipids, vitamins, and antioxidants. In severe disease, important food ingredients, such as arginine, glutamine, taurine, nucleic acids, vitamins, and antioxidants, such as glutathione, are often not supplied in large enough quantities.

Perhaps even more important than the decrease in these food ingredients, is the fact that prehistoric food contained several thousand times more bacteria, mainly the so called probiotic bacteria. Prehistoric methods of food preservation were either drying, or, more commonly, storing in holes dug into the ground, where the food became naturally fermented. This is how Stone Age man learned to produce most of our still common fermented foods, such as beer, wine, green olives, and sauerkraut. Our modern lifestyle has dramatically reduced the availability of foods produced by natural fermentation. After the early …

https://gut.bmj.com/content/gutjnl/42/1/2.full.pdf

Ecological control of the gastrointestinal tract. The role of probiotic flora

Beta-lactamase-producing (Bla+) enterococci have been reported in three state and two countries. Pulsed-field gel electrophoresis was used to compare 14 Bla+ Enterococcus (Streptococcus) faecalis isolated from hospitalized patients in seven states and three continents. The restriction endonuclease digestion patterns of isolates from Connecticut, Massachusetts, Lebanon, and Argentina were all markedly different, indicating that these were different strains. However, isolates from Delaware, Texas, Pennsylvania (Philadelphia and Pittsburgh), Florida, and Virginia were similar, indicating that these isolates were derivatives of a single strain. This conclusion was supported by hybridization using individual fragments as probes. Spread of Bla+ enterococci within the hospital setting was also demonstrated. These findings illustrate the value of pulsed-field gel electrophoresis for epidemiologic analyses and support the importance of identifying and containing organisms with new resistance properties in an effort to decrease their transmission to and from, as well as within, hospitals.

R. Nasnas

Papers

Evidence for Clonal Spread of a Single Strain of β-Lactamase-Producing Enterococcus (Streptococcus) faecalis to Six Hospitals in Five States