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Raising the Alarmone: Within-Host Evolution of Antibiotic-Tolerant Enterococcus faecium

Enterococci are ancient commensal bacteria that recently emerged as leading causes of antibiotic-resistant, hospital-acquired infection. Vancomycin-resistant enterococci (VRE) epitomize why drug-resistant enterococcal infections are a problem: VRE readily colonize the antibiotic-perturbed gastrointestinal (GI) tract where they amplify to large numbers, and from there, they infect other body sites, including the bloodstream, urinary tract, and surgical wounds. VRE are resistant to many antimicrobials and host defenses, which facilitates establishment at the site of infection and confounds therapeutic clearance. Having evolved to colonize the GI tract, VRE are comparatively ill adapted to the…

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Articles of Interest

A Superbug Is Born

The researchers looked at E. faecalis, a naturally occurring and usually beneficial bacterium in the human gut. Over the past 30 years, strains of these bugs have emerged with increased toxicity and resistance to many widely used antibiotics. Many of the genes contributing to virulence are clustered on a large genetic element called a pathogenicity island, which is chiefly responsible for the bacterium’s capacity to cause disease.

Enterococcal Infection—Treatment and Antibiotic Resistance

The clinical importance of the genus Enterococcus is directly related to its antibiotic resistance, which contributes to the risk of colonization and infection. The species of the greatest clinical importance are Enterococcus faecalis and Enterococcus faecium. Although the resistance characteristics of these two species differ in important ways, they can generally be categorized as intrinsic resistance, acquired resistance, and tolerance.

Multiple-Drug Resistant Enterococci: The Nature of the Problem and an Agenda for the Future

The past few years have witnessed increasing interest in enterococci. Until recently, these ordinary bowel commensals languished as misclassified streptococci, commonly perceived "with the exception of endocarditis and rare cases of meningitis … [as] not … a major cause of serious infection". In the last decade, however, enterococci have become recognized as leading causes of nosocomial bacteremia, surgical wound infection, and urinary tract infection. Two types of enterococci cause infections: 1) those originating from patients' native flora, which are unlikely to possess resistance beyond that intrinsic to the genus and are unlikely to be spread from bed to bed, and 2) isolates that possess multiple antibiotic resistance traits and are capable of nosocomial transmission. The therapeutic challenge of multiple-drug resistant (MDR) enterococci—those strains with significant resistance to two or more antibiotics, often including, but not limited to, vancomycin—has brought their role as important nosocomial pathogens into sharper focus.

New Irish study reveals how vancomycin-resistant Enterococcus faecium, a globally emerging hospital superbug, acquires and rapidly transfers resistance to antibiotics of last resort

Infections caused by antibiotic resistant bacteria are a leading threat to public health worldwide. The bacterium Enterococcus faecium has emerged globally as a significant cause of hospital-acquired infections because of its naturally low susceptibility to many commonly used antibiotics. Therapeutic options are limited to a small number of antibiotics including vancomycin. However, rising proportions of vancomycin-resistant E. faecium (VREfm) infections have been reported worldwide with limited treatment options.

Vancomycin-resistant Enterococci (VRE)

Enterococci are gram-positive bacteria that include Enterococcus faecalis and Enterococcus faecium, typically found in the human intestines and female genital tract. E. faecium accounts for more than 70% of VRE strains. Enterococci resistance develops through the gene van A, and leads to resistance to vancomycin, the mainstay antibiotic for Enterococci infections. The most common infections caused by VRE include wound infections, bacteremia, and urinary tract infections (UTIs). Other serious infections include endocarditis and meningitis. Antibiotic treatment options vary by severity, site of infection, and susceptibilities.

Vancomycin-resistant enterococci. The 'superbug' scourge that's coming your way

Strains of vancomycin-resistant enterococci (VRE) have emerged and spread widely throughout the United States during the last few years. Multiply-resistant strains of Enterococcus faecium are especially troublesome because they are often resistant to all commercially available antimicrobial agents. At present, VRE infections occur most often in hospitalized patients with severe underlying disease who have undergone invasive procedures and received prolonged courses of broad-spectrum antimicrobial therapy. Because therapeutic options are limited, prevention of spread from patients with known cases to other vulnerable patients is essential.

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CDC

Enterococci are bacteria normally found in the human intestines, female genital tract and environment (e.g., soil and water). VRE are resistant to vancomycin, the drug often used to treat infections caused by enterococci. Most VRE infections occur in hospitals.