The bacterium Enterococcus faecium is a serious health threat because it has become resistant to all commercially available antibiotics. Patients at particular risk of infection are those with decreased immunity, including patients undergoing transplantation or those receiving intensive-care treatment.
In the USA, E. faecium resistant to the antibiotic vancomycin (vancomycin-resistant Enterococcus faecium, or VREF) is endemic in hospitals, despite a lack of carriage among healthy individuals.
In Europe, hospital outbreaks are rare, but VREF carriage among healthy individuals and livestock is common. However, three instances of hospital-based VREF infections have recently been reported in the Netherlands.
|The epidemic sub-population of E. faecium contained a variant of the ESP gene.
Rob Willems and colleagues from the National Institute of Public Health, Bilthoven, Netherlands, did a genetic analysis of VREF associated with epidemic hospital outbreaks and non-epidemic carriage in the USA, Europe, and Australia.
The investigators found a specific E. faecium sub-population - genetically distinct from non-epidemic VREF - which was the cause of the hospital epidemics in all three continents. This sub-population contained a variant of the ESP gene (the gene associated with increased virulence in patients with E. faecalis, but which has not been detected in E. faecium); this variant was not present in non-epidemic and animal VREF analysis.
Researcher Marc Bonten, from Bilthoven, Netherlands, comments, "Since there are no effective antibiotics against VREF, bacterial colonization cannot be treated. As a result, patients remain infectious for prolonged periods of time. This is an important explanation for the rapid spread of these bacteria in the US; we fear that this will now occur in Europe as well.
"Since bacterial colonization cannot be eradicated, and spread occurs rapidly, a large burden of bacteria will accumulate within hospitals. Once this endemicity has been established, control of further spread is almost impossible, as has been shown in the US."
"However, recognition of bacteria with the ESP gene should identify those that spread rapidly and help infection control," he concludes.