Evidence for clonal spread of a single strain of β-lactamase-producing Enterococcus (Streptococcus) faecalis to six hospitals in five states

β-lactamase-producing (Bla⁺) enterococci have been reported in three states 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-fleld 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.