Comparison of Enterococcus faecium and Enterococcus faecalis Strains isolated from water and clinical samples: antimicrobial susceptibility and genetic relationships.

Enterococci are part of the normal intestinal flora in a large number of mammals, and these microbes are currently used as indicators of fecal contamination in water and food for human consumption. These organisms are considered one of the primary causes of nosocomial and environmental infections due to their ability to survive in the environment and to their intrinsic resistance to antimicrobials. The aims of this study were to determine the biochemical patterns and antimicrobial susceptibilities of Enterococcus faecalis and E. faecium isolates from clinical samples and from water (groundwater, water from the Xochimilco wetland, and treated water from the Mexico City Metropolitan Area) and to determine the genetic relationships among these isolates. A total of 121 enterococcus strains were studied; 31 and 90 strains were isolated from clinical samples and water (groundwater, water from the Xochimilco wetland, and water for agricultural irrigation), respectively. Identification to the species level was performed using a multiplex PCR assay, and antimicrobial profiles were obtained using a commercial kit. Twenty-eight strains were analyzed by pulsed-field gel electrophoresis (PFGE). E. faecium strains isolated from water showed an atypical biochemical pattern. The clinical isolates showed higher resistance to antibiotics than those from water. Both the enterococci isolated from humans, and those isolated from water showed high genetic diversity according to the PFGE analysis, although some strains seemed to be closely related. In conclusion, enterococci isolated from humans and water are genetically different. However, water represents a potential route of transmission to the community and a source of antimicrobial resistance genes that may be readily transmitted to other, different bacterial species

Electrophoretic PFGE patterns from <i>E. faecium</i> and <i>E. faecalis</i>.

<p>A) Agarose gel electrophoresis showing the <i>Sma</i>I digestion patterns of enterococci. B) Graphical representation of the banding patterns. Lane 1) <i>E. faecium</i> (blood); lane 2) <i>E. faecalis</i> (pleural fluid); lane 3) <i>E. faecalis</i> (urine); lane 4) <i>E. faecalis</i> (wound); lane 5) <i>E. faecalis</i> (wetland, rainy season); lane 6) <i>E. faecalis</i> (wetland, dry season); lane 7) <i>E. faecalis</i> (wetland, dry season); and lane 8) <i>E. faecium</i> (wetland, dry season). MWM = Lambda Ladder PFG Marker (New England BioLabs).</p

Biochemical profiles of <i>E. faecium</i> and <i>E. faecalis</i> strains from clinical and water samples.

a<p>All strains hydrolyzed esculin and grew in 40% bile and 6.5% NaCl.</p>b<p>Isolated strain from blood, cerebrospinal fluid, eyes, livers, peripheral venous catheters, pleural fluid, sputum, urine, wounds, and the respiratory system).</p>c<p>Isolated strains from groundwater for human use and consumption (wells), water from the Xochimilco wetland, and water from a water treatment plant (used for agricultural irrigation).</p

Strains with discordant results from the multiplex PCR assay and a commercial kit.

<p>Strains with discordant results from the multiplex PCR assay and a commercial kit.</p

UPGMA dendrogram based on the PFGE patterns of <i>E. faecalis</i> isolates from clinical samples (blood, pleural fluid, urine, wounds, and other respiratory sites) and water samples (wells, wetland and water treatment plant).

<p>The UPGMA dendrogram was constructed with the PFGE patterns of 21 strains using the NTSYS-pc program and Jacquard’s coefficient. Mantel test r = 0.75389, p = 1.0.</p

Percentages of antibiotic resistance for the <i>E. faecium</i> and <i>E. faecalis</i> isolates from clinical and water samples.

a<p>Interpretive criteria are according to CLSI, 2008 (Clinical and Laboratory Standards Institute, 2008); Amp = ampicillin, Fd = nitrofurantoin, Imp = imipenem, Rif = rifampin, Te = tetracycline, Va = vancomycin, HLG = high-level resistance to gentamicin, and HLS = high-level resistance to streptomycin.</p>b<p>The numbers in parentheses are the numbers of strains tested.</p>*<p>Four and **two strains had intermediate resistance to vancomycin (8 µL/mL). Clinical samples (blood, cerebrospinal fluid, eye, liver, peripheral venous catheter, pleural fluid, sputum, urine, wound, and respiratory system). Water samples (groundwater for human use and consumption (wells), water from the Xochimilco wetland and water from a water treatment plant (water used for agricultural irrigation).</p>§<p>Fisher-Freeman-Halton exact test. NS = not significant.</p

Multiplex PCR assay patterns for <i>E. faecium</i> and <i>E. faecalis</i>.

<p>Lane 1) <i>E. faecalis</i> (other respiratory); lane 2) <i>E. faecium</i> (other respiratory); lane 3) <i>E. faecalis</i> (wetland, rainy season); lane 4) <i>E. faecium</i> (water treatment plant); lane 5) <i>E. faecalis</i> (water treatment plant); lane 6) <i>E. faecium</i> (wetland, rainy season); lane 7) <i>E. faecium</i> EF1 (positive control); and lane 8) <i>E. faecalis</i> ATCC 29212 (positive control).</p

UPGMA dendrogram based on PFGE patterns of <i>E. faecium</i> isolates from clinical samples (urine) and water samples (wells, wetland and water treatment plant).

<p>The UPGMA dendrogram was constructed with the PFGE patterns of 7 strains using the NTSYS-pc program and Jacquard’s coefficient. Mantel test r = 0.76432, p = 0.999.</p