TY - JOUR
T1 - Comparative study using type strains and clinical and food isolates to examine hemolytic activity and occurrence of the cyl operon in enterococci
AU - Semedo, Teresa
AU - Santos, Margarida Almeida
AU - Martins, Paula
AU - Silva Lopes, Maria Fátima
AU - Figueiredo Marques, José J.
AU - Tenreiro, Rogério
AU - Barreto Crespo, Maria Teresa
PY - 2003/6/1
Y1 - 2003/6/1
N2 - The hemolytic ability, the presence of cyl genes, and the diagnostic accuracy of cytolysin molecular detection were investigated in the genus Enterococcus by using 164 strains from 20 different species (26 reference strains, 42 clinical isolates from human and veterinary origin, and 96 isolates from ewe cheese and milk). Hemolysis was assayed with sheep and horse erythrocytes and under aerobic or anaerobic conditions. Screening of cytolysin genes (cylLL, cylLS, cylM, cylB, and cyl4) was performed with new specific primers and the anaerobic assay of beta-hemolysis was used as the "gold standard" for the evaluation of cyl gene-based PCRs. Since beta-hemolysis and cyl genes were found in 10 and 14 species, respectively, the hemolytic ability seems to be spread throughout the genus Enterococcus. Beta-hemolysis was observed in 6 of 26 (23%) reference strains, 14 of 42 (33%) clinical isolates, and 6 of 96 (6%) food isolates. The presence of cyl genes was detected in 15 of 26 (58%) reference strains, 37 of 42 (88%) clinical isolates, and 67 of 96 (70%) food isolates. These data indicate a virulence potential in food isolates, reinforcing the need of their safety assessment. Analysis of phenotypicgenotypic congruence suggests a divergent. sequence evolution of cyl genes and the effect of environmental factors in the regulation of cytolysin expression. Evaluation of the diagnostic accuracy of cytolysin molecular detection points to cylLL-based PCR and cylLLLSMBA-based PCR as the most reliable approaches. Nevertheless, the low sensitivity (46%) and gene variability indicated by our study strongly recommend the phenotypic assay for the assessment of hemolytic ability in enterococci, followed by the molecular screening of cyl genes in nonhemolytic strains to evaluate their virulence potential.
AB - The hemolytic ability, the presence of cyl genes, and the diagnostic accuracy of cytolysin molecular detection were investigated in the genus Enterococcus by using 164 strains from 20 different species (26 reference strains, 42 clinical isolates from human and veterinary origin, and 96 isolates from ewe cheese and milk). Hemolysis was assayed with sheep and horse erythrocytes and under aerobic or anaerobic conditions. Screening of cytolysin genes (cylLL, cylLS, cylM, cylB, and cyl4) was performed with new specific primers and the anaerobic assay of beta-hemolysis was used as the "gold standard" for the evaluation of cyl gene-based PCRs. Since beta-hemolysis and cyl genes were found in 10 and 14 species, respectively, the hemolytic ability seems to be spread throughout the genus Enterococcus. Beta-hemolysis was observed in 6 of 26 (23%) reference strains, 14 of 42 (33%) clinical isolates, and 6 of 96 (6%) food isolates. The presence of cyl genes was detected in 15 of 26 (58%) reference strains, 37 of 42 (88%) clinical isolates, and 67 of 96 (70%) food isolates. These data indicate a virulence potential in food isolates, reinforcing the need of their safety assessment. Analysis of phenotypicgenotypic congruence suggests a divergent. sequence evolution of cyl genes and the effect of environmental factors in the regulation of cytolysin expression. Evaluation of the diagnostic accuracy of cytolysin molecular detection points to cylLL-based PCR and cylLLLSMBA-based PCR as the most reliable approaches. Nevertheless, the low sensitivity (46%) and gene variability indicated by our study strongly recommend the phenotypic assay for the assessment of hemolytic ability in enterococci, followed by the molecular screening of cyl genes in nonhemolytic strains to evaluate their virulence potential.
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U2 - 10.1128/JCM.41.6.2569-2576.2003
DO - 10.1128/JCM.41.6.2569-2576.2003
M3 - Article
C2 - 12791882
AN - SCOPUS:0038180549
SN - 0095-1137
VL - 41
SP - 2569
EP - 2576
JO - Journal of Clinical Microbiology
JF - Journal of Clinical Microbiology
IS - 6
ER -