Comparative Study Using Type Strains and Clinical and Food Isolates To Examine Hemolytic Activity and Occurrence of the cyl Operon in Enterococci
Open Access
- 1 June 2003
- journal article
- research article
- Published by American Society for Microbiology in Journal of Clinical Microbiology
- Vol. 41 (6), 2569-2576
- https://doi.org/10.1128/jcm.41.6.2569-2576.2003
Abstract
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 ( cylL L , cylL S , cylM , cylB , and cylA ) 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 phenotypic-genotypic 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 cylL L -based PCR and cylL L L S MBA -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.Keywords
This publication has 38 references indexed in Scilit:
- Identification of the cAD1 Sex Pheromone Precursor in Enterococcus faecalisJournal of Bacteriology, 2002
- Two-component regulator of Enterococcus faecalis cytolysin responds to quorum-sensing autoinductionNature, 2002
- Enterococcus porcinus sp. nov. and Enterococcus ratti sp. nov., associated with enteric disorders in animals.International Journal of Systematic and Evolutionary Microbiology, 2001
- Characterization of Non-Starter Lactic Acid Bacteria from Italian Ewe Cheeses Based on Phenotypic, Genotypic, and Cell Wall Protein AnalysesApplied and Environmental Microbiology, 2001
- Characterization of the 450-kb Linear Plasmid in a Polychlorinated Biphenyl Degrader, Rhodococcus sp. Strain RHA1Applied and Environmental Microbiology, 2001
- Vertebral Osteomyelitis Caused by Enterococcus raffinosusJournal of Clinical Microbiology, 2001
- Infection of Central Nervous System by Motile Enterococcus : First Case ReportJournal of Clinical Microbiology, 2001
- Prophylactic and Therapeutic Efficacy of Antibodies to a Capsular Polysaccharide Shared among Vancomycin-Sensitive and -Resistant EnterococciInfection and Immunity, 2000
- The sex pheromone system of Enterococcus faecalisEuropean Journal of Biochemistry, 1994
- Rapid extraction of bacterial genomic DNA with guanidium thiocyanateLetters in Applied Microbiology, 1989