Comparative Study Using Type Strains and Clinical and Food Isolates To Examine Hemolytic Activity and Occurrence of the cyl Operon in Enterococci

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 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 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.

Molecular Detection of Virulence Factors of Enterococcus Faecalis Isolated From Urine Samples in Duhok City, Kurdistan Region/Iraq

“…Somewhat, similar isolation rates ranged from 45.3 to 70.9% were observed in other studies (De Marques and Suzart, 2004;Arularasi Aberna and Prabakaran, 2011).While higher percentage of this gene have been reported by Semedo et al (2003) and Creti et al (2004). Furthermore, in this study, the frequency of this gene among multiple antibiotic resistant isolates was lower (56%) as compared with the frequency of other genes.…”

Virulence factors and antibiotic resistance in enterococci isolated from food-stuffs

“…The frequency of the cylA gene among enterococci is very variable and does not correlate with clinical or food isolates (Smedo et al, 2003).…”

“…Nevertheless, other enterococcal species have, from time to time, been reported to cause human infections (Smedo et al, 2003). A specific cause for concern regarding enterococci is their resistance to a wide variety of antibiotics, especially vancomycin (Franz et al, 2001;Kayser, 2003;Martin-Platero et al, 2009).…”

Clonal Lineages, Antibiotic Resistance and Virulence Factors in Vancomycin-Resistant Enterococci Isolated from Fecal Samples of Red Foxes (Vulpes Vulpes)

“…Gelatinase production was tested by inoculating enterococci onto fresh tryptic soy agar plates containing 1.5% skim milk (Gilmore et al, 2002). Production of hemolysin was determined by streaking bacterial cultures on Columbia agar supplemented with 5% horse blood (Semedo et al, 2003). Enterococcus faecium vanA isolates were characterized by multilocus sequence typing.…”