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Detection of virulence factors in high-level gentamicin-resistant Enterococcus faecalis and Enterococcus faecium isolates from a Tunisian hospital

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Phenotypic and genotypic determination of virulence factors were carried out in 46 high-level gentamicin-resistant (HLGR) clinical Enterococcus faecalis (n = 34) and Enterococcus faecium (n = 12) isolates recovered from different patients in La Rabta Hospital in Tunis, Tunisia, between 2000 and 2003 (all these isolates harboured the aac(6′)–aph(2″) gene). The genes encoding virulence factors (agg, gelE, ace, cylLLS, esp, cpd, and fsrB) were analysed by PCR and sequencing. The production of gelatinase and hemolysin, the adherence to caco-2 and hep-2 cells, and the capacity for biofilm formation were investigated in all 46 HLGR enterococci. The percentages of E. faecalis isolates harbouring virulence genes were as follows: gelE, cpd, and ace (100%); fsrB (62%); agg (56%); cylLLS (41.2%); and esp (26.5%). The only virulence gene detected among the 12 HLGR E. faecium isolates was esp (58%). Gelatinase activity was detected in 22 of the 34 E. faecalis isolates (65%, most of them with the gelE+fsrB+ genotype); the remaining 12 isolates were gelatinase-negative (with the gelE+fsrB genotype and the deletion of a 23.9 kb fragment of the fsr locus). Overall, 64% of the cylLLS-containing E. faecalis isolates showed -hemolysis. A high proportion of our HLGR E. faecalis isolates, in contrast to E. faecium, showed moderate or strong biofilm formation or adherence to caco-2 and hep-2 cells.

La détermination phénotypique et génotypique des facteurs de virulence a été entreprise chez 46 isolats cliniques hautement résistants à la gentamycine (HRG) constitués de Enterococcus faecalis (n = 34) et Enterococcus faecium (n = 12) obtenus de différents patients traités à l’hôpital La Rabta de Tunis, Tunisie, en 2000–2003 (tous les isolats contenaient le gène aac(6′)-aph(2″)). Les gènes codant les facteurs de virulence (agg, gelE, ace, cylLLS, esp, cpd et fsrB) ont été analysés par PCR et séquençage. La production de gélatinase et d’hémolysine, de même que l’adhérence sur les cellules caco-2 et hep-2 et la capacité de formation d’un biofilm ont aussi été examinées sur les 46 entérocoques HRG. Les pourcentages d’isolats de E. faecalis contenant des gènes de virulence étaient comme suit : gelE, cpd et ace (100 %), fsrB (62 %), agg (56 %), cylLLS (41,2 %) et esp (26,5 %). Le seul gène de virulence détecté parmi les 12 isolats HRG de E. faecium était esp (58 %). L’activité gélatinase a été détectée chez 22 des 34 isolats de E. faecalis (65 %, la plupart d’entre eux ayant le génotype gelE+–fsrB+), les 12 isolats restants étant négatifs relativement à l’activité gélatinase (génotype gelE+–fsrB, et portant une délétion de 23,9 kb du locus fsr). Soixante quatre pourcent des isolats de E. faecalis contenant le gène cylLLS étaient hémolytiques. Une forte proportion de nos isolats HRG de E. faecalis, contrairement à E. faecium, démontrait une formation de biofilm modérée à élevée et de l’adhérence aux cellules caco-2 et hep-2.

Document Type: Research Article

Publication date: March 1, 2007

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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