German Enterococcus faecium bacteraemia isolates from 1991 to 2007 show a complex clonal structure and multiple acquisitions of virulence genes and vancomycin resistance gene clusters
Abstract number: O513
Werner G., Fleige C., Klare I., Laverde-Gomez J., Witte W.
Objectives: To investigate the characteristics and molecular dynamics of Enterococcus faecium bacteraemia isolates from Germany between 19912007 in the background of rising VRE rates in Germany.
Methods: Altogether 124 isolates from 35 German cities were included. The isolates were taken from our strain collection from the last 16 years. Copy isolates were excluded. They were typed by MLST and MLVA. The presence of virulence marker genes esp and hyl and the van genotype (vanA/B) were identified using a multiplex PCR. A PCR for the enterococcal IS element IS16 enriched in hospital-adapted strains was also performed. Antibiotic susceptibilities were determined by microbroth dilution according to the German DIN standard.
Results: Only two isolates were not typeable by MLVA. MLST was more discriminatory than MLVA (discriminatory index 0.897 vs. 0.824) giving altogether 31 different MLST vs. 26 MLVA types. Almost all isolates (n= 119/124) were ampicillin resistant. Based on MLST more than 95% of the E. faecium isolates belonged to the clonal complex CC17 of hospital adapted, epidemic strains. 63 E. faecium were vancomycin resistant (51%; 58 vanA, 5 vanB). About half the isolates possessed the esp gene (n= 64/124; 52%) and 52 (42%) the hyl gene. IS16-PCR was positive in 98 E. faecium (79%). E. faecium isolated before 2000 seldom possess esp or hyl, among isolates from 2004 on both became more frequent. Some clonal types like ST17 and ST18 were isolated over a range of 1012 years. Possession of virulence genes esp and hyl varied suggesting acquisition or loss of those markers at multiple times. Other clonal types like ST192 mainly appeared between 20042007 and showed a fixed virulence gene pattern: 21/24 ST192 isolates possessed both esp and hyl, each one possessed either hyl or esp and one ST192 from 1998 lacks both determinants.
Conclusions: Only few E. faecium from the early 1990ies were included and those mostly did not belong to CC17. They were from single infections and thus not part of a cluster or outbreak. Nowadays the hospital-adapted E. faecium may represent a different pathogenic quality. Our data show association of those isolates mainly with clusters or outbreaks and enrichment of virulence-associated genes (esp, hyl) among different clonal types over time. Even in settings where VRE are still rare, hospital-adapted types are widely distributed awaiting acquisition of vancomycin resistance determinants as a next step.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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