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608 Local Spread of Tn1546 among Three Species of Vancomycin Resistant Enterococci in an Intensive Care Unit

Sunday, April 3, 2011
Trinity Ballroom (Hilton Anatole)
Milica Jovanovic, MD , Clinic for Infectious and Tropical Deseases, Belgrade, Serbia
Tanja Tosic, MD , Clinic for Infectious and Tropical Deseases, Belgrade, Serbia
Branka Stosovic, MD , Clinic for Infectious and Tropical Deseases, Belgrade, Serbia
Zorica Dakic, DVM , Clinic for Infectious and Tropical Deseases, Belgrade, Serbia
Janetta Top , University Medical Center Utrecht, Utrecht, Netherlands
NIkola Indjic, MD , Institute for preventive medicine, Nis, Serbia
Gordana Lazarevic, MD , University Children's Clinic, Belgrade, Serbia
Sladjana Pavic, MD , General Hospital Uzice, Uzice, Serbia
Rob Willems, PhD , University Medical Center Utrecht, Utrecht, Netherlands
Background: Different types of vancomycin-resistance genes exist but the most frequently encountered vancomycin-resistance gene in VRE is the vanA gene contained on the transposon Tn1546.  In an intensive care unit (ICU) of Urgent Center of Clinical Center of Serbia four species of vancomycin resistant enterococci (VRE) were isolated, mostly from patients’ blood cultures, during a one year period.

Objective: Aim of the study was to study the epidemiology of the vanA transposon in VRE from the ICU, by transposon genotyping.

Methods: Enterococcal species were identified using conventional tests and their antimicrobial susceptibility determined by agar dilution. PFGE was used to compare macrorestriction patterns of members of each species and presence of van genes was determined by multiplex PCR. A PCR-based method, using 10 primer pairs (P1/2-P19/20) was used to determine genetic relatedness of Tn1546 in this set of VRE.

Results: Four vanA positive enterococcal species were identified: E. faecalis, E. faecium, E. raffinosus and E. gallinarum. All of them were highly vancomycin resistant and multiresistant. PFGE indicated the presence of two different E. faecium clones, while the other enterococcal species belonged to one clone each. Transposon typing revealed that isolates of E. raffinosus (5), E. gallinarum (4) and E. faecalis (3) yielded a PCR product of similar size with all 10 primer pairs, suggesting identical transposons in these species. The two clones of E. faecium (10 and 7 strains) yielded a PCR product with 6 or 5 primer pairs only, which suggest that transposons contained in E. faecium were not identical to transposons belonging to other species.

Conclusions: Results of the study indicated horizontal spread of Tn1546 in three species of VRE obtained from the same ICU, while a fourth species, E. faecium, contained a different transposon type.