Genetic diversity among VRE isolates from Swedish broilers with the coincidental finding of transferrable decreased susceptibility to narasin.
OBJECTIVE
In this study, the molecular diversity among clones of vancomycin resistant Enterococcus faecium with vanA gene (VRE) is investigated. The aims were to better understand why one clone is predominant in Swedish broiler production and to better assess the potential for zoonotic gene transfer from the different clones.


RESULTS
Twenty-six isolates were separated into 11 clones. Vancomycin resistance was transferrable from the predominant and five minority clones. Decreased susceptibility to narasin was co-transferred with vancomycin resistance in four clones, including the predominant. The plasmid addiction system axe-txe was not detected, and the ω-ε-ζ system was detected in one of the minority clones but was not co-transferred with vancomycin resistance.


CONCLUSIONS
The results do not explain why one clone is predominant among VRE in Swedish broiler production but confirms the potential for zoonotic spread of vancomycin resistance genes. The near absence of investigated plasmid addiction systems indicates that they do not play an important role in the epidemiology of VRE in Swedish broiler production. The finding that decreased susceptibility to narasin can be co-transferred with the vanA gene indicates that the use of narasin might play a role in the persistence of vancomycin resistance in enterococci colonizing Swedish broilers.


CONCLUSIONS
This is, to our knowledge, the first report of transferrable decreased susceptibility to narasin.
National Veterinary Institute, Uppsala, Sweden. oskar.nilsson@sva.se
O
O
Nilsson
C
C
Greko
B
B
Bengtsson
S
S
Englund
D000818:Animals; D002645:Chickens / Q000382:microbiology*; D016984:Enterococcus faecium / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D014644:Genetic Variation; D011714:Pyrans / Q000494:pharmacology*; D020713:Vancomycin Resistance
D011714:Pyrans; C013612:narasin