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Antimicrobial Agents and Chemotherapy, March 1998, p. 502-508, Vol. 42, No. 3
Antibiotic Reference
Unit1 and
Laboratory of Hospital
Infection,2 Central Public Health
Laboratory, London NW9 5HT, United Kingdom
Received 10 July 1997/Returned for modification 15 October
1997/Accepted 26 November 1997
Elements mediating VanA glycopeptide resistance in 106 diverse
enterococci from humans and nonhuman sources were compared with the
prototype VanA transposon, Tn1546, in Enterococcus
faecium BM4147. The isolates included 64 from individual patients
at 15 hospitals in the United Kingdom (isolated between 1987 and 1996) and 42 from nonhuman sources in the United Kingdom (27 from raw meat, 7 from animal feces, and 8 from sewage). VanA elements were assigned to
24 groups (designated groups A to X) with primers that amplified 10 overlapping fragments of Tn1546. Ten groups of elements
were found only in human enterococci, eight groups of elements were
unique to nonhuman strains, and six groups of elements were common in
enterococci from all sources. Elements indistinguishable from
Tn1546 (group A) were observed more frequently in
enterococci from nonhuman sources (34 versus 9%) but were identified in enterococci that caused outbreaks in hospital patients between 1987 and 1995. The most common group found in human enterococci (group H;
33%) was rarely observed in enterococci from other sources (5%).
Group H elements differed from Tn1546 in three regions and included a novel insertion sequence, designated IS1542,
between orf2 and vanR. The VanA elements of 14 other groups had a similar insertion at this position and/or distinct
insertions at other positions. We conclude that VanA elements in
enterococci are heterogeneous, although all show regions of homology
with Tn1546. Furthermore, the elements most common among
the human and nonhuman enterococci studied were different. This
approach may be useful for monitoring the evolution of VanA resistance
and may also be applicable in local "snapshot" epidemiological
studies. However, as transposition events involving insertion sequences
accounted for the differences observed between several groups, the
stability of the elements must be assessed before their true
epidemiological significance can be determined.
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Diversity of VanA Glycopeptide Resistance Elements
in Enterococci from Humans and Nonhuman Sources
*
Corresponding author. Mailing address: Antibiotic
Reference Unit, CPHL, 61 Colindale Ave., London NW9 5HT, United
Kingdom. Phone: 44-181-200-4400. Fax: 44-181-200-7449. E-mail:
nwoodfor{at}phls.co.uk or
nwoodfor{at}hgmp.mrc.ac.uk.
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