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Antimicrobial Agents and Chemotherapy, August 2004, p. 3207-3208, Vol. 48, No. 8
0066-4804/04/$08.00+0 DOI: 10.1128/AAC.48.8.3207-3208.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
nimE Gene in a Metronidazole-Susceptible Veillonella sp. Strain

LETTER
Metronidazole (MTZ) is widely used for the prophylaxis and the
treatment of infections caused by anaerobes. These infections
are mainly due to
Bacteroides fragilis, but several reports
identified
Veillonella spp. as pathogens in severe infections
(
5,
7). Despite the extensive use of MTZ, resistance was maintained
at a very low level for a long time and was first described
for
B. fragilis in 1978 (
4). In contrast, an increasing level
(3 to 5%) of
B. fragilis group strains with decreased susceptibility
to MTZ was observed (
2). The presence of nitroimidazole (
nim)
resistance genes was first reported in 1989 (
3), and five resistance
determinants,
nimA to
nimE, were characterized either on plasmids
or chromosomes (
9). Only the location of
nimE was not reported
when the gene was described for
B. fragilis group strains (
9).
More recently, the
nimF gene, sharing 78% identity in sequence
with
nimD, has been reported in a
B. fragilis group strain (S.
Behrendtz, H. Fang, M. Hedberg, and C. Edlund, Abstr. 3rd World
Congr. Anaerob. Bact. Infect., abstr. 6.003, 2003).
We have studied MTZ susceptibility and presence of nim genes for 116 clinical isolates of Veillonella spp. These strains were recovered either in pure culture or in aerobic-anaerobic polymicrobial cultures from various samples in 106 different patients hospitalized or consulting at the Montpellier University Hospital between March 1999 and July 2001. MTZ MICs were determined by the NCCLS reference agar dilution method (8). According to the NCCLS breakpoints, all the Veillonella sp. strains were susceptible to MTZ (Table 1). A PCR method using universal primers was used to detect nim genes after extraction of total genomic DNA according to the rapid procedure proposed by Trinh and Reysset (10). An amplification product was obtained for one isolate for which the MTZ MIC was 4 mg/liter. The 458-bp amplified fragment obtained was sequenced and gave the maximum identity (99.8%) with the nimE gene sequence of B. fragilis ARU 6881 (GenBank accession number AJ244018). To search for a possible chromosomal location of this nimE gene, DNA electrophoresis of I-CeuI restriction fragments, Southern blotting, and hybridization with a nim digoxigenin-labeled probe were performed (1). None of the I-CeuI-generated fragments hybridized with the probe. A Bacteroides strain known to harbor a chromosomal copy of the nim gene was used as a positive control. On the other hand, plasmid purification was performed by using a Quantum Prep plasmid miniprep kit (Bio-Rad Laboratories). Plasmid DNA was apparently not detectable when analyzed by agarose gel electrophoresis, but plasmid extraction yielded positive nim amplification. Taken together, these results suggested that nimE was probably located on a plasmid present in low copy number in the Veillonella strain, and this could be related to the low MTZ MIC observed for this strain.
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TABLE 1. Repartition of the MTZ MICs obtained by the agar dilution method for the 116 Veillonella sp. clinical isolates
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nim genes were mainly described in
B. fragilis group isolates,
and
nimA is the only one presently recovered in other anaerobic
bacteria:
Propionibacterium spp.,
Actinomyces odontolyticus,
Prevotella bivia, and
Clostridium bifermentans (
6). We report
the first detection of a
nim gene in a
Veillonella sp. It is
also the first description of the
nimE gene outside the
B. fragilis group. As previously described for the genus
Bacteroides, the
presence of
nim genes did not lead systematically to the expression
of MTZ resistance, but the isolation of this
Veillonella sp.
strain extends the list of
nim gene-harboring bacteria.

Nucleotide sequence accession number.
A partial sequence of 448 bp for the
Veillonella sp. nitroimidazole
resistance protein (
nimE) gene has been deposited in GenBank
under accession number
AY575922.

ACKNOWLEDGMENTS
We thank Laurent Calvet for excellent technical assistance in
MTZ MIC determinations.

REFERENCES
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H. Marchandin* H. Jean-Pierre J. Campos
Laboratoire de Bactériologie Hôpital Arnaud de Villeneuve 371 Avenue du Doyen Gaston Giraud 34295 Montpellier Cedex 5, France
L. Dubreuil
Laboratoire de Bactériologie Faculté de Pharmacie Lille, France
C. Teyssier E. Jumas-Bilak
Faculté de Pharmacie Montpellier, France
|
| | | | | |
* Phone: 33 4 67 33 58 84 Fax: 33 4 67 33 58 93. E-mail: h-marchandin{at}chu-montpellier.fr. |
Antimicrobial Agents and Chemotherapy, August 2004, p. 3207-3208, Vol. 48, No. 8
0066-4804/04/$08.00+0 DOI: 10.1128/AAC.48.8.3207-3208.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
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