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Antimicrobial Agents and Chemotherapy, October 2003, p. 3323-3325, Vol. 47, No. 10
0066-4804/03/$08.00+0 DOI: 10.1128/AAC.47.10.3323-3325.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
DNA Gyrase and Topoisomerase IV Mutations in Clinical Isolates of Ureaplasma spp. and Mycoplasma hominis Resistant to Fluoroquinolones
C. M. Bébéar,* H. Renaudin, A. Charron, M. Clerc, S. Pereyre, and C. Bébéar
Laboratoire de Bactériologie, Université Victor Segalen Bordeaux 2, 33076 Bordeaux, France
Received 27 March 2003/
Returned for modification 6 May 2003/
Accepted 3 July 2003

ABSTRACT
Twelve clinical isolates of
Ureaplasma spp. and one isolate
of
Mycoplasma hominis were examined for resistance to fluoroquinolones.
Previously described mutations at positions 83 and 95 in GyrA
(
Escherichia coli numbering) and positions 80 and 87 in ParC
were found. Unusual alterations were described at positions
ParC 123 and 134.

TEXT
Ureaplasma urealyticum and
Mycoplasma hominis are commonly isolated
from the lower urogenital tract of healthy adults but could
be responsible for genital and extragenital infections (
7).
The species
U. urealyticum has been recently divided into two
new species, namely,
Ureaplasma parvum (previously
U. urealyticum biovar 1) and
U. urealyticum (previously
U. urealyticum biovar
2) (
10,
12). In this study, they will be considered together
as
Ureaplasma spp.
Fluoroquinolones interact in bacteria with the type II topoisomerases DNA gyrase and topoisomerase IV, both of which are composed of two A and two B subunits; these subunits are encoded by the gyrA and gyrB genes for DNA gyrase and by the parC and parE genes for topoisomerase IV (8). We recently reported in vitro and in vivo fluoroquinolone-resistant mutants of M. hominis associated with alterations in GyrA, ParC, and ParE quinolone resistance-determining regions (QRDRs) (4, 6). The Ureaplasma spp. quinolone-resistant clinical isolates identified during this study have been characterized for their species identification and subtyping and for their QRDR status in regard to their fluoroquinolone susceptibility. Furthermore, we describe also a new clinical isolate of M. hominis that is highly resistant to fluoroquinolones.
Growth conditions and antibiotic susceptibility testing of the Ureaplasma and M. hominis strains have been previously described (14). The Ureaplasma sp. reference strains, the serovar 3 standard (ATCC 27815) designated as the type strain of U. parvum, and the serovar 8 standard (ATCC 27618) designated as the type strain of U. urealyticum (12), as well as the clinical isolates, were grown in Shepard medium. Thirteen clinical isolates comprising UUb to UUg5 (Table 1), which were obtained at the Pellegrin Hospital in Bordeaux, and UUa, which was isolated at the Hospital of Montpellier, France, all of which were grown in our laboratory between 1989 and 1999, were studied. The M. hominis reference strain PG21 (ATCC 23114) and the clinical isolate MHe obtained at the Foch Hospital in Suresnes, France, were grown in Hayflick modified medium.
PCR was carried out with 1 µM each primer and 5 µl
of template DNA for the
Ureaplasma species identification and
subtyping (
10) and for the QRDR amplification of the four topoisomerase
genes for
Ureaplasma spp. and
M. hominis, as described elsewhere
(
4,
5). PCR products were directly sequenced by using an ABI
PRISM dRhodamine terminator cycle sequencing ready reaction
kit (Applied Biosystems).
Thirteen clinical isolates of Ureaplasma spp. from seven patients were examined; their origin is described in Table 1. The first one, UUa, was previously reported (2, 5). Among the 1,224 Ureaplasma spp. strains isolated in our laboratory between 1989 and 1999, 37 isolates were classified as resistant to ofloxacin by the susceptibility testing kit Mycoplasma SIR (Bio-Rad). Determining the ofloxacin MICs for these 37 isolates led us to study 11 strains for which the ofloxacin MIC is
4 µg/ml, namely, UUb to UUd and UUe2 to UUg5 (Table 1). We report here also a new clinical isolate of M. hominis, named MHe, isolated from a knee synovial fluid of a male patient with hypogammaglobulinemia and a lung transplant. He received at least one regimen of ofloxacin.
We investigated our Ureaplasma isolates for species identification and subtyping using the algorithm recently described by Kong et al. (10). Thus, isolates UUe1 and UUe2, isolated from the same patient, were identified as U. parvum (biovar 1). The other isolates belonged to the species U. urealyticum (biovar 2), subtype 1 or subtype 2. It is tempting to speculate that the paired isolates (UUe1 and UUe2, from the same patient) and the seven isolates from the sexual partners (UUf1-2 from the male, and UUg1-5 from the female) are from the same clonal origin. Furthermore, among the strains resistant to fluoroquinolones, we isolated more U. urealyticum (from six patients) than U. parvum (from one patient), which is not the case commonly. Indeed, U. parvum clinical isolates usually outnumber U. urealyticum clinical isolates (1, 10). There is a probable bias in our study, with nine isolates being possibly from the same clonal origin and with the number of patients studied being statistically too small to be conclusive.
The 13 ureaplasmal clinical strains were characterized for their susceptibilities to eight fluoroquinolones and for the QRDR status of their gyrA, gyrB, parC, and parE genes (Table 2). Except the fluoroquinolone-susceptible isolate UUe1, all other isolates had a high-level resistance to the older fluoroquinolones, such as norfloxacin, pefloxacin, ofloxacin, and ciprofloxacin, with MICs ranging from 4 to >128 µg/ml. Susceptibility to the newer fluoroquinolones, like sparfloxacin, levofloxacin, moxifloxacin, and gemifloxacin, depends on the resistant isolate, but increases in MICs were much less pronounced except for mutant UUa. Thus, the MICs of these fluoroquinolones varied between 0.25 and 16 µg/ml.
The 12 quinolone-resistant isolates were found to carry target
mutations in either
parC (one isolate) or
gyrA and
parC (11
isolates). No mutation was detected in the
gyrB or
parE QRDR
(Table
2). Except isolate UUe2, all other resistant isolates
presented two alterations in ParC, namely, the Ala125(123)-to-Thr
and Ala136(134)-to-Thr changes (
Escherichia coli numbering).
Our data did not allow an assessment of the contribution of
these two mutations to the observed resistance phenotype. However,
these positions are located close to the Tyr122(120) active
site of the protein, and several mutations in this area have
been frequently described for other quinolone-resistant bacteria
(
3,
9), but most of these mutations could not be clearly related
to resistance to fluoroquinolones. All other alterations found
in this study (Table
2) have been already described for other
bacteria concerning either the altered position or the amino
acid change. The hot spots ParC Ser83(80) and Glu87(84) and
GyrA Gln100(83) have been found previously to be mutated in
numerous other bacteria and in mycoplasmas (
4,
6,
11). The GyrA
Asp112-to-Glu alteration, which is rare and which is homologous
to position GyrA 95 in
E. coli, has been found to be mutated
in
Streptococcus pneumoniae (
13) without a clear direct link
to quinolone resistance. Furthermore, in vitro studies with
laboratory mutants would be helpful to determine the preferential
target of fluoroquinolones in ureaplasmas. Some isolates, like
UUb and UUf1 or UUd and UUf1, which had the same amino acid
changes in the QRDR of GyrA and ParC, harbored fourfold differences
in MICs of ciprofloxacin or pefloxacin, respectively. Other
undefined resistance mutations seem likely to be present in
some of the strains studied.
The drug susceptibility profile and the QRDR status of the M. hominis isolate are summarized in Table 2. Compared to the reference strain PG21, isolate MHe harbored a high level cross-resistance to the eight fluoroquinolones tested, with the lowest MIC being that of gemifloxacin at 2 µg/ml. This resistance in an immunodeficiency context, which was found also for the previously described clinical strains of quinolone-resistant M. hominis (6), was associated with four target alterations (Table 2): GyrA 83, ParC 80 and 134, and ParE 462.
In summary, this is the first extensive description of fluoroquinolone resistance in clinical isolates of Ureaplasma spp. In our laboratory during a 10-year period, we found 12 Ureaplasma spp. isolates resistant to fluoroquinolones. The clinical histories of patients showed one or several quinolone regimens before the appearance of resistant bacteria and a correlation with immunosuppression. These findings confirm the necessity to monitor the antibiotic susceptibility of urogenital mycoplasmas isolated in humans and to control it routinely in immunocompromised patients.

ACKNOWLEDGMENTS
We thank P. Honderlick (Laboratoire de Microbiologie, Hôpital
Foch, Suresnes, France) for the gift of strain MHe.

FOOTNOTES
* Corresponding author. Mailing address: Laboratoire de Bactériologie, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France. Phone: (33) 5.57.57.16.25. Fax: (33) 5.56.93.29.40. E-mail:
cecile.bebear{at}u-bordeaux2.fr.


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Antimicrobial Agents and Chemotherapy, October 2003, p. 3323-3325, Vol. 47, No. 10
0066-4804/03/$08.00+0 DOI: 10.1128/AAC.47.10.3323-3325.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
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