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Journal of Clinical Microbiology, May 2008, p. 1818-1823, Vol. 46, No. 5
0095-1137/08/$08.00+0 doi:10.1128/JCM.02255-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Characterization of New Staphylococcal Cassette Chromosome mec (SCCmec) and Topoisomerase Genes in Fluoroquinolone- and Methicillin-Resistant Staphylococcus pseudintermedius
Sybill Descloux,
Alexandra Rossano, and
Vincent Perreten*
Institute of Veterinary Bacteriology, University of Bern, CH-3001 Bern, Switzerland
Received 21 November 2007/
Returned for modification 13 January 2008/
Accepted 20 February 2008

ABSTRACT
Fluoroquinolone- and methicillin-resistant
Staphylococcus pseudintermedius isolates harbor two new staphylococcal cassette chromosome
mec (SCC
mec) elements that belong to class A, allotype 3 (SCC
mec II-III), and to the new allotype 5 (SCC
mec VII). Analysis of
the complete nucleotide sequences of the topoisomerase loci
gyrB/
gyrA and
grlB/
grlA revealed mutations involved in fluoroquinolone
resistance.

TEXT
Staphylococcus pseudintermedius is an opportunistic pathogen
that primarily causes skin and nosocomial infections in dogs
and cats but can also occasionally affect humans (
1,
29). Fluoroquinolones
and cephalosporins are widely used to treat staphylococcal infections
in veterinary medicine (
23). The frequent use of these antibiotics
may augment the risk of rapidly selecting for bacteria resistant
to both classes of antibiotics. In the past year, multidrug-resistant
S. pseudintermedius strains have been isolated with increasing
frequency from infection sites of dogs at our diagnostic unit.
The antibiotic resistance mechanisms of these
S. pseudintermedius strains were characterized with an emphasis on resistance to
methicillin and fluoroquinolone.
Strain identification and antibiotic resistance profile.
The isolated strains (n = 15) were cultured on tryptone soy agar plates containing 5% sheep blood (Oxoid Ltd., Basingstoke, England) and were identified by catalase activity, Gram staining, and sequencing of the sodA gene as described previously (24, 26). All isolates harbored the leukocidin gene lukS (25) but not the Panton-Valentine leukocidin gene lukS-PV (28), as determined by PCR using the primers listed in Table 2. Antibiotic susceptibility was determined by broth microdilution using a custom Sensititre susceptibility plate, model NLV57 (Trek Diagnostics Systems, East Grinstead, England; MCS Diagnostics BV, Swalmen, The Netherlands), according to CLSI (formerly NCCLS) guidelines (4). Resistance genes were detected using a microarray (22) (Table 1). In addition to fluoroquinolone and oxacillin (methicillin) resistance, the isolates also displayed resistance to other antibiotics (Table 1).
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TABLE 2. Oligonucleotides used for PCR amplification of leukocidin genes, SCCmec, topoisomerase IV, and gyrase genes
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TABLE 1. Antibiotic resistance profiles, lukS gene, SCCmec type, and clonal relatedness of 15 Staphylococcus pseudintermedius isolates from dogs and of S. pseudintermedius type strain CCUG49543T
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Characterization of mutations in topoisomerase genes.
The mechanism of resistance to fluoroquinolones was investigated
by sequence analysis of the topoisomerase II (
gyrA and
gyrB)
and IV (
grlA and
grlB) genes, since mutations in these genes
have been shown to confer resistance to fluoroquinolones on
Staphylococcus aureus (
8,
11,
13,
14,
18,
27,
30). Fragments
of
gyrA,
gyrB,
grlA, and
grlB of type strains
S. pseudintermedius CCUG49543
T (also known as LMG 22219
T [
10]) (CCUG, Culture Collection,
University of Göteborg, Göteborg, Sweden) and
Staphylococcus intermedius DSM20373
T (also known as NCTC 11048
T) (DSMZ, German
Collection of Microorganisms and Cell Cultures, Braunschweig,
Germany) were amplified by PCR and sequenced on an ABI Prism
3100 genetic analyzer (Applied Biosystems, Foster City, CA)
using oligonucleotide primers (Table
2) designed from conserved
regions found after alignment of DNA sequences of
grlB/
grlA and
gyrB/gyrA from
S. aureus (GenBank accession no. L25288 and
BA000018),
Staphylococcus epidermidis (GenBank accession no.
CP000029 and AE015929), and
Staphylococcus haemolyticus (GenBank
accession no. AY341071, AY341072, AY341073, and AY341074) using
MultAlin (
7). The nucleotide sequences flanking the amplified
fragments were determined by genome walking using the Universal
Vectorette system according to the manufacturer's protocol (Sigma-Genosys,
St. Louis, MO) and genomic DNA digested with Sau3A, EcoRI, HindIII,
and ApoI. The nucleotide sequences of the g
rlB/
grlA and
gyrB/
gyrA loci of
S. pseudintermedius CCUG49543 share 89% and 94% identity,
respectively, with those of
S. intermedius DSM20373. The entire
gyrB/
gyrA and
grlB/grlA loci of fluoroquinolone-resistant and
fluoroquinolone-susceptible
S. pseudintermedius strains were
then amplified using the Expand Long Template PCR system (Roche
Applied Science, Indianapolis, IN) (annealing at 54°C for
30 s and extension at 68°C for 5 min) with specific primer
pairs gyrB-si-PF0-gyrA-si-RV and grlB-si-PF-grlA-si-R0 and were
sequenced. Nucleotide sequence comparison revealed high levels
of nucleotide polymorphism in the gyrase and topoisomerase IV
genes. Most of the mutations are silent (Fig.
1). Mutations
that cause amino acid substitutions in the topoisomerases were
found in both resistant and susceptible strains and cannot,
therefore, be responsible for resistance. However, other amino
acid mutations were found only in fluoroquinolone-resistant
strains (Table
3). Some of these amino acid changes occurred
at the same positions as those reported for fluoroquinolone-resistant
S. aureus,
S. intermedius, and
Staphylococcus schleiferi strains,
including positions 251 (Ser84Leu) and 263 (Glu88Gly) on
gyrA and positions 239 (Ser80Ile) and 250 (Asp84Asn) on
grlA (
8,
13-
15,
18,
27,
30) (Table
3).
S. pseudintermedius strains harboring
at least one of these mutations showed decreased susceptibility
to enrofloxacin (MICs, 4 to 8 µg/ml). Higher MICs (

16
µg/ml) were observed when two additional mutations (Thr678Ala
and Glu714Lys) were present in
gyrA (Table
3). Additional amino
acid substitutions were found in the topoisomerase genes, but
their roles in fluoroquinolone resistance remain to be determined
(Fig.
1).
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TABLE 3. Nucleotide mutations that cause amino acid substitutions in gyrase and topoisomerase IV in fluoroquinolone-resistant S. pseudintermedius
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Characterization of two new SCCmec elements.
Methicillin resistance is mediated by the
mecA gene, which is
located on a large staphylococcal cassette chromosome
mec (SCC
mec)
element. SCC
mec elements are characterized by the completeness
of the methicillin resistance regulon containing
mecA, by the
allotype of the recombinase genes
ccrA and
ccrB, and by the
general genetic structure (
2,
12,
20). SCC
mec are delineated
by two inverted repeats, IR-L and IR-R (Fig.
2). Six different
SCC
mec (I to VI) have been described to date for
Staphylococcus (
2,
12,
16,
20,
21). In the course of our study, SCC
mec of
S. pseudintermedius could not be classified using PCR methods previously
developed to determine the SCC
mec class (
19,
31) and were therefore
sequenced. First, the regions spanning
orfX to
mecI and
mecI to
ccrA of all methicillin-resistant
S. pseudintermedius strains
were amplified using the Expand Long Template PCR system (Roche
Applied Science, Indianapolis, IN) with primers ccrA4-F1 and
mecI-R (fragment A) and mecI-F and ORFX1r (
9) (fragment B) (annealing
at 50°C for 30 s; extension at 68°C for 15 min) (Table
2; Fig.
2). Restriction analysis of fragments A and B, digested
with HindIII and PstI, respectively, revealed two types of SCC
mec.
The SCC
mec of KM241 had a unique profile, whereas all the other
profiles were identical to that of KM1381. The fragments were
sequenced using a primer-walking strategy. To complete the entire
nucleotide sequence of the cassette, the 5' end of the SCC
mec of KM1381 situated upstream of
ccrA was amplified using primer
ccrA-R and primer SccmecIR-F, which is specific to
S. aureus SCC
mec III IR-L (GenBank accession no. AB037671). The 5'-end
sequence of the SCC
mec of KM241 was determined using the Universal
Vectorette system (Sigma-Genosys Co., St. Louis, MO). Sequence
analysis of the two entire cassettes revealed two new SCC
mec,
SCC
mec II-III in KM1381 and SCC
mec VII in KM241 (Fig.
2). SCC
mec II-III consists of a combination of
S. aureus SCC
mec III (accession
no. AB037671) (100% nucleotide identity from IR-L to ORF12)
and
S. epidermidis SCC
mec II (GenBank accession no. CP000029)
(98.9% nucleotide identity from ORF13 to IR-R) (Fig.
2). SCC
mec VII contains new recombinase genes,
ccrA5 and
ccrB5, classifying
it as a new allotype, allotype 5. The amino acid sequences of
ccrA5 and
ccrB5 showed 75.6% identity overall to
S. aureus CcrA,
allotype 3 (GenBank accession no. BAA88754), and 92.3% identity
overall to
S. aureus CcrB, allotype 3 (GenBank accession no.
BAA88755). The rest of the SCC
mec VII downstream of the
ccrA5 and
ccrB5 loci until IS
431 showed 99% nucleotide identity to
S. aureus SCC
mec III (GenBank accession no. AB037671) (Fig.
2) but differed from SCC
mec III by a complete
mecA regulon.
Both SCC
mec II-III and SCC
mec VII are new cassettes, which belong
to class A, allotype 3, and class A, allotype 5, respectively.
Differentiation of strains by ST.
Sequence typing (ST) of five gene loci (the 16S rRNA gene,
tuf,
cpn60,
pta, and
agrD) and examination of the allelic variation
of
agrD (
1) showed that all methicillin-resistant strains containing
SCC
mec II-III were clonally related. They belong to ST71,
agr type III (Table
1), which is the predominant clonal group in
North and Central Europe (
1). They also contain the same mutations
in the
gyrB/
gyrA and
grlB/
grlA genes (
gyr/
grl group 5), except
for strain KM1395.
S. pseudintermedius strain KM241 (SCC
mec VII) belongs to a new group (ST73,
agr IV). The methicillin-
and fluoroquinolone-susceptible strains belong to the distinct
ST group ST41,
agr II, and to new ST groups ST74,
agr II, and
ST75,
agr I (Table
1).
New SCCmec with new recombinase genes in S. pseudintermedius represent a new reservoir of the mecA gene for methicillin-sensitive Staphylococcus species. Until now, mainly SCCmec III has been detected in S. pseudintermedius (26). Additionally, sequence analysis of topoisomerase genes has allowed us to determine, for the first time for S. pseudintermedius, mutations that play a role in fluoroquinolone resistance.
The presence of multidrug-resistant Staphylococcus of animal origin is a further demonstration that the use of antibiotics in veterinary medicine selects for resistant strains. Guidelines regarding the use and choice of antibiotics should be followed in veterinary medicine to suppress the rapid, nationwide dissemination of multidrug-resistant S. pseudintermedius clones.
Nucleotide sequence accession numbers.
Nucleotide sequences were deposited in the EMBL/GenBank/DDBJ databases. SCCmec II-III and SCCmec VII were assigned accession no. AM904732 and AM904731. The gyrB/gyrA and grlB/grlA loci of S. pseudintermedius CCUG49543T and KM1381 and of S. intermedius DSM20373T were assigned accession no. AM262968 and AM262971, AM262969 and AM262972, and AM262967 and AM262970, respectively.

ACKNOWLEDGMENTS
We thank the personnel of the diagnostic unit of the Institute
of Veterinary Bacteriology of the University of Bern who isolated
the strains. We also thank J. Ross Fitzgerald for helpful advice
on sequence typing.

FOOTNOTES
* Corresponding author. Mailing address: Institute of Veterinary Bacteriology, University of Bern, Länggass-Strasse 122, Postfach, CH-3001 Bern, Switzerland. Phone: 41 31 631 2430. Fax: 41 31 631 2634. E-mail:
vincent.perreten{at}vbi.unibe.ch 
Published ahead of print on 27 February 2008. 

REFERENCES
1 - Bannoehr, J., N. L. Ben Zakour, A. S. Waller, L. Guardabassi, K. L. Thoday, A. H. M. van den Broek, and J. R. Fitzgerald. 2007. Population genetic structure of the Staphylococcus intermedius group: insights into agr diversification and the emergence of methicillin-resistant strains. J. Bacteriol. 189:8685-8692.[Abstract/Free Full Text]
2 - Chongtrakool, P., T. Ito, X. X. Ma, Y. Kondo, S. Trakulsomboon, C. Tiensasitorn, M. Jamklang, T. Chavalit, J. H. Song, and K. Hiramatsu. 2006. Staphylococcal cassette chromosome mec (SCCmec) typing of methicillin-resistant Staphylococcus aureus strains isolated in 11 Asian countries: a proposal for a new nomenclature for SCCmec elements. Antimicrob. Agents Chemother. 50:1001-1012.[Abstract/Free Full Text]
3 - Clinical and Laboratory Standards Institute. 2004. Performance standards for antimicrobial disk and dilution susceptibility tests for bacteria isolated from animals; informational supplement M31-S1, vol. 24, no. 17. Clinical and Laboratory Standards Institute, Wayne, PA.
4 - Clinical and Laboratory Standards Institute. 2006. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, 7th ed., vol. 26, no. 2. Approved standard M7-A7. Clinical and Laboratory Standards Institute, Wayne, PA.
5 - Clinical and Laboratory Standards Institute. 2006. Performance standards for antimicrobial disk susceptibility tests, 9th ed., vol. 26, no. 1. Approved standard M2-A9. Clinical and Laboratory Standards Institute, Wayne, PA.
6 - Clinical and Laboratory Standards Institute. 2006. Performance standards for antimicrobial susceptibility testing; sixteenth informational supplement M100-S16, vol. 26, no. 3. Clinical and Laboratory Standards Institute, Wayne, PA.
7 - Corpet, F. 1988. Multiple sequence alignment with hierarchical clustering. Nucleic Acids Res. 16:10881-10890.[Abstract/Free Full Text]
8 - Couzinet, S., J. Yugueros, C. Barras, N. Visomblin, P. Francois, B. Lacroix, G. Vernet, D. Lew, A. Troesch, J. Schrenzel, and C. Jay. 2005. Evaluation of a high-density oligonucleotide array for characterization of grlA, grlB, gyrA and gyrB mutations in fluoroquinolone resistant Staphylococcus aureus isolates. J. Microbiol. Methods 60:275-279.[CrossRef][Medline]
9 - Cuny, C., and W. Witte. 2005. PCR for the identification of methicillin-resistant Staphylococcus aureus (MRSA) strains using a single primer pair specific for SCCmec elements and the neighbouring chromosome-borne orfX. Clin. Microbiol. Infect. 11:834-837.[CrossRef][Medline]
10 - Devriese, L. A., M. Vancanneyt, M. Baele, M. Vaneechoutte, E. De Graef, C. Snauwaert, I. Cleenwerck, P. Dawyndt, J. Swings, A. Decostere, and F. Haesebrouck. 2005. Staphylococcus pseudintermedius sp. nov., a coagulase-positive species from animals. Int. J. Syst. Evol. Microbiol. 55:1569-1573.[Abstract/Free Full Text]
11 - Ferrero, L., B. Cameron, B. Manse, D. Lagneaux, J. Crouzet, A. Famechon, and F. Blanche. 1994. Cloning and primary structure of Staphylococcus aureus DNA topoisomerase IV: a primary target of fluoroquinolones. Mol. Microbiol. 13:641-653.[CrossRef][Medline]
12 - Hanssen, A. M., and J. U. Ericson Sollid. 2006. SCCmec in staphylococci: genes on the move. FEMS Immunol. Med. Microbiol. 46:8-20.[CrossRef][Medline]
13 - Horii, T., Y. Suzuki, A. Monji, M. Morita, H. Muramatsu, Y. Kondo, M. Doi, A. Takeshita, T. Kanno, and M. Maekawa. 2003. Detection of mutations in quinolone resistance-determining regions in levofloxacin- and methicillin-resistant Staphylococcus aureus: effects of the mutations on fluoroquinolone MICs. Diagn. Microbiol. Infect. Dis. 46:139-145.[CrossRef][Medline]
14 - Iihara, H., T. Suzuki, Y. Kawamura, K. Ohkusu, Y. Inoue, W. Zhang, M. M. Shah, Y. Atagiri, Y. Hashi, and T. Zaki. 2006. Emerging multiple mutations and high-level fluoroquinolone resistance in methicillin-resistant Staphylococcus aureus isolated from ocular infections. Diagn. Microbiol. Infect. Dis. 56:297-303.[CrossRef][Medline]
15 - Intorre, L., M. Vanni, D. Di Bello, C. Pretti, V. Meucci, R. Tognetti, G. Soldani, G. Cardini, and O. Jousson. 2007. Antimicrobial susceptibility and mechanism of resistance to fluoroquinolones in Staphylococcus intermedius and Staphylococcus schleiferi. J. Vet. Pharmacol. Ther. 30:464-469.[CrossRef][Medline]
16 - Ito, T., X. X. Ma, F. Takeuchi, K. Okuma, H. Yuzawa, and K. Hiramatsu. 2004. Novel type V staphylococcal cassette chromosome mec driven by a novel cassette chromosome recombinase, ccrC. Antimicrob. Agents Chemother. 48:2637-2651.[Abstract/Free Full Text]
17 - Lina, G., Y. Piémont, F. Godail-Gamot, M. Bes, M.-O. Peter, V. Gauduchon, F. Vandenesch, and J. Etienne. 1999. Involvement of Panton-Valentine leukocidin-producing Staphylococcus aureus in primary skin infections and pneumonia. Clin. Infect. Dis. 29:1128-1132.[CrossRef][Medline]
18 - Noguchi, N., T. Okihara, Y. Namiki, Y. Kumaki, Y. Yamanaka, M. Koyama, K. Wakasugi, and M. Sasatsu. 2005. Susceptibility and resistance genes to fluoroquinolones in methicillin-resistant Staphylococcus aureus isolated in 2002. Int. J. Antimicrob. Agents 25:374-379.[CrossRef][Medline]
19 - Oliveira, D. C., and H. de Lencastre. 2002. Multiplex PCR strategy for rapid identification of structural types and variants of the mec element in methicillin-resistant Staphylococcus aureus. Antimicrob. Agents Chemother. 46:2155-2161.[Abstract/Free Full Text]
20 - Oliveira, D. C., C. Milheiriço, and H. de Lencastre. 2006. Redefining a structural variant of staphylococcal cassette chromosome mec, SCCmec type VI. Antimicrob. Agents Chemother. 50:3457-3459.[Abstract/Free Full Text]
21 - Oliveira, D. C., C. Milheiriço, S. Vinga, and H. de Lencastre. 2006. Assessment of allelic variation in the ccrAB locus in methicillin-resistant Staphylococcus aureus clones. J. Antimicrob. Chemother. 58:23-30.[Abstract/Free Full Text]
22 - Perreten, V., L. Vorlet-Fawer, P. Slickers, R. Ehricht, P. Kuhnert, and J. Frey. 2005. Microarray-based detection of 90 antibiotic resistance genes of gram-positive bacteria. J. Clin. Microbiol. 43:2291-2302.[Abstract/Free Full Text]
23 - Piriz, S., J. Valle, E. M. Mateos, R. de la Fuente, D. Cid, J. A. Ruiz-Santaquiteria, and S. Vadillo. 1996. In vitro activity of fifteen antimicrobial agents against methicillin-resistant and methicillin-susceptible Staphylococcus intermedius. J. Vet. Pharmacol. Ther. 19:118-123.[CrossRef][Medline]
24 - Poyart, C., G. Quesne, C. Boumaila, and P. Trieu-Cuot. 2001. Rapid and accurate species-level identification of coagulase-negative staphylococci by using the sodA gene as a target. J. Clin. Microbiol. 39:4296-4301.[Abstract/Free Full Text]
25 - Prévost, G., T. Bouakham, Y. Piémont, and H. Monteil. 1995. Characterisation of a synergohymenotropic toxin produced by Staphylococcus intermedius. FEBS Lett. 376:135-140.[CrossRef][Medline]
26 - Sasaki, T., K. Kikuchi, Y. Tanaka, N. Takahashi, S. Kamata, and K. Hiramatsu. 2007. Methicillin-resistant Staphylococcus pseudintermedius in a veterinary teaching hospital. J. Clin. Microbiol. 45:1118-1125.[Abstract/Free Full Text]
27 - Sierra, J. M., J. G. Cabeza, M. Ruiz Chaler, T. Montero, J. Hernandez, J. Mensa, M. Llagostera, and J. Vila. 2005. The selection of resistance to and the mutagenicity of different fluoroquinolones in Staphylococcus aureus and Streptococcus pneumoniae. Clin. Microbiol. Infect. 11:750-758.[CrossRef][Medline]
28 - Tristan, A., T. Ferry, G. Durand, O. Dauwalder, M. Bes, G. Lina, F. Vandenesch, and J. Etienne. 2007. Virulence determinants in community and hospital methicillin-resistant Staphylococcus aureus. J. Hosp. Infect. 65(S2):105-109.[CrossRef][Medline]
29 - Van Hoovels, L., A. Vankeerberghen, A. Boel, K. Van Vaerenbergh, and H. De Beenhouwer. 2006. First case of Staphylococcus pseudintermedius infection in a human. J. Clin. Microbiol. 44:4609-4612.[Abstract/Free Full Text]
30 - Vickers, A. A., A. J. O'Neill, and I. Chopra. 2007. Emergence and maintenance of resistance to fluoroquinolones and coumarins in Staphylococcus aureus: predictions from in vitro studies. J. Antimicrob. Chemother. 60:269-273.[Abstract/Free Full Text]
31 - Zhang, K., J.-A. McClure, S. Elsayed, T. Louie, and J. M. Conly. 2005. Novel multiplex PCR assay for characterization and concomitant subtyping of staphylococcal cassette chromosome mec types I to V in methicillin-resistant Staphylococcus aureus. J. Clin. Microbiol. 43:5026-5033.[Abstract/Free Full Text]
Journal of Clinical Microbiology, May 2008, p. 1818-1823, Vol. 46, No. 5
0095-1137/08/$08.00+0 doi:10.1128/JCM.02255-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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