Frequent recovery of a single clonal type of multidrug-resistant Staphylococcus aureus from patients in two hospitals in Taiwan and China.

Abstract

One hundred thirty-two methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from patients with S. aureus infections between January 1998 and February 1999 in two hospitals, one located in Taipei, Taiwan, and another in Nanjing, People's Republic of China, were examined for antibiotic susceptibility and for clonal type by a combination of three methods: hybridization of ClaI restriction digests with mecA- and Tn554-specific DNA probes and pulsed-field gel electrophoresis of chromosomal SmaI digests. Selected isolates representing each clonal type were also analyzed by spaA typing, multilocus sequence typing, and a multiplex PCR method capable of identifying the structural type of the staphylococcal cassette chromosome mec (SCCmec) carried by the bacteria. The overwhelming majority of isolates (126 of 132 or 95%) belonged to minor variants of a single clonal type resembling the Brazilian and Hungarian epidemic MRSA clones, which showed a common spaA type and which were either sequence type 239 (ST239) or ST241 (a single-locus variant of ST239) in association with SCCmec type III or IIIA.

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JOURNAL OF CLINICAL MICROBIOLOGY, Jan. 2003, p. 159–163
0095-1137/03/$08.00?0DOI: 10.1128/JCM.41.1.159–163.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Vol. 41, No. 1
Frequent Recovery of a Single Clonal Type of Multidrug-Resistant
Staphylococcus aureus from Patients in Two Hospitals
in Taiwan and China
M. Aires de Sousa,1M. I. Criso ´stomo,1,2I. Santos Sanches,1,3J. S. Wu,4J. Fuzhong,5
A. Tomasz,2and H. de Lencastre1,2*
Laborato ´rio de Gene ´tica Molecular, Instituto de Tecnologia Química e Biolo ´gica da Universidade Nova de Lisboa,
Oeiras,1and Faculdade de Cie ˆncias e Tecnologia, Universidade Nova de Lisboa, Monte da Caparica,3Portugal;
Laboratory of Microbiology, The Rockefeller University, New York, New York2; Armed Forces Shun
Shan Hospital, Taipei, Taiwan4; and The First Affiliated Hospital of Nanjing
Medical University, The First Teaching Hospital,
Nanjing, People’s Republic of China5
Received 9 August 2002/Returned for modification 5 October 2002/Accepted 10 October 2002
One hundred thirty-two methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from patients
with S. aureus infections between January 1998 and February 1999 in two hospitals, one located in Taipei,
Taiwan, and another in Nanjing, People’s Republic of China, were examined for antibiotic susceptibility and
for clonal type by a combination of three methods: hybridization of ClaI restriction digests with mecA- and
Tn554-specific DNA probes and pulsed-field gel electrophoresis of chromosomal SmaI digests. Selected isolates
representing each clonal type were also analyzed by spaA typing, multilocus sequence typing, and a multiplex
PCR method capable of identifying the structural type of the staphylococcal cassette chromosome mec
(SCCmec) carried by the bacteria. The overwhelming majority of isolates (126 of 132 or 95%) belonged to minor
variants of a single clonal type resembling the Brazilian and Hungarian epidemic MRSA clones, which showed
a common spaA type and which were either sequence type 239 (ST239) or ST241 (a single-locus variant of
ST239) in association with SCCmec type III or IIIA.
Methicillin-resistant Staphylococcus aureus (MRSA) is a se-
rious problem in both Taiwan and China. The frequency of
nosocomial infections caused by MRSA in Taiwan has in-
creased rapidly during the past 10 years (4). In most major
hospitals, MRSA accounts for more than 60% of the S. aureus
isolates (30). According to a study from 1991 to 1996 at the
Veterans General Hospital of Taipei, the prevalence of MRSA
in this hospital was estimated as 88.2% (28). Furthermore,
community-acquired MRSA infections seem to occur fre-
quently in Taiwan among patients (infants and children) with
no associated risk factors (31). In China the incidence of
MRSA from hospital infection can be over 80% and the inci-
dence of MRSA from community-acquired infections is close
to 22% (14).
The Center for Molecular Epidemiology and International
Network (CEM/NET) has been created to keep track of the
movement of major multidrug-resistant clones of S. aureus and
other gram-positive pathogens and to identify their reservoirs
(6). Under this initiative, clinical isolates of MRSA collected in
different countries were analyzed by molecular typing tech-
niques involving ClaI-mecA polymorphisms, Tn554 insertion
patterns, and pulsed-field gel electrophoresis (PFGE). These
techniques have allowed us to identify so far five multiresistant
MRSA clones (22). The names assigned to these five pandemic
MRSA clones, Iberian (8, 25), Brazilian (27), Hungarian (7,
18), New York/Japan (1, 23), and pediatric (24), reflect the
geographic area in which they were first identified or indicate
some unique epidemiological property. Enright et al. (10) pro-
posed a different nomenclature for these clones based on their
sequence types (ST) (9) and staphylococcal cassette chromo-
some mec (SCCmec) types (I through IV) (11, 12). If subtypes
IA and IIIA are included (20), the designations of the five
pandemic clones are ST247-IA, ST239-IIIA, ST239-III, ST5-II,
and ST5-IV, respectively (10, 19).
The aim of this study was to characterize a collection of
clinical MRSA strains from Taiwan and China and to evaluate
their geographic spread by comparison with information in-
cluded in the CEM/NET and multilocus sequence typing
(MLST) (http://www.mlst.net) databases.
MATERIALS AND METHODS
Bacterial isolates. One hundred thirty-two clinical MRSA isolates were col-
lected from January 1998 to February 1999 from infection sites of individual
patients.
Hospitals. Most of the isolates (n ? 118) were from the Tri-Service General
Hospital/National Defense Medical Center of Taipei, Taiwan, a 1,200-bed med-
ical center. A small sample (14 isolates) was received from the First Teaching
Hospital, Nanjing, People’s Republic of China, a 950-bed general hospital.
Susceptibility tests. Susceptibility tests were performed by standard disk dif-
fusion method according to National Committee for Clinical Laboratory Stan-
dards guidelines (17). Drugs tested included penicillin, oxacillin, trimethoprim-
sulfamethoxazole, ciprofloxacin, chloramphenicol, clindamycin, erythromycin,
gentamicin, rifampin, tetracycline, vancomycin, and teicoplanin. Spectinomycin
and quinupristin-dalfopristin susceptibilities were determined as described pre-
viously (1).
Molecular typing. Southern blot hybridization of ClaI digests with mecA and
Tn554 DNA probes (5), PFGE of SmaI digests of chromosomal DNAs (5), spaA
typing (26), and MLST (9) were performed as previously described. The SCCmec
types were determined by a multiplex PCR strategy (19) or by PCR amplification
* Corresponding author. Mailing address: The Rockefeller Univer-
sity, 1230 York Ave., New York, NY 10021. Phone: (212) 327-8278.
Fax: (212) 327-8688. E-mail: lencash@mail.rockefeller.edu.
159

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of the ccr (cassette chromosome recombinase) gene (12) when ambiguous results
were obtained with the previous methodology.
RESULTS AND DISCUSSION
All isolates studied were multiresistant (Table 1). There
were, however, differences among strains from the two coun-
tries; for instance, resistance or intermediate resistance to
chloramphenicol was found in each of the 14 isolates from
China but only in about one-half (43%) of the 118 isolates
from Taiwan, while resistance to trimethoprim-sulfamethox-
azole was found in 89% of the isolates from Taiwan but in only
21% of the isolates from China. None of the strains was resis-
tant to teicoplanin, vancomycin, and quinupristin-dalfopristin.
The majority of the isolates were also susceptible to rifampin
(94%) and to 500 mg of spectinomycin/liter (94%).
While the 132 MRSA isolates from Taiwan and China could
be separated into six ClaI-mecA polymorphs and three ClaI-
Tn554 polymorphs (Table 1), the great majority of isolates
were characterized as ClaI-mecA polymorph III (13) or the
genetically related polymorphs IX, XI, and III? (21) (n ? 110)
and Tn554 polymorph B (13) (n ? 125).
The PFGE analysis grouped the 132 MRSA strains into four
types (Table 1), of which pattern A was assigned to a surpris-
ingly large proportion of the isolates (Taiwan, n ? 110, 93%;
China, n ? 14, 100%). This pattern showed 10 different sub-
types in Taiwan and 6 in China, but by far the most frequent
were A1 in Taiwan (n ? 49, 42%) and A11 in China (n ? 7,
50%). There are no common PFGE subtypes shared by the
strains from the hospitals in the two countries.
The combination of the three molecular typing methods
(ClaI-mecA and ClaI-Tn554 hybridization and PFGE) distrib-
uted the 118 MRSA isolates from Taiwan and the 14 isolates
from China into seven and two clonal types, respectively (Table
1). However, the overwhelming majority of the strains from
Taipei, Taiwan, and Nanjing, China (82 and 71%, respective-
ly), belonged to the same clone, III::B::A. Interestingly, this
TABLE 1. Phenotypic and genotypic properties of 132 MRSA isolates from Taipei, Taiwan, and Nanjing, China
ClaI-mecA::Tn554
typea
PFGE
type
No. of
isolates
Clonal typeb
Antimicrobial resistance (of the majority
[?50%] of the isolates)c
spaA typeMLST typeST
SCCmec
type
Taiwan isolates
III?::B
III?::B
IX::B
IX::B
IX::B
IX::B
IX::B
XI::B
A1
A7
A2
A4
A5
A9
A10
A8
45III::B::A (n ? 97;
82%)
PEN, OXA, CIP, CLI, ERY, TET,
GEN, SXT
WGKAOMQ 2-3-1-1-4-4-30 241III
4
36 WGKAOMQ2-3-1-1-4-4-30241 IIIA
6
1
1
1
3WGKAOMQ III
XIV::B
XIV::B
XIV::B
XIV::B
A1
A3
A6
A9
3
2
1
1
XIV::B::APEN, OXA, CIP, CLI, ERY, TET,
GEN, SXT
WGKAOMQIII
X?::B A35X?::B::APEN, OXA, CIP, CLI, ERY, TET,
GEN
WGKAOMQIIIA
III?::AAA11III?::AA::APEN, OXA, CIP, CLI, ERY, TET,
GEN, SXT, CHL
WGKAOMQIII
XI::BC2XI::B::CPEN, OXA, CIP, CLI, ERY, TET,
GEN, SXT, CHL, RIF
WGKAOMQ2-3-1-1-4-4-3239IIIA
II::NH B11II::NH::BPEN, OXA, CLI, ERY, TET, GEN,
CHL
ZDMDMOB19-23-15-2-19-20-1559IV
II::NHB23
II::ZZD2II::ZZ::DPEN, OXA, CLI, ERY, TET, GEN,
CHL, RIF
NTd
3-32-1-1-4-4-381II variant
China isolates
III?::B
III?::B
III?::B
A11
A12
A16
7
1
2
III::B::A (n ? 10;
71%)
PEN, OXA, CIP, CLI, ERY, TET,
GEN, CHL
WGKAOMQ2-3-1-1-4-4-3 239III
X?::B
X?::B
X?::B
A13
A14
A15
1
2
1
X?::B::APEN, OXA, CIP, CLI, ERY, TET,
GEN, CHL
WGKAOMQ IIIA
aClaI-mecA polymorphs and respective hybridization fragment sizes: III?, 1.9 and 4.5 kb; IX and XI, see reference 8; XIV, 1.9 and 4.3 kb; X?, 1.9 and 6 kb; II, see
reference 13. Tn554 polymorphs: NH, no homology, lack of transposon; B and AA, see reference 13; ZZ, novel pattern (9.2, 7.1, 6.7, 6.1, and 4.1 kb).
bClaI-mecA polymorphs III?, IX, and XI present minor variations compared to pattern III and were found to be genetically related (21). Therefore strains belonging
to these mecA polymorphs were grouped under type III for the definition of clonal types.
cAbbreviations: PEN, penicillin; OXA, oxacillin; CIP, ciprofloxacin; CLI, clindamycin; ERY, erythromycin; TET, tetracycline; GEN, gentamicin; SXT, trimethoprim-
sulfamethoxazole; CHL, chloramphenicol; RIF, rifampin.
dNT, there was no amplification with the set of primers used.
160AIRES DE SOUSA ET AL.J. CLIN. MICROBIOL.

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clone was apparently already present in 1994 in a hospital in
another city of Taiwan (15). In addition, the MRSA strain
responsible for a hospital-acquired outbreak initiated by a sur-
geon carrier in the beginning of 1997 in a hospital in northern
Taiwan showed the same PFGE pattern, A (29). According to
a recent study involving 22 hospitals distributed throughout
Taiwan, the high prevalence of MRSA in the country was, at
least in past, due to the spreading of a single predominant
strain (30) having a PFGE pattern very similar, if not identical,
to PFGE pattern A, shown by the majority of MRSA isolates
that we studied (Fig. 1). It is probable that clone III::B::A was
spread in different cities in Taiwan and had at least a 5-year
existence in the country.
Representatives of PFGE pattern A were compared to
strains belonging to previously characterized clones (Fig. 1A),
namely, the Brazilian and the Hungarian MRSA clones, which
share some molecular properties (identical mecA and Tn554
polymorphisms). It was found that PFGE type A showed a high
degree of similarity with both clones, in particular with the
Hungarian MRSA (Fig. 1A and B).
Several selected isolates from Taiwan and China represent-
ing the major clonal lineage (PFGE type A) were also exam-
ined by spaA typing, MLST, and SCCmec typing (Table 1). All
shared the same spaA repeat motif, WGKAOMQ, which was
very similar to the one described for the Hungarian and Bra-
zilian clones (18, 20). MLST analysis showed a single-locus
FIG. 1. (A) PFGE of SmaI macrorestriction fragments of MRSA
clinical isolates belonging to the China/Taiwan, Hungarian (7, 18), and
Brazilian clones (2, 3, 27). Lanes 1 and 21, lambda molecular weight
marker; lanes 2, 11, and 20, reference strain NCTC 8325; lanes 3 to 6,
HU25, HSJ216, BRA5, and BRA101, respectively; lanes 7 to 10,
HUSA304, HU101, HUSA88, and HUSA176, respectively; lanes 12 to
15, TAW9 (A2), TAW10 (A1), TAW3 (A1), and TAW5 (A2), respec-
tively; lanes 16 to 19, CHI55 (A11), CHI59 (A11), CHI62 (A11), and
CHI61 (A14), respectively. (B) Computer-generated dendrogram
based on Jaccard matching of pattern similarity of the PFGE of Fig.
1A. The scale at the bottom of the dendrogram represents similarity.
VOL. 41, 2003 SPREAD OF A PANDEMIC MRSA CLONE TO TAIWAN AND CHINA 161

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variant on the basis of a comparison of the ST of isolates from
Taiwan (ST241) and China (ST239): ST239 possesses allele 3
at yqiL, which is found in several other distantly related lin-
eages, whereas ST241 possesses allele 30. According to infor-
mation found in the MLST database, allele 30 is only found in
ST241 and differs from allele 3 at a single nucleotide site,
suggesting that allele 30 arose from allele 3 by a point muta-
tion. Strains from China showed an ST identical to the one
described for the Hungarian and Brazilian clones (ST239)
(20). All isolates were assigned to SCCmec type III or to
variant IIIA, two SCCmec types that differ mainly by the pres-
ence or absence of plasmid pT181 and that are characteristic of
the Hungarian and Brazilian clones, respectively (19). ST241
and ST239 have also been detected in Thailand (10), which
may indicate a possible spread of the Nanjing/Taipei clone to
or from other Asiatic countries.
The application of spaA typing, MLST, and SCCmec assign-
ment to isolates belonging to the minor clones XIV::B::A,
X?::B::A, III?::AA::A, and XI::B::C confirmed that they were
related to the major clonal lineage III::B::A. Representatives
of two other minor groups of isolates were also characterized:
four strains were clonal type II::NH::B, and two strains were
clonal type II::ZZ::D. The strain representing clonal type
II::NH::B had a rare spaA type and belonged to ST59, which
was previously detected only in a few MSSA isolates and in a
single MRSA isolate from the United States and which is
considered one of the most divergent MRSA ST (10). The
strain representing clonal type II::ZZ::D was nontypeable by
spaA and belonged to a new multilocus ST (ST81), which is a
double-locus variant of ST239.
Our study documents the dominance of variants of a single
multiresistant clone (III::B::A or ST239- and ST241-III and
-IIIA) among MRSA isolates (126 of 132 or 95%) from the
hospitals in Taipei, Taiwan, and in Nanjing, People’s Republic
of China. This clone shows high degree of similarity in MLST
type, spaA type, PFGE pattern, and the structural type of the
SCCmec element to the Brazilian and Hungarian epidemic
MRSA (22). MRSA with an identical genetic background
(ST239) has already been recovered in 1982 in Australia and in
1987 in the United States (22), as well as in several countries of
Europe, South America, and Asia since the 1990s (2, 10, 16).
The results of our study document the dissemination of this
highly epidemic MRSA lineage to Taiwan and China.
ACKNOWLEDGMENTS
This work was partially supported by project POCTI/1999/ESP/
34872 from Fundac ¸a ˜o para a Cie ˆncia e Tecnologia, Portugal, and by
project SDH.IC.I.01.13 from Fundac ¸a ˜o Calouste Gulbenkian, Portu-
gal, awarded to H. de Lencastre. M. Aires de Sousa was supported by
grant BD/13731/97 from PRAXIS XXI, and M. I. Criso ´stomo was
supported by grant BD/5205/01 from Fundac ¸a ˜o para a Cie ˆncia e Tec-
nologia, Portugal. The strains from Taipei, Taiwan, and Nanjing, Peo-
ple’s Republic of China, were obtained through Project Resist with a
grant from Rho ˆne-Poulenc Rorer, S. A., awarded to Alexander To-
masz and Hermínia de Lencastre. The Multilocus Sequence Typing
website (http://www.mlst.net), which is hosted at Imperial College
London and at the University of Bath, was used for the studies de-
scribed in this work.
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