Analysis of the Clonality of Candida tropicalis Strains from a General Hospital in Beijing Using Multilocus Sequence Typing
et al. (2012) Analysis of the Clonality of Candida tropicalis Strains from a General Hospital in Beijing Using Multilocus
Sequence Typing. PLoS ONE 7(11): e47767. doi:10.1371/journal.pone.0047767
Analysis of the Clonality of Candida tropicalis Strains from a General Hospital in Beijing Using Multilocus Sequence Typing
Yuan Wu 0
Haijian Zhou 0
Jing Wang 0
Lianqing Li 0
Wenge Li 0
Zhigang Cui 0
Xia Chen 0
Ruiqi Cen 0
Jinxing Lu 0
Ying Cheng 0
Wenjun Li, Duke University Medical Center, United States of America
0 1 State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention , Beijing, People's Republic of China, 2 China- Japan Friendship Hospital , Beijing , People's Republic of China, 3 Shanxi Center for Clinical Laboratories , TaiYuan, Shanxi , People's Republic of China, 4 Department of Critical Care Medicine, Fu Xing Hospital, Capital Medical University , Beijing , People's Republic of China
Multilocus sequence typing (MLST) based on six loci was used to analyze the relationship of 58 Candida tropicalis isolates from individual patients in a general hospital in Beijing, China. A total of 52 diploid sequence types (DSTs) were generated by the MLST, all of which were new to the central database. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) dendrograms were constructed, which showed that the 58 isolates were distributed robustly and 6 main groups were clustered regardless of the specimen source and medical department. The minimum spanning tree (MST) of the 58 isolates (52 DSTs) and all 401 isolates (268 DSTs) in the C. tropicalis central database (http://pubmlst.org/ctropicalis/) indicated that the isolates in this study clustered in three relative pure clonal complexes, and 2 clustered with isolates from Taiwan, Belgium, Brazil, and the US. This study presents the first MLST analysis of C. tropicalis isolates from Mainland China, which may be useful for further studies on the similarity, genetic relationship, and molecular epidemiology of C. tropicalis strains worldwide.
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With the increasing number of immunocompromised patients,
long-term hospitalized patients, and invasive medical inspection
and therapy, the genus Candida has emerged as a major group of
opportunistic pathogens that cause superficial and invasive
infections in humans [15]. Candida is considered the fourth most
commonly isolated organisms from nosocomial bloodstream
infections in United States and sixth in Europe [610]. The
invasive infections caused by Candida species are associated with
significant morbidity and mortality [5,11,12]. Although Candida
albicans accounts for the majority of infections, other non-albicans
Candida species such as Candida tropicalis have increasingly been
recognized as pathogens for these types of infections. C. tropicalis is
considered the leading pathogen in nosocomial fungemia and
hepatosplenic fungal infections in patients with cancer, especially
leukemia [13,14]. C. tropicalis is the second most frequently isolated
non-albicans pathogen in the Asia-Pacific region and in Brazil
[15,16]. In large independent epidemiologic surveys, the isolation
rate of C. tropicalis from blood is 5% to 30% [17,18]. In
evolutionary terms, it is closely related to C. albicans [1921].
Previous studies conducted in Asia show the frequency of
fluconazole resistance in the intermediate C. tropicalis strains,
which was originally found in Candida glabrata that displayed
natural resistance to fluconazole [22,23]. Furthermore, a high
proportion of C. tropicalis isolates has exhibited low susceptibility to
flucytosine [24,25].
Numerous molecular typing methods have been used to
determine the molecular epidemiology and resistance of C.
tropicalis, such as MLST (multilocus sequence typing). MLST is a
useful tool in population analysis within a species [20,26]. The
MLST data is comparable among labs worldwide via the central
database in the Internet (http://www.mlst.net/), and it satisfies the
increasing need for global surveillance [27]. The MLST approach
reveals different geographical origins, anatomic sources, and other
characteristics between clades of closely related isolates [20].
MLST has been developed for C. albicans and C. glabrata [2830],
which offers further information regarding strain variations,
including maintenance, replacement, and microevolution in the
host [27]. The MLST system for C. tropicalis, which comprises six
housekeeping genes (ICL1, MDR1, SAPT2, SAPT4, XYR1 and
ZWF1a), has been described by Tavanti et al. in 2005 [24].
The aim of our study is to examine the clonality of C. tropicalis by
performing successive strain collection for one year in a general
hospital in Beijing, China, and to ascertain whether factors such as
hospital department origin, anatomic source, and so on are related
to certain specific MLST diploid sequence types (DSTs) types.
Furthermore, the cor (...truncated)