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High prevalence of CTX-M-15-producing Klebsiella pneumoniae isolates in Asian countries: diverse clones and clonal dissemination

https://doi.org/10.1016/j.ijantimicag.2011.03.020Get rights and content

Abstract

The characteristics of 218 Klebsiella pneumoniae isolates from patients with hospital-acquired pneumonia in nine Asian countries were investigated. In total, 92 isolates (42.2%) produced extended-spectrum β-lactamases (ESBLs), amongst which 67 (72.8%) possessed CTX-M ESBL genes; CTX-M-15 was the major ESBL (55 isolates; 59.8%). Multilocus sequence typing (MLST) and plasmid replicon typing were performed to investigate the genetic backgrounds of the 55 CTX-M-15-producing K. pneumoniae isolates. Twenty-five sequence types (STs) were identified. Clonal complex 11 (CC11) including ST11 was the most prevalent clone (20 isolates; 36.4%) and was distributed in all Asian countries except Taiwan. ST15 was the next most frequently identified clone (8 isolates; 14.5%). An IncFIIA-type plasmid was predominantly associated with blaCTX-M-15 (45 isolates; 81.8%). However, another plasmid type (IncA/C) was also identified and replicon types of seven isolates could not be determined. The high prevalence of CTX-M-15 amongst K. pneumoniae isolates in Asian countries may be due both to the acquisition of plasmids carrying blaCTX-M-15 and the spread of certain clones such as ST11 and ST15.

Introduction

Extended-spectrum β-lactamases (ESBLs) in Enterobacteriaceae are of great concern in clinical settings and public health. Recently, the distribution and prevalence of ESBLs have changed. TEM- and SHV-type ESBLs have been prevalent in the past, but the CTX-M-type ESBL has disseminated worldwide and has become pandemic [1]. The global spread of CTX-M-producing Enterobacteriaceae is a major concern in most continents, including Asia. In particular, a rapid increase of CTX-M-15 has been widely reported, and CTX-M-15 is now the most common ESBL in much of the world [1]. The spread of CTX-M-15 has been mainly associated with global dissemination of a particular clone of Escherichia coli of sequence type 131 (ST131) that harbours blaCTX-M-15 [2].

In contrast to E. coli, CTX-M-15 has not been the main ESBL in Klebsiella pneumoniae until recently. However, CTX-M-15-producing K. pneumoniae isolates are also disseminating worldwide [3], [4], [5]. It has been proposed that horizontal transfer of blaCTX-M-15 from E. coli to K. pneumoniae has occurred by conjugation of IncFII plasmids [6]. The increase in CTX-M-15-producing K. pneumoniae isolates may be due to frequent incorporation of plasmids containing blaCTX-M-15 or to the dissemination of a limited number of clones. Coelho et al. [3] reported that CTX-M-15-producing K. pneumoniae isolates from Barcelona (Spain) were composed of three main clones that harboured diverse plasmids containing blaCTX-M-15. On the other hand, another study reported diverse clones of CTX-M-15-producing K. pneumoniae isolates from Spain based on multilocus sequence typing (MLST) [7]. However, only limited data on CTX-M-15-producing K. pneumoniae isolates in Asian countries are available.

In this study, we report the high prevalence of CTX-M-15 amongst 218 K. pneumoniae isolates from nine Asian countries. CTX-M-15-producing K. pneumoniae isolates belonged to diverse clones as determined by MLST. However, spread of some K. pneumoniae clones producing CTX-M-15 in several Asian countries was also identified.

Section snippets

Klebsiella pneumoniae isolates

As part of a multinational Asian Network for Surveillance of Resistant Pathogens (ANSORP) surveillance study, a total of 218 K. pneumoniae isolates were obtained from patients with hospital-acquired pneumonia (HAP) in nine Asian countries during 2008 and 2009, including Hong Kong (n = 26), India (n = 7), Indonesia (n = 4), South Korea (n = 18), Malaysia (n = 24), the Philippines (n = 30), Singapore (n = 12), Taiwan (n = 12) and Thailand (n = 85). These represented 16.3% of the total number of isolates causing

Antimicrobial resistance, extended-spectrum β-lactamases and CTX-M-15

Whilst all K. pneumoniae isolates were resistant to ampicillin, only one isolate from Thailand was resistant to imipenem and none were resistant to meropenem. In addition, only one colistin-resistant K. pneumoniae isolate from South Korea was identified. For the other antimicrobial agents (gentamicin, ceftazidime, cefotaxime, cefepime, aztreonam, ciprofloxacin, SXT and TZP), 21.1–46.3% of the K. pneumoniae isolates showed resistance (Table 1). Of note, 92 K. pneumoniae isolates (42.2%) were

Discussion

In this study, we report a high percentage of ESBL-producers amongst K. pneumoniae isolates causing HAP in Asian countries, particularly in South Korea and Thailand. Although only a few K. pneumoniae isolates could be included from some countries and the distribution of isolates was unbalanced amongst the different Asian countries, CTX-M-15-producing K. pneumoniae isolates were prevalent in the surveyed Asian countries. Although a high prevalence of CTX-M-15-producing E. coli isolates

Acknowledgments

The authors thank members of the Asian Network for Surveillance of Resistant Pathogens (ANSORP) for their collaboration. Klebsiella pneumoniae isolates used in this study were obtained from the Asian Bacterial Bank (ABB) of the Asia Pacific Foundation for Infectious Diseases (APFID) (Seoul, South Korea).

Funding: This research was supported by the Basic Science Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0004848

References (15)

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