Molecular Characterization of Vancomycin-Resistant Enterococcus faecium Isolates from Mainland China

Abstract

Little is known about vancomycin-resistant enterococci in China. Thirteen pulsed-field gel electrophoresisconfirmed heterogeneous VanA-type vancomycin-resistant Enterococcus faecium (VRE) isolates were obtained from five Chinese hospitals from 2001 to 2005. The isolates were typed by multilocus sequence typing into nine different sequence types (STs), including five new STs (ST18, ST25, ST78, ST203, ST320, ST321, ST322, ST323, and ST335). Vancomycin resistance in each isolate was encoded on conjugative plasmids; two of the plasmids, pZB18 (67 kbp) and pZB22 (200 kbp), were highly conjugative and were able to transfer at high frequencies of around 10 ؊4 and 10 ؊7 per donor cell in broth mating, respectively. None of the plasmids identified in these isolates carried traA, which is usually conserved in the pMG1-like highly conjugative plasmid for E. faecium, implying that pZB18 and pZB22 were novel types of a highly conjugative plasmid in enterococci. Thirteen Tn1546-like elements encoding VanA-type VRE on the conjugative plasmids were classified into six types (types I to VI), and most of them contained both IS1216V and IS1542 insertions. The isolates carrying the type II element were predominant. The six type elements were different from that of a VanA-type Enterococcus faecalis strain isolated from Chinese chicken meat. The results suggested that the disseminations of VRE in these areas were by Tn1546-like elements being acquired by the conjugative plasmids and transferred among E. faecium strains.

Diversity of Tn 1546 and Its Role in the Dissemination of Vancomycin-Resistant Enterococci in Portugal

“…Difficulties also arise from the different methods used for this purpose, which complicates comparison among studies (14,44,45). Tn1546 may be located in conjugative plasmids (14,20,25,43,47) or in larger composite transposons, as documented for isolates with chromosomally located vanA (15). Horizontal transfer of conjugative plasmids containing Tn1546 seems to have played a relevant role in the recent increase of VRE in Portugal, as vanA was plasmid located in most VRE isolates studied and specific plasmids containing the most prevalent Tn1546 variants were identified in representative distinct clones collected from different cities and years (13).…”

Genetic Variability of Vancomycin-Resistant Enterococcus faecium and Enterococcus faecalis Isolates from Humans, Chickens, and Pigs in Malaysia

“…The most frequent STs observed were ST203 and ST55, which belong to the widespread nosocomial lineage CC17 (6,(32)(33)(34). ST203 was a unique allelic type of E. faecium that caused outbreaks in hospitals in Korea (35,36), Germany (37,38), and China (39,40). At the time this paper was written, there were 43 entries of this ST in the MLST database, of which more than 60% were reported from Asia-Pacific countries.…”

Current Trends of Emergence and Spread of Vancomycin-Resistant Enterococci

“…In South-Korean hospitals (and outside hospitals) vanA-genotype (VanB phenotype) E. faecium were widely prevalent (Ko et al, 2005;Shin et al, 2006;Park et al, 2008). Recent reports from China revealed also a preferred prevalence of vanA-type vancomycin resistance among clinical VRE (Zheng et al, 2007a;Zheng et al, 2007b;Zhu et al, 2009). …”