Characteristics of Carbapenem-Resistant Enterobacteriaceae in Ready-to-Eat Vegetables in China

Abstract

Vegetables harboring bacteria resistant to antibiotics are a growing food safety issue. However, data concerning carbapenem-resistant Enterobacteriaceae (CRE) in ready-to-eat fresh vegetables is still rare. In this study, 411 vegetable samples from 36 supermarkets or farmer's markets in 18 cities in China, were analyzed for CRE. Carbapenemase-encoding genes and other resistance genes were analyzed among the CRE isolates. Plasmids carrying carbapenemase genes were studied by conjugation, replicon typing, S1-PFGE southern blot, restriction fragment length polymorphism (RFLP), and sequencing. CRE isolates were also analyzed by pulsed-field gel electrophoresis (PFGE). Ten vegetable samples yielded one or more CRE isolates. The highest detection rate of CRE (14.3%, 4/28) was found in curly endive. Twelve CRE isolates were obtained and all showed multidrug resistance: Escherichia coli, 5; Citrobacter freundii, 5; and Klebsiella pneumoniae, 2. All E. coli and C. freundii carried blaNDM, while K. pneumoniae harbored blaKPC−2. Notably, E. coli with blaNDM and ST23 hypervirulent Klebsiella pneumoniae (hvKP) carrying blaKPC−2 were found in the same cucumber sample and clonal spread of E. coli, C. freundii, and K. pneumoniae isolates were all observed between vegetable types and/or cities. IncX3 plasmids carrying blaNDM from E. coli and C. freundii showed identical or highly similar RFLP patterns, and the sequenced IncX3 plasmid from cucumber was also identical or highly similar (99%) to the IncX3 plasmids from clinical patients reported in other countries, while blaKPC−2 in K. pneumoniae was mediated by similar F35:A-:B1 plasmids. Our results suggest that both clonal expansion and horizontal transmission of IncX3- or F35:A-:B1-type plasmids may mediate the spread of CRE in ready-to-eat vegetables in China. The presence of CRE in ready-to-eat vegetables is alarming and constitutes a food safety issue. To our knowledge, this is the first report of either the C. freundii carrying blaNDM, or K. pneumoniae harboring blaKPC−2 in vegetables. This is also the first report of ST23 carbapenem-resistant hvKP strain in vegetables.

Characterization of an NDM-5 carbapenemase-producing Escherichia coli ST156 isolate from a poultry farm in Zhejiang, China

“…Among these plasmids, 9 published plasmids were selected and constructed by BRIG (Fig. 2b), including pVH1 (vegetable, China, 46,161 bp) [25], pNDM_MGR194 (human, India, 46,253 bp) [27], pECNDM101 (swine, China, 46,165 bp) [23], pEC463-NDM5 (human, China, 46,145 bp) [28], pBJ114–46 (human, China, 46,161 bp) [29], pEsco-5256cz (human, Czech, 46,161 bp) [30], pEc1929 (human, China, 46,164 bp) [31], pTB203 (layer hen, China, 46,161 bp, in this study), and pZSH6-blaNDM-5 (human, China, 46,161 bp) [32]. The results of BLAST homology analyses showed that these plasmids had more than 99.9% identity and 99.8% query coverage with each other.…”

“…In China, many pathogens carrying bla NDM-5 have been isolated from patients [18–21]. In addition, bla NDM-5 can also be isolated from pigs [22, 23], dairy cows [24] and vegetables [25]. The complete sequences of bla NDM-5 -harboring plasmids have been helpful for the study of the transmission of the bla NDM-5 gene, although not all of these plasmids have been reported.…”

Plasmid evolution in carbapenemase‐producing Enterobacteriaceae: a review

“…A hospital sewage in China was found to contain C. freundii that carried an IncX3 plasmid harboring bla NDM‐1 . Another study in China reported IncX3 plasmids in NDM‐1–producing isolates collected from ready‐to‐eat vegetables . Other countries, such as Australia, Canada, and Italy, reported other plasmid types, including IncFII, IncR, IncP, and L/M, in Citrobacter spp .…”

Characterization of carbapenem non-susceptible Gram-negative Bacilli isolated from the feces of 10,000 inpatients in Southern China

“…In this study, the plasmid harboring the mcr gene in K. pneumoniae was similar to other IncHI2-type plasmids present in E. coli, and upstream of the mcr gene was the common ISApl1 transposon. NDM-5 has been reported in many other countries, including India [19], China [20], Denmark [21], Italy [22], America [23], and Spain [24]; it has also been isolated from pigs [25,26], dairy cows [27], and vegetables [28]. In the present study, the IncX3 plasmids harboring bla NDM−5 were highly similar in various sources, suggesting their ability to be an e cient vehicle for bla NDM−5 dissemination among humans, animals, food, and the environment via the human intestine.…”