The Occurence of Colistin-Resistant Hypervirulent Klebsiellapneumoniae in China

Hypervirulent Klebsiella pneumoniae strains are usually susceptible to many antimicrobial agents including colistin. Here we report the isolation and characterization of several colistin-resistant hypervirulent K. pneumoniae clinical strains. K. pneumoniae strains recovered from blood samples were collected at a university hospital in China. MICs of colistin were determined using microdilution. Colistin-resistant strains were subjected to whole genome sequencing to reveal their clonal background, antimicrobial resistance determinants and virulence factors. Virulence assays were performed with strains carrying the mucoid phenotype regulator gene rmpA using wax moth larvae. The pmrB gene encoding a P344L substitution was cloned into a colistin-susceptible K. pneumoniae strain to examine whether the substitution confers colistin resistance. Five colistin-resistant hypervirulent K. pneumoniae were recovered from blood samples of patients in China, belonging to four sequence/capsular types (ST23:K1, ST412:K57, ST660:K16, and ST700:K1) and carried the virulence factor rmpA. Three strains had the known colistin-resistant D150G substitution in PhoQ including one ST700:K1 strain also carrying mcr-1. The remaining two isolates had a P344L substitution of PmrB but cloning of pmrB encoding the substitution into a colistin-susceptible isolate did not alter MICs of colistin, suggesting that such a substitution did not confer resistance to colistin. In conclusion, the convergence of colistin resistance and hypervirulence in K. pneumoniae of multiple clonal backgrounds has emerged and may warrant further surveillance

Anti-hepatotoxic and anti-oxidant effects of extracts from Piper nigrum L. root

The aim of this study was to investigate the effect of Piper nigrum L. root extracts on carbon tetrachloride (CCl4)-induced rat liver injury. Among the three different extracts (water, ethanol and chloroform extract), ethanol extract exhibits the highest hepatoprotective activity (p < 0.05). When using the ethanol extract at a dose of 120 mg/ kg to treat the CCl4-intoxicated rat, the activities of alanine transaminase (ALT) and aspartate transanimase (AST) in rat serum decreased to 65.7 and 84.5%, respectively. At the same time, the lipid peroxidation (MDA) decreased to 52.3% and glutathione (GSH) increased to 55.8% in the rats liver homogenate, as compared with those of the CCl4 positive control rats. The hepatoprotective effect of ethanol extract was also supported by the histopathological observations. Moreover, the ethanol extract was studied for its in vitro antioxidant activity using the methods of ferric thiocyanate (FTC) and thiobarbituric acid (TBA). The findings indicate that the ethanol extract of P. nigrum L. root is an efficient hepatoprotective and antioxidant agent against CCl4-induced liver injury.Keywords: Piper nigrum L. root, ethanol extract, carbon tetrachloride (CCl4), hepatoprotective, antioxidan

The co-transfer of plasmid-borne colistin-resistant genes mcr-1 and mcr-3.5, the carbapenemase gene blaNDM-5 and the 16S methylase gene rmtB from Escherichia coli

We found an unusual Escherichia coli strain with resistance to colistin, carbapenem and amikacin from sewage. We therefore characterized the strain and determined the co-transfer of the resistance determinants. Whole genome sequencing was performed using both Illumina HiSeq X10 and MinION sequencers. Short and long reads were subjected to de novo hybrid assembly. Sequence type, antimicrobial resistance genes and plasmid replicons were identified from the genome sequences. Phylogenetic analysis of all IncHI2 plasmids carrying mcr-1 available in GenBank was performed based on core genes. Conjugation experiments were performed. mcr-3.5 was cloned into E. coli DH5α. The strain belonged to ST410, a type with a global distribution. Two colistin-resistant genes, mcr-1.1 and mcr-3.5, a carbapenemase gene blaNDM-5, and a 16S methylase gene rmtB were identified on different plasmids of IncHI2(ST3)/IncN, IncP, IncX3 and IncFII, respectively. All of the four plasmids were self-transmissible and mcr-1.1, mcr-3.5, blaNDM-5 and rmtB were transferred together. mcr-1-carrying IncHI2 plasmids belonged to several sequence types with ST3 and ST4 being predominant. MIC of colistin (4 μg/ml) for DH5α containing mcr-3.5 was identical to that containing the original mcr-3 variant. In conclusion, carbapenem resistance, colistin resistance and high-level aminoglycoside resistance can be transferred together even when their encoding genes are not located on the same plasmid. The co-transfer of multiple clinically-important antimicrobial resistance represents a particular challenge for clinical treatment and infection control in healthcare settings. Isolates with resistance to both carbapenem and colistin are not restricted to a given sequence type but rather are diverse in clonal background, which warrants further surveillance. The amino acid substitutions of MCR-3.5 have not altered its activity against colistin.</p

The coexistence of two ^blaNDM-5 genes on an IncF plasmid as revealed by nanopore sequencing

ABSTRACT In a carbapenem-resistant Escherichia coli clinical isolate of sequence type 167, two copies of bla NDM-5 were found on a 144,225-bp IncF self-transmissible plasmid of the F36:A4:B − type. Both bla NDM-5 genes were located in 11,065-bp regions flanked by two copies of IS 26 . The two regions were identical in sequence but were present at different locations on the plasmid, suggesting a duplication of the same region. This study highlights the complex genetic contexts of bla NDM-5 . </jats:p

IncP plasmid carrying the colistin resistance gene mcr-1 in Klebsiella pneumoniae from hospital sewage

A Klebsiella pneumoniae strain of sequence type 313 (ST313) recovered from hospital sewage was found carrying the plasmid-borne colistin resistance gene mcr-1, which was bracketed by two copies of the insertion sequence ISApl1 on a 57-kb self-transmissible IncP-type plasmid of a new IncP-1 clade. The carriage of mcr-1 on a self-transmissible broad-host-range plasmid highlights that mcr-1 has the potential to spread beyond the Enterobacteriaceae family

Cryptic transmission of ST405 Escherichia coli carrying bla_NDM-4 in hospital

Abstract Three carbapenem-resistant Escherichia coli were recovered from rectal swabs of different patients in a tertiary hospital and were found carrying bla NDM-4, an uncommon bla NDM variant. Genome sequences of the isolates were obtained using Illumina technology and the long-read MinION sequencer. The isolates belonged to ST405 and phylogenetic group D, a globally distributed lineage associated with antimicrobial resistance. In addition to bla NDM-4, the three isolates carried 14 known resistance genes including the extended-spectrum β-lactamase gene bla CTX-M-15. There were only 1 or 2 SNPs between the isolates, suggesting a common origin and cryptic transmission in hospital. bla NDM-4 was located on a 46.5-kb IncFIA self-transmissible plasmid, which may facilitate further dissemination of bla NDM-4. Two copies of IS26 bracketed a 14.6-kb region containing bla NDM-4 and have the potential to form a composite transposon for mediating the mobilization of bla NDM-4