Coexistence of tet(A) and blaKPC-2 in the ST11 hypervirulent tigecycline- and carbapenem-resistant Klebsiella pneumoniae isolated from a blood sample.

Carbapenem-resistant Klebsiella pneumoniae are distributed worldwide. This study aimed to characterize a hypervirulent tigecycline-resistant and carbapenem-resistant Klebsiella pneumoniae strain, XJ-K2, collected from a patient's blood. We tested antimicrobial susceptibility, virulence, and whole-genome sequencing (WGS) on strain XJ-K2. WGS data were used to identify virulence and resistance genes and to perform multilocus sequence typing (MLST) and phylogenetic analysis. Three novel plasmids, including a pLVPK-like virulence plasmid (pXJ-K2-p1) and two multiple resistance plasmids (pXJ-K2-KPC-2 and pXJ-K2-p3), were discovered in strain XJ-K2. The IncFII(pCRY) plasmid pXJ-K2-p3 carried the dfrA14, sul2, qnrS1, blaLAP-2, and tet(A) resistance genes. The IncFII(pHN7A8)/IncR plasmid pXJ-K2-KPC-2 also carried a range of resistance elements, containing rmtB, blaKPC-2, blaTEM-1, blaCTX-M-65, and fosA3. MLST analysis revealed that strain XJ-K2 belonged to sequence type 11 (ST11). Seven complete phage sequences and many virulence genes were found in strain XJ-K2. Meanwhile, antimicrobial susceptibility tests and G. mellonella larval infection models confirmed the extensively drug resistance (XDR) and hypervirulence of KJ-K2. To our knowledge, this is the first observation and description of the ST11 hypervirulent tigecycline- and carbapenem-resistant K. pneumoniae strain co-carrying blaKPC-2 and the tet(A) in a patient's blood in China. Further investigation is needed to understand the resistance and virulence mechanisms of this significant hypervirulent tigecycline- and carbapenem-resistant strain.

Phage Selective Pressure Reduces Virulence of Hypervirulent Klebsiella pneumoniae Through Mutation of the wzc Gene.

Hypervirulent Klebsiella pneumoniae (hvKp), one of the major community-acquired pathogens, can cause invasive infections such as liver abscess. In recent years, bacteriophages have been used in the treatment of K. pneumoniae, but the characteristics of the phage-resistant bacteria produced in the process of phage therapy need to be evaluated. In this study, two Podoviridae phages, hvKpP1 and hvKpP2, were isolated and characterized. In vitro and in vivo experiments demonstrated that the virulence of the resistant bacteria was significantly reduced compared with that of the wild type. Comparative genomic analysis of monoclonal sequencing showed that nucleotide deletion mutations of wzc and wcaJ genes led to phage resistance, and the electron microscopy and mucoviscosity results showed that mutations led to the loss of the capsule. Meanwhile, animal assay indicated that loss of capsule reduced the virulence of hvKp. These findings contribute to a better understanding of bacteriophage therapy, which not only can kill bacteria directly but also can reduce the virulence of bacteria by phage screening.

Co-occurrence of three different plasmids in an extensively drug-resistant hypervirulent Klebsiella pneumoniae isolate causing urinary tract infection.

OBJECTIVES: A single carbapenem-resistant, hypervirulent Klebsiella pneumoniae strain has attracted major public concern. The aim of the present study was to better understand the antimicrobial resistance and genetic characteristics of Klebsiella pneumoniae strain XJ-K1. METHODS: Klebsiella pneumoniae strain XJ-K1 was isolated from a urine specimen of a 69-year-old male patient in a teaching hospital in Shanghai, China, in January 2018. Antimicrobial susceptibility testing, string test, whole-genome sequencing, bioinformatics analysis and phylogenetic analysis were performed in this study. RESULTS: Klebsiella pneumoniae XJ-K1 was an extensively drug-resistant (XDR) hypervirulent strain that showed high-level resistance to antibacterial agents. Three novel plasmids were discovered in strain XJ-K1, including a 207,409-bp IncHI1B-type rmpA2-bearing pLVPK-like virulence plasmid, a 130,628-bp Col156/IncFIB/IncFII-type aadA2-, sul1-, mph(A)- and dfrA12-bearing MDR plasmid, and a 99,408-bp IncFII/IncR-type blaKPC-2-, blaTEM-1-, blaCTX-M-65-, blaSHV-12-, rmtB- and fosA3-bearing MDR plasmid. Sequence analysis of the chromosome revealed that the aadA2, fosA and sul1 genes were harboured by XJ-K1. Multilocus sequence typing (MSLT) showed that XJ-K1 was ST11. CONCLUSIONS: A large number of resistance genes and a pLVPK-like virulence plasmid carried by Klebsiella pneumoniae strain XJ-K1 might be the main reasons leading to the XDR and hypervirulent phenotype. To the best of our knowledge, this is the first report in China on the co-occurrence of a pLVPK-like virulence plasmid and two MDR plasmids in a single ST11 XDR and hypervirulent Klebsiella pneumoniae isolated from patient urine, which is a serious concern for its further spread.