"Superbugs" with hypervirulence and carbapenem resistance in Klebsiella pneumoniae: the rise of such emerging nosocomial pathogens in China

Molecular Characteristics of Virulence Genes in Carbapenem-Resistant and Carbapenem-Sensitive Klebsiella Pneumoniae in Relation to Different Capsule Serotypes in Ningbo, China

Background

Klebsiella pneumoniae (KP) is a common nosocomial pathogen. Capsules are an important component of KP's virulence, among which the K1, K2, K5, K20, K54, and K57 serotypes are predominant and exhibit varying degrees of virulence.

Methods

The capsule and virulence genes of 150 carbapenem-resistant Klebsiella pneumoniae (CRKP) and 213 carbapenem-sensitive Klebsiella pneumoniae (CSKP) isolates were examined by polymerase chain reaction (PCR). The isolates were tested for hypermucoviscosity by string tests. Phylogenetic relationships between KP isolates were analyzed using multilocus sequence typing (MLST) and a Galleria mellonella infection model confirmed the differences in virulence.

Results

A total of 111 of 363 isolates of KP were detected, the highest detected serotypes were K1, K5, and K2, and CSKP was detected more frequently than CRKP. There was a greater prevalence of K1 and K2 serotypes in CSKP, while in CRKP, K5 serotypes were more prevalent. K1 isolates had the highest detection rates for hypermucoviscosity Klebsiella pneumoniae (hmKP) and hypervirulent Klebsiella pneumoniae (hvKP), and carried the most virulence genes. K54 isolates had the lowest detection rate of hmKP while K5 isolates had the lowest detection rate of hvKP and carried the fewest virulence genes. MLST results for serotypes K1, K20, and K57 showed significant homogeneity, while those for serotypes K2, K5, and K54 showed diversity. The Galleria mellonella infection model showed that the K1 serotype was the most virulent and the K54 serotype was the weakest.

Conclusion

CSKP isolates were detected more frequently than CRKP isolates for capsular serotype detection. K1 isolates had the most virulence gene and strongest virulence, K5 isolates carried the fewest virulence genes, and K54 isolates had the weakest virulence. Furthermore, significant homogeneity was observed among K1, K20, and K57 isolates.

Combination Therapy for OXA-48 Carbapenemase-Producing Klebsiella Pneumoniae Bloodstream Infections in Premature Infant: A Case Report and Literature Review

The prevalence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has been increasing in recent years. Chinese Infectious Disease Surveillance of Pediatrics (ISPED) showed that in 2022, its resistance rate to meropenem was 18.5%. However, there is limited data available on the treatment of CRKP infection in neonates. In this study, we present a case involving a premature infant infected with OXA-48-producing Klebsiella pneumoniae. The combined susceptibility test revealed a significant synergistic effect between ceftazidime-avibactam(CAZ-AVI), and aztreonam(ATM). The infection was successfully treated with a combination of CAZ-AVI, ATM, and fosfomycin. This case represents the first reported instance of sepsis in a premature infant caused by OXA-48-producing Klebsiella pneumoniae in China. The objective of our study is to evaluate the effectiveness and safety of combination therapy in treating CRKP infections in premature infants. We hope that the findings of this study will provide valuable insights for clinicians in their treatment approach.

Acquisition of a stable and transferable plasmid coharbouring hypervirulence and MDR genes with low fitness cost: Accelerating the dissemination of ST11-KL64 CR-HvKP

OBJECTIVES

This study aimed to delineate the ability of a plasmid, pS130-4, which harboured both hypervirulence and multidrug resistance genes, to disseminate within Klebsiella pneumoniae, as well as its potential formation mechanism.

METHODS

We employed whole-genome sequencing to decipher the genetic architecture of pS130-4. Its capability to conjugate and transfer was assessed through a series of experiments, including plasmid stability, competitive growth, and growth curve analysis. Its expression stability was further evaluated using drug sensitivity, larval survival, and biofilm formation tests.

RESULTS

pS130-4 contained four intact modules typical of self-transmissible plasmids. BLAST analysis revealed a sequence identity exceeding 90% with other plasmids from a variety of hosts, suggesting its broad prevalence. Our findings indicated the plasmid's formation resulted from IS26-mediated recombination, leading us to propose a model detailing the creation of this conjugative fusion plasmid housing both blaKPC-2 and hypervirulence genes. Our conjugation experiments established that pS130-4, when present in the clinical strain S130, was self-transmissible with an estimated efficiency between 10-5 and 10-4. Remarkably, pS130-4 showcased a 90% retention rate and did not impede the growth of host bacteria. Galleria mellonella larval infection assay demonstrated that S130 had pronounced toxicity when juxtaposed with high-virulence control strain NTUH-K2044 and low-toxicity control strain ATCC700603. Furthermore, pS130-4's virulence remained intact postconjugation.

CONCLUSION

A fusion plasmid, encompassing both hypervirulence and multidrug resistance genes, was viable within K. pneumoniae ST11-KL64 and incurred minimal fitness costs. These insights underscored the criticality of rigorous monitoring to pre-empt the escalation and distribution of this formidable super-plasmid.