(See the editorial commentary by Chow, on pages 332–4 ) Background. Despite advances in medical practices, in recent decades permanent reductions in joint function have not been achieved, and the high mortality rate of patients with staphylococcal septic arthritis has not substantially improved. Methods. We evaluated the effects of a combined tumor necrosis factor (TNF) inhibitor and antibiotic therapy on the course of Staphylococcus aureus arthritis and sepsis in mice. Results. Treatment with the combination of a TNF inhibitor and an antibiotic resulted in a quicker relief of clinical arthritis in mice with septic arthritis, compared with an antibiotic monotherapy. Both histopathologically verified synovitis and the extent of joint destruction were reduced by this combined treatment. Importantly, anti-TNF treatment significantly improved the survival rate of mice with S. aureus sepsis and staphylococcal enterotoxin shock syndrome; this effect might be the result of a partial restoration of the hemostatic balance between coagulation and fibrinolysis. Finally, we demonstrated that anti-TNF treatment downregulates high-mobility group protein B1 in staphylococcal enterotoxin shock syndrome. Conclusions. Thus, simultaneous systemic TNF inhibition and antibiotic therapy has beneficial effects on the outcome of S. aureus arthritis and sepsis in a mouse model, suggesting that the combination of a TNF inhibitor and antibiotics represents a novel therapeutic strategy for the treatment of staphylococcal infections.

Autoimmune diseases including rheumatoid arthritis (RA) involve immune reactions against specific antigens. The type I IFN system is suspected to promote autoimmunity in systemic lupus erythematosus, but may also dampen immune reactions in e.g. inflammatory bowel disease. This prompted us to investigate the role of type I IFN in antigen‐induced arthritis (AIA). The importance of type I IFN in methylated (m) BSA‐induced arthritis was studied by using mice deficient for the type I IFN receptor (IFNAR) and by administration of the IFN‐α activator viral double‐stranded (ds) RNA or recombinant IFN‐α at antigen sensitization. In IFNAR knock‐out mice, arthritis severity was significantly higher than in WT mice. Administration of dsRNA at antigen sensitization protected WT but not IFNAR KO mice from arthritis. Also, addition of recombinant IFN‐α during the immunization, but not the induction phase of arthritis, almost abolished arthritis. Protection mediated by IFN‐α was accompanied by delayed and decreased antigen‐specific proliferative responses, including impaired lymph node recall responses after intra‐articular antigenic challenge. In conclusion, we demonstrate that type I IFN can prevent joint inflammation by downregulating antigen‐specific cellular immunity.

The report describes a 44-year-old female patient who died of the rare acute purulent pericarditis caused by Klebsiella pneumoniae (KP). The genomic analysis revealed an extensively drug-resistant ST11-K64 KP strain from five isolates (blood cultures, urine, ascites, pericardial effusion, and sputum). Several high virulence (hv) and carbapenem-resistant (CR) genes were identified in the pericardial effuse isolate. The isolates showed low resistance to healthy human serum. This study highlights the potential lethality of CR-hvKP infections in patients suffering from underlying comorbidities such as diabetes mellitus and chronic ailments.

Background: The rising prevalence of infections caused by carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-hvKP) has outpaced our understanding of their evolutionary diversity. By straining the antimicrobial options and constant horizontal gene transfer of various pathogenic elements, CR-hvKP poses a global health threat. Methods: Six KP isolates (KP1~KP6) from urine, sputum and groin infection secretion of a single patient were characterized phenotypically and genotypically. The antimicrobial susceptibility, carbapenemase production, hypermucoviscosity, serum resistance, virulence factors, MLST and serotypes were profiled. Genomic variations were identified by whole-genome sequencing and the phylogenetic differentiation was analyzed by Enterobacterial repetitive intergenic consensus (ERIC)-PCR. Results: All KP strains were multi-drug resistant. Four of them (KP1, KP3, KP5 and KP6) belonged to ST11-K64, with high genetic closeness (relatedness coefficient above 0.96), sharing most resistance and virulence genes. Compared with KP1, the later isolates KP3, KP5 and KP6 acquired bla_KPC-1 and lost bla_SHV-182 genes. KP2 and KP4 had the same clonal origin of ST35-K16 (relatedness coefficient 0.98), containing almost identical genes for resistance and virulence. They were non-mucoid and carried bla_NDM-5 gene. Conclusion: A co-infection with two types of CR-hvKP affiliated with different clades within a single patient amplified the treatment difficulties. In addition to source control and epidemiological surveillance, investigation of the in-host interactions between CR-hvKP variants may provide valuable treatment solutions.

Carbapenem-resistant Enterobacteriaceae (CRE) infections constitute a threat to public health, and KPC and NDM are the major carbapenemases of concern. Rapid diagnostic tests are highly desirable in point-of-care (POC) and emergency laboratories with limited resources. Here, we developed a multiplex lateral flow assay based on asymmetric PCR and barcode capture probes for the simultaneous detection of KPC-2 and NDM-1. Biotinylated barcode capture probes corresponding to the KPC-2 and NDM-1 genes were designed and cast onto two different sensing zones of a nitrocellulose membrane after reacting with streptavidin to prepare a multiplex lateral flow strip. Streptavidin-coated gold nanoparticles (SA-AuNPs) were used as signal reporters. In response to the target carbapenemase genes, biotin-labelled ssDNA libraries were produced by asymmetric PCR, which bond to SA-AuNPs via biotin and hybridise with the barcode capture probe via a complementary sequence, thereby bridging SA-AuNPs and the barcode capture probe to form visible red lines on the detection zones. The signal intensities were proportional to the number of resistance genes tested. The strip sensor showed detection limits of 0.03 pM for the KPC-2 and 0.07 pM for NDM-1 genes, respectively, and could accurately distinguish between KPC-2 and NDM-1 genes in CRE strains. For the genotyping of clinical isolates, our strip exhibited excellent consistency with real-time fluorescent quantitative PCR and gene sequencing. Given its simplicity, cost-effectiveness, and rapid analysis accomplished by the naked eye, the multiplex strip is promising auxiliary diagnostic tool for KPC-2 and NDM-1 producers in routine clinical laboratories.

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a major pathogen responsible for urinary tract infections (UTIs). However, its role and characteristics in recurrent urinary tract infections (rUTIs) remain poorly understood. Investigating its features in rUTIs may provide insights into effective prevention strategies. Methods: We analyzed a cohort of patients with rUTIs caused by Klebsiella pneumoniae from April 2020 to April 2024. Antibiotic susceptibility of the isolates was evaluated. Biofilm Formation Assay and Galleria mellonella infection models were employed to assess the virulence of the strains. Polymerase Chain Reaction (PCR) and whole-genome sequencing (WGS) were utilized to determine multilocus sequence typing (MLST) and capsular serotyping, as well as to identify resistance genes, virulence genes, and plasmid replicons. Phylogenetic relationships among the isolates were also established. Results: A total of 41 patients with rUTIs were included, with 56.1% caused by CRKP. 97.01% of CRKP carry the bla_KPC-2 gene. Compared to patients infected with carbapenem-susceptible Klebsiella pneumoniae (CSKP), those infected with CRKP had a higher prevalence of underlying diseases and complications. Both groups of strains exhibited a high degree of antibiotic resistance. CRKP strains demonstrated enhanced biofilm formation capacity and greater lethality in Galleria mellonella infection models. The predominant phenotype of the CRKP strain was ST11 KL64, whereas the CSKP strain showed multiple phenotypes in different patients. Sequencing analyses revealed that both groups of strains carried a wide range of virulence genes, resistance genes, and plasmid replicons. Among the cases of rUTIs, 31 were identified as relapses caused by the same strain, with no significant differences between the initial and final infection strains. Conclusion: This study demonstrates that patients with rUTIs caused by CRKP present significant complexity in terms of clinical features, strain resistance and virulence properties. When managing UTIs caused by CRKP, special care needs to be taken to manage recurrent infections.