Objectives: This study aimed to identify differences in risk factors for carbapenem-resistant Enterobacteriaceae (CRE) infections across different anatomical sites and to explore risk factors associated with mortality in CRE-infected patients. Methods: Patients who underwent CRE screening and were subsequently diagnosed with CRE infections were included and categorized by infection site: respiratory tract (RTI), urinary tract (UTI), and bloodstream (BSI). Forty ICU patients without CRE infection were randomly selected as controls. Statistical comparisons were performed using the Mann–Whitney U or Chi-square test, as appropriate. Potential risk factors were evaluated via univariate and multivariate analyses, and a predictive model was constructed, with its performance assessed using ROC curve analysis. Results: CRE colonization was identified as a common independent risk factor across all three groups (RTI, UTI, and BSI). Infection-site-specific analyses revealed independent risk factors: RTI was associated with mechanical ventilation, UTI with trauma, and BSI with gastrointestinal injury. Predictive models for RTI, UTI, and BSI demonstrated good discrimination, with ROC AUCs of 0.94, 0.94, and 0.95, respectively. In the analysis of Survived versus Deceased patients, the BSI group had the highest mortality, though the difference was not statistically significant. Deceased patients exhibited significantly higher PCT levels than Survived patients (p = 0.005). Prior use of carbapenems and antifungal agents, as well as Ln(PCT), were independently associated with mortality in CRE-infected patients. Conclusions: Risk factors for CRE infections vary across anatomical sites, with CRE colonization, mechanical ventilation, trauma, and gastrointestinal injury playing key roles. Overuse of antibiotics and elevated inflammatory responses are associated with increased mortality. These findings provide evidence for early identification of high-risk patients and optimization of individualized treatment strategies.

Background: Trichosporon japonicum is a rare but highly lethal pathogen causing fungemia in immunocompromised patients. With the expanding use of chimeric antigen receptor T (CAR-T) cell therapy, the spectrum of opportunistic fungal infections is changing, yet data on T. japonicum infections in this setting remain scarce. Case Presentation: A 69-year-old man with diffuse large B-cell lymphoma developed catheter-associated fungemia after CAR-T cell reinfusion. He initially presented with neck pain and white oral mucosal patches, followed by fever four days later. T. japonicum was isolated from both peripheral blood and central venous catheter tip cultures, identified by microscopic examination, mass spectrometry, and molecular sequencing. Antifungal prophylaxis was initiated before fever onset based on close monitoring of white blood cell count, procalcitonin, interleukin-6, and C-reactive protein; treatment was subsequently adjusted according to species identification and antifungal susceptibility results. Infection was controlled within two weeks after catheter removal and immune recovery. The patient remained well at six-month follow-up. Conclusion: This case adds to the limited literature on T. japonicum fungemia in patients receiving CAR-T therapy. Our experience, together with a review of the literature, underscores that successful management requires prompt catheter removal, immune restoration, and combination therapy with voriconazole and amphotericin B, as echinocandin monotherapy should be avoided. Awareness of this pathogen in immunocompromised patients is critical.

Background: The emergence of polymyxin-resistant, carbapenem-resistant Klebsiella pneumoniae (CRKP) presents a critical challenge to clinical management. This study aimed to delineate the molecular mechanisms driving the acquisition of polymyxin resistance in CRKP. Methods: We analyzed polymyxin-susceptible and polymyxin-resistant CRKP isolates obtained from a single patient. Antimicrobial susceptibility testing was performed to determine the minimum inhibitory concentrations. Whole genome sequencing was employed to identify variations in two-component systems and to screen for mcr genes, which were involved in polymyxin resistance. Differential gene expression was assessed using RNA sequencing and validated by quantitative real-time PCR. Furthermore, site-directed mutagenesis was utilized to confirm the causal role of specific mutations in conferring the resistant phenotype. Results: An L96P mutation in the PhoQ protein was found in the polymyxin-resistant CRKP isolate. Compared with the PhoQ wild-type, this mutation significantly upregulated expression of phoP/Q, pmrD, and arnBCADTEF operon-related genes. A corresponding L96P mutant was subsequently constructed in the polymyxin-susceptible ATCC 13883 strain via site-directed mutagenesis. Antimicrobial susceptibility testing confirmed that the PhoQ L96P mutation elevates the minimal inhibitory concentrations of colistin and polymyxin B to 64 mg/L and >32 mg/L, respectively, from a baseline of 0.5 mg/L. Conclusions: The PhoQ L96P mutation is a pivotal driver of polymyxin resistance in CRKP, primarily mediated through the upregulation of the arnBCADTEF operon.