To provide an overview of the current epidemiology of resistant bacterial infections in hematopoietic cell transplant (HCT) recipients, evaluate recent outcome data, and discuss available treatment strategies in this population. Recent studies report an increasing incidence of infections caused by multidrug-resistant bacteria among HCT recipients, with marked geographical variability and a significant impact on morbidity and mortality. Several novel agents, including new β-lactam/β-lactamase inhibitors and cefiderocol, have expanded treatment options for resistant Gram-negative infections. However, most evidence supporting their efficacy derives from studies conducted in the general population, as immunocompromised and HCT patients are frequently underrepresented in clinical trials. In recent years, growing real-world and observational data have become available specifically in immunocompromised patients, supporting treatment approaches largely consistent with those recommended for the general population, while highlighting important clinical considerations, such as empirical therapy in patients at risk for resistant infections. Ceftolozane-tazobactam is a preferred option for difficult-to-treat Pseudomonas aeruginosa , with combination therapy reserved for selected severe cases. Cefiderocol should be considered in specific scenarios, particularly infections caused by susceptible metallo-β-lactamase-producing organisms. For resistant Gram-positive infections, optimized daptomycin dosing is recommended. Antimicrobial stewardship strategies, including de-escalation and shorter treatment courses for Gram-negative bloodstream infections, are essential to preserve the efficacy of novel agents.

Conventional microbiological tests have limitations in the microbial diagnosis of immunocompromised patients. Next-generation sequencing (NGS) technologies have the potential to overcome some of these challenges by enabling rapid, comprehensive, and hypothesis-free pathogen detection, potentially improving the speed and accuracy of microbial diagnosis and subsequent clinical outcomes. This review summarizes current evidence for the use of NGS technologies in immunocompromised populations, highlights areas of demonstrated clinical impact, and identifies key priorities for broader clinical integration. Case reports and series have demonstrated the utility of NGS in diagnosing unusual or atypical infections amongst immunocompromised patients that were initially missed by conventional methods. Retrospective observational studies indicate that NGS can achieve higher sensitivity and greater pathogen detection rates than conventional diagnostics, although performance may be limited for certain pathogens, such as Aspergillus and Mycobacterial species. The clinical impact of NGS-guided interventions varies, reflecting both differences in study design and challenges in interpreting metagenomic data. NGS technologies have the potential to enhance microbial diagnosis in immunocompromised patients, particularly in complex, polymicrobial, or atypical infections where conventional methods fail. However, widespread clinical adoption is limited by high costs, complex workflows, and the need for advanced bioinformatics infrastructure and expertise. Further research is required to define clinical impact, cost-effectiveness, and to standardize workflows and guide optimal time for implementation, in order to inform evidence-based integration of NGS into routine clinical practice.

Pleural Tuberculosis.

Mechanistic insights into restoration of gut barrier and microbiota homeostasis by allicin and Qingchang Huashi formula in Cryptosporidium parvum-infected immunosuppressed murine model.

To summarize current approaches to isolation precautions and infection prevention and control (IPC) practices in immunocompromised hosts, including patients with hematologic malignancies, those receiving cellular therapies, and transplant recipients, with attention to variability in evidence and practice. Standard and transmission-based precautions remain foundational but often require adaptation for immunocompromised populations due to increased infection severity, prolonged pathogen shedding, and heightened transmissibility. Protective environments, including HEPA (high-efficiency particulate air) filtration and positive pressure rooms, may be of benefit for the highest risk populations but are resource-intensive and inconsistently applied. Emerging data support strategies such as universal masking to reduce respiratory viral infections (RVIs) and tailored transmission-based precautions. The role of multidrug-resistant organism (MDRO) screening and isolation continues to evolve, with mixed evidence and reconsideration of prior practices. Enhanced environmental cleaning and no-touch disinfection technologies hold potential but lack consistent outcome data. Several long-standing practices, including the neutropenic diet, are increasingly being re-evaluated. IPC in immunocompromised patients is complex and multifaceted, with limited high-quality evidence guiding practice resulting in significant practice variability. A shift toward individualized, risk-adapted strategies - balancing risk mitigation, resource utilization, and patient-centered care - will ultimately optimize outcomes.

Comparative and subtractive genomics reveals novel therapeutic targets in cystic fibrosis-associated multidrug-resistant Pandoraea sputorum.

Multidrug-resistant Gram-negative bloodstream infections (MDR-GNBSI) are increasingly frequent in immunocompromised hosts, particularly solid organ transplant (SOT) recipients and patients with haematological malignancy (HM) receiving intensive chemotherapy and/or cellular therapies. We summarize current evidence and practical approaches across empirical, quasi-targeted and targeted management. Contemporary cohorts show rising rates of MDR-GNBSI in both SOT and HM patients. Appropriate therapeutic management is key to ensure good clinical outcome while minimizing ecological impact. Risk-adapted empirical therapy usually incorporates prior colonization and local epidemiology plus individual risk factors, thus screening could play central role. Rapid diagnostic testing can reduce time to appropriate and proportionate therapy, but currently the majority of them provide genotypic resistance that in Gram negatives can be difficult to interpret, in addition off-target resistance mechanisms should be considered mainly in nonfermenter bacteria. Thus, machine-learning models and structured BSI bundles are emerging tools to support early decision-making and stewardship. For targeted therapy, novel β-lactam/β-lactamase inhibitor combinations and cefiderocol expand options for carbapenem-resistant strains; pharmacokinetics/pharmacodynamics (PK/PD) optimization may improve target attainment and mitigate resistance selection. Evidence supporting oral step-down and shorter courses is growing, whereas routine follow-up blood cultures remain controversial due to observational bias. MDR-GNBSI management in immunocompromised patients requires individualized, data-driven strategies integrating risk stratification, rapid microbiology, and PK/PD optimization. Pursuing antimicrobial stewardship principles in these populations remains a priority.

FTIR spectroscopy of peripheral blood mononuclear cells and machine learning: Spectral biomarkers for bacteremia, focal bacterial, and viral infections.

Bloodstream infections in immunocompromised adult patients.

Seroepidemiology, clinical correlates, and GRA6-based genotyping of Toxoplasma gondii among immunocompromised patients in northeastern Iran.

Genomic surveillance captures resistance evolution in Salmonella enterica ST376 during prolonged disseminated infection in an immunocompromised patient from the United Arab Emirates.

Cyclospora cayetanensis is an emerging notifiable food-and-water-borne coccidian parasite causing gastro-intestinal-disease in humans. Detailed information about its biology-associated risk-factors and routes of transmission remain poorly understood; the lack-of-comprehensive epidemiological data underlines a critical need for targeted research into effective prevention and control. Acid variable (pink to brilliant red colour) oocysts of Cyclospora spp. were observed in 16/162 samples, predominantly in 51-60 years males in October. Most cases were among transplant recipients presenting with diarrhoea, therapeutic options among whom remains limited.

Is it justified to order an upfront cytomegalovirus immunohistochemical stain in patients with severe inflammatory bowel disease and ulceration?

E. bieneusi microsporidiosis is an opportunistic infection in immunocompromised patients. There is a lack of established treatment strategies. In this report, we present an overview of the available literature and three cases of E. bieneusi infection in renal transplant recipients.

Multidrug-resistant Acinetobacter baumannii: Molecular insights, clinical challenges, and therapeutic approaches.

Treatment of acute experimental toxoplasmosis using a promising therapy: Nitrogen-doped carbon dots.

Cost-Effectiveness of Vaccine for the Prevention of Herpes Zoster in Kidney Transplant Recipients in Thailand.

Pneumocystis jirovecii is a major cause of morbidity and mortality in HIV. It also poses a significant risk to non-HIV immunocompromised patients, especially those with cancer or recent chemotherapy. We evaluated risk factors, diagnostic markers-including lactate dehydrogenase (LDH)-and mortality predictors in PCR-confirmed pneumocystis pneumonia (PJP). We retrospectively analyzed patients with hypoxemia, pulmonary involvement and/or fever who underwent PJP PCR testing at Koç University Hospital between January 2020 and November 2023. Cases were defined as patients with a positive PCR result who fulfilled the EORTC/MSGERC criteria for PJP, whereas the non-PJP group included PCR-negative patients and PCR-positive patients without clinically compatible disease. Clinical, laboratory, and radiologic data-including LDH, fungal load, co-infections, and 4-week mortality-were collected. Of 235 patients, 59 had PCR-confirmed PJP. PJP patients were older (median 70 vs. 64.5, p < 0.001), more often had solid organ malignancies (67.8% vs. 41.5%, p < 0.001), recent chemotherapy (66.1% vs. 41.5%, p = 0.001), and higher fungal loads (median 10,892 vs. 0, p < 0.001). Bilateral lung lesions (81% vs. 66.5%, p = 0.037) and ground-glass opacities (82.8% vs. 67.7%, p = 0.041) were more frequent. Serum LDH increased by 81.6% in PJP vs. 20.7% in controls (p = 0.001), whereas no significant difference was observed among patients with elevated baseline LDH (29.7% vs. 16.3%, p = 0.397). Multivariate analysis identified older age (OR 1.042, p = 0.017), solid organ malignancy (OR 2.304, p = 0.048), and CMV co-infection (OR 3.786, p = 0.006) as independent factors associated with PJP, whereas ICU admission at diagnosis was inversely associated with PJP (OR 0.239, p = 0.005). The 4-week mortality was 37%, with bacterial co-infection as the strongest predictor (OR 5.854, p = 0.009). Older age, solid organ malignancy, and CMV co-infection increased PJP risk, while bacterial co-infection predicted mortality. LDH changes supported diagnosis, but not when baseline levels were already elevated, in this predominantly oncology cohort.

To review the efficacy, safety, and clinical selection considerations of azole antifungal agents for prophylaxis of invasive fungal infections (IFIs) in immunocompromised patients using a clinically oriented, pharmacist-focused framework. A literature review was conducted using PubMed and Embase to identify relevant studies evaluating azole antifungal prophylaxis in immunocompromised adult populations. Search terms included combinations of "azole," "antifungal prophylaxis," "immunocompromised," and "invasive fungal infection," with emphasis on contemporary studies reflecting current prophylaxis practices. Studies were included if they evaluated prophylactic use of azole antifungal agents in immunocompromised adults, including patients with hematologic malignancies, hematopoietic stem cell transplantation, or other defined immunocompromised states. Studies focused on treatment rather than prophylaxis, non-azole agents, pediatric populations, or lacking relevant clinical outcomes were excluded. Data extracted included study design, patient population, antifungal agent and dosing, incidence of IFIs, and reported safety outcomes. Randomized controlled trials and observational studies demonstrate that azole antifungal prophylaxis significantly reduces IFI incidence in high-risk immunocompromised populations. Posaconazole has demonstrated superiority over fluconazole and itraconazole in neutropenic leukemia populations, while mold-active azoles including voriconazole and isavuconazole offer expanded prophylactic options in select patients. Therapeutic drug monitoring, drug interaction management, and individualized risk stratification are critical pharmacist-driven components of care. Safety findings remain consistent with known azole-associated toxicities including hepatotoxicity, QT interval alterations, neuropsychiatric effects, and cytochrome P450-mediated drug interactions. Azole antifungal prophylaxis remains a cornerstone strategy for prevention of IFIs in immunocompromised patients. Current evidence supports individualized, risk-based selection of prophylactic agents based on patient-specific risk factors rather than universal application of a single regimen. Pharmacists play a central role in optimizing prophylaxis through therapeutic drug monitoring, medication reconciliation, and toxicity mitigation. Additional studies are needed to optimize prophylaxis strategies and improve patient outcomes.

Human herpesvirus 6 (HHV-6) comprises two genetically and biologically distinct species, HHV-6A and HHV-6B, yet species-level differentiation is rarely performed in clinical practice. We conducted a retrospective study of 119 immunocompromised adults with detectable HHV-6 DNA between 2020 and 2025 to characterize species distribution, compare epidemiological, clinical, and virological features, and evaluate the diagnostic relevance of genotyping. Viral species were detected by real-time polymerase chain reaction (PCR) across multiple sample types, and suspected chromosomal integration was confirmed through detection of endogenous HHV-6 (eHHV-6) DNA in hair follicles by quantitative real-time PCR. HHV-6B accounted for ~96% of infections and was significantly associated with organ involvement, predominantly gastrointestinal disease, irrespective of plasma viral load. In contrast, HHV-6A was less frequently detected in tissues and was consistently associated with viremia and chromosomal integration, independent of viral load. Genotypic concordance across plasma, biopsy, cerebrospinal fluid, bronchoalveolar lavage, and hair follicle samples from the same patient was complete. Incorporating species-level genotyping and targeted testing for chromosomal integration (eHHV-6) into diagnostic workflows may improve interpretation of viral detection and help prevent unnecessary antiviral therapy.IMPORTANCESpecies-specific identification of human herpesvirus 6 (HHV-6A/B) has critical diagnostic implications in immunocompromised patients, although it is rarely performed in diagnostic laboratories. Our study showed that HHV-6A detection is associated with chromosomal integration, whereas HHV-6B is the main species linked to clinically relevant disease and invasive tissue infection. This study emphasizes that implementing species-specific PCR and testing for eHHV-6 in clinical microbiology laboratories may help interpret viral DNA detection, prevent misclassification of integrated virus as active infection, and avoid unnecessary antiviral therapy.