Introduction: Human host immune response following infection with the new variant of A/H1N1 pandemic influenza virus (nvH1N1) is poorly understood. We utilize here systemic cytokine and antibody levels in evaluating differences in early immune response in both mild and severe patients infected with nvH1N1. Methods: We profiled 29 cytokines and chemokines and evaluated the haemagglutination inhibition activity as quantitative and qualitative measurements of host immune responses in serum obtained during the first five days after symptoms onset, in two cohorts of nvH1N1 infected patients. Severe patients required hospitalization (n = 20), due to respiratory insufficiency (10 of them were admitted to the intensive care unit), while mild patients had exclusively flu-like symptoms (n = 15). A group of healthy donors was included as control (n = 15). Differences in levels of mediators between groups were assessed by using the non parametric U-Mann Whitney test. Association between variables was determined by calculating the Spearman correlation coefficient. Viral load was performed in serum by using real-time PCR targeting the neuraminidase gene. Results: Increased levels of innate-immunity mediators (IP-10, MCP-1, MIP-1β), and the absence of anti-nvH1N1 antibodies, characterized the early response to nvH1N1 infection in both hospitalized and mild patients. High systemic levels of type-II interferon (IFN-γ) and also of a group of mediators involved in the development of T-helper 17 (IL-8, IL-9, IL-17, IL-6) and T-helper 1 (TNF-α, IL-15, IL-12p70) responses were exclusively found in hospitalized patients. IL-15, IL-12p70, IL-6 constituted a hallmark of critical illness in our study. A significant inverse association was found between IL-6, IL-8 and PaO2 in critical patients. Conclusions: While infection with the nvH1N1 induces a typical innate response in both mild and severe patients, severe disease with respiratory involvement is characterized by early secretion of Th17 and Th1 cytokines usually associated with cell mediated immunity but also commonly linked to the pathogenesis of autoimmune/inflammatory diseases. The exact role of Th1 and Th17 mediators in the evolution of nvH1N1 mild and severe disease merits further investigation as to the detrimental or beneficial role these cytokines play in severe illness.

Methicillin-resistant Staphylococcus aureus (MRSA) colonization has been considered a risk factor for the development of infection, however, there are no studies that have compared the colonizing and infecting strains using whole-genome sequencing (WGS). The aim of this study is to determine the prevalence of and risk factors for MRSA colonization among long-term care facilities (LTCF) residents of Tenerife (Spain), and to analyze the epidemiological relationship between the colonizing and infecting strains using WGS. A point-prevalence study was carried out at 14 LTCFs in Tenerife from October 2020 to May 2021. Nasal swabs were cultured for MRSA. Colonized residents were followed up for two years. A phylogenetic comparison between colonization and infection strains was performed using WGS. A total of 764 residents were included. The prevalence of colonization by MRSA was 28.1% (n = 215), of which 12 (5.6%) subsequently developed infection. A close genetic relationship between colonization and infection isolates was found in three of the four (75%) residents studied. Our study confirms that colonized residents can develop serious MRSA infections from the same nasal colonization strain. Given the high prevalence of MRSA colonization in these centers, it is necessary to implement strategies with preventive measures to avoid the development of infection and the transmission of MRSA.

BNT162b2 mRNA Covid-19 vaccine has shown an optimal protection for population. However the development of SARS-CoV-2 infection has been reported in persons, who have received one or both doses of vaccine. The Hospital Universitario de Canarias began to vaccinate to healthcare workers on Febraury, 2021. We have detected several asymptomatic cases of SARS-CoV2 infections in healthcare workers. We performed PCR on health staff at our Centre after the two doses of vaccination, which were realized by screening in close contact with positive cases, new addition to the hospital or a requirement before traveling to another region in the country. In positive cases we determined the quantitative IgG (post-vaccine Spike1-RBD and nucleocapside) and IgM (Spike1-RBD). We detected five cases of SARS-CoV-2 infection in properly vaccinated healthcare workers after 15 days of the second dose vaccine. All cases had high Cts values and were asymptomatics. The Post-vaccine IgG level was between 778.9-4,420.7 BAU/ml. This communication reflects how vaccination protected healthcare workers from disease; however, it remains to be analyzed the transmissibility of virus after vaccination. We consider the importance of preserving, at the moment, prevention measures against SARS-CoV-2 virus in the hospital environment, mainly by vaccinated healthcare staff.

C. difficile is a major cause of antibiotic-associated diarrhea and hospital-acquired infections, although increasing community-acquired cases suggest alternative transmission routes. Livestock, particularly pigs, have been proposed as potential reservoirs. This study aimed to investigate the presence of zoonotic ribotypes in piglets from Tenerife (Spain) and to assess their pathogenic potential by detecting toxin genes. A total of 140 samples were analyzed, including 58 fecal samples from slaughtered piglets (4–8 weeks old) and 82 rectal swabs from piglets aged 2–25 days. Samples were cultured, identified by MALDI-TOF MS, and characterized by PCR ribotyping and toxin gene detection. No isolates were obtained from fecal samples collected at slaughter, whereas 14 (17%) rectal swabs were positive. Colonization was strongly age-dependent, with the highest prevalence at 2 days of age (100%), decreasing by day 9 (10.7%), and absent after 21 days (p < 0.05). All isolates were ribotype RT033 with a tcdA⁺/tcdB⁻/cdtA⁺/cdtB⁺ profile. The exclusive detection of RT033, a clade V lineage linked to animal reservoirs and occasional human infections, suggests a potential zoonotic risk, especially for farm workers. These findings reinforce the need for integrated C. difficile surveillance under a One Health framework to monitor emerging ribotypes and their role in community-acquired infections.

Background/Objectives: Clostridioides difficile colonization is common among hospitalized onco-hematological patients, yet its clinical significance and risk factors in this population remain incompletely characterized. This study aimed to determine the prevalence, risk factors, and genomic characteristics of C. difficile colonization among oncology and hematology inpatients, and to assess its relationship with progression to symptomatic infection. Methods: We conducted a prospective cohort study of patients admitted to the oncology and hematology departments of a tertiary-care hospital in the Canary Islands, Spain, between March and October 2025. Weekly active screening for C. difficile colonization was performed on stool samples throughout hospitalization. Risk factors were assessed using multivariable logistic regression, and whole-genome sequencing was performed on 16 of the 23 recovered isolates (after excluding 3 non-recoverable and 4 contaminated isolates) to characterize sequence types, ribotypes, and antimicrobial resistance determinants. Results: Among 215 patients (262 admission episodes), colonization was detected in 23 episodes (8.8%), with higher rates in oncology (10.9%) than hematology (7.2%; adjusted OR 0.37, 95% CI 0.14–0.96, p = 0.042). Chemotherapy administered during hospitalization was the strongest independent risk factor for colonization (adjusted OR 4.16, 95% CI 1.56–11.10, p = 0.004). Only 4.3% of colonizations were classified as truly community-associated, with 95.7% of patients showing documented healthcare contact. Sequencing of 16 isolates identified nine sequence types, including ST11 (ribotype 078, of zoonotic origin) and rare ribotypes (RT010, RT451); four isolates (36%) exhibited moxifloxacin resistance linked to gyrA/gyrB mutations, while all remained susceptible to vancomycin and metronidazole. No colonized patient progressed to symptomatic infection; the single CDI case in the cohort occurred in a non-colonized patient. Conclusions: These findings support current recommendations against isolating or treating asymptomatically colonized patients, while underscoring the need for continued genomic surveillance and reinforced environmental hygiene and antimicrobial stewardship in this high-risk population.