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The role of viral load in the outcome of patients requiring hospital admission due to influenza is not well established. We aim to assess if there is an association between the viral load and the outcome in hospitalized patients with a confirmed influenza virus infection. A retrospective observational study including all adult patients who were hospitalized in our center with a confirmed influenza virus infection from January to May 2016. Viral load was measured by real-time reverse-transcriptase-polymerase chain reaction (rRT-PCR) cycle threshold (Ct) value on upper respiratory tract samples. Its value was categorized into three groups (low Ct,≤ 20; intermediate Ct,(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and high Ct, > 30). Two hundred thirty-nine patients were included. Influenza A/ H1N1pdm09 was isolated in 207 cases (86.6%). The mean Ct value was 26.69 ± 5.81. The viral load was higher in the unvaccinated group when compared with the vaccinated patients (Ct 25.17 ± 5.55 vs. 27.58 ± 4.97, p = 0.004). Only 27 patients (11.29%) presented a high viral load. Patients with a high viral load more often showed abnormal findings on chest X-ray (p = 0.015) and lymphopenia (p = 0.097). By contrast, there were no differences between the three groups (according to viral load), in associated pneumonia, respiratory failure, need for mechanical ventilation, sepsis, or in-hospital mortality. Our findings suggest that in patients admitted to the hospital with confirmed influenza virus infection (mostly A/H1N1pdm09), a high viral load is associated with a higher presence of abnormal findings on chest X-ray but not with a significant worse prognosis. In these cases, standardized quantitative PCR could be useful.

Staphylococcus aureus bacteremia (SAB) is associated with high morbidity and mortality, which varies depending on the source of infection. Nevertheless, the global molecular epidemiology of SAB and its possible association with specific virulence factors remains unclear. Using DNA microarrays, a total of 833 S. aureus strains (785 SAB and 48 colonizing strains) collected in Spain over a period of 15 years (2002–2017) were characterized to determine clonal complex (CC), agr type and repertoire of resistance and virulence genes in order to provide an epidemiological overview of CCs causing bloodstream infection, and to analyze possible associations between virulence genes and the most common sources of bacteremia. The results were also analyzed by acquisition (healthcare-associated [HA] and community-acquired [CA]), methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) strains, and patient age (adults vs. children). Our results revealed high clonal diversity among SAB strains with up to 28 different CCs. The most prevalent CCs were CC5 (30.8%), CC30 (20.3%), CC45 (8.3%), CC8 (8.4%), CC15 (7.5%), and CC22 (5.9%), which together accounted for 80% of all cases. A higher proportion of CC5 was found among HA strains than CA strains (35.6 vs. 20.2%, p < 0.001). CC5 was associated with methicillin resistance (14.7 vs. 79.4%, p < 0.001), whereas CC30, CC45, and CC15 were correlated with MSSA strains (p < 0.001). Pathogen-related molecular markers significantly associated with a specific source of bacteremia included the presence of sea, undisrupted hlb and isaB genes with catheter-related bacteremia; sed, splE, and fib genes with endocarditis; undisrupted hlb with skin and soft tissue infections; and finally, CC5, msrA resistance gene and hla gene with osteoarticular source. Our study suggests an association between S. aureus genotype and place of acquisition, methicillin resistance and sources of bloodstream infection, and provides a valuable starting point for further research insights into intrinsic pathogenic mechanisms involved in the development of SAB.