Introduction: Sepsis is a serious medical condition that requires rapidly administered, appropriate antibiotic treatment. Conventional methods take three or more days for final pathogen identification and antimicrobial susceptibility testing. We organized a prospective observational multicenter study in three study sites to evaluate the diagnostic accuracy and potential clinical utility of the SeptiFast system, a multiplex pathogen detection system used in the clinical setting to support early diagnosis of bloodstream infections. Methods: A total of 212 patients, suspected of having systemic inflammatory response syndrome (SIRS) caused by bacterial or fungal infection, were enrolled in the study. From these patients, 407 blood samples were taken and blood culture analysis was performed to identify pathogens. Whole blood was also collected for DNA Detection Kit analysis immediately after its collection for blood culture. The results of the DNA Detection Kit, blood culture and other culture tests were compared. The chosen antimicrobial treatment in patients whose samples tested positive in the DNA Detection Kit and/or blood culture analysis was examined to evaluate the effect of concomitant antibiotic exposure on the results of these analyses. Results: SeptiFast analysis gave a positive result for 55 samples, while 43 samples were positive in blood culture analysis. The DNA Detection Kit identified a pathogen in 11.3% (45/400) of the samples, compared to 8.0% (32/400) by blood culture analysis. Twenty-three pathogens were detected by SeptiFast only; conversely, this system missed five episodes of clinically significant bacteremia (Methicillin-resistant Staphylococcus aureus (MRSA), 2; Pseudomonas aeruginosa, 1; Klebsiella spp, 1; Enterococcus faecium, 1). The number of samples that tested positive was significantly increased by combining the result of the blood culture analysis with those of the DNA Detection Kit analysis (P = 0.01). Among antibiotic pre-treated patients (prevalence, 72%), SeptiFast analysis detected more bacteria/fungi, and was less influenced by antibiotic exposure, compared with blood culture analysis (P = 0.02). Conclusions: This rapid multiplex pathogen detection system complemented traditional culture-based methods and offered some added diagnostic value for the timely detection of causative pathogens, particularly in antibiotic pre-treated patients. Adequately designed intervention studies are needed to prove its clinical effectiveness in improving appropriate antibiotic selection and patient outcomes.

Influenza virus is a common cause of respiratory infection and morbidity, which is often due to deleterious host immune responses directed against the pathogen. We investigated the role of IL-1 receptor-associated kinase-M (IRAK-M), an inhibitor of MyD88-dependent TLR signaling, in modulating the innate inflammatory response during influenza pneumonia using a murine model. The intranasal administration of influenza resulted in the upregulation of IRAK-M mRNA and protein levels in the lungs within 2 d after infectious challenge. Pulmonary influenza infection in mice deficient in IRAK-M (IRAK-M^−/−) resulted in substantially increased mortality compared with similarly treated wild-type animals. Increased mortality in IRAK-M^−/− mice was associated with enhanced early influx of neutrophils, high permeability edema, apoptosis of lung epithelial cells, markedly increased expression of inflammatory cytokines/chemokines, and release of neutrophil-derived enzymes, including myeloperoxidase and neutrophil elastase. Early viral clearance was not different in mutant mice, whereas viral titers in lungs and blood were significantly higher in IRAK-M^−/−mice compared with wild-type animals. Increased lethality observed in IRAK-M^−/− mice after influenza challenge was abrogated by Ab-mediated blockade of CXCR2. Collectively, our findings indicate that IRAK-M is critical to preventing deleterious neutrophil-dependent lung injury during influenza infection of the respiratory tract.

Recently, it has been reported that circulating free DNA (cf‐DNA) in the blood is increased in various infectious diseases, including sepsis. Moreover, a relationship between cf‐DNA and neutrophil extracellular traps (NETs) has been suggested. However, it is still unclear what the source and physiological role of cf‐DNA in sepsis are. In this study, we examined the source of cf‐DNA by detecting citrullinated histone H3, a characteristic feature of NET formation, in cecal ligation and puncture‐ (CLP‐)operated mice. In addition, neutrophil depletion using anti‐Ly6G antibodies was performed to assess the association between neutrophils and cf‐DNA. Increased cf‐DNA levels were observed only in CLP mice and not in the control groups; the qPCR findings revealed that the cf‐DNA was mainly host‐derived, even in bacteremic conditions. Citrullinated histone H3 was not increased in the neutrophils upon CLP, and the depletion of neutrophils showed limited effects on decreasing the amount of cf‐DNA. Taken together, these results suggested that elevated cf‐DNA levels during early‐phase sepsis may represent a candidate biomarker for the severity of sepsis and that, contrary to previous findings, cf‐DNA is not derived from neutrophils or NETs.

Objective To determine the differences in the clinical features of bacterial pneumonia patients between patients co-infected with influenza virus or not co-infected. Methods Fifteen adult patients with bacterial pneumonia (7 men and 8 women) who also tested positive for influenza virus antigen were compared with those with bacterial pneumonia alone (n=28). Results Complications with chronic lung diseases were more frequently found in bacterial pneumonia patients with influenza virus infection, compared with those who had bacteria pneumonia alone. Statistical differences were also found in body temperature, and heart rates between the two groups. CRP levels, chest X-ray infiltrates and the severity of pneumonia, as determined using the criteria of the Japan Respiratory Society (JRS) and/or the Infectious Diseases Society of America (IDSA), were also significantly worse in patients of bacterial pneumonia infected with influenza virus, than in those who had bacterial pneumonia alone. Conclusions The severity of pneumonia in patients co-infected with influenza virus and bacteria was significantly higher than in those infected with bacteria alone. These data suggested that the influenza virus infection enhanced the bacterial pneumonia. Further study of the pathogenesis of the synergic interaction between influenza virus and bacteria is warranted.