Immune risk phenotype is associated with nosocomial lung infections in elderly in-patients

We included 252 consecutive in-patients aged 70 years or over (mean age, 85 ± 6.2 years), between 2006 and 2008. Among them, 97 experienced nosocomial infections, yielding a prevalence rate of 38.5% (95% confidence interval, 32.5-44.5). The main infection sites were the respiratory tract (21%) and urinary tract (17.1%) When we compared immunological parameters including cell counts determined by flow cytometry in the groups with and without nosocomial infections, we found that the group with nosocomial infections had significantly lower values for the CD4/CD8 ratio and naive CD8 and CD4 T-cell counts and higher counts of memory CD8 T-cells with a significant increase in CD28-negative CD8-T cells. Neither cytomegalovirus status (positive in 193/246 patients) nor presence of the IRP was associated with nosocomial infections. However, nosocomial pneumonia was significantly more common among IRP-positive patients than IRP-negative patients (17/60 versus 28/180; p = 0.036).Immunological parameters that are easy to determine in everyday practice and known to be associated with immune system ageing and shorter survival in the elderly are also associated with an elevated risk of nosocomial pneumonia in the relatively short term.Nosocomial infections (NIs) constitute a major public health concern, as they are common and associated with both high morbidity and mortality rates and high healthcare costs [1,2]. Risk factors for NIs vary with the infection site, healthcare setting, and patient age. The National Nosocomial Infections Survey done in the US in 1986-1990 showed that 54% of all NIs occurred in people aged 65 or over [3]. In elderly individuals, the increased susceptibility to severe infections and decreased efficacy of vaccination may reflect ageing of the immune system, or immunosenescence, which involves nearly all the components of the immune system [4-6].Among the changes characteristic of immunosenescence, those believed to play a major role include the progressi