Highly conserved bifidobacteria in the human gut: Bifidobacterium longum subsp. longum as a potential modulator of elderly innate immunity.

Aging is a physiological and immunological process involving the deterioration of human health, characterised by the progressive alteration of organs and their functions. The speed and extent of such decline are dependent on lifestyle, environment, and genetic factors. Moreover, with advancing age, humans become progressively more fragile and prone to acute and chronic diseases. Although the intestinal microbiota is predisposed to perturbations that accompany aging and frailty, it is generally accepted that the gut microbiota engages in multiple interactions that affect host health throughout the host life span. In the current study, an exhaustive in silico investigation of gut-associated bifidobacteria in healthy individuals from birth to old age revealed that Bifidobacterium longum subsp. longum is the most prevalent member, especially during infancy and in centenarians. Moreover, B. longum subsp. longum genome reconstruction and strain tracing among human gut microbiomes allowed the identification of prototypes of this taxon in the human gut microbiota of healthy elderly individuals. Such analyses guided culturomics attempts to isolate B. longum subsp. longum strains that matched the genomic content of B. longum subsp. longum prototypes from healthy elderly individuals. The molecular effects of selected B. longum subsp. longum strains on the human host were further investigated using in vitro microbe-host interactions, revealing differences in the host immune system transcriptome, with a reduction in gene expression of inflammation-related cytokines. These intriguing findings support the potential anti-aging effects of elderly associated prototypes of B. longum subsp. longum.

Comparison of multiple definitions for ventilator-associated pneumonia in patients requiring mechanical ventilation for non-pulmonary conditions: preliminary data from PULMIVAP, an Italian multi-centre cohort study.

OBJECTIVES: To compare intensivist-diagnosed ventilator-associated pneumonia (iVAP) with four established definitions, assessing their agreement in detecting new episodes. METHODS: A multi-centric prospective study on pulmonary microbiota was carried out in patients requiring mechanical ventilation (MV). Data collected were used to compare hypothetical VAP onset according to iVAP with the study consensus criteria, the European Centre for Disease Control and Prevention definition, and two versions of the latter adjusted for leukocyte count and fever. RESULTS: In our cohort of 186 adult patients, iVAPs were 36.6% (68/186, 95% confidence interval 30.0-44.0%), with an incidence rate of 4.64/100 patient-MV-days, and median MV-day at diagnosis of 6. Forty-seven percent of patients (87/186) were identified as VAP by at least one criterion, with a median MV-day at diagnosis of 5. Agreement between intensivist judgement (iVAP/no-iVAP) and the criteria was highest for the study consensus criteria (50/87, 57.4%), but still one-third of iVAP were not identified and 9% of patients were identified as VAP contrary to intensivist diagnosis. VAP proportion differed between criteria (25.2-30.1%). CONCLUSIONS: Caution is needed when evaluating studies describing VAP incidence. Pre-agreed criteria and definitions that capture VAP's evolving nature provide greater consistency, but new clinically driven definitions are needed to align surveillance and diagnostic criteria with clinical practice.