The unprecedented increase of life expectancy challenges society to protect the elderly from morbidity and mortality making vaccination a crucial mean to safeguard this population. Indeed, infectious diseases, such as influenza and pneumonia, are among the top killers of elderly people in the world. Elderly individuals are more prone to severe infections and less responsive to vaccination prevention, due to immunosenescence combined with the progressive increase of a proinflammatory status characteristic of the aging process (inflammaging). These factors are responsible for most age-related diseases and correlate with poor response to vaccination. Therefore, it is of utmost interest to deepen the knowledge regarding the role of inflammaging in vaccination responsiveness to support the development of effective vaccination strategies designed for elderly. In this review we analyse the impact of age-associated factors such as inflammaging, immunosenescence and immunobiography on immune response to vaccination in the elderly, and we consider systems biology approaches as a mean for integrating a multitude of data in order to rationally design vaccination approaches specifically tailored for the elderly.

The oral and nasopharyngeal streptococci are a major part of the normal microbiota in humans. Most human associated streptococci are considered commensals however a small number of them are pathogenic, causing a wide range of diseases including oral infections such as dental caries and periodontitis and diseases at other body sites including sinusitis and endocarditis, and in the case of Streptococcus pneumoniae, meningitis. Both phenotypic and sequence based studies have shown that the human associated streptococci from the mouth and nasopharynx harbour a large number of antibiotic resistance genes and these are often located on mobile genetic elements known as conjugative transposons or integrative and conjugative elements of the Tn916 / Tn1545 family. These mobile genetic elements are responsible for the spread of the resistance genes between streptococci and also between streptococci and other bacteria. In this review we describe the resistances conferred by, and the genetic variations between the many different Tn916-like elements found in recent studies of oral and nasopharyngeal streptococci and show that Tn916-like elements are important mediators of antibiotic resistance genes within this genus. We will also discuss the role of the oral environment and how this is conducive to the transfer of these elements and discuss the contribution of both transformation and conjugation on the transfer and evolution of these elements in different streptococci.

The mef(A) gene was originally identified as the resistance determinant responsible for type M resistance to macrolides, a phenotype frequently found in clinical isolates of Streptococcus pneumoniae and Streptococcus pyogenes. MefA was defined as a secondary transporter of the major facilitator superfamily driven by proton-motive force. However, when characterizing the mef(A)-carrying elements Tn1207.1 and Φ1207.3, another macrolide resistance gene, msr(D), was found adjacent to mef(A). To define the respective contribution of mef(A) and msr(D) to macrolide resistance, three isogenic deletion mutants were constructed by transformation of a S. pneumoniae strain carrying Φ1207.3: (i) Δmef(A)–Δmsr(D); (ii) Δmef(A)–msr(D); and (iii) mef(A)–Δmsr(D). Susceptibility testing of mutants clearly showed that msr(D) is required for macrolide resistance, while deletion of mef(A) produced only a twofold reduction in the minimal inhibitory concentration (MIC) for erythromycin. The contribution of msr(D) to macrolide resistance was also studied in S. pyogenes, which is the original host of Φ1207.3. Two isogenic strains of S. pyogenes were constructed: (i) FR156, carrying Φ1207.3, and (ii) FR155, carrying Φ1207.3/Δmsr(D). FR155 was susceptible to erythromycin, whereas FR156 was resistant, with an MIC value of 8 μg/ml. Complementation experiments showed that reintroduction of the msr(D) gene could restore macrolide resistance in Δmsr(D) mutants. Radiolabeled erythromycin was retained by strains lacking msr(D), while msr(D)-carrying strains showed erythromycin efflux. Deletion of mef(A) did not affect erythromycin efflux. This data suggest that type M resistance to macrolides in streptococci is due to an efflux transport system of the ATP-binding cassette (ABC) superfamily, in which mef(A) encodes the transmembrane channel, and msr(D) the two ATP-binding domains.

Genetic element Φ1207.3 (formerly Tn1207.3) is a prophage of Streptococcus pyogenes which carries the macrolide efflux resistance genes mef(A)/msr(D) and is capable of conjugal transfer among streptococci. Complete nucleotide sequence showed that Φ1207.3 is 52,491 bp in length and contained 58 open reading frames (ORFs). A manual homology-based annotation with functional prediction of the hypothetical gene product was possible only for 34 out of 58 ORFs. Φ1207.3 codes for two different C-methylation systems, several phage structural genes, a lysis cassette (composed by a holin and a peptidoglycan hydrolase), and three site-specific resolvases of the serine recombinase family.

Aim: The aim of the present study was to investigate and correlate the prevalence of Enterococcus faecalis in saliva and in root canals with different pulpal and periapical conditions.Methodology: Sixty-seven patients were divided into five groups based on pulpal and periapical tissue status: healthy vital teeth (HVT, n=7), healthy treated teeth without lesion (HTT, n=9), irreversible pulpitis (IP, n=13), necrosis (N, n=18), and post-treatment apical periodontitis (PTAP, n=20). Saliva, rubber dam, sterility control and pre-treatment root canal samples were collected and microbiologically processed by culture method. The phylogenetic relationship of E. faecalis isolates collected from root canals and saliva were investigated by whole genome sequencing. Fisher’s exact test was used to correlate the presence of E. faecalis in root canals or saliva with clinical and/or radiographic findings. Linear/logistic regression analyses were performed to establish the relationship between the presence of E. faecalis in root canals, saliva, and the status of periapical tissues.Results: E. faecalis was found in 18 root canal and saliva samples. E. faecalis root canal isolates were recovered with the highest frequency from post-treatment apical periodontitis. The occurrence of E. faecalis in saliva was strongly associated with its detection in the root canals (P < 0.001). The pretreatment presence of E. faecalis in root canals was associated with significantly higher odds of having periapical lesions (OR=11.03; 95% CI, 1.27-95.70; p < 0.05). Saliva and root canal isolates from the same patient were highly correlated at the phylogenetic level (Jaccard index >0.95).Conclusion: This pilot study confirms the role of E. faecalis in developing peri-radicular lesions in secondary endodontic infections and suggests that saliva could be the main source of infection. Further studies are needed to investigate the exact origin of this bacteria and its true role in the pathogenesis of secondary/persistent endodontic infections.