Prevalence of serotypes 1, 5, and 7F over time.

<p>Prevalence of serotypes 1, 5, and 7F over time.</p

Low Prevalence of Pneumococcal Carriage and High Serotype and Genotype Diversity among Adults over 60 Years of Age Living in Portugal

<div><p>Pneumococcal disease is frequent at the extremes of age. While several studies have looked at colonization among young children, much less is known among the elderly. We aimed to evaluate pneumococcal carriage among elderly adults living in Portugal. Between April 2010 and December 2012, nasopharyngeal and oropharyngeal swabs of adults over 60 years of age, living in an urban area (n = 1,945) or in a rural area (n = 1,416), were obtained. Pneumococci were isolated by culture-based standard procedures, identified by optochin susceptibility, bile solubility and PCR screening for <i>lytA</i> and <i>cpsA</i>, and characterized by antibiotype, serotype, and MLST. Associations between pneumococcal carriage, socio-demographic and clinical characteristics were evaluated by univariate analysis and multiple logistic regression. The global prevalence of carriage was 2.3% (95% CI: 1.8–2.8). In the multiple logistic regression analysis, smoking, being at a retirement home, and living in a rural area increased the odds of being a pneumococcal carrier by 4.4-fold (95% CI: 1.9–9.2), 2.0-fold (95% CI: 1.1–3.6) and 2.0-fold (95% CI: 1.2–3.5), respectively. Among the 77 pneumococcal isolates, 26 serotypes and 40 STs were identified. The most prevalent serotypes were (in decreasing order) 19A, 6C, 22F, 23A, 35F, 11A, and 23B, which accounted, in total, for 60.0% of the isolates. Most isolates (93.5%) had STs previously described in the MLST database. Resistance to macrolides, non-susceptibility to penicillin and multidrug resistance were found in 19.5%, 11.7%, and 15.6% of the isolates, respectively. We conclude that the prevalence of pneumococcal carriage in the elderly, in Portugal, as determined by culture-based methods, is low. Serotype and genotype diversity is high. Living in a rural area, in a retirement home, and being a smoker increased the risk of pneumococcal carriage. This study contributes to the establishment of a baseline that may be used to monitor how novel pneumococcal vaccines impact on colonization among the elderly.</p></div

Socio-demographic characteristics and potential risk factors for pneumococcal carriage.

a<p>not available for one participant, reference test was 0 years of school education.</p

Serotype distribution of pneumococcal isolates carried by adults over 60 years of age.

<p>Black bars, isolates susceptible to penicillin and erythromycin. Striped bars, isolates non-susceptible to penicillin; gray bars, isolates resistant to erythromycin; white bars, isolates resistant to erythromycin and non-susceptible to penicillin. * indicates serotypes included in PCV13; # indicates serotypes included in PPV23.</p

Medical conditions and risk factors for pneumococcal carriage.

a<p>23-valent pneumococcal polysaccharide vaccine.</p

Graphical representation of MLST analysis of the 77 pneumococcal isolates (based on goeBURST).

<p>Numbers inside circles indicate sequence type (ST). *indicates novel ST identified in this study. The solid and dotted lines connect single locus variants (SLV) and double locus variants (DLV), respectively. Numbers outside circles indicate serotype. The size of the circles is proportional to the number of isolates of each ST. The smallest circle corresponds to one isolate; the biggest corresponds to seven isolates.</p