Non-invasive pneumococcal pneumonia has its own and distinct serotype distribution in Portugal
Streptococcus pneumoniae is the main etiological agent of pneumonia. Numerous studies have addressed the serotype distribution of invasive pneumococcal disease (IPD) due to the availability of conjugate vaccines targeting the capsular polysaccharides. However, there is more limited information on the serotypes causing non-invasive pneumococcal pneumonia (NIPP). Our aim was to characterize pneumococci causing NIPP in adults, in order to determine recent changes in serotype prevalence and antimicrobial resistance, the potential coverage of pneumococcal vaccines and to compare the results with IPD.
Serotypes and antimicrobial susceptibility profiles of a sample of 1300 isolates recovered from adult patients (≥18 yrs) between 1999 and 2011 (13 years, 100 randomly selected isolates/year) were determined.
Overall, the most frequent serotypes were 3 (18%), 11A (7%), 19F (7%), 19A (5%), 14 (4%), 22F (4%), 23F (4%) and 9N (4%). There were significant changes in the proportion of isolates expressing vaccine serotypes, namely there was a steady decline of the serotypes included in the 7-valent conjugate vaccine from 31% (1999-2003) to 11% (2011). Taking together the most recent study years (2009-2011), the potential coverage of the 13-valent conjugate vaccine was 44% and of the 23-valent polysaccharide vaccine was 66%. Erythromycin resistance increased in the study period, reaching 18% in 2011.
The serotype distribution found in NIPP differed from the one found in IPD, with only two common serotypes among the ones responsible for half of each presentation – serotypes 3 and 19A. Serotypes found to be enriched in NIPP relative to IPD (6A, 11A, 15C, 19F and 23B) had been previously suggested to have a lower invasive disease potential. In spite of these differences, the overall prevalence of resistant isolates was similar in NIPP and in IPD.
Pfizer: Consultant, Grant Investigator and Speaker's Bureau, Consulting fee, Research grant and Speaker honorarium
Gilead: Speaker's Bureau, Speaker honorarium
GlaxoSmithKline: Consultant, Consulting fee
A. N. Horácio, None
J. P. Lopes, None