Nasopharyngeal microbial interactions in the era of pneumococcal conjugate vaccination

Pneumococcal serotype distribution in 1315 nasopharyngeal swabs from a highly vaccinated cohort of Italian children as detected by RT-PCR

The long term impact of 7-valent pneumococcal conjugate vaccine (PCV7) on pneumococcal colonization patterns remains unclear. Carriage and distribution of Streptococcus pneumoniae serotypes as detected by RT-PCR were evaluated in a cohort of 1315 children. S. pneumoniae was identified in the nasopharyngeal swab of 734 children (55.8%); 488/734 (66.5%) children carried more than 1 pneumococcal serotype. As a consequence of co-colonization, a total of 1,728 S. pneumoniae (belonging to 33 serotypes) were identified. As immunogenicity between 2 and 3 doses of PCV7 in the first year of life has been demonstrated to be similar, serotypes distribution was evaluated categorizing vaccination status as 0,1 and 2 or more doses in the first year of life. Among children who started vaccination in the first year of life, PCV7 serotypes were carried in 296 of 1,123 (29.5%) children who had received ≥2 PCV7 doses while were carried in 26 of 108 (26.8%) who had received no doses (p=not significant); only 17 children received 1 PCV7 and 3 of them were found positive for PCV7 serotypes. Among those who had received ≥2 doses of PCV7 in the first year of life, 47 of 192 (19.7%) carried a PCV7 serotype during the first year after last vaccination, 50 of 125 (28.6%) during the second year, 79 of 224 (35.3%) during the third year, and 65 of 143 (45.5%) during the fourth year (p 0.0001). We did not identify risk factors for PCV7 carriage among children that had received >2 vaccine doses. This study suggests that S. pneumoniae is present in the nasopharynx of the majority of children 0-5 years even if vaccinated, that PCV7 serotypes can be found in nasopharyngeal swabs of PCV7 vaccinated children and that the frequency of PCV7 serotypes increases with the increase of interval from vaccination.

Update on otitis media - prevention and treatment

Acute otitis media and otitis media with effusion are common childhood disorders, a source of significant morbidity, and a leading cause of antibiotic prescription in primary health care. Although effective treatments are available, some shortcomings remain, and thus better treatments would be welcome. Recent discoveries within the field of otitis media research relating to its etiology and pathogenesis have led to further investigation aimed at developing novel treatments. This article provides a review of the latest evidence relating to the understanding of acute otitis media and otitis media with effusion, current treatment strategies, their limitations, new areas of research, and novel strategies for treatment.

Staphylococcal vaccine development: review of past failures and plea for a future evaluation of vaccine efficacy not only on staphylococcal infections but also on mucosal carriage

Staphylococcal disease represents a universal burden including acute, life-threatening infections as well as chronic infections usually associated with foreign materials. Infections occur notably in permanent carriers of Staphylococcus aureus. To date, all the attempts to develop an efficacious vaccine against S. aureus have failed. Failures in vaccine clinical trials might be related to a focus on single targets and development of humoral-based vaccines rather than vaccines with a combination of antigens stimulating both humoral and cellular immunity. The end points of these unsuccessful trials were a reduction in mortality or bacteremia, whereas the patient's decolonization was not assessed. Adopting the latter point of view, the aim of this article is to discuss nasal mucosal decolonization as a complementary marker of vaccine efficacy for clinical research in vaccine development.

Expression of Streptococcus pneumoniae Virulence-Related Genes in the Nasopharynx of Healthy Children

Colonization and persistence in the human nasopharynx are prerequisites for Streptococcus pneumoniae disease and carriage acquisition, which normally occurs during early childhood. Animal models and in vitro studies (i.e. cell adhesion and cell cytotoxicity assays) have revealed a number of colonization and virulence factors, as well as regulators, implicated in nasopharyngeal colonization and pathogenesis. Expression of genes encoding these factors has never been studied in the human nasopharynx. Therefore, this study analyzed expression of S. pneumoniae virulence-related genes in human nasopharyngeal samples. Our experiments first demonstrate that a density of ≥10(4) CFU/ml of S. pneumoniae cells in the nasopharynx provides enough DNA and RNA to amplify the lytA gene by conventional PCR and to detect the lytA message, respectively. A panel of 21 primers that amplified S. pneumoniae sequences was designed, and their specificity for S. pneumoniae sequences was analyzed in silico and validated against 20 related strains inhabitants of the human upper respiratory tract. These primers were utilized in molecular reactions to find out that all samples contained the genes ply, pavA, lytC, lytA, comD, codY, and mgrA, whereas nanA, nanB, pspA, and rrgB were present in ∼91-98% of the samples. Gene expression studies of these 11 targets revealed that lytC, lytA, pavA and comD were the most highly expressed pneumococcal genes in the nasopharynx whereas the rest showed a moderate to low level of expression. This is the first study to evaluate expression of virulence- and, colonization-related genes in the nasopharynx of healthy children and establishes the foundation for future gene expression studies during human pneumococcal disease.