Identification of Pneumococcal Serotypes by PCR-Restriction Fragment Length Polymorphism

The Molecular Approaches and Challenges of Streptococcus pneumoniae Serotyping for Epidemiological Surveillance in the Vaccine Era

Streptococcus pneumoniae (pneumococcus) belongs to the Gram-positive cocci. This bacterium typically colonizes the nasopharyngeal region of healthy individuals. It has a distinct polysaccharide capsule - a virulence factor allowing the bacteria to elude the immune defense mechanisms. Consequently, it might trigger aggressive conditions like septicemia and meningitis in immunocompromised or older individuals. Moreover, children below five years of age are at risk of morbidity and mortality. Studies have found 101 S. pneumoniae capsular serotypes, of which several correlate with clinical and carriage isolates with distinct disease aggressiveness. Introducing pneumococcal conjugate vaccines (PCV) targets the most common disease-associated serotypes. Nevertheless, vaccine selection pressure leads to replacing the formerly dominant vaccine serotypes (VTs) by non-vaccine types (NVTs). Therefore, serotyping must be conducted for epidemiological surveillance and vaccine assessment. Serotyping can be performed using numerous techniques, either by the conventional antisera-based (Quellung and latex agglutination) or molecular-based approaches (sequetyping, multiplex PCR, real-time PCR, and PCR-RFLP). A cost-effective and practical approach must be used to enhance serotyping accuracy to monitor the prevalence of VTs and NVTs. Therefore, dependable pneumococcal serotyping techniques are essential to precisely monitor virulent lineages, NVT emergence, and genetic associations of isolates. This review discusses the principles, associated benefits, and drawbacks of the respective available conventional and molecular approaches, and potentially the whole genome sequencing (WGS) to be directed for future exploration.

Bacterial Meningitis Due to Streptococcus pneumoniae in a 7-Month-Old Girl Who Received Three Doses of 13-Valent Pneumococcal Conjugate Vaccine

In Japan, pneumococcal vaccine has been routinely administered since 2010 to prevent invasive pneumococcal diseases such as Streptococcus pneumoniae meningitis. We describe a case of pneumococcal meningitis in a 7-month-old girl who had received three doses of 13-valent pneumococcal conjugate vaccine. Brain magnetic resonance imaging showed infarcts in the right frontal region, and she was treated with antibiotics, intravenous immunoglobulin, dexamethasone, and edaravone. On day 27, an enhanced brain CT scan showed improvement of abnormal findings in the frontal region, except for slight atrophy. The S. pneumoniae serotype was 12F, which is not included in the 13-valent pneumococcal conjugate vaccine. A future vaccine is expected to use cross-reactivity to target common antigens.