Streptococcus pneumoniae, or pneumococcus, is a type of bacteria that causes pneumococcal disease. Pneumococcal infections can range from ear and sinus infections to pneumonia and bloodstream infections. Children younger than 2 years old and adults 65 years or older are among those most at risk for disease.

CDC inventors have developed a simple, rapid flow, cytometric opsonophagocytic (mOPA) assay for the detection of functional antibodies against Streptococcus pneumoniae (S. pneumoniae). This in vitro assay measures functional antibody activity (of the phagocytes ingesting and eliminating pathogens) in samples from a subject vaccinated with a multivalent vaccine or after exposure to a bacterial pathogen. This assay can use a metabolic dye indicator that provides a colorimetric indicator of bacterial growth. As a result, neither growing bacteria into colonies, nor colony counting is needed, hence minimizing handling of viable bacteria. Alternately, the assay can also use fluorescently labelled beads conjugated with bacterial antigens, allowing rapid readout by flow cytometry. CDC’s technology demonstrates high reproducibility, detects up to 90 different S. pneumoniae serotypes, and can be adapted easily for automation.

Additionally, CDC’s technology will save time and resources versus the standard opsonophagocytic killing assay (OPK), a singleplex resource-intensive cell-based assay. At present time, OPK stands as the only in vitro correlate accepted by regulatory agencies for pneumococcal vaccine licensure. CDC’s mOPA addresses this major bottleneck in the pneumococcal vaccine evaluation by demonstrating efficacy of multivalent (i.e., 13-valent) vaccines. With more countries including pneumococcal vaccines in their immunization schedules, there is a strong need for this technique.