Vaccinating laboratory mice with Streptococcus mitis bacteria prevents their virulent sibling, Streptococcus pneumoniae from infecting the mice. The research suggests that vaccination of humans with live S. mitis might offer protection from some of the many serotypes of S. pneumoniae that vaccines currently do not exist for.
This pathogen is one of the most common causes of severe pneumonia, and can also cause meningitis, bloodstream and sinus infections, endocarditis, and middle ear infections in young children. The research is published January 25th in Applied and Environmental Microbiology.
S. pneumoniae afflicts about 14 million children, annually, killing 2-3 million, including around a million under age five. Resistance to antibiotics is an increasing problem, underscoring the need for vaccines, according to the report. And current vaccines target only 13 of more than 90 serotypes of S. pneumoniae.
S. mitis, which lacks many of the virulence genes present in S. pneumoniae, but is otherwise quite similar, commonly inhabits the oral cavity and the upper respiratory tract, living in peaceful coexistence with the host.
The investigators intranasally vaccinated mice with two different versions of S. mitis, to compare their efficacy: wild type S. mitis, and S. mitis which they had genetically engineered to express a sugar coat that is found on the exterior of the cell wall of S. pneumoniae. Serotype 4, they posited, might strengthen the antibody response to S. penumoniae.
Read more at ASM