SEM of Streptococcus pneumoniae. Streptococcus pneumoniae, the bacteria responsible for pneumococcal meningitis, is very common, and normally lives in the back of the nose and throat, or the upper respiratory tract. However, it is also the cause of significant disease being a leading cause of pneumonia, bacterial meningitis, and sepsis. The World Health Organization estimate that in 2005 pneumococcal infections were responsible for the death of 1.6 million children worldwide. Magnification unknown.