Streptococcus pneumoniae (S. pneumoniae)

Pneumococcal infections are caused by S. pneumoniae.23 There are more than 90 known serotypes, but most infections are caused by serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F. They commonly colonize the nasopharynx and are transmitted person-to-person via airborne droplets generated by coughing and sneezing and by direct contact with respiratory secretions and saliva. Many people are asymptomatic carriers of S. pneumoniae.

Clinical Features

S. pneumoniae causes up to half of the middle ear infections (acute otitis media) in children. Signs and symptoms include ear pain, red and swollen ear drum, fever, and sleepiness. While ear infections are usually mild, some children develop mastoiditis and repeated ear infections and may need ear tubes. Long-term consequences may include hearing loss.

Complications of acute otitis media include meningitis. S. pneumoniae cause over 50% of all cases of bacterial meningitis in the United States. Symptoms may include headache, lethargy, vomiting, irritability, fever, nuchal rigidity, cranial nerve signs, seizures, and coma. The case-fatality rate of pneumococcal meningitis is about 8% among children and 22% among adults.

S. pneumoniae is the most common cause of pneumonia among adults. Symptoms include fever, chills or rigors, a productive cough, rapid breathing or difficulty breathing, chest pain and in older adults confusion. The case-fatality rate is 5-7%. Complications of include empyema, pericarditis, and respiratory failure. Bacteremia occurs in up to 25–30% of the patients.


Pneumococcal infections are vaccine-preventable. The pneumococcal conjugate vaccine (PCV13 or Prevnar 13®) provides protection against the 13 serotypes responsible for most severe illness. The 23-valent pneumococcal polysaccharide vaccine (PPSV23 or Pneumovax 23®) is recommended for use in all adults over the age of 65 and for use in adults who smoke cigarettes or who have asthma.

Medical Management

Early diagnosis and treatment with an antibacterial agent is the cornerstone of treating pneumococcal infections. S. pneumoniae are resistant to one or more antibacterial agent in 30% of cases. The initial therapeutic strategy is to administer a broad-spectrum antibiotic until results of susceptibility testing are available. Once bacterial susceptibility is known, a more targeted (or ‘narrow spectrum’) antibiotic may be selected.