Author(s): Jennifer Loo Farrar

Infectious Agent

A gram-positive diplococcus Streptococcus pneumoniae, also called pneumococcus, causes pneumococcal disease.

Transmission

S. pneumoniae is transmitted person-to-person through close contact via respiratory droplets.

Epidemiology

S. pneumoniae is a major cause of bacterial meningitis and the most common bacterial cause of community-acquired pneumonia worldwide. Disease incidence is higher in low- and middle-income countries than in high-income countries. Pneumococcal meningitis outbreaks have occurred recently in countries in the meningitis belt of Africa (see Sec. 5, Part 1, Ch. 13, Meningococcal Disease). Infections from pneumococcus also have been reported in travelers attending mass gatherings (e.g., the Hajj pilgrimage, Olympic Games) due to crowded conditions and limited space. Risk for infection is greatest in very young children, older adults, and people with chronic illnesses or immune suppression.

Clinical Presentation

The major clinical syndromes of pneumococcal disease are pneumonia, bacteremia, and meningitis. Pneumococcal pneumonia classically presents with sudden onset of fever and malaise, pleuritic chest pain, cough with purulent or blood-tinged sputum, or dyspnea. In older people, fever, shortness of breath, or altered mental status are possible initial symptoms.

Symptoms of pneumococcal meningitis include headache, lethargy, vomiting, irritability, fever, neck stiffness, and seizures. People with cochlear implants are at increased risk for pneumococcal meningitis. S. pneumoniae infection causes meningitis less frequently than it causes pneumonia.

Diagnosis

S. pneumoniae infection is diagnosed by isolation of the organism from blood or other normally sterile body sites (e.g., pleural fluid, cerebrospinal fluid [CSF]). Tests are also available to detect pneumococcal antigen in body fluids (e.g., urine). The urinary antigen test is commercially available, simple to use, and has reasonable specificity to detect pneumococcal infection in adults, making it a useful addition for diagnostic evaluation.

Suspect pneumococcal pneumonia when a sputum specimen contains gram-positive diplococci, polymorphonuclear leukocytes, and few epithelial cells. Gram-positive diplococci on staining of CSF might indicate pneumococcal meningitis. High white blood cell counts should raise suspicion for bacterial infection.

Treatment

Therapy depends on the syndrome, and clinicians should treat patients presenting with community-acquired pneumonia empirically for pneumococcal infection. In 30% of severe cases, pneumococcal bacteria are resistant to ≥1 antimicrobial drug, although the level and type of resistance varies geographically. Studies show that pneumococcal macrolide resistance is widely variable, between 20%–90%. Pneumococcal resistance to fluoroquinolones is relatively low in the United States and Europe. Global prevalence of drug-resistant S. pneumoniae causing community-acquired pneumonia is currently unknown.

In outpatient settings, current clinical practice guidelines for pneumonia management recommend amoxicillin for children, and macrolides (e.g., azithromycin) or doxycycline for previously healthy adults. For adults with chronic or immunosuppressing conditions, a respiratory fluoroquinolone (e.g., moxifloxacin, levofloxacin) or a β-lactam plus a macrolide are recommended.

In inpatient settings, the initial treatment includes a broad-spectrum cephalosporin plus a macrolide or a respiratory fluoroquinolone alone. For some pneumococcal infections, consider adding vancomycin until antimicrobial susceptibility results are available. Use a broad-spectrum cephalosporin plus vancomycin to treat patients with presumptive pneumococcal meningitis by CSF staining until susceptibility results are available.

Prevention

The 13-valent pneumococcal conjugate vaccine (PCV13) provides protection against the 13 serotypes responsible for most severe illness. PCV13 has been part of the US infant immunization schedule since 2010, and Advisory Committee on Immunization Practices (ACIP) recommends PCV13 for some adults aged ≥65 years and adults aged 19–64 with immunocompromising conditions.

ACIP recommends 23-valent pneumococcal polysaccharide vaccine (PPSV23) for all adults aged ≥65 years and people aged 2–64 years with underlying medical conditions. PCV13 and PPSV23 should not be coadministered. Intervals between administering PCV13 and PPSV23 differ by age and risk group.

A 20-valent pneumococcal conjugate vaccine (PCV20) was licensed for use in adults in June 2021, and the 15-valent pneumococcal conjugate vaccine (PCV15) was licensed for use in adults in July 2021. On October 20, 2021, the ACIP approved recommendations to use PCV20 alone, or PCV15 in series with PPSV23, for all adults aged ≥65 years and for adults aged 19–64 years with underlying medical conditions who have not previously received a pneumococcal conjugate vaccine or whose vaccination history is unknown. Official guidance on use of these vaccines is being developed.

CDC website: Pneumococcal disease