Pneumonia may be caused by a variety of microorganisms, including bacteria and viruses, however, one of the primary causes of severe pneumonia is Streptococcus pneumoniae (S. pneumoniae or pneumococcus).
The most common and serious form of pneumococcal disease is the lung infection, pneumococcal pneumonia. Common symptoms of pneumococcal pneumonia include fever and chills, cough, hyperventilation, difficulty breathing and chest pain  .
Classic symptoms of pneumococcal pneumonia are typically observed in older children and adults, while young children and the elderly will present differently (discussed later) . Infected patients typically have an ill or anxious appearance . Initially a viral illness is followed by an acute onset of high fever, rigors, productive cough, chest pain, dyspnea, tachypnea, tachycardia, excess perspiration, general discomfort and fatigue  . A detailed physical exam will identify rales in most patients, dullness on percussion (along with other signs of empyema) and splinting due to pain in about half of patients. Decreased diaphragmatic motion from what is expected (considering tachypnea) may be observed .
Symptoms of pneumococcal pneumonia in younger children are generally much broader and non-specific compared to older children and adults    . These symptoms may include mild respiratory symptoms, initial presentation of cough, tachypnea, dyspnea, splinting, high fever, abdominal pain and distention and/or anorexia  . Young patients may also present emesis which suggests primary gastrointestinal disease, meningeal signs due to meningeal irritation (in right upper lobe pneumonias), and/or chest pain due to pleural irritation  . The primary presenting symptom of pneumococcal pneumonia in elderly patients may be tachypnea and often elevated temperatures are absent or mild in this patient population   . The most common cause of CAP in human immunodeficiency virus (HIV) patients is pneumococcus infection .
Pleural effusion is the most common complication from pneumococcal pneumonia occurring in 40% of patients . Only 10% of patients have enough fluid in their pleural cavity to aspirate and only 2% of these patients meet the criteria for true empyema  . Nonetheless, pneumococcal infection is one of the most common causes of pediatric empyema   .
Diagnosing pneumococcal pneumonia most often starts by establishing the presence of pneumonia . Pneumonia is diagnosed by clinical symptoms, including cough, dyspnea and tachypnea, and radiologic evidence  . Representative chest radiographs in older children and adults with pneumococcal pneumonia show lobar consolidation while younger children and infants more often display patterns of scattered parenchymal consolidation   . Sputum Gram staining and culture are also primary steps for diagnosing pneumonia   .
The gold standard to determine pneumococcal pneumonia is by identifying S. pneumoniae in a normally sterile body fluid  . In suspected pneumonia cases that require hospitalization, sputum cultures should be attempted . Suitable sputum samples should have a few epithelial cells (<10 at 100X) and many polymorphonuclear neutrophils (>25 at 100X) with a ratio between 1:10 and 1:20  . The presence of pneumococcus is likely if Gram staining of sputum reveals numerous pairs of Gram-positive cocci organized in chains (characteristic of S. pneumoniae)   . Blood cultures should be obtained from patients with pneumonia, which will stain positive for S. pneumoniae in 10% of children and up to 25% of adults with pneumococcal pneumonia   . Chest ultrasonography or computerized tomography may be performed to determine the presence and extent of pleural effusion . In extreme cases of pleural effusion/empyema, attempts should be made to aspirate pleural fluid for Gram staining and culture of S. pneumoniae   .
The majority of patients with pneumococcal pneumonia present leukocytosis (>12,000 cells/µL) and one out of four patients have low hemoglobin levels (<10 mg/dL)  . If Howell-Jolly bodies are observed in peripheral smears this indicates splenic dysfunction . Additionally, pneumococcal pneumonia patients may display elevated neutrophil levels, C-reactive protein (CRP) levels and erythrocyte sedimentation rate (ESR)  .
Severity and presentation of symptoms among patients with pneumococcal pneumonia vary widely, from mild illness to respiratory distress requiring intensive care  . Hospitalized patients should be administered parenteral antibiotics along with medications to manage nutrition and symptoms, including pulmonary symptoms, pain medications, intravenous (IV) fluids and nutrition, and other medications administered on a case by case basis     . Severe and/or complicated cases may require a chest tube to drain pleural fluid, video-assisted thoracoscopic surgery (VATS) or decortication   . New Clinical Practice Guidelines (CPG) for infants and children were released by the Infectious Disease Society of America (IDSA) in 2011 . Briefly, these guidelines recommend IV administration of amoxicillin (90 mg/kg/day or 45 mg/kg/day in 2 or 3 doses, respectively) as the first-line therapy for previously healthy and immunized patients from the infant to adolescent ages with mild to moderate pneumococcal pneumonia . Additionally, children greater than 5 years of age should be administered macrolide if clinical symptoms are compatible with atypical organism infection . Children who are incompletely immunized, live in areas with prevalent penicillin resistance or who have life threatening conditions (including empyema) should be given third-generation parenteral cephalosporin (ceftriaxone or cefotaxime) . If there is a suspicion of S. aureus infection non-beta-lactam agents, such as vancomycin, should also be administered .
Worldwide, pneumococcal disease caused an estimated 1.6 million deaths in 2005, with the majority of these deaths (40-60%) occurring in young children (less than 5 years of age)   . The mortality rate associated with pneumococcal pneumonia is 10-20% in adults, even in developed countries, and can be much higher in individuals with risk factors for this disease, such as compromised immune system, smoking and drug use  .
S. pneumoniae is an encapsulated, Gram-positive, catalase-negative, facultative anaerobe that displays characteristic chains of lancet-shaped diplococcic on Gram stains   . Along with Gram staining, pneumococcus can be detected on blood or chocolate agar plates where they form a green zone around colonies due to the production of pneumolysin (making them hemolytic)    . These organisms can be distinguished from other alpha-hemolytic streptococci based on their optochin-sensitivity and bile solubility .
S. pneumoniae, which is the leading cause of CAP, is responsible for approximately two million deaths worldwide and costs hundreds of billions of dollars annually . Worldwide, children under the age of two are the most common individuals to contract pneumococcal disease, followed by adults older than 55 years of age   . Disease prevalence in developing countries is higher in children under 6 months of age, whereas, developed countries have higher incidence in children between 6 months and 1 year or age   . Most studies indicate males have a higher prevalence of pneumococcal infection compared to females . Certain ethnic groups in the United States have higher incidence of invasive pneumococcal disease including, native Alaskans, Navajo and Apache Indians, and African Americans   . The reasons for these discrepancies remain unclear. Individuals with suppressed immune systems have a higher risk for contracting pneumococcal disease   .
S. pneumoniae is an extracellular bacterial pathogen that can be found in the nose and throat of 5-10% and 20-40% of healthy adults and children, respectively   . Clinical manifestation in patients requires S. pneumoniae to access and colonize the upper and/or lower respiratory tract, which occurs via direct extension, lymphatic spread or hematogenous spread . In healthy individuals under normal conditions, successful clearance mechanisms (anatomic and ciliary) prevent clinical infection/symptoms . Therefore, pathogenicity involves bacterial adhesion proteins and capsule proteins that allow adherence to host cells, escape from clearance and/or phagocytosis and the ability to replicate   .
Few toxins have been identified from pneumococcal isolates aside from pneumolysin, which is expressed by all serotypes  . Pneumolysin is an important virulence factor (classified as a cholesterol-dependent cytolysin), released by S. pneumoniae, that produces pores in host cell membranes leading to cell death  . Additionally, pnuemolysin is a potent activator of the complement system and causes the release of inflammatory cytokines, tumor necrosis factor and interleukin-1 . Other important virulence factors may include adhesion proteins, such as surface protein A and surface adhesion A, and enzymes, such as autolysin, hyaluronidase and neuraminidase  . The composition and size of the bacterial capsule is another determinant of virulence . Individuals with no previous exposure to S. pneumoniae (or no antibodies to pneumococcal capsule) display a limited immune response, including diminished phagocytosis and activation of the classical complement pathway  .
Patient symptoms primarily arise from activation of the complement pathway and robust inflammation caused by inflammatory cytokine release . The alternative complement pathway is directly activated by S. pneumoniae cell wall and capsule components, whereas, the classical complement pathway is activated by antibodies to the cell wall of S. pneumoniae  . Bacterial cell wall proteins and deoxyribonucleic acid (DNA) along with pnuemolysin and autolysin are the primary causes of inflammatory cytokine production .
There is an increased risk for invasive pneumococcal disease associated with cigarette smoking, therefore, smoking cessation should be encouraged   . A healthy diet and ideal living conditions may decrease disease risk and when applicable breastfeeding should be encouraged  . Children who attend daycare have an increased risk for acquisition, carriage and infection with pneumococcal disease which is directly correlated with the number of children that attend a daycare . Doctors may consider antimicrobial prophylaxis for at risk patients with recurrent otitis media . Children with true anatomical or functional asplenia should be administered prophylaxis with penicillin to help prevent pneumococcal disease   .
S. pneumoniae is a member of the genus Streptococcus that is characterized by being Gram-positive, catalase-negative, alpha-hemolytic and anaerobic . Along with being the most common cause of community-acquired pneumonia (CAP), S. pneumoniae also causes bacterial meningitis, bacteremia, otitis media, sinusitis, septic arthritis, osteomyelitis, peritonitis and endocarditis .
Pneumococcal pneumonia is a serious condition caused by S. pneumoniae, which are easily identified in the sputum of infected individuals by their characteristic organization in Gram-positive diplococci chains. S. pneumoniae release toxins that activate the complement system and induce inflammation leading to a wide range of symptoms, that may include fever and chills, cough, hyperventilation, difficulty breathing and chest pain. An estimated two million deaths per year are caused by pneumococcal pneumonia (mortality rate ~ 10-20%) with the majority of these deaths occurring in children 5 years of age or younger. Antibiotics, such as penicillin, are typically used to treat this disease but with the emergence of resistant strains, cephalosporins, vancomycin or fluoroquinolones may be administered. Presentation of disease varies greatly and the patient’s age should be considered for diagnosis and treatment of pneumococcal pneumonia.
Pneumococcal pneumonia is a serious and sometimes life threatening disease caused by the bacteria S. pneumoniae (also known as pneumococcus)  . This bacterium may be spread by water droplets that are released through the air when infected individuals cough or sneeze. Symptoms of pneumococcal pneumonia often arise suddenly and may include fever, chills, malaise (general discomfort), shortness of breath and a cough that produces rust colored sputum  . Sharp stabbing chest pains on one side, which are worsened by deep breathing and cough, often occur . A little less than half of patients will develop fluid accumulation in the lining around their lungs (pleural effusion) which also contributes to chest pain and difficulty breathing . Your doctor will perform chest X-rays to look for pneumonia and take sputum samples to look for pathogens  . Sputum, blood and pus samples may be sent to a laboratory to identify S. pneumoniae through growth (culture) and staining methods, which easily identify the presence of S. pneumoniae   . If bacteria are present, the effectiveness of different antibiotics can be tested through a process known as susceptibility testing   .
Currently, there are two types of vaccines for S. pneumoniae available. The PCV13 is a conjugate vaccine that protects against 13 different type of pneumococcus and the PPS23 is a non-conjugate vaccine that protects against 23 different types of pneumococcus  . Children under 5 years of age with an absent or dysfunctional spleen are often given recurrent antibiotics that may continue into adulthood   . The most common antibiotics administered for pneumococcal infections are penicillin, ampicillin and amoxicillin  . Typically, antibiotics are given orally, however, in severe cases intravenous administration may be required   . The recent increase in penicillin resistant strains of pneumococcus has led to the use of other antibiotics, such as ceftriaxone, cefotaxime, vancomycin or fluoroquinolones (eg. levofloxacin)  .