Pneumococcal Pneumonia

Clinical Description

Identification

Streptococcus pneumoniae (pneumococcus) is the most common bacterial etiology of community-acquired pneumonia among all ages. In Europe and North America, estimates of the rate of pneumococcal pneumonia vary widely, from approximately 30 cases per 100 000 to nearly 100 per 100 000 adults each year, depending on the population studied and the diagnostic tests used. Clinical manifestations include sudden onset, high fever, rigors, pleuritic chest pain, dyspnea, tachypnea, and cough productive of “rusty” sputum. Onset may be less abrupt, especially among the elderly; fever, shortness of breath, or altered mental status may provide the first evidence of pneumonia. In infants and young children, fever, vomiting and convulsions may be the initial manifestations. Laboratory findings include leukocytosis (neutrophilia) and elevated C-reactive protein. Typical chest radiograph findings show lobar or segmental consolidation; consolidation may be bronchopneumonic, especially in children and the elderly. Pneumococcal pneumonia is an important cause of death in infants and the elderly. Persons suffering from chronic conditions and immune deficiencies are at increased risk. Infection can be complicated by empyema, acute respiratory distress syndrome, septic shock, and purpura fulminans. The case-fatality rate also varies widely, from 5–35%, depending on the setting (e.g., outpatients vs. inpatients) and the population (e.g., healthy adults vs. persons with alcoholism). In developing countries, case-fatality rates among children are often over 10%, and as high as 60% among infants under 6 months of age. Pneumococcal pneumonia among previously healthy individuals with other respiratory infections (e.g., influenza) is well-described.

Pneumonia is generally treated empirically with antimicrobial agents that have good activity against pneumococcus.

Infectious Agents

Streptococcus pneumoniae (pneumococcus) is a Gram-positive, lancet-shaped, encapsulated diplococcus that often asymptomatically colonizes the human nasopharynx. Children are colonized with S. pneumoniae more often than adults. Current data suggest that a hypothetical vaccine including six serotypes (1, 5, 6B, 14, 19F, 23F, assuming 6A cross-protection from 6B) could cover 70% of invasive disease worldwide, ranging from 66% in North America to 76% in Africa.
 


Diagnosis

A microbiologic diagnosis of pneumococcal pneumonia can further guide antibiotic therapy. The presence in sputum of many Gram-positive diplococci together with polymorphonuclear leukocytes suggests pneumococcal pneumonia; however, Gram stain and culture of respiratory secretions are performed less frequently than previously, largely due to technical aspects of obtaining good quality specimens and the difficulty of distinguishing infection from respiratory tract colonization. Definitive diagnosis of pneumococcal pneumonia is established by isolation of pneumococci from blood or, less commonly, pleural fluid. Among adults, the diagnosis can also be established by identification of pneumococcal polysaccharide in urine. For children, urine antigen testing is not useful because nasopharyngeal colonization can cause excretion of pneumococcal antigen in urine. Most pediatric cases are diagnosed by isolation of pneumococci from blood. Patients suspected of having pneumococcal pneumonia should be treated promptly, preferably after collection of appropriate diagnostic specimens, according to established guidelines. If pneumococcus is isolated, susceptibility testing should be performed, and antimicrobial therapy tailored to susceptibility results.
 


Epidemiology

Mode of Transmission

Droplet spread. Person-to-person transmission of the organisms is common, but illness among casual contacts and attendants is infrequent.

Incubation Period

Not well determined; may be as short as 1–3 days. Infection is thought to be preceded by asymptomatic colonization.

Period of Communicability

Presumably until discharges of mouth and nose no longer contain sufficient numbers of pneumococci, which usually occurs within 24 hours of initiation of effective antibiotic therapy.

Reservoir

Humans. Pneumococci are commonly found in the upper respiratory tract of healthy people worldwide.

Susceptibility

Susceptibility is increased among certain populations, including infants, the elderly, and persons with underlying illnesses such as anatomical or functional asplenia, sickle cell disease, cardiovascular disease, diabetes mellitus, cirrhosis, Hodgkin's disease, lymphoma, multiple myeloma, chronic renal failure, nephrotic syndrome, HIV infection, and recent organ transplantation. Malnutrition and low birthweight are important risk factors for infection among infants and young children in developing countries. Susceptibility to infection is also increased by processes affecting the integrity of the lower respiratory tract, including influenza, pulmonary edema, aspiration following alcoholic intoxication or other causes, chronic lung disease, or exposure to irritants (e.g., cigarettes, cooking fire smoke). Previously healthy persons can develop pneumococcal pneumonia. Serotype-specific immunity usually follows infection and may last for years.

Occurrence

Pneumococcal pneumonia is an endemic disease among the elderly and those with underlying medical conditions. Infection is more frequent among malnourished populations and lower socioeconomic groups, especially in developing countries. It occurs in all climates and seasons, peaking in winter in temperate zones. Certain serotypes may cause epidemics, especially among institutionalized populations, the homeless, and in developing countries. Incidence is high in certain geographic areas (e.g., Papua New Guinea) and in certain ethnic groups, such as Alaska Natives and Australian Aboriginals. An increased incidence often accompanies epidemics of influenza.
 


Prevention and Control

1)    Preventive measures:

a)    Avoid crowding in living quarters whenever practical, particularly in institutions. Prevent malnutrition and encourage physical activity. Bedridden patients should lie in an upright position, at a 30- to 45-degree incline.

b)    A protein-polysaccharide conjugate vaccine including seven of the commonest serotypes was introduced in 2000 and subsequently included in the routine infant immunization schedules in many countries. The vaccine has been shown to be highly effective at preventing invasive pneumococcal disease and pneumococcal pneumonia, with important reductions in disease incidence demonstrated in the target age population (direct effects) as well as those too old or too young to receive the vaccine (indirect, or herd, effects). It should be noted that the evidence for this is mostly from developed countries, and at time of writing in early 2008 there is little information about the effectiveness of the vaccine in developing countries.

WHO considers that it should be a priority to include pneumococcal conjugate vaccine in all national immunization programs—though countries, and particularly developing countries, should consider switching to newer vaccines with more serotypes once these are available and affordable.

c)    A 23-valent polysaccharide vaccine (PPV23) is available for persons aged more than two years. In some countries it is recommended for high-risk persons (individuals 65 years of age and older and those with anatomic or functional asplenia, sickle cell disease, HIV infection and a variety of chronic systemic illnesses, including heart and lung disease, cirrhosis of the liver, renal insufficiency and diabetes mellitus). The role of PPV23 in preventing pneumococcal disease among HIV-infected persons in sub-Saharan Africa is unclear. WHO has recently convened a working group to prepare a revised position statement on the use of this vaccine. More information can be found at http://www.who.int/immunization/sage/ppv_membership/en/index.html

d)    PPV23 is not effective in children under two years of age and has no impact on pneumococcal carriage. For most eligible patients, vaccine need be given only once; however, re-immunization is generally safe, and vaccine should be offered to eligible patients whose immunization status cannot be determined. Re-immunization is recommended once for persons over 2 years of age who are at highest risk for serious pneumococcal infection (e.g., asplenic patients), and those likely to have a rapid decline in pneumococcal antibody levels, provided that 5 years or more have elapsed since receipt of the 1st dose of vaccine. Re-immunization after 3 years should also be considered for children with functional or anatomic asplenia, and those who present conditions associated with rapid antibody decline after initial immunization (e.g., nephrotic syndrome, renal failure, renal transplantation) who would be 10 years or younger at re-immunization. In addition, persons aged 65 years and older should be given another dose of vaccine if they received the vaccine more than 5 years previously and were under 65 at the time of primary immunization.

2)    Control of patient, contacts and the immediate environment:

a)    Report to local health authority: Obligatory report of epidemics in some countries; no individual case report, Class 4.

b)    Isolation: Respiratory isolation may be warranted for hospitalized patients with highly antibiotic resistant infection, who may transmit it to patients at high risk of pneumococcal disease.

c)    Concurrent disinfection: Hand hygiene and cough etiquette.

d)    Quarantine: Not applicable.

e)    Immunization of contacts: Not applicable.

f)    Investigation of contacts and source of infection: Of no practical value.

g)    Specific treatment: Antibiotic treatment of infants and young children with pneumonia should start presumptively based on a clinical diagnosis. If tachypnea and chest indrawing are present, infants aged less than 2 months should be transferred to hospital care without delay; if pneumococcal pneumonia is identified, parenteral penicillin G or ampicillin are preferred treatments (or erythromycin for those hypersensitive to penicillin). Based on a recent clinical trial in Pakistan, immediate treatment of children aged 3–59 months with severe pneumonia with oral amoxicillin may result in equivalent outcome compared to hospitalization and intravenous ampicillin. Because pneumococci resistant to penicillin and other antimicrobials are increasingly recognized, sensitivities of strains isolated from normally sterile sites, including blood or CSF, should be determined. Caution should be exercised in interpreting susceptibility results, as the same isolate may be considered susceptible or resistant to certain antibiotics (e.g., penicillin, third generation cephalosporins) depending on the site of infection (e.g., blood vs. meninges). In developing countries, WHO guidelines recommend trimethoprim-sulfamethazole, ampicillin or amoxicillin for home-treatment of non-severe pneumonia for children under 5 years of age (NB: recommended duration of treatment in non-severe pneumonia, based on findings from RCTs, is 3 days, instead of the standard 5 days). WHO guidelines are not intended for industrialized countries, most of which have no unified guidelines for the treatment of pneumococcal disease, although professional societies have published recommendations for the treatment of community-acquired pneumonia and pneumonia in children.

3)    Epidemic measures:

In outbreaks in institutions or in other closed groups, immunization may be carried out unless it is known that the type causing disease is not included in the vaccine. Based on experience with Haemophilus influenzae type b vaccine, there is a theoretical concern that immunization with PPV23 may be followed by a period of a few days of increased susceptibility to infection. If PPV23 is used, or if the outbreak is particularly explosive, antibiotic prophylaxis may need to be considered.

4)    Disaster implications:

Crowding of populations in temporary shelters bears a risk of disease, especially for the very young and the elderly.

5)    International measures:

None.

Source: Heymann (Ed.). (2008). Control of Communicable Diseases Manual, 19th edition. Washington, DC: American Public Health Association.
 


Available Vaccines

WHO-Prequalified pneumococcal pneumonia vaccines

 

Common Disease Taxonomy: