Pneumococcal Infections
Pneumococcal infections are caused by Streptococcus pneumoniae (pneumococcus), a gram-positive coccus that usually infects the lungs.
Pneumococci commonly inhabit the upper respiratory tract of people, their natural host, particularly during the winter and early spring. Despite their presence, pneumococci only occasionally cause illness. The most common serious pneumococcal disease is pneumonia, an infection of the tissues of the lungs (see Section 4, Chapter 42).
Pneumococci may also cause infections in the ear (otitis media), paranasal sinuses (sinusitis), the tissues covering the brain and spinal cord (meningitis), and, less often, the heart valves, joints, and abdominal cavity. Sometimes these areas become infected because the pneumococci have spread through the bloodstream from another site of infection.
People at particular risk of developing pneumococcal infection include those with chronic illnesses and a weakened immune system--for example, people with Hodgkin's disease, lymphoma, multiple myeloma, malnutrition, and sickle cell disease. Older people also often develop pneumococcal infections. Because antibodies produced in the spleen normally help prevent pneumococcal infection, people who have had their spleen removed or who have a nonfunctioning spleen are also at risk. Pneumococcal pneumonia also may develop after chronic bronchitis or if a common respiratory virus, notably the influenza virus, damages the lining of the respiratory tract.
Symptoms and Diagnosis
Symptoms begin suddenly with sharp chest pains and shaking chills. Sometimes, these symptoms follow the symptoms of a viral upper respiratory tract infection (sore throat, stuffed nasal passages, runny nose, and nonproductive cough). Fever and cough develop, and the cough produces sputum, which may have a rusty color. The person feels generally sick and is often short of breath.
Sometimes, doctors can recognize pneumococci when examining a sample of sputum under a microscope. Usually, however, a sample of sputum, pus, or blood is sent for culture. Chest x-rays are taken to look for pneumonia.
People with pneumococcal meningitis have fever, headache, and a general feeling of illness (malaise). The neck becomes stiff and painful to move, although this is not always obvious early in the disease. As soon as doctors suspect meningitis, they perform a spinal tap (lumbar puncture (see Section 6, Chapter 77)) to look for signs of infection, such as white blood cells and bacteria, in the cerebrospinal fluid.
Pneumococcal ear infections are common in children. These infections cause ear pain and a red, bulging eardrum. Cultures and other diagnostic tests are usually not done. The use of a vaccine against pneumococci in children very significantly lowers the rate of serious infection.
Prevention and Treatment
Two types of pneumococcal vaccines are available. One (conjugate vaccine) can be given to children as young as 2 months of age (see Section 4, Chapter 263). The other (nonconjugate vaccine) is for older children and adults; this vaccine protects against the most common strains of pneumococci, substantially reducing the chance of developing pneumococcal pneumonia and bacteremia. Pneumococcal vaccine is recommended for people 55 and older, infants, and some older children, and should also be given to people with chronic heart and lung diseases, diabetes, sickle cell disease, Hodgkin's disease, HIV infection, and metabolic disorders. People who have had their spleen removed or who have a nonfunctioning spleen also should be given pneumococcal vaccine.
Penicillin is the preferred antibiotic for most pneumococcal infections. It is taken by mouth for ear and sinus infections and given intravenously for more severe infections. Pneumococci that are resistant to penicillin are becoming increasingly common, so newer quinolone antibiotics are often used.
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