Text C 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. 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) 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.

Two types of pneumococcal vaccines are available. One (conjugate vaccine) can be given to children as young as 2 months of age. 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.

Notes:

gram-positive bacterium грамм позитивная бактерия

rusty color рыживатый оттенок

be short of breath задыхаться

Tuberculosis

Tuberculosis is a contagious, potentially fatal infec­tion caused by the airborne bacterium Mycobacterium tuberculosis, M. bovis, or M.africanum.

Tuberculosis refers to disease most commonly caused by Mycobacterium tuberculosis, but occa­sionally caused by M. bovis or M. africanum. Al­though other mycobacteria cause diseases that mimic tuberculosis, those infections are not con­tagious, and most respond poorly to drugs that are very effective against tuberculosis.

People have been contracting tuberculosis since ancient times. Tuberculosis became a major scourge in Europe during the Industrial Revolu­tion, when overcrowding in cities was common, accounting for more than 30 percent of all deaths. With the development of the antibiotics strepto­mycin in the 1940s, isoniazid in the 1950s, etham-butol in the 1960s, and rifampin in the 1970s, the battle against tuberculosis seemed to be won. However, in the mid-1980s, the number of cases in the United States began to rise again. AIDS, combined with overcrowding and unsanitary con­ditions in many urban areas, homeless shelters, and prisons, has again made tuberculosis a seri­ous public health problem. The problem is espe­cially worrisome because some strains of tuber­culosis bacteria have become resistant to the antibiotics used to treat the disease. Nonetheless, in the United States, tuberculosis is starting again to decline as an epidemic.

Tuberculosis is more common among the el­derly. Of almost 23,000 cases reported in the United States in 1995, about 28 percent involved persons over age 65. There are three basic rea­sons why there are more cases in the elderly: (1) Many older persons became infected when tuberculosis was more common; (2) aging may reduce the effectiveness of the body's immune system, which can allow dormant bacteria to become re­activated; and (3) elderly people in chronic care facilities are likely to be in close contact with other elderly people at risk of contracting tuber­culosis.

The disease is also more common in blacks than in whites, partly because blacks are more likely to live in poverty and partly because of how tuberculosis has evolved. For thousands of years, tuberculosis exacted a heavy toll in Europe, which was populated primarily by whites; those who happened to be more resistant to the disease were favored for survival and reproduction. These people thus passed on their tuberculosis-resistance genes to subsequent generations. In contrast, ancestors of American blacks first en-countered tuberculosis after arrival in America, allowing much less time for them to develop tuberculosis-resistance genes to pass on to their progeny.

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