Pneumonia

DEFINITION: An infection of one of several possible areas of the respiratory system, mainly in the lungs or bronchial passageways

ANATOMY OR SYSTEM AFFECTED: Lungs, respiratory system

CAUSES: Bacterial or viral infection

SYMPTOMS: Lung inflammation, painful coughing, high fever, reduced sputum production, rust-tinged or greenish sputum

DURATION: Acute

TREATMENTS: Antibiotics (tetracycline, erythromycin), supportive care

Causes and Symptoms

Although modern medicine succeeded several generations ago in identifying the key viruses and bacteria responsible for pneumonia and in developing efficient medications for its treatment, a surprisingly high number of deaths from the complications of pneumonia continue to occur. Pneumonia is a leading cause of morbidity and mortality worldwide. In large part this is the case because pneumonia, which involves infection and inflammation in the respiratory system, occurs not only on its own but also as a complication brought about by other serious illnesses. In older patients, especially, deterioration of the body’s resistance to bacterial or viral infection can lead to death from pneumonia.

Just as the causes of pneumonia can vary, the disease itself may take different forms. Some sources postulate that pneumonia is not a single disease but a group of advanced lung inflammations. Because they are so similar in their symptoms and effects on the body, all members of this family of diseases are labeled as one form or another of pneumonia. Specific forms range from lobar pneumonia (caused by the bacterial invasion of Streptococcus pneumoniae into a single lobe of one lung) and bronchopneumonia (from Haemophilus influenzae infection in the bronchi) to viral pneumonia (which may be caused by complications originating from chickenpox or influenza virus). In all cases, symptoms include painful coughing, but other symptoms, such as high fever, increased sputum production, chills, leukocytosis, chest pain, or shortness of breath, may differ. It follows that the drugs that have been developed to treat pneumonia necessarily vary according to the variety of the disease involved.

Lobar pneumonia and bronchopneumonia are the two main classes of disease. The former occurs when an initial infection attacks only one lobe of one lung. Bronchopneumonia results from an initial inflammation in the bronchi and bronchioles (air passages to the lungs), which then spreads to the internal tissue of one or both lungs. Once the symptoms of pneumonia have become visible, any of the following may occur: fever, chills, shortness of breath, chest pains, or a painful cough that produces yellow-green or brownish sputum. These symptoms occur because of a condition called pleurisy, which is an inflammation of the membrane lining the lungs themselves and the general chest cavity area.

Some assumptions about the causes of pneumonia being limited to bacterial or viral sources have been altered. In particular, clinical observation of patients suffering from AIDS reveals that certain fungi, yeasts, or protozoa can cause pneumonia in these and other cases where immunodeficiency disorders are present.

Although it is apparent that pneumococci can thrive in various parts of the bodies of animals, particularly monkeys and humans, the process that leads to general infection and a concentrated and dangerous attack on the pulmonary system has been the subject of many medical investigations. The presence of viruses that cause the common cold in the upper respiratory tract can create the conditions needed for the movement of pneumococci from areas of the body where they may be generally present without causing harm (mainly in saliva) into the pulmonary system. Under conditions of normal health, many body mechanisms can stop a potential invasion of the pulmonary system. This process may involve nasal mucus, although it is not itself bactericidal (bacteria-killing), and other mucous membranes in the region of the larynx. Even beyond the larynx and vocal cords, mechanical means associated with the upward sweep of hairlike protrusions called cilia on the inner linings of deeper respiratory membranes tend to protect the bronchial tree.

When normal protective processes are reduced, as when the cold virus is present or the patient is a former or current smoker, pneumococci may reach the lower respiratory zone and the parenchyma of the lung, where they settle and multiply. The metabolic products that accumulate as a result of this reproductive process begin to have injurious effects on the respiratory organs. Such injuries become actual lesions in the internal respiratory tissues. The process of infection that follows involves the deposition of fibrin in the adjacent blood and lymph vessels. This phenomenon actually tends to shield the invading organisms from the effects normally produced by antipneumococcal immune substances carried by the blood. If unchecked by medical treatment, reproduction of the invading pneumococci can lead to more extensive lesions. If tissue damage occurs, this can cause the formation of edema, a dangerous accumulation of fluids in spaces where fluids are not normally found. At a later stage of the disease, it appears that the pneumococci enter the interstitial and lymphatic tissues. The unchecked advance of pneumonia infection produces a general deterioration of vital breathing processes as excess fluids spread farther into the respiratory system. In weakened or immunocompromised individuals, this process can lead to death.

Treatment and Therapy

Medical treatments of different types of pneumonia are not the same. Treatment also depends on the severity of symptoms and the patient's overall health and age. Viral pneumonia may be treated with antiviral medication in cases where the patient also has influenza and severe health problems. Pneumonia caused by a bacterial infection is typically treated with antibiotics. If the patient is otherwise healthy and has no risk factors for drug-resistant organisms, such as use of antibiotics within the past three months, a macrolide such as azithromycin or doxycycline may be prescribed. If that patient has chronic comorbidities such as diabetes or heart, lung, or liver disease, a respiratory fluoroquinolone such as levofloxacin may be used. Symptoms typically subside within a few days of taking antibiotics, although a cough can last for several weeks. Over-the-counter medications such as acetaminophen and ibuprofen can be used to reduce fever and pain. Contact your doctor before using a cough suppressant because coughing is helpful in clearing the lungs. Patients with pneumonia should drink plenty of fluid, get plenty of rest, and avoid cigarette smoking and secondhand smoke.

Most people who are otherwise healthy will recover with outpatient treatment. Hospitalization may be required for individuals who have serious medical problems, are experiencing severe symptoms, are over the age of sixty-five, have weakened immune systems, or have not responded to outpatient treatment. Inpatient treatment may involve oxygen therapy or adjunctive corticosteroids. The risk of developing pneumonia can be reduced with the flu vaccine and the pneumococcal vaccine, frequent handwashing, and not smoking.

Perspective and Prospects

Although modern medicine has not been able to reduce substantially or eliminate totally the number of cases of pneumonia, much has been learned about the disease and its causes. Scientific advances began with the first isolation of Streptococcus pneumoniae in France and the United States in 1880. The French discovery of pneumococci is associated with the laboratory of Louis Pasteur. Simultaneously, George Sternberg was completing work in the medical department of the US Army. In the first decade after the isolation of pneumococci, many different researchers contributed to laboratory findings that linked these bacteria to inflammatory infections in the lungs of animals. They extended their research to include the effects on humans.

One of the most important early breakthroughs came in 1884 when the Danish researcher Hans Christian Joachim Gram developed a laboratory method for identifying specific bacteria in tissue specimens. This technique, called Gram’s stain, revealed that different chemical reactions occur when samples of lung tissue and secretions from individuals ill with pneumonia and healthy persons are tested. The tissues stain very differently. The next step would lead to research into the phenomenon of phagocytosis, a process within pulmonary tissue that combats inapparent pneumococcus infection in healthy people. This specific discovery became linked with efforts to develop an immunization technology against pneumonia.

Until the 1980s, medical researchers used their knowledge of pneumonia mainly to develop methods of immunization against the disease. They also tried to diversify the drugs used in treating pneumonia. Efforts to produce a vaccine against pneumonia began with experiments by the German researchers George and Felix Klemperer, who tested antiserum in animals in 1891. The Klemperers were able to show that the offspring of adult rabbits which had been immunized were resistant to pneumococcal invasion and infection. Soon thereafter, they carried out the first injections of immune serum into human patients. This research ultimately led to the finding that there was no actual antitoxin or antibacterial property in the serum. Instead, it promoted phagocytosis, a process of encapsulation around pneumococci that aids in the immunological response of white blood cells in the body. The vaccine stimulates the body to create its own defenses.

In 1911 in South Africa, an experimental pneumonia vaccine program was undertaken. Although the specific program was not successful, the British physician and scientist Frederick Lister extended its theory. Unequivocal success with a pneumonia vaccine did not come until the last year of World War II. In 1945, C. M. MacLeod and several colleagues published research findings proving that pneumococcal infection in humans was preventable through the use of vaccines containing as many as fourteen specific antigens. These were termed capsular polysaccharides. The breakthrough that made those findings possible had been pioneered in 1930 when these antigens were injected into human beings for the first time. Previously, they had been used only in experiments with mice.

The pneumococcal conjugate vaccine (PCV13) protects against thirteen types of pneumococcal bacteria and provides protection against pneumonia. However, there are more than ninety types of pneumococcal bacteria. Furthermore, the PCV13 vaccine will not prevent pneumonia caused by viruses or fungi. The PCV13 vaccine is recommended with doses at two months, four months, six months, and twelve to fifteen months. One dose of the PCV13 vaccine is recommended for all adults over the age of sixty-five who have not already received the vaccine.

Children under the age of five are also at high risk for catching pneumonia. The World Health Organization reported that pneumonia accounted for 14 percent of all deaths of children under the age of five in 2019, the most recent year for which statistics are available. Only one-third of children with pneumonia receive antibiotic treatment. As a result, an estimated 740,180 children under the age of five died of pneumonia in 2019.

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