The ability to exchange oxygen and carbon dioxide through the lungs is critical to life. The lungs are a common sight, however, for infections because the natural environment of the lungs is moist and well oxygenated--a perfect breeding ground for bacteria to grow. Infections compromise the ability to move oxygen through the system, so lung infections can be very serious.
Tuberculosis kills 2 million people a year worldwide, according to MayoClinic.com. Tuberculosis is a respiratory infection that is spread from person to person by airborne droplets. Mycobacterium tuberculosis is the pathogen responsible for this disease. When tuberculosis pathogens enter the lungs, they begin to multiply. As the disease progresses, the immune system kicks in and builds up a wall around the infection which will appear as a lung mass on a chest X-ray. If the immune system is overwhelmed by the infection, large air spaces called cavities develop in the lungs. These cavities represent destroyed lung tissue and provide a perfect environment for continued breeding of the mycobacteria.
Histoplasmosis capsulatum grows as a fungus in nature, and is associated with bird and bat droppings. It is highly prevalent in the Ohio-Mississippi River Valley, according to The Merck Manuals. Histoplasmosis develops after inhalation of the spores that develop on the fungus. An acute infection is accompanied by fever, cough and symptoms of pneumonia. A chronic cavitary histomplasmosis infection is characterized by lung masses that develop in the apical, or upper, regions of the lungs. This infection can spread via the blood to other organs such as the liver and spleen.
Actinomycosis israelii causes lung infections that show up as a mass on X-rays. This type of lung infection involves other bacteria as well, such as Staphylococci and Streptococci, according to The Merck Manuals. Actinomycosis usually develops in adult males, and the pulmonary form results from aspiration of the pathogen in oral secretions. Actinomycosis of the lung can resemble tuberculosis on X-rays.