The lower portions of the lungs are normally sterile, that is, free of bacteria. When normal lung defenses fail, bacteria can infect the lungs, causing pneumonia. While most people recover from pneumonia, it can be life threatening. According to the Centers for Disease Control and Prevention, pneumonia and influenza are the eighth leading cause of death in the United States. Certain species of bacteria have a propensity for infecting the lungs.
Pneumococcus
Streptococcus pneumoniae, or pneumococcus, is a common cause of bacterial pneumonia. The Centers for Disease Control and Prevention, CDC, reports that pneumococcus causes approximately one-half million cases of pneumonia yearly in the United States. Children younger than age two and those older than age 65 are at greatest risk for pneumococcal disease. CDC recommends the pneumococcal vaccine for all persons older than age 65, and for those age two through 64 with chronic diseases that increase the risk for pneumococcal disease and its complications.
Mycoplasma Bacteria
Mycoplasma pneumoniae is a common causative agent of atypical pneumonia, reports the University of Maryland Medical Center. Atypical pneumonia is usually milder than other types of bacterial pneumonia. The illness most commonly affects adults younger than age 40 and children. According to CDC, 100,000 hospitalizations occur annually in the United States due to pneumonia caused by Mycoplasma pneumoniae.
Meningococcus
Neisseria meningitidis, or meningococcus, is most commonly known as a causative agent of bacterial meningitis. However, this bacterium can also cause pneumonia, notes Dr. D. Kaufman on Medline Plus. In "Todar's Online Textbook of Bacteriology," Dr. Kenneth Todar reports that 5 to 30 percent of the population are carriers of Neisseria meningitidis. The bacteria inhabit the nose and throat of carriers. While carriers do not typically develop disease from Neisseria meningitidis, they pass the bacteria on to others, who may become ill.
Haemophilus Bacteria
Haemophilus influenzae type b is a significant cause of bacterial pneumonia, notes the University of Virginia Health System. According to CDC, infants and young children are particularly vulnerable to Haemophilus influenzae infections. CDC and the Advisory Committee on Immunization Practices recommend routine vaccination of all children against Haemophilus influenzae type b.
Klebsiella Bacteria
The bacterium Klebsiella pneumoniae is a normal inhabitant of the intestine in many people. In this location, the bacteria do not cause disease. However, if the bacteria gain entry to the lungs, they may cause pneumonia. CDC reports that Klebsiella pneumoniae most commonly affects people in the hospital or in long-term care facilities.
Tubercle Bacillus
Mycobacterium tuberculosis, or tubercle bacillus, is the causative agent of tuberculosis. This disease typically begins in the lungs and may spread to other organs, including the kidneys and brain. CDC notes that Mycobacterium tuberculosis can live in the body without causing disease; this is known as latent tuberculosis. Active tuberculosis causes cough, fatigue, weight loss and chest pain.
References
- Centers for Disease Control and Prevention: Leading Causes of Death
- Centers for Disease Control and Prevention: Streptococcus pneumoniae Disease
- Centers for Disease Control and Prevention, MMWR: Prevention of Pneumococcal Disease: Recommendations of the Advisory Committee on Immunization Practices (ACIP)
- Centers for Disease Control and Prevention: Mycoplasma pneumoniae
- University of Maryland Medical Center: Mycoplasma pneumoniae
