What Is Bacterial Pneumonia?
Pneumonia is an infection in one or both lungs. It can be caused by a number of different germs, including bacteria, viruses, and fungi. When caused by bacteria, the illness is known as bacterial pneumonia.
Bacterial pneumonia can affect both adults and children
(see Pneumonia in Children). It is more common in older adults (over the age of 65), infants, those with chronic conditions (such as
COPD,
diabetes, or
heart disease), and those with a weakened immune system. This type of pneumonia can happen at any time of the year, although it is more common in winter months.
Which Bacteria Cause Pneumonia?
A number of different bacteria can cause bacterial pneumonia. Some are more likely to cause an infection within the community (known as community-acquired bacterial pneumonia), while others are more likely to cause infections within the hospital (known as hospital-acquired bacterial pneumonia).
The bacteria more likely to cause community-acquired pneumonia include:
- Streptococcus pneumoniae, also known as just pneumococcus (the most common cause of pneumonia worldwide)
- Mycoplasma pneumoniae, the main cause of walking pneumonia (see Mycoplasma Pneumonia)
- Haemophilus influenzae
- Chlamydophila pneumoniae (more common in children under four months of age or over the age of five)
- Legionella pneumophila
- Bordetella pertussis (the bacteria that cause whooping cough).
While less common, methicillin-resistant
Staphylococcus aureus (
MRSA) is starting to become a more important and concerning cause of pneumonia in children and adults.
Hospital-acquired pneumonia tends to be more serious than community-acquired pneumonia. This is because the person is already sick. Also, hospitals tend to have more germs that are resistant to antibiotics -- a treatment for pneumonia.
Some bacteria that can cause hospital-acquired pneumonia include:
- Gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, Enterobacter species, Pseudomonas aeruginosa, and Acinetobacter species
- Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA)
- Streptococcus species.
Is Bacterial Pneumonia Contagious?
A person with bacterial
pneumonia is contagious. However, when the bacteria are spread, they are more likely to cause an upper respiratory infection than pneumonia in another person.
These bacteria are usually found in the mouth and nose of the infected person. They can be spread easily to another person, either through the air or by touching a contaminated surface. Most often, they enter the person's body through the mouth, nose, or eyes.
Why Do Some People Get Bacterial Pneumonia and Others Don't?
Although the body has an advanced system for getting rid of potentially harmful substances that make their way into the lungs, it is not perfect. In some cases, so many bacteria get into the lungs that they simply overwhelm the defense system.
Other times, the particular bacteria are just so potent that the body can't handle them.
With any of these situations, a person risk for developing bacterial pneumonia is increased.
(Click Pneumonia Risk Factors to learn about other things that increase a person's chances of getting pneumonia.)
Are Antibiotics Needed for Bacterial Pneumonia?
Bacterial pneumonia is treated with antibiotics
(see Antibiotics and Pneumonia). When these medications are prescribed, they should be taken exactly as prescribed and for the entire period, even when you start to feel better. If you stop taking them too soon, the pneumonia may come back.
Sometimes, a person is sick enough that he or she needs to stay in the hospital while receiving antibiotics. They often require more potent antibiotics, which are given through an IV. These drugs include:
- Ceftriaxone (Rocephin®)
- Cefotaxime (Claforan®)
- Ampicillin/sulbactam (Unasyn®)
- Ertapenem (Invanz®)
- Vancomycin (Vancocin®)
- Linezolid (Zyvox®).
Other times, a person with bacterial pneumonia can be treated at home. Antibiotics that are often prescribed in this case include one or more of the following:
How Long Do Symptoms Last?
A person with bacterial
pneumonia usually starts to feel better three to five days after the medicines are started. He or she can usually return to normal activities within a week. Tiredness and a mild cough can take longer to improve -- in some cases, taking upwards of a month or longer to get better.
People who are treated in the hospital may need at least three weeks before they can go back to their normal routines.
Vaccines Used to Prevent Bacterial Pneumonia
Several vaccines are available to prevent certain
types of bacterial pneumonia. These vaccines can't prevent all cases, but they definitely help.
Pneumococcal Vaccine
Hib Vaccine
Haemophilus influenzae type b (
Hib) disease is a serious illness caused by bacteria. Before the
Hib vaccine, this disease was the leading cause of
bacterial meningitis among children younger than five years old in the United States.
Meningitis is an infection of the brain and spinal cord coverings, which can lead to lasting brain damage and deafness. Hib disease can also cause pneumonia, among other serious conditions.
The Hib vaccine is recommended for all children in the United States who are younger than five years old. It's often given to infants, starting at two months of age.
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