Bacterial Pneumonia

Bacterial Pneumonia Overview

Pneumonia is an infection of the lungs. People with pneumonia often complain about coughing, fever, shaking chills, and shortness of breath.

  • Your body's immune system usually keeps bacteria from infecting your lungs. In pneumonia, bacteria reproduce in your lungs, while your body tries to fight off the infection. This response to bacterial invaders is called inflammation.
  • When the inflammation occurs in the alveoli (microscopic air sacs in the lungs), they fill with fluid. Your lungs become less elastic and cannot take oxygen into the blood, or remove carbon dioxide from the blood, as efficiently as usual. When the alveoli don't work efficiently, your lungs have to work harder to satisfy your body's need for oxygen. This causes the feeling of being short of breath, which is one of the most common symptoms of pneumonia. Inflammation causes many of the other symptoms, including fever and chest pain.
  • Pneumonia can be very serious, because it directly interferes with your body's ability to exchange carbon dioxide and oxygen.
  • Pneumonia is different in this way from acute bronchitis, which is another disease that can cause fever, cough, chest pain, and shortness of breath. Bronchitis is caused by inflammation in the air passages (called bronchi) leading to the alveoli, not the alveoli themselves. Sometimes it is very difficult, even for a doctor, to tell pneumonia and bronchitis apart. The symptoms and physical exam can be identical. Sometimes a chest X-ray is the only way to tell the two apart.

Bacterial Pneumonia Causes

  • Most pneumonia is caused by bacteria or a virus. Pneumonia from any cause can occur at any age, but people in certain age groups are at higher risk for certain types of pneumonia.
  • The most common cause of bacterial pneumonia is Streptococcus pneumoniae.Haemophilus influenzae, Chlamydia trachomatis, Mycoplasma pneumoniae, and Legionella pneumophila are some other major bacteria that cause pneumonia.
  • The most common way you catch pneumonia is to breathe infected air droplets from someone who has pneumonia. Another cause is an improperly cleaned air conditioner. Yet another source of infection in your lungs is spread by an infection from somewhere else in your body, such as your kidney. Your risk of catching pneumonia is determined by the specific bacteria, virus, or fungus, the number of organisms you inhale, and your body's ability to fight infections.
  • You do not catch pneumonia by not dressing properly for cold weather or by being caught in the rain.

Other Causes of Pneumonia:

If you inhale toxic materials, you can injure your lungs and cause chemical pneumonia. Fungus also can cause pneumonia. In certain areas of the United States, specific fungi are well known. Coccidioidomycosis causes a pneumonia called "San Joaquin fever" or "Valley fever" in the desert regions of California. Histoplasmosis and blastomycosis cause pneumonias in the Ohio and Mississippi river valleys.

Bacterial Pneumonia Symptoms

Doctors often refer to typical and atypical pneumonias, based on your signs and symptoms. This can help to predict the type of bacteria causing your pneumonia, how long you can expect to be sick, and your best treatment.

  • Typical pneumonia usually comes on very quickly.
    • You often have a high fever and shaking chills.
    • When you cough, your sputum may be yellow or brown.
    • You may have sharp chest pain, which is usually worse with breathing or coughing. Your chest also may be sore when you touch or press it.
    • You may be very short of breath, especially if you have any chronic lung conditions such as asthma or emphysema.
    • Because chest pain also can be a sign of other serious medical conditions, do not try to diagnose yourself. Call 911 if you are having pain.
  • Atypical pneumonia usually has a more gradual onset.
    • It is sometimes called "walking pneumonia."
    • You may have had another illness in the days to weeks before the pneumonia.
    • Your temperature may be lower (although it will still be high), and shaking chills are less likely.
    • You may have a headache, body aches, and joint pain.
    • Your cough may be dry or produce only a little sputum. You may or may not have any chest pain.
    • You may have abdominal pain.
    • You may have other symptoms, such as feeling tired or weak.
    • Some people can have confusion or a change in their mental abilities as a sign of pneumonia or other infection. This is more common in the elderly or those with Legionnaires' disease.

When to Seek Medical Care

When to call the doctor

  • If you suspect that you may have pneumonia or have any of the symptoms listed above, call your doctor.

When to go to the hospital

Call 911 for any chest pain, difficulty breathing, or confusion.

Anyone with shortness of breath should always seek emergency care. Shortness of breath is not simply the feeling that you can't take a full breath. It is the feeling that you cannot take in enough air to meet your body’s needs. It is a potentially serious symptom and always requires a visit to an Emergency Department, no matter how healthy you are.

You are at higher risk to catch pneumonia if you have the following:

  • A chronic health problem, such as diabetes
  • A poor immune system because of HIV, AIDS, steroid use, or anti-rejection medications (people with organ transplants take these medications)
  • Diseased or damaged lungs, such as with asthma or emphysema
  • Are very young or very old

Exams and Tests

Pneumonia can often be diagnosed simply by a doctor listening to your lungs. Certain sounds heard through a stethoscope may indicate infection.

  • One of the easiest tests to perform is pulse oximetry, sometimes called "pulse ox." A probe that looks like a clothespin is gently attached to your finger, toe, or ear. A special light shines through your skin to estimate how much oxygen you have in your bloodstream. If your oxygen level is lower than expected, it may mean you have pneumonia.
  • An X-ray of your chest can help identify which part of your lung is infected. An X-ray also can show abnormal fluid collections, which also can help diagnose pneumonia.
  • You may have blood drawn. Laboratory tests can show that your immune system is working properly to fight off your infection. Certain lab tests can also show whether you have enough red blood cells to carry oxygen or whether the bacteria have gotten into your bloodstream.
  • Occasionally your doctor may need to sample blood from one of your arteries (usually in your wrist) in order to get an exact measurement of how well you are exchanging oxygen and carbon dioxide. This test, called an arterial blood gas ("ABG" or "blood gas"), is very important, takes only a minute, and is done with a very small needle and syringe. This test cannot be run on the other blood that is sampled from your veins.
  • Sometimes your doctor will collect some of your sputum and look at it under a microscope. Certain stains, or dyes, help your doctor tell which specific bacterium is causing your pneumonia. Your sputum also may be put on a plate to help it grow, so a laboratory specialist can look at it under a microscope and identify the specific bacteria.

Bacterial Pneumonia Treatment: Self-Care at Home

If you suspect pneumonia based on the signs or symptoms, see your doctor as soon as possible. There is no home treatment for pneumonia. Although cough suppressants, expectorants, or fever-lowering drugs may be helpful, they should not be started without discussing their use with your doctor.

Medical Treatment

  • If you have a bacterial pneumonia, you will need to take an antibiotic. The antibiotic choice depends on which bacteria is involved, your age, your chronic medical conditions, whether or not you smoke or drink alcohol, and other medications you are taking. Tell your doctor about allergies or bad reactions to any medicines you have taken before and bring a list of your current medicines with you.
  • Drink plenty of nonalcoholic fluids to stay hydrated. This helps your body fight the pneumonia. Anti-fever medicines such as acetaminophen (Tylenol) or ibuprofen (Advil) may also help you feel better.
  • Because coughing helps clear infection out of your lungs, your doctor may recommend that you not use a cough suppressant.
  • You must avoid cigarette or other tobacco smoke while you recover from pneumonia. Smoking hurts your body's ability to fight infection and makes your healing process take a lot longer.
  • If you are severely short of breath, or if you are getting poor oxygen levels in your bloodstream, you may need to be admitted to the hospital. You will get extra oxygen to help you breathe, and you can get your antibiotic by IV through your veins.
  • If your pneumonia is very severe, you may need a breathing tube in your windpipe so that a machine can do the work of breathing for you. If you need a breathing machine, you will be admitted to an intensive care unit in the hospital.

Next Steps

Depending on the severity of your pneumonia, you may need follow-up visits. This is especially important because many bacteria have developed the ability to resist certain antibiotics. Your doctor may need to adjust the dose of your medication or change it to another antibiotic.

Sometimes you need a repeat chest X-ray 4-6 weeks after your symptoms go away just to make sure that your infection is gone. Good communication with your doctor is your most important follow-up. Your doctor should tell you how long to expect your fever to last and when your cough should start to go away. Tell your doctor if you are not improving as quickly as expected.


Vaccines are available that prevent certain types of pneumonia. Yet there are so many bacteria that cause pneumonia, you are not guaranteed to avoid it even with an immunization shot.

There are two pneumonia vaccines and they are given by injection. If you are a healthy adult over age 65, it's now recommended you receive both vaccines. The timing and sequence of the vaccines will vary depending on which vaccine you may have had previously. A vaccine is also recommended if your are under 65 and have chronic lung or heart disease, diabetes, certain kidney or liver diseases, alcoholism, and some other conditions. It may also be recommended if you are a smoker. Talk to your health care provider to see if you need a pneumococcal vaccine.


Pneumonia and influenza is the ninth most common cause of death in the United States. Most people with bacterial pneumonia get better with antibiotics. But some people develop very serious complications such as sepsis (blood poisoning), meningitis, and lung failure.

There is no way to predict who is at risk for severe complications. In general, if you have a weak immune system, you are more likely to be sicker.

WebMD Medical Reference from eMedicineHealth

Reviewed by Melinda Ratini, DO, MS on June 02, 2014

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