What is bacterial pneumonia?

Pneumonia is a common lung infection where the lungs’ air sacks become inflamed. These sacs may also fill with fluid, pus, and cellular debris. It can be caused by viruses, fungi, or bacteria. This article is about pneumonia caused by bacteria.

Bacterial pneumonia may involve just one small section of your lung, or it may encompass your entire lung. Pneumonia can make it difficult for your body to get enough oxygen to your blood, which can cause cells to not work properly.

Bacterial pneumonia can be mild or serious. The severity of your pneumonia depends on:

  • the strength of the bacteria
  • how quickly you are diagnosed and treated
  • your age
  • overall health
  • if you have other conditions or diseases

The most common symptoms of bacterial pneumonia are:

Other symptoms that may follow include:

Older adults will share all the symptoms with younger adults, but are much more likely to experience confusion and dizziness. Older adults may also be less likely to have a fever.

Symptoms in children

Pneumonia can be particularly dangerous for infants, children, and toddlers. They may display similar symptoms to the ones above. In infants, difficulty breathing may show up as flaring nostrils or chest sinking when breathing. They may also exhibit blueish lips or nails, which indicates that they aren’t getting enough oxygen.

Emergency symptoms

Seek immediate medical attention if you are experiencing:

  • blood in mucus
  • trouble breathing
  • high fever of 102.5°F of higher
  • confusion
  • rapid heartbeat
  • skin with a bluish tone

Bacteria pneumonia is caused by bacteria that works its way into the lungs and then multiplies. It can occur on its own or develop after another illness, like a cold or the flu. People who have a higher risk for pneumonia may:

  • have weakened immune systems (due to age, diseases, or malnutrition)
  • have respiratory diseases
  • be recovering from surgery

Doctors classify bacterial pneumonia based on whether it developed inside or outside a hospital.

Community-acquired pneumonia (CAP): This is the most common type of bacterial pneumonia. CAP occurs when you get an infection after exposure to bacterial agents outside of a healthcare setting. You can get CAP by breathing in respiratory droplets from coughs or sneezes, or by skin-to-skin contact.

Hospital-acquired pneumonia (HAP): HAP occurs within two to three days of exposure to germs in a medical setting, such as a hospital or doctor’s office. This is also called a “nosocomial infection.” This type of pneumonia is often more resistant to antibiotics and more is difficult to treat than CAP.

Types of bacteria

Streptococcus pneumonia is the leading cause of bacterial pneumonia. It can enter your lungs through inhalation or through your bloodstream. There is a vaccination for this type.

Haemophilus influenzae is the second most common cause of bacterial pneumonia. This bacterium may live in your upper respiratory tract. It doesn’t usually cause harm or illness unless you have a weakened immune system.

Other bacteria that can cause pneumonia include:

  • Staphylococcusaureus
  • Moraxellacatarrhalis
  • Streptococcuspyogenes
  • Neisseriameningitidis
  • Klebsiellapneumoniae

Environmental and lifestyle factors

These include:

  • smoking
  • working in an environment with a lot of pollution
  • living or working in a hospital setting or nursing facility

Medical risk factors

People who have these conditions may be at an increased risk for pneumonia:

Age groups

People over the age of 65 and children 2 and younger are also at a higher risk for developing pneumonia. Make an appointment with your doctor if you or someone you know has symptoms of pneumonia. Pneumonia for this group can be life-threatening.

The two most common causes of pneumonia are bacteria and viruses. The flu is one of the most common causes of viral pneumonia in adults, though post-flu complications can also cause bacterial pneumonia.

Viral pneumoniaBacterial pneumonia
Who?most likely to affect healthy people with strong immune systemsmore likely to affect someone with a lowered immune system, or someone who is recovering from a respiratory infection
Treatmentantibiotics don’t workantibiotics may be prescribed
Outlookcan be severe and fatalmay be more aggressive and difficult to treat

In bacterial pneumonia, there will likely be a much more visible presence of fluid in the lungs than viral pneumonia. Bacterial pneumonia is also more likely to enter the blood stream and infect other parts of the body.

To diagnose bacterial pneumonia, your doctor will:

  • Listen for abnormal chest sounds that indicate a heavy secretion of mucus.
  • Take a blood sample to determine if your white blood cell count is high, which usually indicates infection.
  • Take a blood culture, which can help determine if the bacteria have spread to your bloodstream and also help identify the bacterium causing the infection.
  • Take a sample of mucus, or a sputum culture, to identify the bacterium causing the infection.
  • Order chest X-rays to confirm the presence and extent of the infection.

Most cases can be treated at home, with medications, to prevent complications from a hospital setting. A healthy person may recover within one to three weeks. Someone with a weakened immune system may take longer before they feel normal again.

Hospital care

Some cases of bacterial pneumonia will require hospitalization for treatment. Young children and the elderly are more likely to need to go to the hospital to receive intravenous antibiotics, medical care and respiratory therapy.

In the hospital, you’ll be given antibiotics to treat the specific type of bacteria causing your pneumonia. This will likely be given intravenously, along with fluids to prevent dehydration.


Without treatment, pneumonia may develop into:

  • organ failure, due to bacterial infection
  • difficulty breathing
  • pleural effusion, buildup of fluid in the lungs
  • lung abscess, cavity in the lung

Bacterial pneumonia itself is not contagious, but the infection that caused bacterial pneumonia is contagious. It can spread through coughs, sneezes, and contamination on objects. Practicing good hygiene can help prevent the spread of pneumonia or the risk of catching it.

The Centers for Disease Control and Prevention (CDC) also recommends a pneumonia vaccine for infants, young children, and adults age 65 and older.