Bacterial Pneumonia

Bacterial Pneumonia Definition

Pneumonia is a fungal, viral, or bacterial infection of the lungs.
Pneumonia is a fungal, viral, or bacterial infection of the lungs.

Pneumonia is an infection of the lungs. People with pneumonia usually complain of coughing, mucus production, fever, shortness of breath, and/or chest pain.

  • The body's immune system usually keeps bacteria from infecting the lungs. In bacterial pneumonia, bacteria reproduce in the lungs, while the 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. The 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, the lungs are less able to extract oxygen from the air. This causes the feeling of being short of breath (dyspnea), which is one of the most common symptoms of pneumonia. Inflammation is the body's attempt to destroy infection, and causes many of the other symptoms of bacterial pneumonia, including fever and chest pain. The lungs themselves do not have any pain fibers but are surrounded by a membrane called the pleura. The pleura does contain many nerve fibers, and if it becomes inflamed by an adjacent infection in the lungs, significant pain can result. This is called pleurisy and often can accompany pneumonia. It is not infrequent, however, for inflammation not to involve the surface of the lung and therefore, little if any pain may be present.
  • Pneumonia can be very serious, because it directly interferes with the body's ability to exchange carbon dioxide and oxygen.
  • Pneumonia is different from acute bronchitis (another disease that can cause fever, cough, chest pain, and shortness of breath) because acute 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 examination can be identical. Sometimes a chest X-ray is the only way to distinguish pneumonia from bronchitis. There is also an entity in which both the airways and air sacs are involved with infection, and this is referred to as bronchopneumonia. As noted above, if the surface of the lung is inflamed, pleurisy may result. "Itis" is added to the end of the anatomical location to describe where the inflammation is. The symptoms often follow the location (for example, tracheitis [trachea, the main airway in the lung], laryngitis [larynx or voice box], pharyngitis [throat], bronchitis [bronchi, smaller lung airways], or pneumonitis [pneumonia]).

What Causes Bacterial Pneumonia?

  • 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 a type of bacteria known as Streptococcus pneumoniae. Haemophilus influenzae, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila are some other major bacteria that cause pneumonia. Pneumonias of these type are quite common and are often referred to as community-acquired pneumonia (CAP). People who spend significant time around or in hospitals or other health-care facilities can be exposed to other types of bacteria that are much more dangerous. Pneumonia from these types of bacteria are referred to as health-care-associated pneumonia (HAP). Doctors use this information in deciding the most appropriate antibiotic treatment.
  • People who inhale toxic materials can injure the lungs and cause chemical pneumonia. This is more accurately referred to as chemical pneumonitis, since the process is mainly due to inflammation not from an infectious source.
  • Fungi can also cause pneumonia. In certain areas of the United States, specific fungi are well known. Coccidioidomycosis, usually seen in the Southwest, is a type of fungal infection that causes a pneumonia called "San Joaquin fever" or "Valley fever." Histoplasmosis (seen primarily in the Midwest) and blastomycosis (seen primarily in the Southeast) are other fungal diseases that cause pneumonias.
  • The most common way you catch pneumonia is to aspirate bacteria from the upper airway, usually the oral cavity. Other ways to catch pneumonia can be by breathing in infected air droplets from someone who has pneumonia. In some cases, the bacteria can be generated by an improperly cleaned air conditioner or Jacuzzi. Yet another source of infection in the lungs is spread from an infection somewhere else in the body, such as the kidney. Bacteria can enter the bloodstream from any source and be deposited in the lungs, resulting in pneumonia.
  • The risk of catching pneumonia is determined by the specific bacteria, virus, or fungus, the number of organisms the person inhales, and the body's ability to fight infections.
  • A person cannot "catch pneumonia" by not dressing properly for cold weather or by being caught in the rain.

What Are Bacterial Pneumonia Symptoms and Signs?

Doctors often refer to typical and atypical pneumonias, based on the signs and symptoms of the condition. This can help to predict the type of bacteria causing the pneumonia, the duration of the illness, and the optimal treatment method.

Typical pneumonia comes on very quickly.

  • Typical pneumonia usually results in a high fever and shaking chills.
  • Typical pneumonia usually leads to the production of yellow or brown sputum when coughing.
  • There may be chest pain, which is usually worse with breathing or coughing. The chest also may be sore when it is touched or pressed.
  • Typical pneumonia can cause shortness of breath, especially if the person has 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 self-diagnose.
  • Older people can have confusion or a change in their mental abilities as a sign of pneumonia or other infection.

Atypical pneumonia has a gradual onset.

  • It is often referred to as "walking pneumonia."
  • Sometimes it follows another illness in the days to weeks before the pneumonia.
  • The fever is usually lower, and shaking chills are less likely.
  • There may be headache, body aches, and joint pain.
  • Coughing may be dry or produce only a little sputum. The person may not have any chest pain.
  • Abdominal pain may be present.
  • There may be other symptoms, such as feeling tired or weak.
  • Often the abnormalities on the chest X-ray appear worse than what the patient appears to have clinically, hence the term "walking pneumonia."

Is Bacterial Pneumonia Contagious?

Whether or not bacterial pneumonia is contagious depends upon the type of bacteria causing the infection. In many cases, people contract pneumonia when bacteria they normally carry in the nose or throat are spread to the lungs. Most kinds of bacterial pneumonia are not highly contagious. However, pneumonia due to Mycoplasma pneumoniae and tuberculosis are exceptions. Both these types of bacterial pneumonia are highly contagious. These are spread among people by breathing in infected droplets that come from coughing or sneezing, similar to the spread of viral infections.

When Should Someone Seek Medical Care for Bacterial Pneumonia?

When to call the doctor

  • If you have a fever and cough up yellow, green, or brown sputum, make an appointment with your doctor.
  • If you have shortness of breath, chest pain, or confusion, you should seek emergency care.
  • If you are healthy, you can safely make an appointment to see your doctor. It is best to contact your physician if you have concerns about possible pneumonia.

When to go to the hospital

  • If you have shortness of breath, you should always seek emergency care. Shortness of breath is not simply the feeling that you can't take a full breath; shortness of breath means 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.
  • If you have chest pain or confusion, you should seek emergency care.
  • You are at higher risk of developing pneumonia if you have the following:
    • a chronic health problem, such as diabetes;
    • a poor immune system because of HIV, AIDS, steroid use, or immune-suppressant medications (people with organ transplants take these medications);
    • diseased or damaged lungs, such as with asthma or emphysema;
    • are very young or very old;
    • or you have had your spleen removed.

What Tests Do Doctors Use to Diagnose Bacterial Pneumonia?

Pneumonia can be diagnosed simply by a doctor listening to the patient's 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 the patient's finger, toe, or ear. A special light shines through the skin to estimate how much oxygen the patient has in the bloodstream. If the oxygen level is lower than expected, the lungs are not working properly and it may mean the patient has pneumonia.
  • A chest X-ray can help identify which part of the patient's lung is infected. An X-ray also can show abnormal fluid collections which also can help diagnose pneumonia.
  • The patient may have blood drawn. Laboratory tests can show that the immune system is working properly to fight off infection. They also show whether the patient has enough red blood cells to carry oxygen or whether the bacteria is in the bloodstream.
  • Occasionally the doctor may need to sample blood from one of the patient's arteries (usually in the wrist) in order to get an exact measurement of how well the patient is 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 use the blood sampled from the patient's veins.
  • Sometimes the doctor will collect some of the patient's sputum and view it under a microscope. Certain stains, or dyes, used on the sputum can assist the doctor in diagnosing the bacterium that is causing pneumonia. Sputum cultures may also be performed. In these tests, the sputum is put on a plate to help it grow so a laboratory specialist can identify the specific bacteria.
  • If the patient is admitted to the hospital, the doctor will draw blood and send it to the laboratory so that it may also be cultured to determine whether bacteria are present in the bloodstream. There are also urine (urinalysis) and blood tests that examine the patient's immune system response to infection. These can also help determine the cause of the pneumonia.

What Is the Treatment for Bacterial Pneumonia?

Treatment for bacterial pneumonia includes antibiotics, fluid hydration, anti-fever medication such as acetaminophen or ibuprofen, cough suppressant if necessary, avoidance of smoking tobacco, and hospitalization if necessary.

Are There Home Remedies for Bacterial Pneumonia?

If you suspect you have pneumonia based on the signs or symptoms, see a 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 a doctor.

What Is the Medical Treatment for Bacterial Pneumonia? Are Antibiotics Necessary?

  • Patients with bacterial pneumonia will need to take an antibiotic. The antibiotic choice depends on the patient's age, any chronic medical conditions, tobacco and alcohol use, and other medications the patient is taking. The patient should tell the doctor about any allergies or reactions to any medicines he or she had taken previously and bring a list of all current medicines to the doctor's office or hospital.
  • Drink plenty of nonalcoholic fluids to stay hydrated. This helps the body fight pneumonia. Anti-fever medicines such as acetaminophen (Tylenol) or ibuprofen (Advil) may also help the patient feel better.
  • Coughing helps clear infection in the lungs.
  • Avoid cigarette or other tobacco smoke while recovering from pneumonia. Smoking suppresses the body's ability to fight infection and extends the healing process.
  • The patient may be admitted to the hospital if he or she is severely short of breath or has significantly lowered oxygen levels in the bloodstream. During hospitalization the patient will receive supplemental oxygen to assist breathing. The patient also may receive antibiotics via an IV catheter through a vein.
  • In cases of severe pneumonia, patients may require a breathing tube in the windpipe so that a machine can breathe for them. If the patient needs a breathing machine, he or she will be admitted to an intensive-care unit in the hospital.

Is It Possible to Prevent Bacterial Pneumonia?

  • Vaccines are available that prevent certain types of pneumonia. However, since there are many bacteria that cause pneumonia, a person may contract pneumonia despite receiving the vaccine.
  • Pneumovax and Pnu-Immune are vaccines to prevent Streptococcus pneumoniae infection. According to the U.S. Centers for Disease Control and Prevention (CDC), people in the following groups should ask their doctor about receiving the pneumococcus immunization:
    • people age 65 and older,
    • people with serious long-term health problems such as heart failure, liver failure (cirrhosis of the liver), diabetes, or lung disease (other than asthma),
    • people with lowered immunity due to cancer, chemotherapy, removal or diseases of the spleen, chronic kidney problems, or have had an organ or bone marrow transplant, or
    • people who are Alaskan Native Americans or certain other Native American populations.
  • In 2000, the U.S. Food and Drug Administration (FDA) licensed a new vaccine, Prevnar 13, for the prevention of pneumococcal disease in children.
  • This vaccine is recommended for healthy infants under the age of 2 and for children between the ages of 2 and 5 who have not previously been vaccinated and who are at highest risk for developing pneumococcal disease, such as those with HIV/AIDS, certain chronic diseases, and decreased immune function.
  • More recently, the candidates for Prevnar 13 have significantly expanded to include all adults over 65 years of age. It is also recommended for adults ages 19 and over if they have a condition that may weaken their immune system.

Bacterial Pneumonia Follow-up

Depending on the severity of pneumonia, the patient may need a follow-up visit. This is especially important because many bacteria have developed the ability to resist certain antibiotics. The doctor may need to adjust the dose of the patient's medication or change to another antibiotic.

  • A repeat chest X-ray in the weeks after symptoms have resolved may be ordered to confirm the infection has resolved, and to assure that the chest X-ray is clear of any abnormalities. Some pneumonias can occur when an airway is blocked by a growth or foreign body that has aspirated into the lung. The X-ray may not appear free of pneumonia if one of these events has occurred.
  • Good communication with the doctor is the most important step in follow-up care. The doctor should tell the patient how long to expect the fever to last and when the cough should begin to resolve. The patient should tell the doctor if he or she is not improving as told.

What Is the Prognosis of Bacterial Pneumonia?

Pneumonia is the sixth most common cause of death in the United States. It is the top cause of death from infection.

  • Most people with pneumonia improve with antibiotics. Some people develop complications such as sepsis, meningitis, and lung failure. Many of these people die.
  • There is no way to predict who is at risk for severe complications. However, the elderly, those with chronic medical conditions, those with lowered immunity, and those who have had a bone marrow or organ transplant have a higher risk for complications.

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bacterial pneumonia diagnosis, chest x-ray

Bacterial Pneumonia Diagnosis

Chest X-Ray

Many diseases or conditions may be detected or diagnosed based on a chest X-ray test. A chest X-ray test can also be very helpful in ruling out suspected diagnoses. Some of the common conditions that can be evaluated by a chest X-ray test are:

  • pneumonia,
  • congestive heart failure,
  • emphysema,
  • lung mass or lung nodule,
  • tuberculosis,
  • fluid around the lung (pleural effusion),
  • fracture of the vertebrae (bones of the back),
  • rib fractures, or
  • cardiomegaly, or enlarged heart.
Gamache, J., et al. "Bacterial Pneumonia." Medscape. Aug. 22, 2019.
<>. Lim, W.S., et al. "British Thoracic Society community acquired pneumonia guideline and the NICE pneumonia guideline: how they fit together." Thorax 2015 Jul;70(7):698-700.

United States. Centers for Disease Control and Prevention. "Pneumococcal Vaccination." Sept. 6, 2017.