An Overview of Bacterial Infections

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Bacterial infections are common, but they're not all the same. There are many types of bacteria and they can each have different effects on the body. And there are plenty of ways you can become exposed to them.

But what are bacteria, exactly?

They're small organisms that can invade the body and cause infections. This triggers your body to mount a protective immune response.

You also have "good" bacteria that belong in your body and help you. These bacteria digest your food and protect your body from harmful bacteria.

This article goes over what you need to know about bacterial infections. You'll learn about the symptoms, causes, and types of bacterial infections. Diagnostic tests and treatment options are also covered.

Bacterial Infection Symptoms

Verywell / Laura Porter


Children and adults of any age can develop a bacterial infection. Bacteria can infect every area of the body, including your:

  • Bladder
  • Brain
  • Intestines
  • Lungs
  • Skin

A bacterial infection can also spread throughout the blood, triggering a potentially life-threatening blood infection called septicemia. That, in turn, can lead to sepsis, a condition that happens when your body has a severe response to an infection.

You can feel generalized symptoms as a result of a bacterial infection. Generalized symptoms affect the whole body and include fevers, chills, and fatigue.

Localized Symptoms

You can also experience localized symptoms (local effects) of a bacterial infection.

These symptoms affect the specific area or areas of the body that are infected. Pain, swelling, redness, and problems with organ function are typical localized symptoms.

Pain is common with bacterial infections. You can experience skin pain with a bacterial skin infection. A lung infection can cause pain when breathing. And you can feel abdominal (stomach) pain with an intestinal (or bowel) infection.

You can easily notice redness or swelling on parts of the body that you can see, such as the skin, throat, or ears.

Internal organs can become inflamed and swollen when you have a bacterial infection, too. While you can't see it, you may feel pain or other effects in these areas.

Consider a bacterial infection of the respiratory tract that can affect your throat, bronchi, or lungs. As a result, you might develop a productive (wet) cough with thick mucus.

Bacterial infections can reduce or alter the affected body part's ability to function.

For instance, meningitis (an infection surrounding the brain) can impair your concentration. Pyelonephritis (a kidney infection) could worsen kidney function.


All bacterial infections have an incubation period, and symptoms can rapidly worsen or progress slowly.


Symptoms of a bacterial infection can be generalized, or nonspecific, and include fever, chills, and fatigue. Symptoms can also affect the specific areas that are infected, causing pain, redness, swelling, or problems with organ function.


The transmission (passing) of bacteria is what causes bacterial infections. You can become exposed to bacteria from other people, the environment, or by eating or drinking contaminated food or water.

Anyone can get sick when exposed to bacteria. But having a weakened immune system puts you at a higher risk of severe bacterial infections.

Certain conditions and medications can suppress your immune system, making it weaker. Even bacteria that normally belong in your body can put you at risk.

Types of Bacterial Infections

The severity of bacterial infections can vary widely and depends on the type of bacteria involved.

On one hand, there are relatively minor illnesses like strep throat and ear infections. But bacterial infections can also cause potentially life-threatening conditions like meningitis and encephalitis.

Common bacterial infections include:

  • Salmonella is an infection often linked to food poisoning. Eating undercooked poultry is a common method of getting infected. Symptoms include severe stomach upset, diarrhea, and vomiting. Nontyphoidal salmonellae bacteria cause salmonella. These bacteria live in the gastrointestinal (GI) tracts of humans and other animals.
  • Escherichia coli (E. coli) also causes GI distress. The infection usually improves on its own, but it can be severe or even fatal. Contaminated food—including uncooked vegetables—can spread E. Coli bacteria.
  • Tuberculosis is a highly contagious disease caused by the Mycobacterium tuberculosis bacteria. It usually leads to a lung infection.
  • Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that's become resistant to antibiotics. It's very dangerous, especially for people who have compromised immune systems.
  • Clostridium difficile (C. diff) is a type of bacteria in your intestines that's normally harmless. However, using antibiotics or having an weakened immune system can cause overgrowth of these bacteria. This leads to a GI infection characterized by an inflamed colon and persistent diarrhea.
  • Bacterial pneumonia is a lung infection that can be caused by different kinds of bacteria, like Streptococcus pneumoniae, Klebsiella pneumoniae, or Pseudomonas aeruginosa. The infections spread through air particles from coughing or sneezing.
  • Bacterial vaginosis is an infection of the vagina that causes itchiness, discharge, and painful urination. It happens because of an imbalance in the normal bacterial flora of the vagina.
  • Heliobacter pylori (H. pylori) bacteria cause stomach ulcers and chronic gastritis, or inflammation of the stomach. Acid reflux, acidity, and smoking increase the risk of this bacterial infection.
  • Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae.
  • Vibrio vulnificus is a rare, "flesh-eating" bacteria found in warm seawater.

Bacterial organisms tend to target specific areas of the body. For example, syphilis, a sexually transmitted infection, is unlikely to affect the stomach or lungs. Haemophilus Influenzae Type B (Hib) can cause ear, throat, and lung infections. But it won't harm the skin or bladder.


The pattern of your symptoms can help your doctor diagnose your bacterial infection. The location, timing, and severity of your symptoms can point to a bacterial infection.

Your doctor may then want to confirm the diagnosis before prescribing any medicine. They can do this by taking a sample of fluids such as pus or mucus and sending it to a laboratory. They can also use a fluid sample to identify sexually transmitted infections (STIs).

Alternatively, they might send in a swab sample for evaluation. For this, they might swab your throat, ear, or infected areas of your skin.

A urine sample can identify bladder and kidney bacterial infections. A fecal (stool) sample might help determine the bacterial cause of persistent GI upset.

Blood Tests

Sometimes, blood tests can help identify infectious bacteria. Usually, people have increased white blood cells (WBCs) with a bacterial infection. A blood test called a complete blood count (CBC) can detect elevated WBCs.

But that's not all. Your doctor may also order what's known as a CBC with differential. This test tells whether specific types of WBCs have increased in your blood.

Various types of WBCs work together to defend your body from infections. And different infections prompt an increase in different types of WBCs. So, your doctor can use this pattern of data to identify which infection you have.

Imaging Studies

Infectious bacteria can cause a bacterial abscess (an enclosed, pus-filled area). If your doctor thinks you might have an abscess in or near internal organs, you may need an imaging study to help identify it. An X-ray, for example, can help diagnose pneumonia.

Other Infectious Organisms

Other organisms besides bacteria can also cause infections. Viruses, parasites, protozoa, fungi, worms, and prions (infectious proteins) are some examples.

Viruses are 10 to 100 times smaller than bacteria, while parasites, protozoa, and fungi are larger than bacteria.

These organisms all look different under a microscope. So it's no surprise they behave differently in the body.

For example, parasites have a complicated life cycle. First, the eggs enter the body and hatch. Then, they may turn into infectious, worm-like organisms that invade human tissue. On the other hand, fungi are often long-lasting, slow-growing infections.

The most important distinction between infectious microorganisms is that treatments are different. For instance, antibiotics are medications that kill bacteria. But they don't affect or treat other infectious organisms.


Bacterial infections often get better quickly on their own without treatment. That said, you may need prescription antibiotics to treat your bacterial infection.

Untreated bacterial infections can spread or linger, causing major health problems. Although it's rare, untreated bacterial infections can even be life-threatening.

Symptoms like fever, pain, swelling, coughing, or dehydration might occur with an infection. In this case, your doctor may suggest supportive care (like anti-inflammatory medication).


The type of bacteria you have will help determine which antibiotics you need to take. Most antibiotics work against more than one type of bacteria, but not against them all.

There are different ways that you can take antibiotics. You can take them by mouth, topically (on the surface of the skin or eye), or through intravenous therapy (IV).

If you're using a prescription antibiotic, make sure you use it as directed. For example, don't use a skin antibiotic on your eyes. It's important to take your medication exactly as prescribed and for the complete duration of your prescription.

Supportive Care

Your doctor might prescribe pain medicine or anti-inflammatory medication. These medications can help ease the pain and swelling from your bacterial infection.

If you have a fever, your doctor may also recommend fever-reducing medication. Non-steroidal anti-inflammatories (NSAIDs) can reduce fevers, swelling, and pain.

If you have a painful cough, your doctor may suggest anti-cough medication. And you may need IV fluids if you're becoming dehydrated.


If you have an abscess, you may need to have surgery to treat it. This can be a simple procedure for a superficial abscess in the skin. But an abscess located deep in the body—like in the brain or intestines—may require a more extensive surgery to remove it.


Bacterial infections are incredibly common and are also quite different from one to another. The type of bacteria involved, its cause, location, and timing all influence the course of your infection.

Even symptoms vary a great deal. Some infections can worsen and cause severe complications. Even diagnosis and treatment options depend on the specific infection you may have.

A Word From Verywell

You're likely going to have at least a few bacterial infections throughout your life. These infections can cause a range of symptoms and effects. Your doctor can use diagnostic testing to determine which specific infection you have. Sometimes, you may need prescription medicine, such as antibiotics, to treat your condition.

Using an antibiotic "just in case" you have a bacterial infection is never a good idea. Reusing an old prescription is also not recommended. Your infection could get worse from taking the wrong medicine. And you could develop bacterial resistance if you use antibiotics unnecessarily.

If you think you have a bacterial infection that needs treatment, talk to your doctor.

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6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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