An Overview of Bacterial Infections

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Bacterial infections are caused by small, single-cell organisms called bacteria that invade the body. These infections are common and there are many ways you can get them.

There are many types of bacteria and they can each have different effects on the body. This can impact your symptoms and treatment options.

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.

While certain bacteria can trigger your body to mount a protective immune response, you also have "good" bacteria that belong in your body. These help you digest food and protect your body from harmful bacteria.

Bacterial Infection Symptoms

Verywell / Laura Porter

Bacterial Infection Symptoms

Bacterial infections can cause generalized symptoms, which impact the whole body. These include:

Children and adults of any age can develop a bacterial infection. Bacteria can infect every area of the body like the bladder, brain, intestines, lungs, and 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.

Localized Symptoms

You can also experience localized symptoms of a bacterial infection, which affect the specific area of the body that is infected. Localized symptoms of a bacterial infection may include:

  • Pain: This is common with bacterial infections. You can experience skin pain with a bacterial infection on the skin. A lung infection can cause pain when breathing and you can feel abdominal (stomach) pain with an intestinal (or bowel) infection.
  • Swelling and redness: You may notice redness or swelling on parts of the body that you can see, such as the skin, throat, or ears.
  • Problems with organ function: Internal organs can become inflamed and swollen. While you can't see it, you may feel pain or other effects in these areas. For example, pyelonephritis (a kidney infection) could worsen kidney function.

Additional examples of localized symptoms of bacterial infections:


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

Causes of Bacterial Infections

Bacterial infections are caused by the transmission, or spread, of bacteria. You can become exposed to bacteria from:

  • Other people
  • The environment
  • 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.

How to Prevent Bacterial Infections

To prevent bacterial infections:

List of Bacterial Infections

The most common bacterial infections include:

  • Salmonella is an infection often linked to food poisoning. It is caused by nontyphoidal salmonellae bacteria, which live in the gastrointestinal tracts (GI) of humans and other animals. Symptoms include severe stomach upset, diarrhea, and vomiting.
  • 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.
  • Clostridioides 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 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 bacterial 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 (STI) caused by the bacteria Neisseria gonorrhoeae.
  • Vibrio vulnificus is a rare, "flesh-eating" bacteria found in warm seawater.

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.

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.


To diagnose a bacterial infection, your healthcare provider may:

  • Take a sample of fluids such as pus or mucus, which can help identify an STI, and send it to a laboratory
  • Send in a swab sample from your throat, ear, or infected area of your skin for evaluation
  • Evaluate a urine sample, which can identify bladder and kidney bacterial infections
  • Evaluate a stool sample to help determine the bacterial cause of persistent GI upset

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

Blood Tests

Blood tests can help identify a bacterial infection. With a bacterial infection, people tend to have increased white blood cells (WBCs), which work together to defend your body from infections. A blood test called a complete blood count (CBC) can detect elevated WBCs.

Your healthcare provider may also order what's known as a CBC with differential. This test tells whether specific types of WBCs have increased in your blood.

Imaging Studies

Infectious bacteria can cause a bacterial abscess (an enclosed, pus-filled area). If your healthcare provider 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.

Bacterial Infection Treatment

Bacterial infections can last for days to weeks, but often go away on their own without antibiotics. That said, you may need prescription antibiotics if your body is unable to fight off a bacterial infection.

If you have symptoms like fever, pain, swelling, coughing, or dehydration your healthcare provider may suggest anti-inflammatory medication.

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

Other organisms, like viruses, parasites, and worms, can also cause infections. Treatment depends on the infectious microorganism.


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, or on the surface of the skin or eye
  • 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 healthcare provider 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. 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. Diagnosis and treatment options depend on the specific bacterial infection you may have.

A Word From Verywell

You're likely going to have at least a few bacterial infections throughout your life. 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 healthcare provider.

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.
  1. Grant SS, Hung DT. Persistent bacterial infections, antibiotic tolerance, and the oxidative stress response.Virulence. 2013;4(4):273–283. doi:10.4161/viru.23987

  2. Wong D, Nielsen TB, Bonomo RA, Pantapalangkoor P, Luna B, Spellberg B. Clinical and pathophysiological overview of acinetobacter infections: a century of challenges. Clin Microbiol Rev. 2017;30(1):409-447. doi:10.1128/CMR.00058-16

  3. Harvard Health Publishing. How to prevent infections.

  4. Ishimine N, Honda T, Yoshizawa A, et al. Combination of white blood cell count and left shift level real-timely reflects a course of bacterial infectionJ Clin Lab Anal. 2013;27(5):407-411. doi:10.1002/jcla.21619

  5. Onakpoya IJ, Walker AS, Tan PS, et al. Overview of systematic reviews assessing the evidence for shorter versus longer duration antibiotic treatment for bacterial infections in secondary care. PLoS ONE. 2018;13(3):e0194858. doi:10.1371/journal.pone.0194858

  6. Shih RY, Koeller KK. Bacterial, fungal, and parasitic infections of the central nervous system: radiologic-pathologic correlation and historical perspectives. Radiographics. 2015;35(4):1141-69. doi:10.1148/rg.2015140317

Additional Reading

By Kristina Duda, RN
Kristina Duda, BSN, RN, CPN, has been working in healthcare since 2002. She specializes in pediatrics and disease and infection prevention.