Bacterial Infection

Overview

What is a bacterial infection?

Bacterial infections are any illness or condition caused by bacterial growth or poisons (toxins). You can get sick from getting harmful bacteria in your skin, gut (GI tract), lungs, heart, brain, blood or anywhere else in your body.

Harmful bacteria from the environment, an infected person or animal, a bug bite or something contaminated (like food, water or surfaces) can cause infections. Bacteria that’s not normally harmful but that gets into a place in your body where it shouldn’t be can also cause infections.

What is bacteria?

Bacteria are living things with only a single cell that can reproduce quickly. There are millions of bacteria that live all around us — in soil or water and on surfaces in our homes and workplaces. There are even millions of bacteria that live on your skin and inside of your body.

Most bacteria aren’t harmful, and many are even helpful. They can help you digest food and kill off other harmful forms of bacteria that try to invade your body. But even the helpful ones can hurt you if they grow where they’re not supposed to.

What’s the difference between a bacterial infection and viral infection?

Living, single-celled organisms that can reproduce on their own cause bacterial infections. Only a few types of bacteria cause illness in people.

An organism that’s not made up of cells causes viral infections. Viruses always need to infect humans or other living things to create more copies of itself.

Antibiotics can treat most bacterial infections, but only a few viral infections have medications that treat them.

What are the types of bacterial infections?

Bacteria can cause many types of infections, depending on how you’re exposed and what part of your body it infects. Some common types of bacterial infections include:

What are some examples of bacterial infections?

Common bacterial infections include:

Is a bacterial infection serious?

There are many bacterial infections that aren’t usually serious or can be treated easily with antibiotics. Impetigo and boils are examples. However, any bacterial infection that gets deep into your body, like in your blood, heart, lungs or brain, can be life-threatening.

How do bacterial infections spread?

Bacterial infections can spread through droplets or dust in the air, direct or indirect contact, a vector (like a tick or mosquito) or contaminated food or water (vehicular).

Airborne or droplet

You can get bacterial infections through the air from contaminated dust or droplets of water or mucus (like phlegm or snot). Legionnaires’ disease, pertussis (whooping cough), tuberculosis, meningococcal disease and strep throat spread this way.

Contact

You can get bacterial infections from direct contact with infected skin or mucous membranes, or from indirect contact with contaminated surfaces. Bacterial diseases you get by contact include skin infections and some sexually transmitted infections (STIs) like gonorrhea and chlamydia.

Vector

Infections you get from bugs (like mosquitos, ticks or fleas) are called vector-borne. You can get Rocky Mountain spotted fever, Lyme disease and shigellosis through vectors.

Vehicular

While it sounds like something you get from your car, “vehicular” usually means you get sick from water or food (the “vehicle” of transmission). You can get gut (gastrointestinal) infections from E. coli, _Campylobacter _and _Salmonella_ bacteria in contaminated food or water.

Who do bacterial diseases affect?

Anyone can get a bacterial disease, and most of us will at some point in our lives. You’re at higher risk for getting an infection if you have:

How does a bacterial infection affect my body?

Bacteria can hurt your body either when they reproduce or by releasing poisons (toxins) that damage your cells. Infections that only affect the surface of your skin or mucous membranes (like your throat or intestines) aren’t usually serious, but sometimes, bacteria can spread in your body and cause life-threatening illnesses. If bacteria gets into your blood, it can cause sepsis, a reaction to the infection that causes organ damage, which is sometimes fatal.

Symptoms and Causes

What are common symptoms of a bacterial infection?

Symptoms of bacterial infections vary depending on where in your body is infected. The main symptom is often fever, except skin infections, which usually cause redness or pain on your skin. Common symptoms of bacterial infections include:

  • Fever.
  • Chills.
  • Fatigue (tiredness).
  • Headache.

Additional symptoms can include:

LocationSymptoms
Skin.Redness, blisters, ulcers, swollen or painful skin.
GI tract.Diarrhea, stomach pain, nausea, vomiting.
Lungs.Cough, shortness of breath, chest pain, phlegm (sputum).
Lining around your brain (meningitis).Neck stiffness, nausea or vomiting, sensitivity to light, confusion.
In your bloodstream and spreading (septicemia).High fever, weakness, sweating, low blood pressure.
Heart (endocarditis).High fever, chest pain, night sweats, shortness of breath, cough, muscle, joint pain.
Urinary tract or genitals.Burning or pain when you pee, discharge from your penis or vagina, increased need to pee, painful intercourse.

What causes bacterial diseases?

Many kinds of bacteria cause infections. You usually get bacterial infections when bacteria get into your body through your mouth, your nose, your eyes or a cut in your skin. Sometimes, bacteria that normally live on your skin or in your body get into places they’re not supposed to (like through an injury) and reproduce.

How do you get a bacterial infection?

Common ways you can get bacterial infections include:

  • Eating or drinking contaminated food or water.
  • Eating or drinking unpasteurized dairy products.
  • Antibiotic use, which can kill the good bacteria that usually fight off bad bacteria.
  • From contaminated surfaces.
  • From other people (through coughing or close contact).
  • From getting contaminated water into your lungs (aspirating).
  • Through oral, anal or vaginal sex.
  • Through contaminated dirt (soil).
  • From a bite from an infected tick, mosquito or flea.
  • From a surgery or intubation (tube in your throat).

Are bacterial infections contagious?

Yes, many bacterial infections are contagious from person to person, including pertussis, tuberculosis, strep throat, meningococcal disease, bacterial STIs and MRSA. Infections you get from food, mosquitos or ticks are usually not contagious.

Diagnosis and Tests

How are bacterial infections diagnosed?

A healthcare provider diagnoses a bacterial infection by listening to your symptoms, doing an examination (listening to your heart and lungs, feeling your abdomen, looking at your skin) and taking samples to test for bacteria.

If they think you have bacteria in your lungs, brain or other internal organ, they might get X-rays, ultrasound, MRI or CT imaging to look for signs of infection.

Tests for bacterial infections

Your provider might send body fluid or tissue samples to a lab to look for signs of an infection (antibodies or antigens). A lab technician might also try to grow bacteria from your samples. Types of samples they might take include:

Management and Treatment

How are bacterial infections treated?

Not all bacterial infections need to be treated — some go away on their own. When you do need treatment, healthcare providers use antibiotics. Depending on where your infection is and how serious it is, antibiotics can be prescribed as:

  • Oral medication (pills).
  • IV medication, given to you at a doctor’s office or hospital directly into a vein.
  • Ointment or cream.
  • Eye drops.

Complications/side effects of the treatment

Sometimes, certain antibiotics stop working and don’t kill or slow down bacteria (antibiotic resistance). Because of this, doctors and nurse practitioners are careful about when and how they prescribe antibiotics. They only prescribe them if they think they’ll help you. It’s important for you to take any medication as prescribed for the full course, even if you start to feel better.

Prevention

How can I prevent bacterial infections?

Ways to reduce your risk of various types of bacterial infections include:

  • Get vaccinated. There are vaccines for many bacterial diseases, including tetanus, whooping cough, diphtheria and bacteria that cause certain forms of meningitis (Neisseria meningitides), pneumonia (Streptococcus pneumoniae, Haemophilus influenzae type b) and bloodstream infections.
  • Practice good hygiene. This includes maintaining good hand-washing habits, wearing clean and dry clothes and not sharing personal items with other people.
  • Keep wounds clean. Breaks in your skin allow bacteria to get in. Clean and cover cuts or wounds in your skin.
  • Practice safe food habits. This includes storing food properly, heating meat and poultry to a temperature that kills bacteria and washing or peeling fruits and vegetables before eating.
  • Use a condom or dental dam during any kind of sex.
  • Protect yourself from bug bites. Wear protective clothing, use bug spray and check yourself and your pets for ticks after being outdoors.

Outlook / Prognosis

What can I expect if I have a bacterial infection?

What to expect depends on what kind of bacterial infection you have. Less serious bacterial infections are treatable with medication at home. Others require a hospital stay and can cause lasting damage. Bacterial infections in your internal organs or blood can be life-threatening.

Complications of bacterial infections

Bacterial infections inside of your body can cause serious complications. The most serious complication is sepsis, a life-threatening reaction to an infection that causes organ damage. Sepsis can be fatal.

How long do bacterial infections last?

If you’re prescribed antibiotics for a bacterial infection, you’ll usually have to take them for a week or two, though you’ll probably feel better sooner. Take all of your medication as prescribed, otherwise, you might not get rid of all of the bacteria.

What is the cure for bacterial infections?

Antibiotics usually cure bacterial infections. They sometimes go away on their own or can be treated without antibiotics, but it’s always best to check with a healthcare provider for the best way to treat them.

Living With

When should I see my healthcare provider?

Contact a healthcare provider if you have symptoms of a bacterial infection, especially if you’ve had them for more than a couple of days. Make sure to follow up with your provider if you’ve been treating an infection and your symptoms aren’t getting better or are getting worse.

When should I go to the ER?

Go to the nearest ER or seek immediate medical attention if you have signs of a serious infection, including:

  • High fever (103 degrees Fahrenheit or 39.4 degrees Celsius).
  • Confusion or other mental changes.
  • Neck stiffness with other symptoms of meningitis (headache, nausea, vomiting).
  • Low blood pressure.

What questions should I ask my doctor?

  • What caused this and how can I avoid it in the future?
  • How do I prevent spreading this to other people?
  • How do I use my medication?
  • How long will it take to feel better?
  • When should I follow up with you?
  • What can I do to help my symptoms at home?

A note from Cleveland Clinic

Bacteria live all around us — millions even live on or in us. They help us digest nutrients, protect us from harmful invaders and even help in making delicious foods. But, like puppies in a shoe factory, they can cause a lot of damage if they’re somewhere they’re not supposed to be. Bacterial infections can be a temporary nuisance, but they can also turn into a life-threatening situation. Always check with a healthcare provider to make sure you know the best way to manage a bacterial disease.

Last reviewed by a Cleveland Clinic medical professional on 09/20/2022.

References

  • Boull CL. Bacterial Infections. In: Soutor C, Hordinsky MK, eds. Clinical Dermatology: Diagnosis and Management of Common Disorders. 2nd edition. McGraw Hill; 2022.
  • Gerba CP. Environmentally Transmitted Pathogens. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7173582/) Environmental Microbiology. 2009:445–84. Accessed 9/20/2022.
  • Merck Manuals. Bacterial Infections: Overview. (https://www.merckmanuals.com/home/infections/bacterial-infections-overview/overview-of-bacteria) Accessed 9/20/2022.
  • Merck Manuals. Overview of Bacterial Skin Infections. (https://www.merckmanuals.com/home/skin-disorders/bacterial-skin-infections/overview-of-bacterial-skin-infections) Accessed 9/20/2022.
  • Sepsis Alliance. Bacterial Infections. (https://www.sepsis.org/sepsisand/bacterial-infections/) Accessed 9/20/2022.
  • The National Academy of Sciences. How Infection Works: Entering the Human Host. (http://needtoknow.nas.edu/id/infection/encountering-microbes/entering-the-human-host/) Accessed 9/20/2022.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy