What Is a Bacterial Infection?

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LightFieldStudios / Getty Images

Medically reviewed by Kashif J. Piracha, MD

A bacterial infection is a common type of illness that occurs when harmful bacteria invade your body and start to multiply. There are several types of bacterial infections, all of which cause their own set of symptoms. While some bacterial infections are mild and can be treated with antibiotics, other infections can be more serious and cause life-threatening complications.

Though anyone can develop a bacterial infection, factors such as compromised immune systems, environmental exposures to bacteria, and improper personal hygiene can increase your risk of developing a bacterial infection. If you develop an infection, getting a diagnosis is crucial to keep symptoms at bay and reduce your risk of complications.

Related: What Is a Viral Infection?

Types of Bacterial Infections

There are several types of bacterial infections, and each of them can affect different parts of your body. The most common types include:

  • Respiratory infections: Affect the lungs, which may include infections such as pneumonia, bronchitis, and sinusitis

  • Urinary tract infections (UTIs): Affect your urinary system (e.g., kidneys, bladder, or urethra)

  • Skin infections: Affect the skin, and may include infections like impetigo and folliculitis

  • Sexually transmitted infections (STIs): Affect your genitals, rectum (butt), and sometimes your mouth, which may occur due to infections such as gonorrhea and chlamydia that you can develop after sexual contact

  • Ear infections: Affect the middle ear, but may cause symptoms like headaches and dizziness in addition to ear pain

  • Gastrointestinal infections: Affect the digestive system, which may caused by infections like H. Pylori

  • Meningitis: Affects the membranes surrounding your brain and spinal cord, and can be life-threatening without prompt treatment

  • Bloodstream infections: Affect the bloodstream and can enter various organs, which may be caused by serious infections like sepsis

Bacterial Infection Symptoms

The symptoms of a bacterial infection will usually depend on the type of bacterial infection you have and which body parts are most affected by a specific bacteria. However, most bacterial infections do share some common symptoms, including:

  • Fever

  • Chills

  • Pain or discomfort in the affected body part (e.g., throat, joints, chest, ears, urethra, etc.)

  • Skin swelling or redness at the site of infection

  • Persistent cough

  • Shortness of breath

  • Fatigue

  • Headache

Depending on the type of bacterial infection you have, you may also experience additional symptoms. UTIs can often cause pain while urinating or needing to use the bathroom often. Gastrointestinal infections can cause diarrhea, nausea, vomiting, or abdominal pain. Skin infections may lead to boils, rashes, or pus-filled bumps.


Several types of bacteria can cause infections. These bacteria often enter the body through avenues such as the mouth, nose, eyes, or openings in the skin. The bacteria may target specific organs, tissues, or systems, causing disruptions in your normal bodily functions.

Some common bacteria that are known to cause infections include:

  • Streptococcus (strep): Usually causes infections such as strep throat, pneumonia, and skin infections like cellulitis

  • Staphylococcus (staph): Responsible for staph infections, abscesses, bone infections, food poisoning, and endocarditis

  • Escherichia coli (E. coli): Commonly associated with gastrointestinal infections

  • Salmonella: Often leads to food poisoning and bacterial gastroenteritis (stomach flu)

  • Neisseria gonorrhoeae: Causes gonorrhea, a common STI

  • Haemophilus influenzae: Can lead to respiratory tract infections, meningitis, bloodstream infections, and pneumonia

The above list compiles only a few examples. In fact, there are many other bacterial species that can cause infections in different parts of your body. Identifying the specific bacteria that is affecting your body is an important part of the diagnostic process.

Risk Factors

Anyone can get a bacterial infection. However, certain factors can increase your risk, including:

  • Being immunocompromised

  • Living with a chronic health condition

  • Spending time with people who are sick

  • Not washing hands regularly

  • Not getting vaccinated

  • Not practicing safe sex


If you're experiencing symptoms of a bacterial infection or are feeling sick, it's important to reach out to your healthcare provider and make an appointment under their guidance. Diagnosing bacterial infections often involves a combination of clinical assessments, laboratory tests, and imaging studies. Some common diagnostic measures that your provider may use to test for bacterial infections include:

  • Blood test to identify the presence of bacteria in the bloodstream

  • Urine test to check for bacteria, white blood cells, or other signs of infection in your pee

  • Culture tests (such as skin samples or throat swabs) to learn which bacteria are causing your symptoms

  • Imaging tests like X-rays, CT scans, or MRIs to visualize signs of infection in your internal organs

  • Stool tests to analyze samples of your poop for potential signs of bacteria

  • Lumbar puncture, which takes a sample of cerebrospinal fluid (the fluid surrounding the brain and spine) to diagnose meningitis

  • Rapid antigen tests to quickly detect specific bacteria for common infections like strep throat

The exact tests your healthcare provider will choose will depend on your symptoms and where in the body you're experiencing them.


Not every bacterial infection requires antibiotics. But, antibiotic medications are the most common treatment for people with bacterial infections. If your specific infection requires antibiotics, your provider may prescribe a medication that you can take orally (by mouth), apply topically (directly onto your skin), or use intravenously (through an IV injection).

It's essential to take antibiotics only when needed and prescribed. Mishandling antibiotics or using them when they're not necessary can lead to antibiotic resistance—which occurs when bacteria in your body start to evolve and resist the healing effects of antibiotic medication, making them no longer effective for your infection.

How to Prevent Bacterial Infections

While bacterial infections are common, there are ways to reduce your risk of developing one. Follow these seven prevention strategies to keep yourself safe from an infection:

  1. Washing your hands regularly to prevent the spread of bacteria

  2. Getting vaccinated against bacterial infections, such as bacteria that can cause pneumonia or meningitis

  3. Using proper food handling practices, such as washing vegetables, cooking food thoroughly, and avoiding eating raw or uncooked meat

  4. Drinking clean water

  5. Practicing safe sex to prevent STIs

  6. Limiting contact with people who have a bacterial infection or are sick

  7. Cleaning wounds and applying bandages on the skin to prevent bacteria from spreading


If you suspect that you have a bacterial infection, it is essential to see your healthcare provider for treatment. Untreated bacterial infections can lead to serious and even life-threatening health conditions. These complications may include:

  • Cellulitis: A serious skin infection that can occur if you do not treat an infected wound or cut on the skin. Cellulitis can develop when bacteria enter the skin through a cut or wound, which may cause symptoms like redness, swelling, and tenderness. Antibiotic treatment is necessary to treat symptoms.

  • Sepsis: A life-threatening illness that occurs when your whole body responds to an infection. Sepsis can cause widespread inflammation in your body and affect the functioning of your organs. Without prompt treatment, your organs can start to fail and increase your risk of death. If you or a loved one is experiencing sepsis, it's essential to call 911 or go to the emergency room as soon as possible.

A Quick Review

Bacterial infections can develop due to a variety of bacteria. Each bacterial infection can affect your body a little differently. But, common symptoms include fever, chills, headaches, fatigue, and coughing. Most bacterial infections use antibiotics for treatment, which are effective in reducing symptoms. But don't wait to get tested. If you have symptoms, early treatment is crucial to limit your risk of complications.

Frequently Asked Questions

Do bacterial infections go away on their own?

Some bacterial infections, such as ear infections, may resolve on their own. However, many require prompt and appropriate antibiotic treatment to prevent complications and ensure a complete recovery.

How long do bacterial infections usually last?

The length of a bacterial infection will depend on the type of infection you have and your overall health status. Some infections resolve in a week while others may last for weeks or longer, especially if you don't receive proper treatment.

How do you tell if an infection is viral or bacterial?

You will need to see your healthcare provider to learn whether your symptoms are caused by a viral or bacterial infection. They may perform diagnostic tests, such as a blood test, nose or throat swab, stool sample, or urinalysis to detect what type of pathogen (harmful cell) is causing your infection.

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