Types of Bacterial Infections

Medically Reviewed By Alana Biggers, M.D., MPH
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A bacterial infection is an overgrowth of bacteria that can negatively affect your health and may cause a serious disease. There are many types of bacterial infections including skin, bladder, and lung infections. Some are relatively easy to treat with antibiotics that target bacteria. Many bacteria live in and on your body. This includes on your skin and in the respiratory and intestinal tract. For example, there are 500–1,000 species in the intestinal tract alone.

Bacteria are beneficial to our health but can sometimes lead to potentially harmful infections if they multiply too much. Bacterial species in the environment can also cause infections and disease.

Learn more about the types of bacterial infections and how treatment varies by the type and location of the infection.

Types of bacterial infections on the skin

germs on hands concept
Marc Tran/Stocksy United

Skin punctures or cuts can allow bacteria to enter and cause an infection. Many types of bacteria can cause skin infections including Streptococcus and Staphylococcusaureus. Although these bacteria live on our skin without causing problems, they can enter any type of break in the skin and multiply uncontrollably. 

Bacterial skin infections include:

Symptoms of a bacterial skin infection can include:

  • swelling
  • skin discoloration
  • warmth
  • pain
  • itching
  • rash
  • pus, which may be visible

Healthcare professionals treat some bacterial skin infections with antibiotics. Medicated skin creams and ointments may clear up the infection or you may need to take an antibiotic by mouth. Severe skin infections may also require surgical draining if an abscess forms.

Learn more about staph infections here.

Types of bacterial lung infections

Bacterial lung infections often cause fever, cough, and phlegm production. Pneumonia is a type of bacterial lung infection. The most common cause of bacterial pneumonia is Streptococcus pneumoniae. It is also known as pneumococcal pneumonia. Other bacteria that can cause pneumonia include:

  • Haemophilus influenzae
  • Legionella pneumophila, which causes Legionnaires’ disease
  • Mycoplasma pneumoniae, which causes walking pneumonia
  • Pseudomonas aeruginosa
  • Chlamydophila pneumoniae

Bacterial infections also cause conditions such as:

Vaccines are available to prevent some bacterial lung infections, such as pneumococcal pneumonia and pertussis. Bacterial lung infections require treatment with antibiotics.

Types of bacterial infections in the digestive tract

Infection of the stomach, intestines, or a diverticulum are examples of bacterial digestive infections. These infections occur when existing bacteria overmultiply or enter the stomach or intestines. Some bacteria release toxins, which irritate the lining of the gastrointestinal (GI) tract. A few of the many types of bacteria that can cause digestive infections include:

When a bacterium from the environment infects the GI tract, this is food poisoning. These bacteria can enter your body when you eat food that is undercooked, improperly preserved, or spoiled. You also can get a GI infection by drinking unpurified water. This is also called traveler’s diarrhea. C. diff, by contrast, can be caused by antibiotic treatment for another bacterial infection.

Bacterial infections of the digestive tract can cause:

Mild forms of bacterial gastrointestinal infections may not require treatment. They often clear up on their own after a few days. More serious infections, like C. diff, require medical intervention.

Learn about bacterial digestive infections here.

Other types of bacterial infections

Bacteria can infect any area of the body. Other bacterial infections include:

Learn more about bacterial diseases here.

Diagnosing bacterial infections

Healthcare professionals may diagnose some bacterial infections by symptoms alone. However, sometimes the symptoms are similar to those of an infection caused by a virus, fungus, or parasite. In this case, the only way to be sure is to examine samples of fluid and tissue from the site of the infection. Under a microscope, bacteria look different from other types of pathogens. A laboratory may also attempt to culture, or grow, the bacteria from the sample to identify it.

When to contact a doctor

You should contact a healthcare professional for symptoms of an infection.

Seek immediate medical attention for these symptoms:

If a bacterial infection is causing your symptoms, your doctor may treat the illness with antibiotics. These drugs can eliminate most bacteria. Severe infections and antibiotic-resistant bacterial infections may require hospitalization.

Learn about methicillin-resistant Staphylococcus aureus here.

What are bacteria?

Bacteria are single-celled organisms. They are so small you need a microscope to see them, with few exceptions. When they multiply to large numbers, they are visible as a “colony” on a solid surface and can make a liquid look cloudy.

Scientists classify bacteria according to certain characteristics. The classification system is complex. There are several species within a genus and several genuses (genera) within a family. For example, Streptococcus pyogenes, which can cause strep throat, is within the genus Streptococcus (“strep”) and family Streptococcaceae.

Each genus and sometimes the species of bacteria can cause different symptoms of bacterial infection. For nonscientific educational writing, people may use the word “type” to describe a particular genus or family of bacteria.

Frequently asked questions

Below are some questions that people ask about bacterial infections.

What is the strongest antibiotic for bacterial infection?

Vancomycin is considered the strongest antibiotic. A modified version of vancomycin is about 25,000 times more potent than vancomycin against vancomycin-resistant Enterococci. These bacteria, including E. faecalis and E. faecium, cause many hospital-acquired infections.

What is the most common bacterial infection?

Chlamydia is the most common bacterial infection of nationally notifiable diseases. Those are diseases mandated by state legislation and regulations to be reported to the Centers for Disease Control and Prevention (CDC).

What are the worst bacterial infections?

The worst bacterial infections are difficult to define because “worst” can mean different things depending on the context. The worst bacterial infections may be those that are the most difficult to treat due to antibiotic resistance. According to the CDC, these include carbapenem-resistant Acinetobacter, carbapenem-resistant Enterobacterales, and drug-resistant Neisseria gonorrhoeae, as well as C. difficile.


Cellulitis, bacterial pneumonia, tuberculosis, ear infections, C. diff, and chlamydia are different types of bacterial infections. Sometimes it can be difficult to tell apart a bacterial infection from a viral or other type of infection. However, it is important to diagnose one from the other because the treatment is different. Left untreated, some bacterial infections can lead to serious complications. Contact a physician or other medical professional for signs and symptoms of infection.

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Medical Reviewer: Alana Biggers, M.D., MPH
Last Review Date: 2022 Jul 18
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