Learn about 14 common types of bacteria and 13 infections they can cause, including their symptoms, transmission, prevention, and when medical attention may be needed.
14 Types of Bacteria and 13 Types of Infections
Bacteria are microscopic organisms found almost everywhere. Many are harmless or even beneficial, but some can cause infections when they enter the body, multiply excessively, or reach tissues where they do not belong.
Different bacteria can affect different parts of the body, including the skin, lungs, digestive system, urinary tract, and bloodstream.
Below are 14 important types of bacteria and examples of infections associated with them.
1. Escherichia coli (E. coli)
E. coli normally lives in the intestines of humans and animals. Most strains are harmless, but certain strains can cause illness.
Associated infections:
- Urinary tract infections
- Gastrointestinal infections
- Foodborne illness
Some harmful strains can cause severe diarrhea and abdominal cramps.
2. Staphylococcus aureus
Staphylococcus aureus can live on the skin or in the nose without causing illness. However, it can cause infections when it enters damaged skin or deeper tissues.
Associated infections:
- Skin infections
- Abscesses
- Pneumonia
- Bloodstream infections
Some strains, such as MRSA, are resistant to several commonly used antibiotics.
3. Streptococcus pyogenes
This bacterium is commonly associated with infections of the throat and skin.
Associated infection:
- Strep throat
It can also cause scarlet fever, impetigo, and other infections.
4. Streptococcus pneumoniae
This bacterium can cause respiratory and invasive infections, particularly in young children, older adults, and people with certain medical conditions.
Associated infections:
- Pneumonia
- Meningitis
- Sinus infections
- Middle-ear infections
Vaccination can help protect against serious pneumococcal disease.
5. Salmonella
Salmonella is commonly transmitted through contaminated food or water.
Associated infection:
- Salmonellosis
Symptoms can include diarrhea, fever, stomach cramps, nausea, and vomiting.
6. Shigella
Shigella primarily affects the digestive system and spreads through contaminated food, water, or contact with an infected person.
Associated infection:
- Shigellosis
It can cause diarrhea, abdominal pain, fever, and sometimes bloody stools.
7. Campylobacter jejuni
Campylobacter is a common cause of bacterial gastroenteritis.
Associated infection:
- Campylobacteriosis
Undercooked poultry is an important source of exposure.
8. Clostridioides difficile
C. difficile can cause severe diarrhea and inflammation of the colon, particularly after antibiotic use has disrupted normal intestinal bacteria.
Associated infection:
- C. difficile infection
Persistent or severe diarrhea after taking antibiotics should be medically evaluated.
9. Helicobacter pylori
H. pylori can colonize the stomach and is strongly associated with peptic ulcer disease.
Associated infections/conditions:
- H. pylori infection
- Gastritis
- Peptic ulcers
Long-term infection can increase the risk of certain stomach cancers.
10. Mycobacterium tuberculosis
Mycobacterium tuberculosis is the bacterium responsible for tuberculosis.
Associated infection:
- Tuberculosis
TB most commonly affects the lungs but can also affect other parts of the body.
11. Neisseria meningitidis
This bacterium can cause serious invasive disease.
Associated infections:
- Meningitis
- Meningococcal bloodstream infection
Meningococcal disease can progress rapidly and requires urgent medical attention.
12. Neisseria gonorrhoeae
This bacterium causes gonorrhea, a sexually transmitted infection.
Associated infection:
- Gonorrhea
Some infections cause few or no symptoms, particularly in women, which is why testing can be important when exposure is possible.
13. Treponema pallidum
Treponema pallidum is the bacterium responsible for syphilis.
Associated infection:
- Syphilis
Without treatment, syphilis can progress through several stages and eventually affect multiple organs.
14. Vibrio cholerae
Vibrio cholerae can cause cholera, a serious intestinal infection that can lead to severe watery diarrhea.
Associated infection:
- Cholera
Rapid loss of fluids and electrolytes can cause dangerous dehydration.
13 Important Bacterial Infections at a Glance
Here are 13 examples worth remembering:
- Urinary tract infection — commonly caused by E. coli
- Strep throat — commonly caused by Streptococcus pyogenes
- Pneumococcal pneumonia — Streptococcus pneumoniae
- Salmonellosis — Salmonella
- Shigellosis — Shigella
- Campylobacteriosis — Campylobacter
- C. difficile infection — Clostridioides difficile
- Tuberculosis — Mycobacterium tuberculosis
- Meningococcal disease — Neisseria meningitidis
- Gonorrhea — Neisseria gonorrhoeae
- Syphilis — Treponema pallidum
- Cholera — Vibrio cholerae
- H. pylori infection — Helicobacter pylori
How Can Bacterial Infections Be Prevented?
Simple habits can reduce the risk of many bacterial infections:
- Wash your hands regularly with soap and water.
- Cook meat, poultry, and eggs thoroughly.
- Avoid cross-contamination when preparing food.
- Drink safe water.
- Keep wounds clean and covered.
- Stay up to date with recommended vaccinations.
- Practice safer sex.
- Take antibiotics only when prescribed and use them exactly as directed.
When Should You Seek Medical Care?
A bacterial infection can sometimes become serious, particularly when it spreads beyond the original site.
Seek medical attention for symptoms such as difficulty breathing, severe dehydration, persistent high fever, confusion, severe weakness, a rapidly spreading skin infection, or other symptoms that are sudden or worsening.
Remember that not every infection requires antibiotics. Antibiotics treat certain bacterial infections, but they do not work against viruses such as the common cold or influenza.
Understanding the difference between bacteria and the infections they can cause is important—but diagnosis should be based on symptoms, examination, and appropriate testing rather than a symptom list alone.