Bacterial infections are caused by bacteria, a kind of microorganisms that are made of only one cell. Bacteria live in all kinds of the environment including extreme hot and cold conditions. Millions of bacteria are present in the environment around us, on our body and inside it.

Bacteria are both harmful and useful to us. In fact, only a small number of bacteria are responsible for illnesses. Many are beneficial, such as those involved in immunity, digestion, and production of antibiotics and food products.

Bacteria are important for digestion of food. There are some that fight diseases and those that help make healthful food.

Some examples of good bacteria include:

1. Lactobacillus is used in making yogurt and cheese.

2. Escherichia coli are present in intestines and help in digestion of food, and production of vitamin K.

3. Bacteroides thetaiotaomicron and Bacteroides fragilis live in the gut and help in digestion of carbohydrates and sugar transport and utilization.

Some bacteria cause illness. They invade and quickly multiply in the body to form colonies. When this happens in the respiratory tract, the following diseases may occur:

1. Pharyngitis — Streptococcus pyogenes

2. Diphtheria — Corynebacterium diphtheria

3. Pertussis — Bordetella pertussis

4. Tuberculosis — Mycobacterium tuberculosis

Gastrointestinal infections caused by bacteria include:

1. Peptic ulcers — Helicobacter pylori

2. Enteric (typhoid) fever — Salmonella typhi

3. Gastroenteritis — Shigella, Salmonella, and Escherichia coli

Bacteria cause infections of the nervous system such as:

1. Meningitis — Streptococcus pneumonia and Neisseria meningitidis

2. Tetanus — Clostridium tetani

3. Botulism — Clostridium botulinum

Urogenital infections caused by bacteria include:

1. Urinary tract infections — Escherichia coli

2. Gonorrhea — Neisseria gonorrhoeae

3. Chlamydia — Chlamydia trachomatis

4. Syphilis — Treponema pallidum

Bacteria also cause skin infections such as:

1. Leprosy — Mycobacterium leprae

2. Abscess — Staphylococcus aureus

The symptoms of bacterial infection would depend on the condition, the organ affected, and the kind of bacteria causing the infection.

The diagnosis of bacterial infections would depend on the symptomatic history of the patient. The tests that may be done include:

1. Physical examination

2. Blood tests

3. Urine tests

4. Urine culture

5. Gram stain to identify bacteria

6. Toxin assay to look for the toxins made by the bacteria

7. Culture or biopsy of the tissue infected

The treatment will depend on the kind of infection. Antibiotics are usually prescribed to treat bacterial infections. These are medicines that kill the bacteria. They may be given in the oral or injectable form. Some antibiotics that may be prescribed for a bacterial infection may include:

1. Amoxicillin

2. Azithromycin

3. Doxycycline

4. Ofloxacin

5. Tetracycline

6. Gentamycin

7. Metronidazole

8. Clindamycin

Supportive therapy may be required for other symptoms, such as fever.

The complications will depend on the kind of bacterial infection.

Antibiotics must be taken carefully and for the duration, they are prescribed for. Taking them too frequently, taking them without a prescription or not completing the full course of treatment may lead to a development of antibiotic resistance, where antibiotics fail to kill bacteria.

Antibiotic resistance makes treatment of bacterial infections difficult and may prolong the illness and severity.