Some microscopic organisms called bacteria can cause diseases in humans. When this occurs, it is called a bacterial infection.
There are thousands of different types of bacteria that live around the world. Only a few types of bacteria cause disease in humans.
Some bacteria are actually beneficial for humans. For examples, bacteria help humans digest certain types of food and keep infectious organisms at bay. Bacteria may be found in the environment, on the skin, in the airways, in the mouth, in the vagina, and in the digestive tract.
Disease-causing bacteria can cause an illness in humans when they enter the body. The bacteria may enter the body through the skin, nose, eyes, vagina, or mouth. Once the invading bacteria start to multiply and harm the body, it is called an infection. Infections can develop in any area of the body.
In some cases, the bacteria in the digestive tract, called the intestinal flora, can cause a severe infection if they move into the bloodstream. This process, called bacterial translocation, is most likely to occur during surgery on the digestive tract.
When the bacteria enter the body, they begin multiplying. If the infection is not treated, it may spread to other areas of the body. Bacteria cause different diseases depending on the specific type of bacteria and where they are in the body. Examples of bacterial infections include cellulitis, cholera, Fournier's gangrene, methicillin-resistant Staphylococcus aureus (MRSA), trachoma, and tuberculosis.
If left untreated, some bacterial infections may lead to death. However, if diagnosed and treated quickly, most patients with bacterial infections experience a complete recovery. Bacterial infections are treated with medications called antibiotics. Depending on the type and severity of the infection, as well as the patient's overall health, antibiotics may be taken by mouth, applied to the skin, or injected into the vein.
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examples of infections
Cellulitis: Cellulitis is a bacterial infection of the deep layers of the skin. The bacteria that cause the infection may enter the skin through a cut, scrape, scratch, or other wound. The infected area may become red, hot, swollen, irritated, and painful. Other symptoms may include fever, chills, and muscle aches. Over time, the infection may expand over a larger area of the skin. In rare cases, fluid-filled blisters may develop on the affected area of skin. Cellulitis can be deadly if not treated. Patients typically take antibiotics, such as cephalexin (Keflex®), by mouth for about ten days.
Cholera: Cholera is a bacterial infection of the small intestine that causes diarrhea. Bacteria called Vibrio cholerae cause the infection. Cholera usually spreads through contaminated water and it is most common in underdeveloped areas of the world that have poor sanitation, such as sub-Saharan Africa. In addition to diarrhea, patients may experience dehydration, abdominal cramps, nausea, and vomiting. Most patients with cholera only require treatment with hydration. Severe infections may be treated with antibiotics, such as azithromycin (Zithromax® or Zmax®).
Fournier's gangrene: Fournier's gangrene is a serious infection of the skin that affects the genitals and perineum. The infection develops when a combination of microorganisms, including bacteria, fungi, and yeasts, enter the body. Fournier's gangrene is usually caused by an injury, which may occur as a result of surgical procedures or urinary tract disease. The infection spreads quickly, destroying the skin, tissue under the skin, and muscle. Symptoms may include fever, drowsiness, reddening of the skin, dead and discolored skin, odor, pain, swelling, and skin that is spongy to the touch. Patients typically take a combination of antibiotics to treat the infection. Surgery may also be needed to remove dead tissue.
Methicillin-resistant Staphylococcus aureus (MRSA): Methicillin-resistant Staphylococcus Aureus (MRSA) is a type of bacteria that does not respond to treatment with certain antibiotics, including ampicillin (Principen®) and other penicillins. Individuals can become infected with the bacteria through airborne droplets. It can be transmitted when an individual inhales particles of infected sputum from the air. The bacteria become airborne when an infected person expels saliva (when they cough, sneeze, talk, spit, etc.). Symptoms of an MRSA infection are the same as non-resistant Staphylococcus aureus infections, and they may include red and swollen skin, fever, and headache. Patients infected with MRSA are treated with antibiotics, such as sulfamethoxazole/trimethoprim (Bactrim®) or vancomycin (Vancocine®).
In some patients, the MRSA become colonized. This means that the bacteria are growing and multiply in the patient, but the patient does not experience any signs of symptoms of an infection. These patients do not require treatment.
Trachoma (chlamydia eye infection): Trachoma is a bacterial infection of the eyes that is caused by the bacteria Chlamydia trachomatis. Trachoma is spread through direct contact with infected eye, nose, or throat secretions or by contact with contaminated objects, such as towels or clothes. In addition, certain flies can spread the bacteria. The eye becomes red and irritated. If left untreated, the condition may cause scarring. If the eyelids are severely irritated, the eyelashes may turn in and rub against the cornea. This can cause eye ulcers, further scarring, vision loss, and even blindness. Patients typically receive antibiotics, such as erythromycin (ERYC®, Ery-Tab®, Erythromycin Base Filmtab®, PCE®, or Dispertab®) or doxycycline (e.g. Doryx®). In some cases, eyelid surgery may be needed to prevent long-term scarring. Scarring may eventually lead to permanent blindness, if not properly treated.
Tuberculosis: Tuberculosis (TB) is a bacterial infection of the lungs that is caused by the microorganism Mycobacterium tuberculosis. Symptoms may include cough, shortness of breath, pleurisy (inflamed membranes around the lungs), fever, weight loss, night sweats, chills, and loss of appetite. The disease can cause serious respiratory problems, which can be life threatening, especially if left untreated.
Tuberculosis is transmitted through airborne droplets. People become infected with TB when they inhale particles of infected sputum from the air. The bacteria become airborne when an infected person expels saliva (when they cough, sneeze, talk, spit, etc.). Patients typically receive a combination of antibiotics for several months to treat the infection. Commonly prescribed antibiotics include isoniazid/rifampin (Rifamate®), ethambutol (Myambutol®), and pyrazinamide.