From the moment of entry into this world, bacteria surround you. They are abundant in all environments. Bacteria live on your skin, in your intestine and in many other body locations. The overwhelming majority of bacteria do not cause disease. However, disease-causing species cause a range of human bacterial illnesses that range from mild to potentially life-threatening.
Upper Respiratory, Mouth and Ear Infections
Most upper respiratory infections are caused by viruses and typically go away on their own without treatment. When these infections are caused by bacteria, however, antibiotic therapy is needed. Examples include strep throat, tonsillitis, sinusitis and epiglottitis -- a serious infection of the tissue above the voice box. Infections of the outer and middle ear can also be caused by bacteria. Tooth decay and gingivitis -- inflammation of the gums -- are common oral diseases caused by bacteria.
The lungs are particularly vulnerable to bacterial infections. Pneumococcal pneumonia is a common example, although other types of bacteria and viruses can also cause pneumonia. Other examples of bacterial lung diseases include Legionnaire's disease, inhalation anthrax and whooping cough, also known as pertussis. Pneumococcal pneumonia and whooping cough are both vaccine-preventable diseases.
Sexually Transmitted Infections
Certain sexually transmitted infections remain among the most common bacterial infections worldwide, including chlamydia, gonorrhea and syphilis. These infections are curable with appropriate antibiotic treatment. Left untreated, however, these infections can lead to serious complications including pelvic inflammatory disease in women, and spread to other body organs and tissues.
Urinary Tract and Prostate Infections
Urinary tract infections are usually caused by bacteria, and disproportionately affect women. An infection of the bladder may spread to the kidneys, a condition known as pyelonephritis. Prostatitis -- bacterial infection of the prostate gland -- can occur in men of any age. This condition can develop suddenly or gradually.
Gastrointestinal Infections and Food Poisoning
Many types of bacteria can cause food poisoning, including certain species of Salmonella, Shigella, Campylobacter, E coli and Listeria. Some of these food-borne bacterial infections cause serious diseases, such as typhoid fever, cholera and botulism. Infection of the stomach with the bacterium Heliobacter pylori is a well-known cause of peptic ulcer disease and may increase the risk for stomach cancer.
Although many types of harmless bacteria live on the skin, disease-causing bacteria can cause a variety of skin infections. An abscess or boil is a common example, typically developing when an opening in the skin leads to a pocket of infection. Cellulitis is a more widespread infection involving the superficial layers of the skin. The most severe type of bacterial skin infection is necrotizing fasciitis, commonly known as "flesh-eating bacteria" disease. With this life-threatening infection, the skin and deep underlying tissues are not "eaten" by the bacteria. Rather, the rapidly spreading infection causes the infected tissues to die.
Other Bacterial Diseases
Any body tissue can potentially be infected with bacteria. Osteomyelitis and septic arthritis refer to bacterial infection of the bones and joints, respectively. Meningitis -- infection of the tissues that cover and protect the brain and spinal cord -- can be caused by viruses, bacteria or fungi. Common bacterial causes include meningococcus, pneumococcus and streptococcus. Serious bacterial infection anywhere in the body can potentially spread to the bloodstream -- a condition known as septicemia -- and infect other body tissues. Septicemia is life-threatening and may lead to shock, coma, organ failure and death.