Skip to main content icon/video/no-internet
icon backReturn to Entries

Bacterial Infections

Bacterial infections occur when single-celled microorganisms called bacteria colonize the human body. While this colonization is usually fended off by the immune system, bacteria cause disease when they cannot be controlled and begin to interfere with normal function. Bacteria can invade almost any system of the body, and do so through many routes of entry. Some types of bacteria normally live symbiotically with humans, especially on the skin and in the gut, but these can cause disease when they grow out of control or enter parts of the body where they are not normally found. There are millions of different species of bacteria, but only a handful account for the majority of infections in humans. It is difficult to quantify exactly how much disease is caused by bacterial infections, but it is significant. In 2002, lower respiratory infections and diarrheal diseases, which are usually caused by bacteria, were the two leading causes of death in children under 5 years, accounting for 17.7 percent and 14.9 percent of all deaths before age 5, respectively. For adults, tuberculosis alone was the third leading cause of death for those ages 15–59, accounting for 1,036,000 deaths in 2002. These numbers give an indication of the devastating impact that bacterial infections have on human health.

Some bacteria tend to infect certain populations, such as children, the elderly, or people with compromised immune systems. This last group has grown recently with the emergence of the HIV/AIDS epidemic, and subsequently many types of bacterial infections are reemerging as major threats to public health. The most striking example of this is tuberculosis, which was thought to be well controlled in the 1970s, but has now resurfaced, especially in areas where AIDS is prevalent. In addition to these challenges, many bacteria are quickly developing resistance to the drugs currently used to treat them. Bacterial infections are a critical challenge in current global health, especially in the context of the AIDS pandemic and emerging drug resistance.

Types of Bacterial Infections

Respiratory infections can be divided into two categories: upper respiratory infections (URIs) and lower respiratory infections (LRIs). Upper respiratory infections involve the nasal cavities, sinuses, pharynx, and larynx, and are most commonly caused by viruses. However, some URIs are caused by bacteria, including group A beta-hemolytic Streptococcus, which causes the syndrome known as strep throat. Other bacterial causes of URIs include Streptococcus pneumoniae and Haemophilus influenzae type B, although the latter has been largely eliminated in nations with vaccination programs. Symptoms of URIs include runny nose, cough, sore throat, fever, and sneezing. Otitis media, infection of the middle ear, is also commonly associated with URIs because the middle ear and the nasal cavity are anatomically connected by the Eustachian tube.

Lower respiratory infections involve the lungs and bronchi, and lead to the most mortality of all infectious diseases, causing around 6.8 percent of all deaths worldwide, and one in three newborn deaths. Often used synonymously with pneumonia, LRIs are much more commonly caused by bacteria than URIs. Common bacterial pathogens include Streptococcus pneumoniae and Staphylococcus aureus, which are both gram-positive bacteria. Many strains of gram-negative bacteria also cause pneumonia; these tend to originate in the gastrointestinal tract and get into the lungs when vomit is aspirated. LRIs are characterized by high fever, shortness of breath, chest pain, and productive cough with yellow-green sputum and blood. The alveoli of the lungs become filled with fluid, compromising the exchange of oxygen for carbon dioxide. When severe, this can be fatal. LRIs can also lead to acute respiratory distress syndrome (ARDS), which is an inflammatory response in the lungs leading to rapid filling of the alveoli with fluid, respiratory failure, and death. Bacterial infections in the lungs can also lead to abscesses or collections of fluid in the space surrounding the lungs called pleural effusions.

...

  • Loading...
locked icon

Sign in to access this content

Get a 30 day FREE TRIAL

  • Watch videos from a variety of sources bringing classroom topics to life
  • Read modern, diverse business cases
  • Explore hundreds of books and reference titles

Read next

More like this

Sage Recommends

We found other relevant content for you on other Sage platforms.

close

Have you created a personal profile? Login or create a profile so that you can save clips, playlists and searches

close
close
close Signed In to profile You are signed in as:
close
Logged in Institution Institution