An infection occurs when agents capable of causing diseases invade an organism. These agents multiply and attack the body. In response, the body attempts to prevent damage. In normal situations, blood is a sterile environment. Since there are usually no disease-causing agents in the blood, a bloodstream infection or bacteremia is very rare. Bacteria appearing in the bloodstream is abnormal and could be a sign of a major illness. Bloodstream infections have various causes and side effects.

Blood and Infections

Infectious agents such as viruses, bacteria, viroids, and prions can invade our bodies. In humans, the immune system responds to these threats. This response frequently involves inflammation and an adaptive reaction specific to the infectious agent. Infectious agents typically can’t invade the bloodstream. Occasionally, small amounts of bacteria enter the bloodstream but pose no risk because of their low population count -- the immune system quickly removes them.

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At various points in medical history, experts referred to bacteria in the blood as blood poisoning and septicemia. The medical community now views those terms as outdated. The modern term for any bacteria in the bloodstream is bacteremia. During ordinary activities, small amounts of bacteria may enter the bloodstream. This level of bacteria does not generally cause any issues. However, large numbers of bacteria can enter the bloodstream as the result of another infection or similar problem. In these instances, bacteremia can become a serious health risk.

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Occult Bacteremia

It is common for children under the age of three to develop fevers. Usually, other symptoms accompany the fever. However, if a child has a fever with no other symptoms, it could be a sign of occult bacteremia. This is similar to normal bacteremia but occurs only in children. It is rare and has become increasingly rarer as vaccines become more widespread, but some children are still susceptible. Experts believe affected children are those who cannot receive vaccines, whose parents chose not to vaccinate them, or those who already have weakened immune systems. In these cases, a physician may choose to prescribe preemptive antibiotics.


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Entry Methods

The bacteria can enter the bloodstream through many different avenues. The least likely to cause harm are insect bites, toothbrushing, and leaving small wounds exposed. Certain medical procedures such as dental extractions or inserting a catheter can introduce dangerous bacteria. If bacteremia is a concern, physicians will usually prescribe antibiotics before or after the procedure. Serious infections such as pneumonia or meningitis can also spread bacteria to the bloodstream. Bacteria from these sources are more likely to cause a major health issue.

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The Gram Stain Test

Medical professionals use the Gram stain test to classify various bacteria. Because there are so many possible interactions and methods bacteria can use to enter the body, these classifications are useful. The test involves staining bacteria and then quickly decolorizing them to determine their classification. Bacteria that retain the coloration are Gram-positive. Those that lose the coloration are Gram-negative. Knowing the classification not only helps physicians understand how the bacteria spread, but also how to effectively fight them. Gram-positive bacteremia is typically the result of outside influence, such as an open wound, intravenous drugs, or a catheter. Gram-negative bacteremia is more commonly a product of another infection.

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The Threat of Bacteremia

Usually, there are no signs of bacteremia because the bacteria in the bloodstream isn’t a threat to the body. However, if the bacteria manage to survive in the bloodstream or if a person has a weak immune system, bacteremia becomes dangerous. The bacteria can travel along the bloodstream and accumulate in locations, causing infection. It is also possible for bacteremia to lead to sepsis, which occurs when the body begins to harm itself as part of its response to an infection. Signs of bacteremia and sepsis include chills, weakness, fever, and pale skin.

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Resulting Infections

When bacteria begin to travel through the bloodstream, they are more likely to settle on foreign material in the human body such as catheters and artificial joints or heart valves. As a result, the cells lining the heart can develop endocarditis. Bone implants may lead to osteomyelitis. Additionally, just as bacteremia can be the result of certain infections, it can also cause them. For example, bacteria in the tissue around the brain can cause meningitis.

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Sepsis is one of the most dangerous outcomes of the body’s response to an infection. Essentially, the body begins to attack its own organs, tissues, and other structures in an attempt to kill the infection. Widespread inflammation is the first stage. If sepsis progresses, it can cause organ failure. People experiencing sepsis can have fevers or low body temperatures. They may also exhibit signs of confusion, or their bodies may begin to swell. If the person’s blood pressure drops, it could be a sign of septic shock.

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Septic Shock

A subclass of distributive shock, septic shock causes disturbances in the blood flow of the smallest blood vessels. This means the body’s tissues do not receive the amount of blood they need. Tissues may tear and various organs, including the heart, can function improperly. Though it is almost always a product of sepsis, in rare instances, the body can experience septic shock without it. Bacteremia is one of the several infections that can lead directly to septic shock.

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Treating Bacteremia and Sepsis

The treatment for bacteremia is usually fairly straightforward. Doctors remove any foreign matter such as catheters if they are the source of the bacteria. Antibiotics can help treat sepsis, septic shock, and bacteremia. In the case of septic shock, the body requires fluid transfers as well. The Gram-stain test helped discover which antibiotics are most effective for certain bacteria, streamlining the process for treating these issues. Despite the straightforward nature of the treatment, bacteremia is still a serious health condition. If it progresses too far and leads to sepsis or septic shock, there is a high risk of death.


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