Bacteremia | Diagnosis, Causes, Symptoms & Treatment

Haripriya Munipalli, Artem Cheprasov
  • Author
    Haripriya Munipalli

    Haripriya Munipalli has taught botany and biochemistry to undergraduates for 7 years. She has M.Sc. in Plant Sciences degree from University of Hyderabad, India and Master of Philosophy degree from Annamalai University.

  • Instructor
    Artem Cheprasov

    Artem has a doctor of veterinary medicine degree.

What is bacteremia? Learn bacteremia signs and symptoms and complications of bacteremia. Learn the causes and treatment plans available. Updated: 12/06/2021

What is Bacteremia?

Bacteremia is a condition where viable bacteria are present in the bloodstream. Clinically benign infections are possible for a healthy individual and they remain transient without creating any further consequences. Bacteremia might occur right after any medical surgery or while conducting usual oral hygiene.

When the immune responses against the bacterial infection are unsuccessful or become overwhelmed, bacteremia or a bloodstream infection results. Bacteremia can later get converted into many other clinical spectrums. It is also differentiated as septicemia.

The sum of all the bacteria, archaea and eukarya, that are colonizing the gastrointestinal (GI) tract is called the 'gut micro biota'. These microorganisms in the GI tract have co-evolved with the human host for thousands of years to form a mutually beneficial relationship. The number of microorganisms that inhabit the digestive tract of humans was estimated to be more than 10^14. This is approximately 10 times more bacterial cells than the number of human cells and nearly 100 times more than the genomic content in the human genome.

A recently revised estimation showed that the ratio of human cells to bacterial cells is almost equal to 1:1. As there are many bacterial cells in the human body, the host and the microbiota inhabiting it are usually referred to as a 'super organism'.

Bacteremia and sepsis are used interchangeably although they are two different terms. Bacteremia refers to the presence of bacteria inside the blood of an individual. In some cases, bacteremia does not cause any symptoms and does not actually appear to be dangerous to the affected victim. Sepsis is the clinical condition that is associated with the bacteria in the blood. Sepsis involves the inflammation of the body with a range of other symptoms like fever, rapid breathing, and confusion.

Sepsis and septicemia are related to infection in the blood that can result in severe side effects and it can also be fatal. But sepsis and septicemia are different in the clinical sense.

What Is Bacteremia?

If you are healthy, there should be somewhere around 100 trillion bacteria in your digestive tract and 0 bacteria in your blood. Quite the contrast, right? But if you do happen to have bacteria in your bloodstream, you have bacteremia, and this can prove deadly in some cases. The 'bacter-' refers to bacteria and the suffix of '-emia' refers to a condition of the blood. Let's find out this condition's signs, symptoms, possible complications, and treatment options.

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Numerous clumps of methicillin-resistant Staphylococcus aureus bacteria

methicillin-resistant Staphylococcus aureus bacteria

Bacteremia Causes

Bacteremia typically begins with a small localized infection such as an infected incision, a urinary tract infection, or another type of infection. The individual sometimes will not be able to identify the location of the presence of infection as well as does not notice the signs and symptoms.

For example, the individual has an infected tooth. Initially, the patient might have a small toothache. As the infection continues, the toothache might become very painful. Gradually, the person develops a bad taste in the mouth resulting in pus formation around the teeth. It slowly worsens in spite of the usage of mouthwash and ibuprofen.

Micrograph of a blood smear containing yersinia pestis plague bacteria

yersinia pestis plague bacteria

Bacteremia Mechanism

Many bacteria make use of the regulatory proteins of the host to escape from the complement-mediated killing. Pathogens have various different common mechanisms of complement escape. A few of such strategies include the expression of host complement regulator binding proteins, protease secretion, and the release of the inhibitors of the complement system. Various strategies are followed by the invading pathogens to escape from complement attack and immune recognition.

Making use of such complement escape proteins, bacteria like Streptococcus pyogenes, Streptococcus pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and so on, can escape from the host immune responses and enter into the bloodstream. For example, Prc, an E. coli bacterial periplasmic protease, was found to have a critical role in avoiding complement-mediated killing.

Therefore, when the immune mechanism of the host is not able to contain the spread of the bacteria due to avoiding host immune strategies by the bacteria or due to the defect in the immune response, bacteremia can develop.

The below illustration explains the interaction between the pathogens that are invading and the host defense mechanism resulting in bacteremia.

INVADING MICROORGANISMS HOST DEFENSE
MONOCYTES/MACROPHAGES
CYTOKINE STORM
NEUTROPHILS
COMPLEMENT ACTIVATION

SPECIFIC TRENDS
* NKT CELLS
* HEPATIC CLEARANCE
* SPLEEN PHAGOCYTOSIS
* COMPARTMENTALIZED LIPID PEROXIDATION

BACTEREMIA/DNAemia

GENETIC MAKEUP (SNPs)
* TNF, IL-1BETA, TLR4, NOD2, FCGR2A, MBL2, MSP2, SUFU

Bacteremia Symptoms

Some bacteremia cases are asymptomatic. In these cases, the immune system will clean the bacteria without the patient knowledge about the presence of this condition. When bacteremia results in an infection in the bloodstream, the likely symptoms that are experienced include fever, chills, and shivering.

Occult bacteremia is the presence of the bacteria in the bloodstream of a child suffering typically from fever. The source of infection here is unknown. Most commonly occult bacteremia is caused by Streptococcus pneumoniae. Typically no symptoms are observed in this case.

Signs, Symptoms, & Complications

Although bacteria can be dangerous, and bacteria found where they're not supposed to can be even more so, the reality is that many cases of bacteremia resolve without any obvious clinical signs or symptoms.

Of course, this is by no means always the case. Some people may develop a mild fever. The worst signs and symptoms stemming from bacteremia actually result from a major complication of bacteremia known as sepsis. Sepsis is a collection of signs and symptoms that occur as a result of an exaggerated immune system response to a systemic infection, like bacteremia. Sepsis can lead to signs such as:

  • Fever
  • Chills, which may include shaking
  • A rapid heart rate
  • A rapid and shallow rate of breathing
  • Mental changes, like confusion

In the worst cases, sepsis can turn into septic shock. This is where a person's blood pressure drops to dangerously low levels, organs begin to fail as a result, and death is a very real possibility.

Other possible complications of bacteremia include:

  • Endocarditis, the inflammation of the inner lining of the heart. By extension, this often implies an infection of the inner lining of the heart as well. This can damage a person's heart valves.
  • Infection of the protective layers of the brain, the meninges
  • Joint infections

Treatment

The most important treatment for bacteremia itself is the use of antibiotics. Antibiotics are drugs that either kill bacteria or inhibit their growth. This might include antibiotics called amoxicillin, ampicillin, gentamicin, or vancomycin among many others. The choice depends on the doctor's assessment of the patient's state as well as any test results that may reveal whether one antibiotic will be more effective than another.

The source of bacteria, if identified, must also be removed. For example, this could be something like a catheter placed into a person's vein in order to deliver medications and/or fluids.

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Video Transcript

What Is Bacteremia?

If you are healthy, there should be somewhere around 100 trillion bacteria in your digestive tract and 0 bacteria in your blood. Quite the contrast, right? But if you do happen to have bacteria in your bloodstream, you have bacteremia, and this can prove deadly in some cases. The 'bacter-' refers to bacteria and the suffix of '-emia' refers to a condition of the blood. Let's find out this condition's signs, symptoms, possible complications, and treatment options.

Signs, Symptoms, & Complications

Although bacteria can be dangerous, and bacteria found where they're not supposed to can be even more so, the reality is that many cases of bacteremia resolve without any obvious clinical signs or symptoms.

Of course, this is by no means always the case. Some people may develop a mild fever. The worst signs and symptoms stemming from bacteremia actually result from a major complication of bacteremia known as sepsis. Sepsis is a collection of signs and symptoms that occur as a result of an exaggerated immune system response to a systemic infection, like bacteremia. Sepsis can lead to signs such as:

  • Fever
  • Chills, which may include shaking
  • A rapid heart rate
  • A rapid and shallow rate of breathing
  • Mental changes, like confusion

In the worst cases, sepsis can turn into septic shock. This is where a person's blood pressure drops to dangerously low levels, organs begin to fail as a result, and death is a very real possibility.

Other possible complications of bacteremia include:

  • Endocarditis, the inflammation of the inner lining of the heart. By extension, this often implies an infection of the inner lining of the heart as well. This can damage a person's heart valves.
  • Infection of the protective layers of the brain, the meninges
  • Joint infections

Treatment

The most important treatment for bacteremia itself is the use of antibiotics. Antibiotics are drugs that either kill bacteria or inhibit their growth. This might include antibiotics called amoxicillin, ampicillin, gentamicin, or vancomycin among many others. The choice depends on the doctor's assessment of the patient's state as well as any test results that may reveal whether one antibiotic will be more effective than another.

The source of bacteria, if identified, must also be removed. For example, this could be something like a catheter placed into a person's vein in order to deliver medications and/or fluids.

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Frequently Asked Questions

Can bacteremia be cured?

In most healthy people, bacteremia will get cleared without any serious complications. If the infection has spread very intensely into the bloodstream, the bacteremia is described as septicemia. It has to be treated to avoid serious complications.

What is the treatment for bacteremia?

Bacteremia is treated with antibiotics taken for a 1 to 2 weeks period. Severe cases are treated via an intravenous method of antibiotic administration. Ampicillin, penicillin, and a few choices of antibiotics are used here.

What is the difference between sepsis and bacteremia?

Bacteremia refers to the presence of bacteria in the bloodstream. It is just a microbiological finding. Sepsis is a medical condition that has to be further investigated to find out the focus of infection and its localization.

What is the most common cause of bacteremia?

The most common causes of bacteremia infection are an incision that is infected, an infected tooth, any medical surgery, or a urinary tract infection. A small localized infection can also be the cause of bacteremia.

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