Everything You Want to Know About Bacteremia

What Is Bacteremia?

Bacteraemia is the most common cause of death in critically ill patients [1]. A high mortality rate occurs due to its high morbidity and mortality rate. The overall survival time after diagnosis with bacterial meningitis is less than 10 days. However, it may take longer if the patient has other underlying medical conditions or complications such as sepsis or shock [2]. The mortality rate is higher among those with severe disease and poor prognosis.

The main symptoms are fever, headache, muscle aches, nausea and vomiting. Other signs include rash, arthralgia (joint pain), myalgia (muscle weakness) and neurologic deficits [3]. Bacterial meningitis causes a wide range of clinical manifestations including seizures, coma or even death depending on the severity of infection [4].

The bacteria causing bacterial pneumonia are Gram-negative bacilli. They are commonly found in the nasopharynx, tonsils, throat and lungs. These organisms have been associated with infections of the brain, spinal cord and heart [5]. The organism responsible for bacterial meningitis is Streptococcus pneumoniae. It usually causes mild illness but when it reaches the blood stream it becomes life threatening [6].

Bacterial meningitis has a mortality rate of 10-15 percent. The mortality rate from the pneumococcal type is higher than the Haemophilus influenzae and Neisseria meningitides type. The bacteria usually enter the blood stream through a break in the skin or an underlying medical condition such as cancer, alcoholism or asplenia. Other conditions that can increase the risk of getting blood stream infection are liver disease, sickle cell anemia and human immunodeficiency virus (HIV) infection. Pneumococcal meningitis is more common in people over 65 years with underlying medical conditions.

What Are the Risk Factors for Bacteremia?

The risk factors for bacteremia are listed below.

The rate of bacteremia is higher in the following individuals:

Neonates (infants younger than one month) with invasive procedures such as intubation or surgery, patients with burns on more than 10 percent of their total body surface, and patients who have multiple medical devices such as intravenous lines and catheters.

Frequent hospital visitors, particularly those who have a family member in an intensive care unit (ICU).

Patients with indwelling medical devices such as arterial lines, central venous lines or urinary catheters.

Burn patients whose wounds involve deeper tissues, bone or have large surface areas.

Patients undergoing invasive procedures such as endoscopies or surgery.

Surgery patients.

A patient with a history of indwelling medical devices such as central venous catheters, arterial lines, or urinary catheters.

A patient with a recent hospitalization.

Bacteremia can also occur in the following situations:

The patient with an invasive procedure such as intravenous catheter placement, endoscopy or surgery on an infected site.

A patient who has been intubated and is receiving mechanical ventilation.

A patient who has a urinary catheter and develops a fever.

An immunosuppressed patient such as a human immunodeficiency virus (HIV) patient.

Any patient with an infected site such as ears, chest or urinary tract infection who develops a fever.

A neonate who develops a fever.

A patient with medical conditions such as cancer, cirrhosis, sickle cell anemia or immunosuppression.

A patient who recently underwent surgery and has an abnormal wound.

A patient who has a chromosomal defect such as Down syndrome or a congenital infection.

What Conditions Can Bacteremia Occur With?

Bacteremia can occur alone or it can be associated with other medical conditions such as endocarditis, osteomyelitis, meningitis, and pneumonia.

What Is Endocarditis?

Endocarditis is an infection of the endocardium, the lining of the heart chambers. It can be caused by bacteria such as Staphylococcus aureus, Streptococcus species or Haemophilus influenza type B. It can also be caused by fungal organisms such as Candida albicans or Aspergillus fumigatus.

What Is Osteomyelitis?

Osteomyelitis is an infection of the bone and the bone marrow and can be caused by bacteria, such as Staphylococcus aureus, Streptococcus species, Haemophilus influenza type B or Pseudomonas aeruginosa or by a fungus such as Aspergillus fumigates or Candida albicans.

What Is Pneumonia?

Pneumonia is an infection or inflammation of the lungs parenchyma (the tissues of the organ). It can be caused by a virus, such as respiratory syncytial virus, or a bacterium such as Streptococcus pneumoniae.

What Is Meningitis?

Meningitis is an infection of the meninges, (the membranes that surround the brain and the spinal cord). It can be caused by bacteria such as Neisseria meningitidis or Haemophilus influenza type B, a virus such as the herpes simplex virus or a fungus such as Cryptococcus.

What Conditions are Associated With Bacteremia?

Bacteremia can be found in conjunction with the following conditions:





Wound infections.

Bloodstream infection (bacteremia).

Unusual organisms causing bacteremia such as aerobic Gram-negative bacilli, fungi or other unusual causes.

Chromosomal abnormalities such as Down syndrome or a congenital infection.

What Are the Symptoms of Bacteremia?

The patient may have symptoms such as fever, chills, or sick feeling.

How Is Bacteremia Diagnosed?

Bacteremia can be diagnosed by reviewing a patient’s medical history, performing a physical exam and finding evidence of infection through various laboratory tests. The medical history can reveal conditions such as indwelling medical devices or recent surgeries or infections. The physical exam can reveal findings such as a rapid heart rate, an abnormally fast breathing rate, or an elevated body temperature. Laboratory tests can reveal the presence of microorganisms in the blood such as bacteria. In addition, a blood culture can be performed in order to identify the causative organism(s).

How Is Bacteremia Treated?


Antibiotic treatment is essential to treating bacteremia. Antibiotics can be given either intravenously or orally depending on the severity of the infection.

Bacteremia is the presence of live bacteria in the blood, it can be found in conjunction with many other medical conditions such as endocarditis (infection of the heart valves), osteomyelitis (infection of the bone), meningitis (infection of the membranes that surround the brain and spinal cord), pneumonia (lung infection) and wound infections.

The most common causative organism is the common bacteria, “Streptococcus pneumoniae”. Other bacteria, viruses and even fungi can also cause bacteremia.

Bacteremia occurs when bacteria that are normally only found in the blood are able to multiply and grow uncontrollably. This condition can be life-threatening because it can lead to sepsis, a whole-body inflammatory response caused by severe bacterial infection.

If the immune system is functioning properly, pathogens such as the bacteria that causes bacteremia are unable to grow in the blood and therefore cannot cause bacteremia. The immune system includes white blood cells that are able to recognize harmful foreign invaders such as bacteria and attack them. These white blood cells are able to engulf and destroy bacteria through a process known as phagocytosis. If the bacteria are able to grow and survive in the blood, the white blood cells will be able to limit their growth through a process known as inhibition. If neither of these processes is successful and the immune system is weakened in some way, bacteremia may develop.

The following conditions: endocarditis, osteomyelitis, meningitis, pneumonia and wound infections can all cause bacteremia. If an infection from these conditions spreads throughout the blood, it is known as sepsis. These two conditions are very serious and, if left untreated, can cause organ failure and death.

Endocarditis is an infection of the heart valves and lining of the heart. If bacteria enter the bloodstream and reach the heart, they can become trapped on damaged heart valves where they will multiply, forming a vegetation. This vegetation can destroy the heart valves and cause endocarditis.

Osteomyelitis is a condition in which bacteria invade the bone and begin to multiply. The bone begins to dissolve and become infected. Osteomyelitis most commonly occurs as a result of an injury or surgery in the affected area, but any type of injury can cause the skin or soft tissue to be exposed to bacteria that are able to enter the blood stream and travel to the bone. Once in the bone, bacteria begin to multiply and destroy the bone tissue.

Meningitis is an infection or inflammation of the membranes that cover the brain and spinal cord. It is most common in infants and young children and is usually caused by viral infections such as herpes, influenza, HIV or hepatitis. Bacterial meningitis is less common than viral meningitis but is much more serious. Bacteria that cause meningitis are often able to travel through the bloodstream and into the brain and spinal cord, where they begin to multiply.

Most cases of meningitis are caused by a specific type of bacteria, known as Haemophilus influenzae. Other types of bacteria that may cause meningitis include Streptococcus pneumoniae and Neisseria meningitidis.

Pneumonia is an infection or inflammation of the lungs. Pneumonia is usually caused by bacteria or viruses and often begins in the upper respiratory tract. The symptoms may be similar to the common cold and may include fever, shivering, headache and a sore throat. In more serious infections the patient may begin to experience difficulty breathing and may cough up blood.

Wound infections are most commonly caused by bacteria that enter an open wound. The most common bacteria responsible for wound infections are “Staphylococcus aureus” and “Streptococcus pyogenes”.

Bacteremia is the presence of bacteria in the blood.

The condition is most commonly caused by a bacterial infection in another part of the body such as an abscess or sore throat. It can also be caused by invasive procedures, such as injections, intubation and catheter insertion.

If bacteremia occurs in the heart valves it is known as endocarditis. If it occurs in bone it is known as osteomyelitis. If it occurs in the brain or spinal cord it is known as meningitis.

Bacteremia can also be divided into two groups: transient and persistent.

Transient bacteremia is the presence of bacteria in the blood stream which are unable to be cultured from the blood after 48 hours of sampling. Most cases of transient bacteremia resolve on their own with no treatment.

Persistent bacteremia is the presence of bacteria in the blood which can be cultured from blood cultures after 48 hours of sampling.

Most cases of endocarditis are caused by a specific type of streptococcal bacteria, known as Group A beta-hemolytic Streptococcus (GABHS).

S. pneumoniae is a type of bacteria that can cause meningitis and other infections. Pneumococcal meningitis is most often seen in infants and in adults over the age of 65. It is also more common in people with a compromised immune system such as those with HIV or those who have had an organ transplant.

The symptoms of pneumococcal meningitis are very similar to those of viral meningitis, making the condition difficult to diagnose. The most common symptom of pneumococcal meningitis is a severe headache that begins suddenly. The headache may be accompanied by sensitivity to light, nausea and vomiting, lack of appetite and fever.

Endocarditis is an infection of the inner lining of the heart, also known as the endothelium. Endocarditis can also involve the tissue that lines the heart chambers (myocardium) or the heart valves. Endocarditis is most commonly caused by bacteria.

Infection of the endothelium most commonly occurs in people with damaged or abnormal heart valves. This is known as acquired endocarditis. Infection can also rarely occur in people with normal heart valves, this is known as primary or native valve endocarditis. This type of endocarditis occurs most commonly in the following groups:

Endocarditis can be classified into four different types.

These types are defined based upon the site of the infection.

Blood cultures are the most accurate way to confirm bacteremia. A positive blood culture indicates the presence of viable bacteria in the blood. However, a negative result does not rule out bacteremia, as it is possible that not all bacteria have grown on the culture medium.

The term “septicemia” has fallen out of use, as it is not specific to bacterial infection. “Bacteremia” is used to describe the presence of bacteria in the blood.

Bacteremia often leads to endocarditis, a potentially life-threatening complication.

Treatment with antibiotics for bacteremia is typically begun empirically based on risk factors and signs and symptoms. The patient’s medical history will also be taken, as underlying diseases such as cancer or diabetes increase the risk of bacteremia. The patient’s immunization history is also taken into account, as those who have not been immunized for pneumococcus are given immunoglobulin and the vaccine if necessary.

The antibiotics chosen for treatment are based upon the most likely pathogen in the blood. This is often S aureus or streptococcus species, but other strains of bacteria may also be present. The patient’s overall health and medical history is also taken into account when choosing the most effective treatment.

Antibiotics can be delivered intravenously (directly into the blood stream) or by injection into muscle.

The antibiotics most commonly used to treat bacteremia are:

Amoxicillin-Clavulanic acid and Tetracycline are typically given for 10 days, while the rest are given for up to one week.

While on antibiotics, those with bacteremia should be monitored for side effects and symptoms of an allergic reaction to the medication.

An echocardiogram is typically used to diagnose endocarditis. This test uses sound waves to create a moving picture of the heart. It can identify damaged valves and detect any excess buildup of fluid around the heart.

The blood is tested for the presence of bacteria by taking a sample of blood from the vein. This can be done by an invasive procedure or by pricking the skin with a needle and collecting a sample of blood from under the surface. The blood is then cultured to determine which bacteria are present. A transthoracic echocardiogram (TTE) can be used to view the valves of the heart and rule out endocarditis. In some cases, transesophageal echocardiogram (TEE) is used to obtain a more accurate evaluation of the valves.

During a TEE, the probe is passed down the throat and into the esophagus to view the heart valves directly. An endocarditis is identified by damaged valves, rough edges of the heart valves or other signs of damage to the valves.

Invasive: A small sample of blood is taken from the vein.

The blood is tested for the presence of bacteria.

The patient is given an antibiotic based on the results and their medical history.

The patient may be given an injection of immunoglobulin or immunization if they haven’t had one before.

The patient may be given a vaccine if they are not up to date with immunizations.

The patient is given the appropriate antibiotic based on test results.

The patient is monitored for side effects and allergic reactions to antibiotics, as well as signs of endocarditis.


The patient’s bacteremia resolves with treatment.

The patient’s condition worsens despite antibiotic treatment, and surgical intervention for valve repair or replacement is required.

Rates of mortality and complications are high.

The overall rate of endocarditis in patients with bacteremia is 15%.

30-50% of cases of endocarditis are caused by “staphylococci”.

The overall case fatality rate for bacteremia resulting in endocarditis is between 15 and 30%.

The case fatality rate for streptococcal endocarditis can be as high as 75%.

The case fatality rate for infective endocarditis is between 20 and 40% even with treatment.

Endocarditis is an uncommon complication of bacteremia, but it can be a serious one.

The Duke Endocarditis Database found the five-year survival rate in people with endocarditis caused by streptococcal infection was only 46%.

Endocarditis requires aggressive treatment with antibiotics given through an IV for at least four to six weeks and, in many cases, surgery as well.

Two percent of all bacteremia patients develop endocarditis.

If left untreated streptococcal endocarditis has a case fatality rate of 75%.

Mortality rates are higher for people over 40 and in those with serious underlying medical conditions such as cancer.

The highest mortality rates are in people with:

Involvement of more than one valve raises the risk of death to 60-70%, even with treatment.

The most common bacteria causing bacteremia are “Staphylococcus aureus”, “Streptococcus pneumoniae”, and “Streptococcus viridans”.

Bacteremia caused by “viridans streptococci” is usually acquired in the dental workplace and is associated with dental procedures. It is the most common cause of dental-related bacteremia.

Bacteremia caused by “Streptococcus milleri” usually affects people with artificial heart valves. It has been also linked to endocarditis in people living with diabetes and cirrhosis of the liver.

Other organisms that can cause bacteremia are:

Other risk factors for bacteremia include liver disease, heart disease, cancer, and the use of immunosuppressive medication.

Immunocompromised people such as people with HIV or those on immunosuppressive drugs following an organ transplant are also at risk of bacteremia.

People with catheters or other types of indwelling medical devices are also at greater risk.

Dental procedures are a common cause of bacteremia due to infection of the blood by “viridans streptococci”.

Antibiotics can be given systemically (by mouth or injection) or topically (directly in the region of the infection). The choice of drug, dosage, route and duration of treatment is determined by many factors such as:

The site and cause of the infection must also be determined.

Endocarditis often requires surgical intervention to remove the infected tissue causing the problem. The type of surgery performed depends on the part of the heart infected. For example, if the heart valves are infected then surgery may involve replacing them with a mechanical or biological valve. If the myocardium is infected then surgery may involve removing the infected tissue and closing off the area surgically.

While people with bacteremia often start to feel better within a week following treatment, they should be monitored for recurrence of the infection. This is especially important if the cause of their bacteremia is still present. A person’s urine and blood may be sampled on a regular basis following treatment to check for the presence of bacteria. Antibiotics may also be prescribed to prevent a relapse of infection.

As with most diseases, the earlier bacteremia is detected and treatment begins, the more successful it will be. People with bacteremia should monitor themselves for signs of relapse.

The word “bacteremia” is derived from the Greek noun βακτήριον (baktérion), meaning “spindle”, and the suffix -emia, denoting “blood flow”. The term was coined in 1884 by the American physician Charles Sedgwick Minot.

Sources & references used in this article:

Biliary bacteremia by SH Chetlin, DW Elliott – Archives of Surgery, 1971 – jamanetwork.com

Staphylococcus aureus Bacteremia: Factors Predicting Hospital Mortality by JM Mylotte, JR Aeschlimann… – Infection Control & Hospital …, 1996 – cambridge.org

Incidence of bacteremia after burn wound manipulation in the early postburn period by DW Mozingo, AT McManus, SH Kim… – Journal of Trauma and …, 1997 – journals.lww.com

Anaerobic bacteremia. by WR Wilson, WJ Martin, CJ Wilkowske… – Mayo Clinic …, 1972 – cabdirect.org

Bacteremia following surgical dental extraction with an emphasis on anaerobic strains by A Rajasuo, K Perkki, S Nyfors… – Journal of dental …, 2004 – journals.sagepub.com

Serum procalcitonin elevation in critically ill patients at the onset of bacteremia caused by either Gram negative or Gram positive bacteria by PE Charles, S Ladoire, S Aho, JP Quenot… – BMC infectious …, 2008 – Springer

Nosocomial bacteremia clinical significance of a single blood culture positive for coagulase-negative staphylococci by B Favre, S Hugonnet, L Correa, H Sax… – Infection Control & …, 2005 – cambridge.org

Pharmacokinetics and pharmacodynamics of meropenem in febrile neutropenic patients with bacteremia by RE Ariano, A Nyhlén, JP Donnelly… – Annals of …, 2005 – journals.sagepub.com