Help someone with useful health advice.

Blood Infection Causes

Blood Infection Causes

The term 'sepsis' refers to a medical condition which is caused by the response of the immune system to an infection wherein the pathogenic organisms invade the bloodstream. If left untreated, a blood infection could cause a systemic inflammatory response. The following write-up provides information on the contributing factors for this condition.
Bidisha Mukherjee
Last Updated: Apr 12, 2018
Though the human body employs various mechanisms to fight off the pathogens that come in contact with it, these disease-causing agents can enter the body and multiply in case of people with a compromised immune system. Bacteria, viruses, fungi, parasites, etc., are some of the common types of pathogens that cause infections. The portal of entry, which refers to the route through which pathogens enter the host includes the skin, mucous membranes, respiratory tract, digestive tract, or the urinary tract. Pathogens can enter the skin through open wounds, blisters, cuts, or surgical incisions. Disease-causing agents can enter the respiratory tract via inhaled air, digestive tract via ingestion of contaminated food or water, or the urinary tract through the urethra.

Pathogens can even enter the bloodstream and spread to other parts of the body. This could lead to a systemic blood infection, which in turn may cause life-threatening complications. Under such circumstances, the immune system may respond to the blood infection by triggering inflammation in the whole body, thereby causing septic shock. Septic shock is a life-threatening event that is characterized by low blood pressure and reduced supply of oxygen to the tissues. In the absence of treatment, it could lead to multiple organ dysfunction or failure. It is considered to be a medical emergency, and requires prompt medical treatment.

Contributing Factors

The term 'bacteremia' refers to the presence of bacteria in blood. Though sepsis is often associated with bacteremia, viruses, fungi, or parasites could also be responsible for causing a blood infection. A localized infection of the lungs, abdomen, pelvis, or the urinary tract could lead to sepsis in the absence of medical treatment, especially in the case of immunocompromised individuals. Here are some of the conditions that could make a person susceptible to sepsis:

Urinary Tract Infections
The urinary tract consists of the kidneys, ureters, bladder, and the urethra. The kidneys filter out the wastes from the blood, and produce urine, which flows through the ureters to the bladder. Normally, urine is sterile, and doesn't contain pathogens. However, bacteria or pathogens can grow if the flow of urine is obstructed. People who use a urinary catheter, which a tube that is inserted into the bladder through the urethra for the drainage of urine, are also susceptible to infections. Infection could also spread to the ureters or kidneys. In some cases, a urinary tract infection could lead to an infection in the bloodstream.

Pneumonia is a lung infection that could be caused by bacteria, viruses, or fungi. It could be community-acquired or hospital-acquired. Disease-causing agents that are present in the environment could enter our body through the air that we inhale. Viruses that cause common cold and flu could spread to others through person-to-person contact. Pathogens can become airborne when the infected person coughs or sneezes. Inhalation of the respiratory secretions of an infected person can put others at a risk of getting flu, which could worsen into pneumonia. At times, infections could also be hospital-acquired. Patients could come in contact with pathogens during the course of receiving treatment in hospitals. The use of unsterilized equipment, or non-compliance with the hygiene practices, or negligence on the part of hospital staff while dealing with patients could increase the risk of infections. If left untreated, pneumonia could lead to a blood infection.

Skin Infections
Pathogens can enter the body through skin or mucous membranes. Certain species of bacteria are normally found on the skin and the mucous membranes. These could enter the body through cuts or open wounds. Trauma to the skin could also occur during surgical procedures. Bacteria can enter through open cuts, wounds, or incisions. Infections could also occur at the site of intradermal, intramuscular or subcutaneous injections. The term 'cellulitis' refers to a bacterial skin infection that is characterized by inflammation of the dermal and subcutaneous layers of the skin, as well as the connective tissue. If left untreated, the toxins that are released by the bacteria can diffuse into bloodstream, and move through blood to other parts of the body to cause a systemic infection.

Abdominal Infections
Pathogens could also cause inflammation of peritoneum, which is the membrane that lines the abdominal cavity, and the organs present in the abdomen. Infections that affect any of the abdominal organs can spread to the abdominal cavity or the bloodstream in the event of rupturing of that organ. The risk of infection is high in case of penetrating abdominal trauma. Traumatic injuries could put a person at a risk of developing intra-abdominal abscess or necrotizing soft tissue infection. Necrotizing soft tissue infection, which is medically referred to as necrotizing fasciitis, is a bacterial infection wherein bacterial overgrowth leads to tissue death. The infection could even spread to the bloodstream in the absence of proper treatment. Infections could also occur as a complication of surgery. Bacteria can enter the body through the site of incision.

Besides the aforementioned causes, sepsis could also be associated with meningitis (inflammation of the membranes that cover the brain and the spinal cord). The risk of infection in newborns is associated with complications associated with pregnancy. Infants are susceptible to infections as their immune system is undeveloped. Infection can spread from the mother to the newborn. Premature babies are at a greater risk of developing infections.

Risk Factors

People who are at a risk of developing a blood infection include:

Immunocompromised individuals
Those who have been taking immunosuppressants or steroids for a long time
People who are undergoing chemotherapy
Those who have undergone an invasive surgery
People with pre-existing infections or serious conditions such as cirrhosis, cancer, or AIDS
People affected by a chronic illness
People in hospitals or nursing homes

Immune system may be weak in case of very old people or newborns. This puts them at a risk as well. The chances of an infection are higher in old people who are diabetic.


Some of the commonly observed symptoms of sepsis include:
High fever or low body temperature
Rapid heartbeat
Low blood pressure
Skin rash
Decreased urine output

Diagnosis and Treatment

Blood infection can be diagnosed with the help of a physical examination and the analysis of the medical history of the patient. Other diagnostic tests that may be conducted include Complete Blood Count, blood culture, urine culture, X-ray examination, CT scan, etc. Various tests may be done to determine if the vital organs are working properly. Severe sepsis or septic shock are considered to be medical emergencies and must be treated at the earliest.

Patients who have been diagnosed with a blood infection are treated in an intensive care unit (ICU), where doctors monitor their condition constantly.
They are put on a mechanical ventilator to prevent respiratory organ failure.
The treatment involves intravenous administration of antibiotics to destroy bacteria and prevent them from multiplying.
Fluids are also administered intravenously in order to increase the blood pressure.
Dialysis may be required in case the kidneys fail to carry out their function.
Once the causative bacteria is identified with the help of blood culture, suitable antibiotics are given to the patient that can destroy the causative bacteria successfully.

The prognosis of sepsis is unfavorable in the absence of prompt medical treatment, and in case of people with a serious, pre-existing medical condition. However, the chances of full recovery are high in case of uncomplicated sepsis, wherein the functioning of organs has not been affected. Timely treatment increases the chances of recovery, which is why medical help must be sought at the earliest.

Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.