Bacteremia
Encyclopedia
Bacteremia is the presence of bacteria
in the blood
. The blood is normally a sterile
environment, so the detection of bacteria in the blood (most commonly with blood culture
s) is always abnormal.
Bacteria can enter the bloodstream as a severe complication of infection
s (like pneumonia
or meningitis
), during surgery (especially when involving mucous membranes such as the gastrointestinal tract
), or due to catheters and other foreign bodies entering the arteries or veins (including intravenous drug abuse
).
Bacteremia can have several consequences. The immune response to the bacteria can cause sepsis
and septic shock
, which has a relatively high mortality rate
. Bacteria can also use the blood to spread to other parts of the body (which is called hematogenous spread), causing infections away from the original site of infection. Examples include endocarditis
or osteomyelitis
. Treatment is with antibiotics, and prevention with antibiotic prophylaxis can be given in situations where problems are to be expected.
Bacteremia is different from sepsis
(so-called blood poisoning or toxemia), which is a condition where bacteremia is associated with an inflammatory
response from the body (causing systemic inflammatory response syndrome
, characterised by rapid breathing
, low blood pressure
, fever
, etc.). Common dental procedures, such as brushing teeth
, are the most common cause of bacteremia, introducing a detectable amount of bacteria into the bloodstream, even if these rarely cause any clinical condition. Some patients with prosthetic heart valves however need antibiotic
prophylaxis for dental surgery because bacteremia might lead to endocarditis
(infection
causing inflammation of the interior lining of the heart
).
Septicemia is an ill-defined non-scientific term introducing more confusion between sepsis and bacteremia: it suggests there is something in the bloodstream causing sepsis.
s are a frequent cause of bacteremia and subsequent nosocomial infections, because they provide a means by which bacteria normally found on the skin can enter the bloodstream. Other causes of bacteremia include dental procedures (occasionally including simple tooth brushing), herpes (including herpetic whitlow
), urinary tract infection
s, peritonitis
, Clostridium difficile colitis, intravenous drug use, and colorectal cancer
. Bacteremia may also be seen in oropharyngeal, gastrointestinal or genitourinary surgery
or exploration. Salmonella
infection, despite mainly only resulting in gastroenteritis in the developed world, is a common cause of bacteremia in Africa. It principally affects children who lack antibodies to Salmonella and HIV+ patients of all ages.
, chills, or hypotension
) is referred to as sepsis
. In the setting of more severe disturbances of temperature, respiration, heart rate or white blood cell
count, the response is characterized as septic shock
, and may result in multiple organ dysfunction syndrome
.
Bacteremia is the principal means by which local infection
s are spread to distant organs (referred to as hematogenous spread). Bacteremia is typically transient rather than continuous, due to a vigorous immune system
response when bacteria are detected in the blood. Hematogenous dissemination of bacteria is part of the pathophysiology of meningitis
and endocarditis
, and of Pott's disease
and many other forms of osteomyelitis
.
, in which a sample of blood is allowed to incubate with a medium that promotes bacterial growth. Since blood is normally sterile, this process does not normally lead to the isolation of bacteria. If, however, bacteria are present in the bloodstream at the time the sample is obtained, the bacteria will multiply and can thereby be detected. Any bacteria that incidentally find their way to the culture medium will also multiply. For this reason, blood cultures must be drawn with great attention to sterile process. Occasionally, blood cultures will reveal the presence of bacteria that represent contamination from the skin
through which the culture was obtained. Blood cultures must be repeated at intervals to determine if persistent — rather than transient — bacteremia is present.
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
in the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
. The blood is normally a sterile
Asepsis
Asepsis is the state of being free from disease-causing contaminants or, preventing contact with microorganisms. The term asepsis often refers to those practices used to promote or induce asepsis in an operative field in surgery or medicine to prevent infection...
environment, so the detection of bacteria in the blood (most commonly with blood culture
Blood culture
Blood culture is a microbiological culture of blood. It is employed to detect infections that are spreading through the bloodstream...
s) is always abnormal.
Bacteria can enter the bloodstream as a severe complication of infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
s (like pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
or meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
), during surgery (especially when involving mucous membranes such as the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
), or due to catheters and other foreign bodies entering the arteries or veins (including intravenous drug abuse
Drug abuse
Substance abuse, also known as drug abuse, refers to a maladaptive pattern of use of a substance that is not considered dependent. The term "drug abuse" does not exclude dependency, but is otherwise used in a similar manner in nonmedical contexts...
).
Bacteremia can have several consequences. The immune response to the bacteria can cause sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
and septic shock
Septic shock
Septic shock is a medical emergency caused by decreased tissue perfusion and oxygen delivery as a result of severe infection and sepsis, though the microbe may be systemic or localized to a particular site. It can cause multiple organ dysfunction syndrome and death...
, which has a relatively high mortality rate
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...
. Bacteria can also use the blood to spread to other parts of the body (which is called hematogenous spread), causing infections away from the original site of infection. Examples include endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
or osteomyelitis
Osteomyelitis
Osteomyelitis simply means an infection of the bone or bone marrow...
. Treatment is with antibiotics, and prevention with antibiotic prophylaxis can be given in situations where problems are to be expected.
Definition
Bacteremia is the presence of viable bacteria in the blood stream.Bacteremia is different from sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
(so-called blood poisoning or toxemia), which is a condition where bacteremia is associated with an inflammatory
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
response from the body (causing systemic inflammatory response syndrome
Systemic inflammatory response syndrome
Systemic inflammatory response syndrome is an inflammatory state affecting the whole body, frequently a response of the immune system to infection, but not necessarily so...
, characterised by rapid breathing
Tachypnea
Tachypnea means rapid breathing. Any rate between 12-20 breaths per minute is normal. Tachypnea is a respiration rate greater than 20 breaths per minute. - Distinction from other breathing terms :...
, low blood pressure
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
, fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, etc.). Common dental procedures, such as brushing teeth
Toothbrush
The toothbrush is an oral hygiene instrument used to clean the teeth and gums that consists of a head of tightly clustered bristles mounted on a handle, which facilitates the cleansing of hard-to-reach areas of the mouth. Toothpaste, which often contains fluoride, is commonly used in conjunction...
, are the most common cause of bacteremia, introducing a detectable amount of bacteria into the bloodstream, even if these rarely cause any clinical condition. Some patients with prosthetic heart valves however need antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
prophylaxis for dental surgery because bacteremia might lead to endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
(infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
causing inflammation of the interior lining of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
).
Septicemia is an ill-defined non-scientific term introducing more confusion between sepsis and bacteremia: it suggests there is something in the bloodstream causing sepsis.
Causes
In the hospital, indwelling catheterCatheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...
s are a frequent cause of bacteremia and subsequent nosocomial infections, because they provide a means by which bacteria normally found on the skin can enter the bloodstream. Other causes of bacteremia include dental procedures (occasionally including simple tooth brushing), herpes (including herpetic whitlow
Herpetic whitlow
A herpetic whitlow is a lesion on a finger or thumb caused by the herpes simplex virus. It is a painful infection that typically affects the fingers or thumbs. Occasionally infection occurs on the toes or on the nail cuticle. Herpes whitlow can be caused by infection by HSV-1 or HSV-2...
), urinary tract infection
Urinary tract infection
A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...
s, peritonitis
Peritonitis
Peritonitis is an inflammation of the peritoneum, the serous membrane that lines part of the abdominal cavity and viscera. Peritonitis may be localised or generalised, and may result from infection or from a non-infectious process.-Abdominal pain and tenderness:The main manifestations of...
, Clostridium difficile colitis, intravenous drug use, and colorectal cancer
Colorectal cancer
Colorectal cancer, commonly known as bowel cancer, is a cancer caused by uncontrolled cell growth , in the colon, rectum, or vermiform appendix. Colorectal cancer is clinically distinct from anal cancer, which affects the anus....
. Bacteremia may also be seen in oropharyngeal, gastrointestinal or genitourinary surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
or exploration. Salmonella
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...
infection, despite mainly only resulting in gastroenteritis in the developed world, is a common cause of bacteremia in Africa. It principally affects children who lack antibodies to Salmonella and HIV+ patients of all ages.
Consequences
Bacteremia, as noted above, frequently elicits a vigorous immune system response. The constellation of findings related to this response (such as feverFever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, chills, or hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
) is referred to as sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
. In the setting of more severe disturbances of temperature, respiration, heart rate or white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
count, the response is characterized as septic shock
Septic shock
Septic shock is a medical emergency caused by decreased tissue perfusion and oxygen delivery as a result of severe infection and sepsis, though the microbe may be systemic or localized to a particular site. It can cause multiple organ dysfunction syndrome and death...
, and may result in multiple organ dysfunction syndrome
Multiple organ dysfunction syndrome
Multiple organ dysfunction syndrome ', previously known as multiple organ failure or multisystem organ failure , is altered organ function in an acutely ill patient requiring medical intervention to achieve homeostasis...
.
Bacteremia is the principal means by which local infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
s are spread to distant organs (referred to as hematogenous spread). Bacteremia is typically transient rather than continuous, due to a vigorous immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
response when bacteria are detected in the blood. Hematogenous dissemination of bacteria is part of the pathophysiology of meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
and endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
, and of Pott's disease
Pott's disease
Pott's disease is a presentation of extrapulmonary tuberculosis that affects the spine, a kind of tuberculous arthritis of the intervertebral joints...
and many other forms of osteomyelitis
Osteomyelitis
Osteomyelitis simply means an infection of the bone or bone marrow...
.
Diagnosis
Bacteremia is most commonly diagnosed by blood cultureBlood culture
Blood culture is a microbiological culture of blood. It is employed to detect infections that are spreading through the bloodstream...
, in which a sample of blood is allowed to incubate with a medium that promotes bacterial growth. Since blood is normally sterile, this process does not normally lead to the isolation of bacteria. If, however, bacteria are present in the bloodstream at the time the sample is obtained, the bacteria will multiply and can thereby be detected. Any bacteria that incidentally find their way to the culture medium will also multiply. For this reason, blood cultures must be drawn with great attention to sterile process. Occasionally, blood cultures will reveal the presence of bacteria that represent contamination from the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
through which the culture was obtained. Blood cultures must be repeated at intervals to determine if persistent — rather than transient — bacteremia is present.
See also
- Antibiotic prophylaxis
- Dental antibiotic prophylaxisDental antibiotic prophylaxisDental antibiotic prophylaxis is the admission of antibiotics to a dental patient for prevention of harmful consequences of bacteremia, that may be caused by invasion of the oral flora into an injured gingival or peri-apical vessel during dental treatment...
- FungemiaFungemia-Pathogens:The most commonly known pathogen is Candida albicans, causing roughly 70% of fungemias, followed by Candida glabrata with 10%, Aspergillus with 1% and Saccharomyces as the fourth most common. However, the frequency of infection by C. glabrata, Saccharomyces boulardii, Candida tropicalis,...
- SepsisSepsisSepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
- ViremiaViremiaViremia is a medical condition where viruses enter the bloodstream and hence have access to the rest of the body. It is similar to bacteremia, a condition where bacteria enter the bloodstream.- Primary versus Secondary :...