(See Neonatal Sepsis Neonatal Sepsis Neonatal sepsis is invasive infection, usually bacterial, occurring during the neonatal period. Signs are multiple, nonspecific, and include diminished spontaneous activity, less vigorous sucking... read more ; see Occult Bacteremia and Fever Without Apparent Source in Infants and Young Children Occult Bacteremia and Fever Without Apparent Source in Infants and Young Children Occult bacteremia is the presence of bacteria in the bloodstream of febrile young children who have no apparent foci of infection and look well. Diagnosis is by blood culture and exclusion of... read more .)
Bacteremia may be transient and cause no sequelae, or it may have metastatic or systemic consequences. Systemic consequences include
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Sepsis Sepsis is a clinical syndrome of life-threatening organ dysfunction caused by a dysregulated response to infection. In septic shock, there is critical reduction in tissue perfusion; acute failure... read more (previously referred to as systemic inflammatory response syndrome)
Etiology of Bacteremia
Bacteremia has many possible causes, including
Gram-negative bacteremia secondary to infection usually originates in the genitourinary or gastrointestinal tract or in the skin of patients with decubitus ulcers Pressure Ulcers Pressure ulcers are areas of necrosis and ulceration where soft tissues are compressed between bony prominences and external hard surfaces. They are caused by unrelieved mechanical pressure... read more 
. Chronically ill and immunocompromised patients have an increased risk of gram-negative bacteremia. They may also develop bacteremia with gram-positive cocci and anaerobes, and are at risk of fungemia. Staphylococcal bacteremia is common among injection drug users, patients with IV catheters, and patients with complicated skin and soft tissue infections. Bacteroides bacteremia may develop in patients with infections of the abdomen and the pelvis, particularly the female genital tract. If an infection in the abdomen causes bacteremia, the organism is most likely a gram-negative bacillus Introduction to Gram-Negative Bacilli Gram-negative bacilli are responsible for numerous diseases. Some are commensal organisms present among normal intestinal flora. These commensal organisms plus others from animal or environmental... read more . If an infection above the diaphragm causes bacteremia, the organism is most likely a gram-positive bacillus.
Pathophysiology of Bacteremia
Transient or sustained bacteremia can cause metastatic infection of the meninges or serous cavities, such as the pericardium or larger joints. Metastatic abscesses may occur almost anywhere. Multiple abscess formation is especially common with staphylococcal bacteremia.
Bacteremia may cause endocarditis Infective Endocarditis Infective endocarditis is infection of the endocardium, usually with bacteria (commonly, streptococci or staphylococci) or fungi. It may cause fever, heart murmurs, petechiae, anemia, embolic... read more 
, most commonly with staphylococcal, streptococcal, or enterococcal bacteremia and less commonly with gram-negative bacteremia or fungemia. Patients with structural heart disease (eg, valvular disease, certain congenital anomalies), prosthetic heart valves, or other intravascular prostheses are predisposed to endocarditis. Staphylococci can cause bacterial endocarditis, particularly in injection drug users, and usually involving the tricuspid valve. Staphylococcus is also the most common cause of hematogenously spread vertebral osteomyelitis Osteomyelitis Osteomyelitis is inflammation and destruction of bone caused by bacteria, mycobacteria, or fungi. Common symptoms are localized bone pain and tenderness with constitutional symptoms (in acute... read more 
and diskitis.
Symptoms and Signs of Bacteremia
Some patients are asymptomatic or have only mild fever.
Development of symptoms such as tachypnea, shaking chills, persistent fever, altered sensorium, hypotension, and gastrointestinal symptoms (abdominal pain, nausea, vomiting, diarrhea) suggests sepsis or septic shock. Septic shock develops in 25 to 40% of patients with significant bacteremia. Sustained bacteremia may cause metastatic focal infection or sepsis.
Diagnosis of Bacteremia
If bacteremia, sepsis, or septic shock is suspected, cultures Culture Culture is microbial growth on or in a nutritional solid or liquid medium; increased numbers of organisms simplify identification. Culture also facilitates testing of antimicrobial susceptibility... read more of blood and any other appropriate specimens are obtained.
Treatment of Bacteremia
In patients with suspected bacteremia, empiric antibiotics are given after appropriate cultures are obtained. Early treatment of bacteremia with an appropriate antimicrobial regimen appears to improve survival.
Continuing therapy involves adjusting antibiotics according to the results of culture and susceptibility testing, surgically draining any abscesses, and usually removing any internal devices that are the suspected source of bacteria.
Key Points
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Bacteremia may be transient and of no consequence or lead to metastatic focal infection or sepsis.
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Bacteremia is more common after invasive procedures, particularly those involving indwelling devices or material.
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If bacteremia is suspected, give empiric antibiotics after cultures of potential sources and blood are obtained.
