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(See also Infections in Neonates: Neonatal Sepsis; see Infections in Infants and Children: Occult Bacteremia.)
Bacteremia
is the presence of bacteria in the bloodstream. It can occur spontaneously,
from indwelling GU or IV catheters, or after dental, GI, GU, wound
care, or other procedures. Bacteremia may cause metastatic infections,
including endocarditis, especially in those with valvular heart
abnormalities. Transient bacteremia is often asymptomatic but may
cause fever. Development of other symptoms usually suggests more
serious infection, such as sepsis or septic shock (see Sepsis and Septic Shock). Patients with
certain underlying heart conditions should receive prophylactic antibiotics
before procedures that can cause significant bacteremia.
Bacteremia may be transient and cause no sequelae, or it may cause metastatic or systemic consequences.
Etiology
and Pathophysiology
Bacteremia has many possible causes, including dental procedures or even vigorous toothbrushing; catheterization of an infected lower urinary tract; surgical treatment of an abscess or infected wound; and colonization of indwelling devices, especially IV and intracardiac catheters, urethral catheters, and ostomy devices and tubes. Gram-negative bacteremia secondary to infection usually originates in the GU or GI tract, or the skin in patients with decubitus ulcers. Chronically ill and immunocompromised patients have an increased risk of gram-negative bacteremia. They may also develop bacteremia with gram-positive cocci, anaerobes, and fungi. Staphylococcal bacteremia is common in injection drug users. 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. If an infection above the diaphragm causes bacteremia, the organism is most likely gram positive.
Metastatic infection of the meninges or serous cavities, such as the pericardium or larger joints, can result from transient or sustained bacteremia. Metastatic abscesses may occur almost anywhere. Multiple abscess formation is especially common with staphylococcal bacteremia. Bacteremia may cause endocarditis (see Endocarditis), most commonly if the pathogen is an enterococcus, streptococcus, or staphylococcus, and less commonly with gram-negative bacteremia and fungemia. Patients with valvular heart disease, prosthetic heart valves, or other intravascular prostheses are predisposed to endocarditis, which may occur after certain dental procedures. Staphylococci can cause gram-positive bacterial endocarditis, particularly in injection drug users, and may involve the tricuspid valve.
Symptoms,
Signs, and Diagnosis
Development of symptoms such as tachypnea, shaking chills, persistent fever, altered sensorium, hypotension, and GI symptoms (abdominal pain, nausea, vomiting, and diarrhea) suggests sepsis or septic shock. Septic shock develops in 25 to 40% of patients with significant bacteremia.
If bacteremia, sepsis, or septic shock is suspected, cultures are obtained of blood (see Endocarditis: Diagnosis) and any other appropriate specimens as described elsewhere in The Manual.
Prognosis
and Treatment
In patients at risk for endocarditis or who are immunocompromised, prophylactic antibiotics are indicated before procedures likely to cause significant bacteremia (see Table 3: Endocarditis: Procedures Requiring Antimicrobial Endocarditis Prophylaxis , Table 4: Endocarditis: Recommended Endocarditis Prophylaxis During Oral-Dental, Respiratory Tract, or Esophageal Procedures*, and Table 5: Endocarditis: Recommended Endocarditis Prophylaxis During GI or GU Procedures). In patients with suspected bacteremia, empiric antibiotics are given after appropriate cultures are obtained. Continuing therapy involves adjusting antibiotics according to the results of culture and sensitivity testing and usually removing any internal devices that are the suspected source of bacteria.
Last full review/revision November 2005
Content last modified November 2005
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