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For further information, see CMDT Part 33-16: Gram-Negative Bacteremia & Sepsis

Key Features

  • Most common sites for gram-negative bacteremia

    • Genitourinary system

    • Hepatobiliary tract

    • Gastrointestinal tract

    • Lungs

  • Less common sources include

    • Intravenous lines

    • Infusion fluids

    • Surgical wounds

    • Drains

    • Pressure injuries

Clinical Findings

  • Fevers and chills, often with abrupt onset

  • However, some patients are hypothermic (temperature ≤ 36.4 °C) at presentation

  • Hyperventilation with respiratory alkalosis and changes in mental status are important early manifestations

  • Hypotension and shock are unfavorable prognostic signs

Diagnosis

  • Neutropenia or neutrophilia, often with increased numbers of immature forms of polymorphonuclear leukocytes

  • If possible, three sets of blood cultures from separate sites should be obtained in rapid succession before starting antimicrobial therapy

Treatment

  • See Table 30–4

  • Antibiotics should be given as soon as the diagnosis is suspected, since delays in therapy have been associated with increased mortality rates, particularly once hypotension develops

  • In general, bactericidal antibiotics should be used and given intravenously to ensure therapeutic serum levels

  • Penetration of antibiotics into the site of primary infection is critical for successful therapy—ie, if the infection originates in the CNS, antibiotics that penetrate the blood-brain barrier should be used—eg, third- or fourth-generation cephalosporin—but not first-generation cephalosporins or aminoglycosides, which penetrate poorly

  • Initial therapy for sepsis should include antibiotics active against both gram-positive and gram-negative organisms

  • Combination therapy has not been shown to be superior to a single-drug regimen with any of several broad-spectrum antibiotics (eg, a third-generation cephalosporin, piperacillin-tazobactam, carbapenem)

  • If multiple drugs are used initially, the regimen should be modified and coverage narrowed based on the results of culture and sensitivity testing

  • Remove predisposing factors

    • Decrease or stop immunosuppressive medications

    • Give granulocyte colony-stimulating factor (filgrastim; G-CSF) to the neutropenic patient with positive blood cultures

  • Identify source of bacteremia and remove it (central venous catheter) or drain it (abscess)

  • Supportive measures include maintaining blood pressure with vasopressor medications and managing disseminated intravascular coagulation with antimicrobials for underlying infection and blood products for significant bleeding (Table 14–6)

  • Corticosteroids are not helpful

Table 30–4.Medication of choice for suspected or documented microbial pathogens (listed in alphabetical order, within classes).

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