Bacteremia
Bacteremia is the presence of viable bacteria in the blood, confirmed by positive blood cultures, that ranges from transient and clinically silent to the trigger for sepsis and septic shock requiring urgent source identification and antimicrobial therapy.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Bacteremia is the presence of viable bacteria in the bloodstream, documented by a positive blood culture; it ranges from transient and self-limited (for example after dental manipulation) to the driving event of sepsis and septic shock.
- Epidemiology
Sepsis mortality is markedly elevated: a septic patient has a mortality rate four or more times that of the same underlying condition without sepsis, and mortality rises roughly 15% for each additional sepsis-related organ system failure.
- Risk factors
Indwelling central venous catheter (CVC) use, with femoral site, multiple lumens, multiple catheters, and prolonged catheterization each independently increasing risk (femoral site raises risk about 3.4-fold).
- Pathophysiology
Bacterial entry into the bloodstream occurs from a localized focus (pneumonia, urinary tract infection, abscess, skin/soft tissue infection) seeding the blood, or directly through a breached barrier…
- Clinical features
Fever is the most consistent finding, though it may be blunted or absent in elderly, immunosuppressed, or neutropenic patients, so a normal temperature does not exclude bacteremia.
- Differential diagnosis
Contaminant blood culture: coagulase-negative staphylococci or other skin flora in only one of several sets, without clinical correlation, favors contamination over true bacteremia.
- Diagnosis
Bacteremia is confirmed by a positive blood culture, and sepsis is diagnosed operationally when infection is known or suspected and organ dysfunction criteria are met (Sequential Organ Failure…
- Management
First, give broad-spectrum empiric antibiotics within 1 hour of suspected sepsis, covering the most likely gram-negative, gram-positive, and mixed pathogens for the suspected source.
- Complications
Septic shock, 40% or greater in-hospital mortality when vasopressor-requiring hypotension and elevated lactate persist despite fluids.
- Prognosis
An initial SOFA score of 2 or greater, or an increase of 2 or more, predicts hospital mortality greater than 10%, and mortality rises roughly 15% for each additional organ system failure.
- Prevention
CVC insertion bundle: hand hygiene, chlorhexidine skin antisepsis, maximal sterile barrier precautions, and preferred subclavian site (avoid femoral, which raises CLABSI risk about 3.4-fold), placed only by experienced personnel.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Bacterial infective endocarditis
Bacterial infection of the endocardial surface, usually a heart valve, producing vegetations that destroy the valve and embolize; diagnosis rests on the modified Duke criteria (blood cultures plus echocardiography) and treatment is a prolonged organism-directed intravenous antibiotic course, with valve surgery for heart failure, uncontrolled infection, or embolic recurrence.
- Osteomyelitis
Osteomyelitis is bone infection from hematogenous seeding or contiguous spread, most often from Staphylococcus aureus, presenting as subacute pain with or without a draining sinus tract and confirmed by bone biopsy culture. Empiric antibiotics are withheld until biopsy in a stable patient, and treatment combines source control with 4 to 6 weeks of culture-directed antibiotics, extended to 6 weeks or indefinite suppression for hardware-associated or chronic disease.
- Candida infections
Candida species cause a spectrum from mucocutaneous disease (thrush, esophagitis, vulvovaginal candidiasis, intertrigo) to candidemia and invasive candidiasis, the fourth most common cause of bloodstream infection with 30-40% mortality. Diagnosis of invasive disease requires recognizing risk factors because only 40-60% of infected patients have positive blood cultures, and initial therapy is an echinocandin with prompt catheter removal.
- Pseudomonas aeruginosa infection
Pseudomonas aeruginosa is a nosocomial, opportunistic gram-negative bacillus that causes hot-tub folliculitis, malignant otitis externa, ventilator-associated pneumonia, febrile-neutropenia bacteremia with ecthyma gangrenosum, and device-associated infections. Empiric therapy requires an antipseudomonal agent and, in resistance-risk or unstable patients, double coverage until susceptibilities return.
- Escherichia coli infection
Escherichia coli is a gram-negative bacillus that causes most urinary tract infections and catheter-associated bloodstream infections, plus distinct diarrheagenic syndromes including travelers' diarrhea (ETEC) and hemorrhagic colitis with hemolytic uremic syndrome (EHEC/STEC). Diagnosis rests on culture with syndrome-specific colony-count thresholds, and management ranges from short-course oral antibiotics for cystitis to strictly supportive, antibiotic-avoiding care for EHEC.