{
 "topic": "Bacteremia",
 "slug": "bacteremia",
 "category_id": 15485,
 "summary": "Bacteria in the bloodstream in children, from occult bacteremia of infancy to catheter- and vulnerable-host-associated bacteremia, its causative organisms, risk stratification, and outcomes.",
 "written_by": "claude-sonnet",
 "references": [
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 ],
 "short": [
  {
   "title": "In short",
   "content": "- Occult bacteremia is bacteremia occurring without the expected symptoms of toxicity, cardiorespiratory change, or a focal source of infection.\n- Before routine pneumococcal conjugate vaccination, occult pneumococcal bacteremia accounted for 90% or more of positive blood cultures in febrile children under 3 years in the US; about 8% of febrile children with an ANC over 10,000/\u00b5L had pneumococcal bacteremia, rising to about 20% if fever exceeded 41\u00b0C.\n- Of children with pneumococcal bacteremia, most recovered spontaneously, but about 3-5% developed meningitis and another 5% developed another focal infection (most commonly pneumonia).\n- Bacteremia occurs in 3-5% of children with fever without a source in the at-risk age group, especially with fever over 39\u00b0C; Streptococcus pneumoniae, Staphylococcus, and Haemophilus influenzae predominate in children under 2, while typhoid/paratyphoid fever is a more common bacterial cause in older children in endemic settings.\n- Children at highest risk of bacteremia are under 2 years old; meningococcal bacteremia has a biphasic age pattern with peaks in infancy and again in adolescence.\n- Special high-risk hosts include asplenic children, those with central venous catheters, neutropenic children, and those with short gut; coagulase-negative staphylococci are a classic cause of catheter-, vascular-graft-, prosthetic-valve-, and pacemaker-wire-associated bacteremia.\n- Warning signs suggesting serious bacterial illness include lethargy, irritability or altered mental status, tachycardia out of proportion to fever, tachypnea or labored breathing, a bulging or depressed fontanel, nuchal rigidity, petechiae, localized erythema/tenderness/swelling, and abdominal or flank tenderness.\n- Bacteremia is usually accompanied by fever in older children but is often not associated with fever in infants; in newborns it can present as apnea, bradycardia, respiratory dysfunction, fever or hypothermia, and abdominal distention.\n- Bacteremia without a focal source can be self-limited or life-threatening, particularly in newborns or children with underlying disease; mortality reaches up to 25% in some series, though it is hard to separate from the contribution of underlying illness.\n- Knowledge of locally prevalent organisms and antibiotic resistance patterns is essential to guiding empiric treatment for suspected pediatric bacteremia."
  }
 ],
 "long": [
  {
   "title": "Definition",
   "content": "Bacteremia is the presence of bacteria in the bloodstream. Occult bacteremia refers specifically to bacteremia occurring without the expected symptoms of toxicity, cardiorespiratory changes, or evidence of a focal source of infection."
  },
  {
   "title": "Epidemiology",
   "content": "Bacteremia occurs in about 3-5% of children with fever without a source in the at-risk age group, particularly when fever exceeds 39\u00b0C. Before routine pneumococcal conjugate vaccination, occult pneumococcal bacteremia was a relatively common cause of fever in young children, accounting for 90% or more of positive blood cultures in children under 3 years old in the US; roughly 8% of febrile children with an absolute neutrophil count (ANC) over 10,000/\u00b5L had a positive blood culture for Streptococcus pneumoniae, rising to about 20% when the ANC was elevated and fever exceeded 41\u00b0C. Children at highest risk of bacteremia are under 2 years of age. Meningococcal bacteremia shows a biphasic age distribution, with one peak in infancy and a second in adolescence."
  },
  {
   "title": "Etiology",
   "content": "In children younger than 2 years, Streptococcus pneumoniae, Staphylococcus species, and Haemophilus influenzae are the more common causes of bacteremia; in older children in some regions, typhoid and paratyphoid fever account for the majority of bacterial causes, with parasitic infestations like malaria also contributing substantially to fever in certain areas and seasons. Nontyphoidal Salmonella bacteremia is usually accompanied by fever in older children but is often not associated with fever in infants; vulnerable hosts, including children with HIV, are far more susceptible to systemic nontyphoidal Salmonella infection, sometimes recurrent despite antibiotic therapy, and certain strains (S. dublin, S. choleraesuis) are more likely to cause bacteremia even without GI symptoms \u2014 nontyphoidal Salmonella is a much more common cause of pediatric bacteremia in Africa. Brucella species are an important cause of occult bacteremia in endemic countries, capable of establishing chronic infection with hepatic or splenic abscesses; children with Brucella bacteremia typically have high-grade fever and elevated liver enzymes, and children with positive blood cultures show more acute presentations with higher inflammatory markers (leukocyte count, CRP, ferritin) than culture-negative cases \u2014 recurrent Brucella bacteremia occurs in under 10% of cases, especially with inadequate initial treatment, and recurrences are less often febrile (about 40% of cases), reflecting the indolent nature of chronic infection. Coagulase-negative staphylococci are a classic cause of bacteremia in children with intravascular catheters, vascular grafts, intracardiac patches, prosthetic valves, or pacemaker wires, and bacteremia can also arise from other indwelling foreign bodies (CSF shunts, peritoneal catheters, prosthetic joints), from mediastinitis after open-heart surgery, endophthalmitis after ocular trauma, or omphalitis/scalp abscess in preterm neonates. Bacteremia and septicemia are particularly seen in preterm neonates, typically those under 1500 g at birth, and in healthcare-associated bloodstream infections at any age. Certain vulnerable hosts \u2014 asplenic children, those with central venous catheters, neutropenic children, and those with short gut \u2014 carry a substantially higher risk of bacteremia than the general pediatric population, and knowledge of the most common regional organisms and local antibiotic resistance patterns is important for guiding empiric therapy."
  },
  {
   "title": "Clinical features",
   "content": "Features suggesting serious bacterial illness include lethargy, irritability, or altered mental status; tachycardia disproportionate to the degree of fever; tachypnea or labored respirations; a bulging or depressed anterior fontanel; nuchal rigidity; petechiae; localized erythema, tenderness, or swelling; and abdominal or flank tenderness. Bacteremia is usually accompanied by fever in older children but is often not associated with fever in infants, making recognition harder in this age group. In newborns, bacteremia and sepsis can present as apnea, bradycardia, respiratory dysfunction, fever or hypothermia, and abdominal distention rather than classic signs. High-risk children with baseline tachycardia (for example, from anemia related to a CVC, neutropenia, or short gut) can be harder to triage because their baseline vital signs already deviate from normal. In the absence of a preexisting skin lesion, or with fever or systemic symptoms in a very young child with a new skin/soft-tissue infection, bacteremia should also be considered."
  },
  {
   "title": "Diagnostics",
   "content": "Recognition of abnormal vital signs (tachycardia, hypothermia) and signs of poor perfusion is critical for prompt resuscitation; because normal vital sign ranges vary substantially across the pediatric age spectrum, electronic health record alerts can help flag abnormal values. Blood culture remains central to diagnosis. Determining the etiology of associated infections, such as pneumonia, can be challenging, since bacteremia is uncommon even in children thought to have bacterial pneumonia, antimicrobial therapy is often already given before cultures are obtained, and nasopharyngeal cultures do not reliably represent lower respiratory tract organisms."
  },
  {
   "title": "Complications",
   "content": "Of children with pneumococcal bacteremia, most recover spontaneously, but about 3-5% develop meningitis and another 5% develop a different focal infection, most commonly pneumonia. Bacteremia without a focal infection can range from self-limited illness to a severe, life-threatening illness, particularly in newborns or children with underlying disease, and mortality reaches up to 25% in some reported series, though this is difficult to separate from the contribution of underlying health problems. Bacteremia is sometimes polymicrobial, involving other enteric organisms alongside the primary pathogen."
  },
  {
   "title": "Treatment",
   "content": "Management goals center on recognizing which children are at higher risk of bacteremia than the general pediatric population \u2014 asplenic children, those with central venous catheters, and neutropenic children among them \u2014 and selecting empiric therapy informed by the most common regional causative organisms and local antibiotic resistance patterns."
  }
 ],
 "clinical": [
  {
   "title": "Recognizing the child at risk for bacteremia",
   "content": "Consider occult or overt bacteremia in a febrile child, particularly one under 2 years old with fever over 39\u00b0C and no clear source, and pay special attention to lethargy, irritability, altered mental status, tachycardia out of proportion to the fever, tachypnea or labored breathing, a bulging or depressed fontanel, nuchal rigidity, petechiae, or abdominal/flank tenderness \u2014 any of which raises concern for serious bacterial illness. Remember that bacteremia in infants is often not accompanied by fever, and in newborns can instead present with apnea, bradycardia, respiratory dysfunction, temperature instability (fever or hypothermia), or abdominal distention. Identify vulnerable hosts specifically \u2014 asplenic children, those with central venous catheters, neutropenic children, and those with short gut \u2014 since they carry substantially higher bacteremia risk and may have a confounding baseline tachycardia that complicates triage."
  },
  {
   "title": "Workup and empiric management",
   "content": "Obtain blood cultures and assess vital signs carefully against age-appropriate normal ranges, since abnormal ranges vary substantially across childhood and subtle deviations can be missed without this context. Base empiric antibiotic choice on the most likely regional organisms for the child's age (S. pneumoniae, Staphylococcus, and H. influenzae predominate under age 2) and known local antibiotic resistance patterns, adjusting quickly if a specific risk factor points elsewhere \u2014 for example, a central venous catheter raising suspicion for coagulase-negative staphylococci, or travel/endemic exposure raising suspicion for typhoidal or nontyphoidal Salmonella or Brucella. Recognize that most children with pneumococcal bacteremia recover spontaneously, but monitor closely for the roughly 3-5% who develop meningitis or the additional 5% who develop another focal infection, most often pneumonia."
  }
 ]
}