Neonatal sepsis is a systemic infection occurring within the first month of a newborn’s life. It arises when an infant’s underdeveloped immune system is overwhelmed by a bacterial, viral, or fungal infection in the bloodstream, leading to a widespread inflammatory response that can affect multiple organs. Due to its subtle initial signs and potential for rapid progression, the diagnostic process relies on recognizing risk factors, observing clinical signs, and interpreting laboratory tests.
Risk Factors and Types of Neonatal Sepsis
Maternal health factors are a significant consideration, including infections in the mother such as Group B Streptococcus (GBS) colonization, chorioamnionitis, or fever during labor. A prolonged period between the rupture of the amniotic sac and delivery also elevates the risk. Infant-specific factors, particularly prematurity and low birth weight, are strongly associated with a higher incidence of neonatal sepsis.
Neonatal sepsis is categorized into two types based on when symptoms appear. Early-onset sepsis (EOS) manifests within the first 72 hours after birth. This type is linked to infections acquired from the mother before or during the birthing process, with pathogens like E. coli and Group B streptococcus being common causes.
Late-onset sepsis (LOS) develops after the initial 72-hour period. This form is caused by pathogens acquired from the infant’s environment after birth, such as from caregivers or contaminated equipment in a hospital setting. The organisms responsible for LOS can differ from those causing EOS and may include a wider variety of bacteria and fungi.
Clinical Presentation and Physical Signs
The initial signs of neonatal sepsis are often subtle and nonspecific. Common early indicators include a change in the baby’s activity level, such as lethargy, or poor feeding. Temperature instability is another frequent sign, which can present as either a fever or, more commonly in newborns, a low body temperature (hypothermia).
Respiratory difficulties are a prominent feature in many cases. An infant may exhibit rapid breathing (tachypnea), periods where they stop breathing for a short time (apnea), or audible grunting sounds with each breath. These are all signs of respiratory distress.
Changes in circulation and neurological status can signal a more severe progression. The infant’s skin might appear pale, bluish, or mottled as a sign of poor blood flow. An evaluation may reveal low blood pressure or an unusually fast or slow heart rate. Neurological signs can include irritability, jitteriness, or seizures, while a bulging fontanelle can indicate increased pressure within the skull.
Laboratory Findings and Diagnostic Workup
When clinical signs suggest sepsis, laboratory tests are performed to find evidence of infection and inflammation. A complete blood count (CBC) is a fundamental test that provides information about blood cells. Clinicians look at the white blood cell count, which can be either abnormally high or low in sepsis.
The CBC also includes an analysis of neutrophils, a type of white blood cell that fights infection. An elevated ratio of immature to total neutrophils (I/T ratio) suggests the bone marrow is responding to a significant infection. A low platelet count (thrombocytopenia) can also be an indicator of a systemic infection.
Beyond the CBC, specific markers of inflammation are measured. C-reactive protein (CRP) is produced by the liver in response to inflammation, and its levels rise within 10 to 12 hours of an infection’s onset. Another marker, procalcitonin (PCT), can also become elevated during bacterial infections, though both markers can also increase due to non-infectious stress from birth.
The definitive method for confirming a bacterial infection is a blood culture. This test involves drawing a blood sample and placing it in a medium to see if microorganisms grow. While considered the gold standard, a blood culture can take 24 to 48 hours for results. Depending on the infant’s symptoms, other cultures may be performed, such as a urine culture or a cerebrospinal fluid culture to check for meningitis.
Confirmation and Immediate Medical Response
Due to the speed at which neonatal sepsis can progress, treatment is often started based on a strong suspicion of infection, without waiting for definitive culture results. This approach involves the immediate administration of broad-spectrum intravenous (IV) antibiotics to target the most likely bacterial culprits while the diagnostic workup is ongoing.
Once blood culture results identify a specific pathogen, the antibiotic therapy is tailored. This involves switching to a narrow-spectrum antibiotic that is most effective against the identified bacteria. This adjustment helps ensure the most effective treatment while minimizing the risk of promoting antibiotic resistance.
In addition to antibiotics, infants with sepsis often require intensive supportive care. This may include IV fluids to maintain hydration and circulation, oxygen therapy or mechanical ventilation for respiratory distress, and medications to support blood pressure if the infection has caused circulatory instability.