Neonatal Sepsis

1. Overview
2. Causes and Risk Factors
3. Signs and Symptoms
4. Diagnosis
5. Antibiotic Treatment
6. Complications
7. Prevention
8. What Parents Should Know
9. Key Research Papers
10. Connections
11. Featured Videos

Overview — What is Neonatal Sepsis?

Neonatal sepsis is a life-threatening infection of the bloodstream in infants 28 days old or younger. Bacteria, viruses, or fungi invade the baby's blood and trigger a whole-body inflammatory response that can rapidly shut down vital organs. It is the leading infectious cause of neonatal death worldwide, responsible for an estimated 700,000 deaths globally each year — the vast majority in low- and middle-income countries where access to antibiotics and intensive care is limited.

Doctors divide neonatal sepsis into two types based on when it appears:

• Early-Onset Sepsis (EOS) — develops within the first 72 hours of life. The infection is almost always passed from mother to baby during pregnancy or delivery (vertical transmission). The most common culprits are bacteria that colonize the maternal birth canal: Group B Streptococcus (GBS) and Escherichia coli.
• Late-Onset Sepsis (LOS) — appears between 3 and 28 days of age. In the NICU, LOS is most often hospital-acquired, spread via hands, catheters, and breathing tubes. In otherwise healthy infants sent home, LOS can be community-acquired — GBS and Listeria are the main offenders.

How common is it? In full-term healthy babies, neonatal sepsis affects approximately 1 to 5 per 1,000 births. For very low birthweight (VLBW) premature infants — those born under 1,500 grams (about 3.3 lb) — the risk is 10 to 30 times higher. Mortality reflects this disparity: full-term infants with bacterial sepsis have a death rate of roughly 5–10%, while VLBW infants with fungal (Candida) sepsis face mortality rates as high as 25–50%.

Speed is everything in neonatal sepsis. A newborn's immune system is immature and cannot contain infection the way an older child's can. What begins as subtle feeding changes can escalate to shock within hours. Any parent, nurse, or doctor who feels a newborn "just looks wrong" should act immediately — clinical instinct is one of the most reliable early warning signs.

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Causes and Risk Factors

The bacteria responsible for neonatal sepsis differ significantly depending on whether infection strikes in the first three days or in the weeks that follow.

Early-Onset Sepsis (EOS) — the first 72 hours

• Group B Streptococcus (GBS) — the single most common cause of EOS in the United States. GBS colonizes the vagina and rectum of about 25% of pregnant women without causing them any symptoms. If the baby passes through a colonized birth canal without the mother receiving preventive antibiotics, the risk of transmission is significant. Universal screening programs and intrapartum antibiotic prophylaxis (IAP) have dramatically reduced GBS-EOS over the past 30 years — but it remains the leading cause.
• Escherichia coli (E. coli) — the second most common EOS pathogen and increasingly the more lethal one, especially in premature infants. Extended-spectrum beta-lactamase (ESBL)-producing E. coli strains are rising in frequency and are resistant to the standard first-line antibiotic ampicillin, making treatment more complicated.
• Listeria monocytogenes — rare but serious. Mothers acquire Listeria by eating contaminated soft cheeses, deli meats, or raw sprouts. Listeria causes prominent meningitis in newborns and can also cause late miscarriage and preterm labor.

Risk factors for Early-Onset Sepsis

• GBS colonization in mother without receiving adequate intrapartum antibiotic prophylaxis (IAP)
• Prolonged rupture of membranes (PROM) — membranes broken more than 18 hours before delivery
• Maternal chorioamnionitis (infection/inflammation of the placental membranes) or maternal fever during labor
• Preterm birth before 37 weeks — immature immune defenses and less maternal antibody transfer
• Previous sibling with invasive GBS disease
• GBS bacteriuria (GBS found in mother's urine) during this pregnancy

Late-Onset Sepsis (LOS) in the NICU — 3 to 28 days

• Coagulase-negative Staphylococcus (CONS / Staph epidermidis) — the most common NICU pathogen overall. CONS lives harmlessly on everyone's skin but can enter the bloodstream through indwelling central venous lines (PICC lines, umbilical catheters). Although generally less virulent than other bacteria, CONS causes prolonged illness in fragile premature infants.
• Staphylococcus aureus including MRSA — more aggressive than CONS; can cause pneumonia, deep tissue infections, and endocarditis. Methicillin-resistant S. aureus (MRSA) requires vancomycin rather than standard antibiotics.
• Gram-negative rods — Klebsiella pneumoniae, Pseudomonas aeruginosa, and Enterobacter species. These organisms cause severe and rapidly progressive disease and are increasingly resistant to multiple antibiotics.
• Candida species — fungal sepsis primarily affecting VLBW infants, especially those who have had prolonged antibiotics, central lines, or abdominal surgery. Mortality can approach 50%. Fluconazole prophylaxis has reduced rates substantially in high-risk units.

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Signs and Symptoms

One of the most important things to know about neonatal sepsis is that the signs are often subtle and nonspecific. A newborn cannot tell you what hurts. What experienced NICU nurses describe as a baby who "looks wrong" — not quite right, not feeding normally, somehow different — is a legitimate clinical signal that demands evaluation.

Temperature Instability

Many parents expect a sick baby to have a fever, but in neonatal sepsis, both high and low temperatures are danger signs. Premature infants in particular often respond to infection with hypothermia (temperature dropping below 36°C / 96.8°F) rather than fever. Any temperature above 38°C (100.4°F) or below 36°C in a newborn should be evaluated urgently.

The 3-Month Fever Rule — Know This

Any fever of 38°C (100.4°F) or higher in an infant under 3 months old is a medical emergency until proven otherwise. Do not give fever medicine and wait. Do not call the pediatrician's office and wait for a callback. Go to the emergency room now. Bacterial sepsis and meningitis in this age group move fast, and antibiotics cannot be delayed.

Other Warning Signs

• Feeding refusal or poor feeding — baby is not interested in the breast or bottle, sucks weakly, or tires out before finishing
• Lethargy or unusual sleepiness — difficult to wake, floppy, less responsive than usual
• Tone changes — limpness (hypotonia) or abnormal stiffness
• Apnea — pauses in breathing, particularly in premature infants; often the first sign of LOS in the NICU
• Bradycardia — heart rate drops; another common NICU early-warning sign
• Respiratory distress — grunting with each breath, nostrils flaring, chest pulling in (retractions), rapid breathing rate
• Bulging fontanelle — the soft spot on the top of the head becomes tense and elevated; a sign of increased pressure from meningitis
• Petechiae or purpura — tiny pinpoint red-purple spots or larger bruised-looking patches on the skin that do not fade when pressed; this is a true emergency sign of meningococcal or overwhelming sepsis — call 911
• Jaundice — yellow skin color that appears in the first 24 hours of life or rises unusually fast; conjugated (dark) jaundice is always abnormal and may signal liver involvement in sepsis
• Abdominal distension — a swollen, firm belly
• Seizures — rhythmic jerking, eye deviation, or subtle repetitive movements like lip-smacking or bicycling of the legs
• Skin color changes — pallor, mottling (blotchy red and white skin), or a grayish-blue tinge (cyanosis)

If your baby has any combination of these signs — especially if your gut tells you something is wrong — go to the emergency room. You will not be judged for bringing your baby in unnecessarily. You may be saving their life.

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Diagnosis

When a newborn is evaluated for possible sepsis, doctors perform a standardized "sepsis workup." The goal is to identify infection as quickly as possible so antibiotics can be started — often before culture results come back, which can take 24 to 72 hours. All of the following are part of the standard evaluation:

Blood Culture

The gold standard for diagnosing bacterial sepsis. A sample of blood is drawn and placed in a culture bottle where bacteria, if present, will grow over 24–72 hours. At least 1–2 mL of blood is needed for an adequate sample. Blood culture must be drawn before antibiotics are started; antibiotics given even one dose early can sterilize the blood and cause a false-negative result. A positive culture identifies the bacteria and allows targeted treatment.

Complete Blood Count (CBC) with Differential

Measures white blood cells (WBCs). In sepsis, the WBC count may be either too high (neutrophilia) or too low (neutropenia — actually a more ominous sign in neonates). The proportion of immature neutrophils (called bands or band cells) rises during infection. An immature-to-total (I:T) neutrophil ratio above 0.2 is a concerning marker of early infection.

CRP and Procalcitonin

C-reactive protein (CRP) and procalcitonin are inflammatory markers that rise in response to bacterial infection. They are not elevated immediately — CRP peaks at 24 hours, procalcitonin a little earlier — so a normal value in the first hours does not rule out sepsis. Serial measurements (checking again at 12–24 hours) are more informative than a single value. If both remain normal over 24–36 hours in a well-appearing infant, the likelihood of bacterial sepsis decreases substantially.

Lumbar Puncture (Spinal Tap)

Analysis of cerebrospinal fluid (CSF) from a lumbar puncture (LP) detects meningitis — infection of the membranes around the brain. LP is performed when the doctor suspects meningitis based on clinical signs (bulging fontanelle, seizures, irritability, positive blood culture). In critically unstable infants, LP is sometimes deferred until the baby is stabilized enough to safely tolerate the procedure.

Urine Culture

Collected by urinary catheter (not a bag specimen, which is contaminated). Urine culture is a standard part of the LOS workup but is not routinely performed in EOS in the first 72 hours of life, because the urinary tract is very rarely the source of infection in EOS.

Chest X-Ray

Identifies pneumonia (particularly GBS pneumonia, which can look like respiratory distress syndrome in a premature infant) and helps assess the degree of respiratory compromise.

The EOS Risk Calculator

For well-appearing term infants whose mothers had some (but not all) EOS risk factors, the Kaiser Permanente Neonatal Early-Onset Sepsis (EOS) Calculator can estimate the probability of EOS based on gestational age, highest maternal temperature, GBS status, duration of membrane rupture, and type of antibiotic prophylaxis given. Studies have shown that using this calculator reduces unnecessary antibiotic treatment in well-appearing term newborns without missing cases of true sepsis — an important advance because unnecessary antibiotics carry their own risks.

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Antibiotic Treatment

Antibiotics are started immediately when sepsis is suspected — before culture results return. The choice of antibiotics depends on whether EOS or LOS is suspected and on the local pattern of antibiotic resistance in the NICU.

Early-Onset Sepsis — First-Line Treatment

• Ampicillin + Gentamicin — the standard first-line combination for EOS worldwide. This pair covers GBS, E. coli, and Listeria monocytogenes with a narrow spectrum that minimizes disruption to the newborn's developing microbiome. Together they work synergistically — better together than either alone.
• If meningitis is suspected or the organism appears likely to be a gram-negative rod causing meningitis, cefotaxime may be added or substituted for gentamicin, because cefotaxime penetrates the blood-brain barrier more reliably.

Late-Onset Sepsis (NICU) — First-Line Treatment

• Vancomycin + Gentamicin (or piperacillin-tazobactam) — empiric treatment chosen to cover MRSA (via vancomycin) and gram-negative rods (via gentamicin or pip-tazo). This broader coverage reflects the NICU pathogen landscape where CONS, MRSA, and resistant gram-negatives are common.

Antifungal Treatment

• Fluconazole (first-line for susceptible Candida species) or amphotericin B (if fluconazole-resistant Candida or if the infant is very critically ill) — started when Candida sepsis is confirmed or strongly suspected. Candida sepsis requires removing central lines immediately in addition to antifungal therapy.

How Long are Antibiotics Given?

• Uncomplicated bacteremia (no meningitis, no source of infection): 7–10 days
• GBS meningitis: 14 days minimum
• Gram-negative meningitis: 21 days minimum (gram-negative meningitis has a worse prognosis and requires a longer course)
• Candida sepsis: 21 days minimum from the first negative blood culture

De-escalation and Stewardship

Once blood culture results and sensitivity testing are available (usually within 48–72 hours), antibiotics are narrowed to the most targeted regimen possible — a practice called de-escalation. If cultures are negative and the infant looks clinically well, antibiotics are stopped early. This matters: unnecessary prolonged antibiotic exposure in the NICU alters the infant microbiome, increases the risk of necrotizing enterocolitis (NEC), promotes colonization with resistant organisms, and raises the risk of subsequent fungal infection. Antibiotic stewardship — using the right drug at the right dose for the right duration — is one of the most important practices in modern neonatal medicine.

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Complications

When neonatal sepsis is caught early and treated promptly, most infants recover fully. When diagnosis is delayed or infection is overwhelming, serious complications can occur:

Meningitis

The most feared neurological complication. Among infants with positive blood cultures for EOS, meningitis is present in 10–30% of cases. GBS meningitis carries a mortality rate of 5–10% even with appropriate antibiotics; survivors face significant risk of long-term neurological damage, including hearing loss (the most common lasting deficit), cerebral palsy, epilepsy, and cognitive or learning impairment. Gram-negative meningitis (E. coli) is even more difficult to treat and has higher rates of brain injury.

Septic Shock

Overwhelming infection causes blood vessels to dilate and "leak," dropping blood pressure to dangerous levels. Treatment requires aggressive IV fluid resuscitation and vasopressor medications (dopamine, norepinephrine) to support blood pressure. The threshold for intubation and mechanical ventilation is low in neonates because their respiratory muscles fatigue quickly.

Disseminated Intravascular Coagulation (DIC)

Sepsis triggers widespread activation of the clotting system, which paradoxically consumes clotting factors and platelets faster than the body can replace them. The result is simultaneous abnormal clotting and abnormal bleeding. Treatment includes transfusions of fresh frozen plasma and platelets. Petechiae and purpura on the skin are the visible signs of DIC.

Multi-Organ Failure

Sepsis can damage the kidneys (acute kidney injury requiring careful fluid and medication dosing), the liver (elevated enzymes, conjugated jaundice, coagulopathy), and the adrenal glands (adrenal insufficiency causing refractory low blood pressure). Managing multi-organ failure in a premature infant requires intensive care expertise.

Necrotizing Enterocolitis (NEC)

NEC — a devastating inflammatory destruction of the bowel wall — is closely associated with gram-negative sepsis in premature infants. The connection between sepsis and NEC involves shared bacterial triggers and intestinal barrier dysfunction. NEC can require emergency surgery and has its own high mortality rate.

Long-Term Neurodevelopmental Impairment

Even infants who survive neonatal sepsis and appear to recover fully are at increased risk for subtle developmental challenges — mild learning difficulties, attention problems, and behavioral differences — that may not become apparent until school age. This makes long-term developmental follow-up after NICU discharge essential, not optional.

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Prevention

Many cases of neonatal sepsis are preventable. The measures that matter most are:

GBS Prevention — Universal Screening and Intrapartum Antibiotics

In the United States, all pregnant women are screened for GBS vaginal/rectal colonization at 35–37 weeks of pregnancy. Women who test positive (or who have other GBS risk factors) receive intravenous penicillin G during labor — intrapartum antibiotic prophylaxis (IAP). This single measure has reduced early-onset GBS disease by approximately 80% since universal screening was adopted in 1996. If you are pregnant, ask your midwife or OB whether your GBS screening result is on file and whether you will receive antibiotics in labor.

Hand Hygiene in the NICU

Handwashing is the single most effective measure to prevent LOS in the NICU. Every person who touches a premature or ill newborn — nurses, doctors, respiratory therapists, parents, grandparents, siblings — must wash hands thoroughly with soap and water or alcohol-based hand rub before touching the baby. NICU teams routinely audit compliance and display rates publicly. As a parent, you are not only allowed to ask anyone who approaches your baby if they have washed their hands — you are encouraged to.

Central Line Bundles

PICC lines and umbilical catheters are the most common entry points for NICU-acquired infection. Evidence-based "bundles" — standardized checklists that include chlorhexidine skin preparation, sterile technique during insertion, daily assessment of whether the line is still needed, and prompt removal when no longer needed — dramatically reduce central line-associated bloodstream infections (CLABSIs). Ask the NICU team: "When can this line come out?"

Fluconazole Prophylaxis

In NICUs with high rates of invasive Candida infection, infants weighing less than 1,000 grams are often given fluconazole twice weekly as prophylaxis. Meta-analyses show this reduces invasive candidiasis without promoting resistance in most settings.

Human Breast Milk

Human breast milk — especially colostrum (the earliest milk, full of antibodies and immune cells) — is powerfully protective against both LOS and NEC in premature infants. If pumping is difficult after an unexpected NICU admission, ask about donor breast milk. Even a small volume of breast milk matters. The NICU team can connect you with lactation support.

Skin-to-Skin / Kangaroo Care

Holding a premature infant skin-to-skin on a parent's chest promotes normal bacterial colonization with maternal microbiota rather than hospital pathogens, supports the baby's temperature regulation and breathing, and is associated with reduced rates of LOS. Ask when you can start kangaroo care if your baby is in the NICU.

Antenatal Corticosteroids

Mothers at risk of preterm delivery before 34 weeks receive steroid injections (betamethasone or dexamethasone) to accelerate lung maturation. Beyond reducing respiratory distress syndrome, antenatal steroids also improve immune function, reducing LOS risk in the smallest infants.

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What Parents Should Know

If your baby has been in the NICU for sepsis — or if you are pregnant and want to be prepared — here is the most important practical guidance:

The 3-Month Fever Rule (Again)

Fever (38°C / 100.4°F or higher) in any infant under 3 months = ER immediately. Do not give acetaminophen and call the nurse line. Do not wait until morning. This is not anxiety — this is the correct medical response. Bacterial meningitis and sepsis at this age can progress from subtle to life-threatening in hours.

Trust Your Instincts

Pediatric emergency medicine literature documents that parental concern — "something is just wrong" without a specific symptom — is an independent predictor of serious illness. You know your baby's normal. If your baby seems different, act on that feeling. You will never be made to feel foolish for bringing a newborn to be evaluated.

GBS Testing in Pregnancy

If you are pregnant, confirm your GBS status was checked at 35–37 weeks. If you are GBS-positive, remind your labor team when you arrive to the hospital — especially if labor moves quickly or if you arrive near delivery. The antibiotic needs to be given at least 4 hours before delivery to be most protective.

After NICU Discharge

Babies discharged after neonatal sepsis or meningitis need careful follow-up:

• Hearing test (ABR or OAE) — GBS meningitis can cause sensorineural hearing loss; confirm this is scheduled before discharge
• Developmental surveillance — at every well-child visit; referral to early intervention programs (available in all US states under Part C of IDEA) at the first sign of delay
• Ophthalmology — retinal screening for premature infants (ROP); vision follow-up for any infant who had meningitis
• Neurology — for infants who had seizures or documented brain injury during their NICU course

Vaccinations

Keeping your baby on schedule with vaccinations — Hib (Haemophilus influenzae type b), meningococcal vaccine, and pneumococcal vaccine (PCV15/PCV20) — protects against some of the organisms that cause serious bacterial infections in the months after the neonatal period. Premature infants receive vaccines based on their chronological age, not adjusted age — they should not wait.

Support for NICU Families

A NICU stay is traumatic. Many parents develop post-traumatic stress, anxiety, or depression. Resources include:

• Graham's Foundation (premature birth support): grahamsfoundation.org
• March of Dimes NICU Support: marchofdimes.org/nicu
• Hand to Hold (peer mentoring for NICU and bereaved parents): handtohold.org
• Your NICU's social worker, chaplain, and lactation consultant are on your team — use them

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Key Research Papers

1. Stoll BJ et al., 2011 — Trends in care practices, morbidity, and mortality of extremely preterm neonates: NICHD Neonatal Research Network (JAMA) — PMID: 21536860
2. Puopolo KM et al., 2011 — Estimating the probability of neonatal early-onset infection on the basis of maternal risk factors (Pediatrics) — PMID: 22291118
3. Shane AL et al., 2017 — Neonatal sepsis: an international perspective (Infect Dis Clin North Am) — PMID: 27737679
4. Verani JR et al., 2010 — Prevention of perinatal Group B streptococcal disease — CDC revised guidelines (MMWR) — PMID: 20110952
5. Downey LC et al., 2010 — Antibiotic stewardship in the newborn nursery (Pediatr Clin North Am) — PMID: 20150705
6. Stoll BJ et al., 1996 — Late-onset sepsis in very low birth weight neonates: NICHD Neonatal Research Network (J Pediatr) — PMID: 8649875
7. Kaufman DA, Fairchild KD, 2004 — Clinical microbiology of bacterial and fungal sepsis in very-low-birth-weight infants (Clin Microbiol Rev) — PMID: 15286231
8. Benjamin DK et al., 2006 — Neonatal candidiasis among extremely low birth weight infants: risk factors, mortality rates, and neurodevelopmental outcomes (Pediatrics) — PMID: 16585303
9. Schrag SJ et al., 2002 — A population-based comparison of strategies to prevent early-onset Group B streptococcal disease in neonates (N Engl J Med) — PMID: 11869667
10. Heath PT, 2016 — Status of vaccine research and development of vaccines for GBS (Vaccine) — PMID: 26443894
11. Wynn JL, Wong HR, 2010 — Pathophysiology and treatment of septic shock in neonates (Clin Perinatol) — PMID: 20671439
12. Puopolo KM, 2008 — Epidemiology of neonatal early-onset sepsis (NeoReviews) — PMID: 18515996

PubMed Topic Searches

1. Neonatal sepsis early-onset Group B Streptococcus
2. Neonatal late-onset sepsis NICU prevention
3. Neonatal sepsis antibiotic stewardship
4. Neonatal Candida sepsis VLBW fluconazole prophylaxis
5. Neonatal meningitis GBS neurodevelopmental outcome

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Connections

• Neonatal Jaundice
• Necrotizing Enterocolitis
• Congenital Heart Disease
• RSV Bronchiolitis
• Febrile Seizures
• Pertussis (Whooping Cough)
• Galactosemia
• Infectious Disease

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