What is the most likely causative organism of neonatal sepsis in a pregnant woman experiencing diarrhea on the day of delivery, is it Listeria (Listeria monocytogenes)?

Listeria monocytogenes is the Most Likely Causative Organism in Pregnant Women with Diarrhea on Delivery Day Leading to Neonatal Sepsis

Listeria monocytogenes should be strongly suspected as the causative organism for neonatal sepsis in pregnant women presenting with diarrhea on the day of delivery, and empiric treatment should be initiated immediately.

Pathophysiology and Clinical Presentation

Listeria monocytogenes has a unique ability to infect the fetoplacental unit with several key characteristics:

• It can invade cells, multiply intracellularly, and transmit cell-to-cell 1
• It possesses virulence factors (internalin A and B) that facilitate direct invasion of cells 1
• The organism disproportionately affects pregnant women and their newborns 1

Maternal Presentation

When pregnant women develop listeriosis, they typically present with:

• Fever (most common symptom) 2
• Influenza-like illness 3, 4
• Gastrointestinal symptoms including diarrhea 5
• Reduced fetal movements 3
• Premature labor 3, 2

Neonatal Presentation

Neonatal listeriosis typically manifests as:

• Early-onset sepsis (within first week of life) 1, 4
• Respiratory distress requiring ventilatory support 4
• Hepatosplenomegaly 4
• Maculopapular rash 4
• Meningitis (less common in early-onset disease) 1, 4

Diagnostic Approach

When a pregnant woman presents with diarrhea on the day of delivery, particularly with fever or flu-like symptoms, immediate diagnostic workup should include:

• Blood cultures from mother 3, 5
• Cervical swabs 3
• Midstream urine 3
• Amniotic fluid cultures 5, 2
• Placental cultures after delivery 5
• Blood cultures and CSF cultures from the neonate 1, 5

Treatment Protocol

Maternal Treatment

• Empiric treatment with ampicillin should be initiated immediately while awaiting culture results 3
• High-dose intravenous amoxicillin (>6 g/day) for at least 14 days is recommended for confirmed cases 5
• For penicillin-allergic patients, alternative regimens should be considered based on susceptibility testing

Neonatal Treatment

• Ampicillin plus gentamicin for 14-21 days is the recommended treatment for neonatal listeriosis 1
• Close monitoring for respiratory failure is essential as this is a common cause of mortality 4

Outcomes and Prognosis

The consequences of untreated or inadequately treated listeriosis in pregnancy are severe:

• Overall mortality rate can reach 50% in neonates 4
• Respiratory failure is a common cause of death in the first week 4
• Complications include preterm delivery, spontaneous abortion, and stillbirth 3, 2
• Early diagnosis and aggressive therapy is associated with better outcomes 3

Prevention Strategies

Pregnant women should receive dietary guidance to reduce the risk of listeriosis:

• Avoid unpasteurized dairy products
• Thoroughly cook all meats
• Wash fruits and vegetables carefully
• Avoid ready-to-eat deli meats unless heated to steaming hot
• Practice proper food handling and storage 5

Clinical Pearls and Pitfalls

• Pregnancy itself can be the only risk factor for listeriosis 2
• Maternal symptoms may be mild or nonspecific, leading to delayed diagnosis 3, 4
• Clinicians must maintain a high index of suspicion for listeriosis in pregnant women with fever and flu-like symptoms 3
• Early empiric treatment while awaiting culture results is critical for improving outcomes 3, 5

While Group B Streptococcus (GBS) is a common cause of neonatal sepsis 6, the presentation of diarrhea in the mother on the day of delivery strongly suggests Listeria monocytogenes as the causative organism, which requires immediate attention and specific treatment.