What is the most likely causative organism of neonatal sepsis in a newborn whose mother has diarrhea on the day of delivery?

Escherichia coli is the Most Likely Causative Organism of Neonatal Sepsis in Newborns Whose Mothers Have Diarrhea on Delivery Day

In a pregnant woman with diarrhea on the day of delivery, Escherichia coli (E. coli) is the most likely causative organism of neonatal sepsis in the newborn. 1

Pathophysiology and Risk Factors

E. coli is the second leading bacterial cause of neonatal sepsis after Group B Streptococcus (GBS), but becomes particularly concerning in mothers with gastrointestinal symptoms like diarrhea 1. This is due to several factors:

• Maternal diarrhea indicates potential gastrointestinal colonization with pathogenic bacteria
• The gastrointestinal tract serves as the natural reservoir for many bacteria including E. coli
• Vertical transmission can occur during labor and delivery
• Microbial translocation from the gut is a suggested pathophysiological mechanism, particularly when E. coli is isolated in blood cultures 2

Epidemiological Evidence

Recent studies confirm E. coli as a predominant pathogen in neonatal sepsis:

• E. coli is the most common pathogen in early-onset sepsis (EOS) in very low birth weight infants 3
• E. coli infections are increasingly resistant to conventional antibiotics 4
• The role of E. coli in neonatal sepsis has become increasingly important since the widespread use of intrapartum antibiotic prophylaxis for GBS 2

Clinical Presentation and Diagnosis

Neonates with sepsis caused by E. coli may present with:

• Fever or temperature instability
• Respiratory distress
• Poor feeding
• Lethargy
• In some cases, skin manifestations including dermohypodermitis 2

Antibiotic Resistance Concerns

A significant concern with E. coli sepsis is increasing antibiotic resistance:

• Up to 75% of E. coli isolates in early-onset sepsis have been found to be ampicillin-resistant 4
• Gentamicin resistance has been reported in 50% of early-onset E. coli sepsis cases 4
• Some isolates show resistance to both ampicillin and gentamicin, which are commonly used for empiric treatment 4, 5

Management Recommendations

Given the high likelihood of E. coli as the causative organism and concerns about antibiotic resistance:

1. Obtain blood cultures before initiating antibiotics
2. Start empiric antibiotic therapy that covers resistant E. coli strains
   • Consider third-generation cephalosporins like ceftazidime which show better sensitivity profiles 5
   • Amikacin may be more effective than gentamicin for resistant strains 5
3. Adjust therapy based on culture results and antibiotic sensitivity testing
4. Monitor closely for clinical improvement

Preventive Measures

While intrapartum antibiotic prophylaxis is standard for GBS prevention, special consideration should be given to mothers with diarrhea:

• Evaluate maternal diarrhea for potential pathogens
• Consider broader spectrum antibiotic coverage if sepsis is suspected in the newborn
• Be vigilant for signs of sepsis in the newborn, especially in the first 72 hours

Pitfalls to Avoid

1. Assuming GBS is always the primary concern: While GBS is the most common cause of neonatal sepsis overall, E. coli is more likely when maternal diarrhea is present 1
2. Relying solely on ampicillin and gentamicin: Given increasing resistance patterns, these traditional first-line antibiotics may be ineffective 4, 5
3. Delayed recognition: Neonatal sepsis presents with non-specific symptoms; maintain high suspicion in infants of mothers with diarrhea 6
4. Overlooking antibiotic resistance: Always consider local resistance patterns when selecting empiric therapy 5

Early recognition and appropriate antibiotic therapy are crucial for improving outcomes in neonatal sepsis caused by E. coli in infants born to mothers with diarrhea on the day of delivery.