Severe Early-Onset Neonatal Listeriosis: An Unusual Diagnosis

Listeria monocytogenes is a Gram-positive bacterium with a low incidence of diagnosed infections. Maternal-fetal transmission can generate severe conditions in neonates manifested as sepsis, often clinically indistinguishable from other causes of neonatal sepsis, and is a particularly important cause of meningitis. Herein, we report a case of a 31-week and 3-day preterm male infant, weighing 1545 g (P10-50, Fenton chart), with Apgar scores of 0, 4, and 6 at 1, 5, and 10 minutes, respectively, who required advanced resuscitation and ventilatory support. He presented with severe respiratory distress and hemodynamic instability. Diagnosis was made by isolation of Listeria monocytogenes from the newborn's blood culture and molecular testing of the placenta using polymerase chain reaction (PCR). Prompt empiric antibiotic therapy with ampicillin, gentamicin, and cefotaxime was initiated and later adjusted based on microbiological findings, leading to complete recovery of the neonate. This case illustrates the diagnostic challenges of early-onset listeriosis, which often presents with non-specific signs in clinically unstable preterm infants. This presentation reinforces the need for a high index of clinical suspicion and appropriate microbiological and molecular investigations.