Granulomatosis infantiseptica

Listeria monocytogenes is a gram-positive, facultative intracellular, catalase-positive, motile (tumbling motility) bacillus that can cross the placenta, causing early-onset neonatal listeriosis. Granulomatosis infantiseptica represents the severe, disseminated manifestation acquired via transplacental (in utero) infection, typically resulting from maternal listeriosis (often subclinical, flu-like illness in pregnancy from contaminated foods like unpasteurized dairy, deli meats, or soft cheeses). Pathologically, it is characterized by widespread pyogranulomas with microabscesses containing neutrophils and macrophages, disseminated to the liver, spleen, lungs, adrenal glands, brain, and skin (classic finding: pale nodules or papular skin lesions). Clinical presentation includes preterm birth, respiratory distress, sepsis, meningitis, and skin granulomas; it carries a high mortality rate, especially if untreated. Diagnosis involves blood/CSF cultures growing small gram-positive rods with a characteristic beta-hemolysis on blood agar and tumbling motility at room temperature. Treatment is ampicillin (often combined with an aminoglycoside like gentamicin for synergistic effect), as Listeria is intrinsically resistant to cephalosporins. This is an important teaching point for boards: Listeria is one of the classic causes of neonatal meningitis (along with Group B Streptococcus and E. coli), and pregnant women are advised to avoid unpasteurized dairy and deli meats due to Listeria's ability to grow at refrigeration temperatures.