Listeria monocytogenes

A 34-year-old pregnant woman at 28 weeks of gestation presents to the antenatal clinic with a 3-day history of fever (38.5°C), myalgia, and malaise. She denies vaginal bleeding or abdominal pain. Blood cultures are drawn and subsequently grow a gram-positive rod that is catalase-positive, oxidase-negative, and displays characteristic tumbling motility at room temperature. The organism is resistant to cephalosporins. What is the most likely causative organism and the most appropriate antibiotic for maternal-fetal infection prevention?

A 72-year-old man with a history of chronic lymphocytic leukemia (CLL) on no active chemotherapy presents with a 5-day history of fever, severe frontal headache, neck stiffness, and confusion. Lumbar puncture is performed. CSF analysis shows: WBC 850/μL (80% lymphocytes, 20% neutrophils), glucose 35 mg/dL (serum glucose 120 mg/dL), protein 180 mg/dL. Gram stain reveals scattered gram-positive rods. Culture and PCR are pending. What is the most appropriate empiric antibiotic regimen for this patient?

Which of the following is the characteristic motility pattern of Listeria monocytogenes at room temperature (20–25°C)?

Listeria monocytogenes produces which virulence factor that enables it to escape from the phagolysosome and spread directly to adjacent cells?