A 33-year-old pregnant woman, Stephanie, reported to the emergency department with premature labor. Shestated that she had been feeling a little "under the weather" for the past week with slight fever, some backpain, and headache. She explained that she began to feel occasional cramping" over the previous 24-hours butdid not think this could be contractions because she was only 30 weeks' pregnant. She was surprised withmembrane rupture about 2-hours ago and had experienced an increase in frequency of the contractions,which were now approximately 3 minutes apart. She was taken to the delivery room and eventually delivereda 2.5 lb boy. The infant was in severe respiratory distress and was intubated immediately. Gross examinationof the placenta revealed ischemic areas, and samples of the tissue were sent to pathology and microbiology.Cerebrospinal fluid (CSF) and blood cultures from the baby were also collected.RESULTS:Direct Gram's stain of the CSF revealed many neutrophils and short gram-positive bacilli. The pathologyexamination showed multiple abscesses approximately 1 to 3 cm in diameter. Upon microscopic examination,the abscesses revealed neutrophilic infiltration and aggregates of necrotic villi. Placental tissue, CSF, and bloodcultures were all positive within 24 hours. The colonies on blood-agar plate (BAP) were small, translucent, andgray with a very narrow zone of beta-hemolysis. (The microbiologist did not even notice the hemolysis untilshe had removed a colony for further testing.) Further testing included a positive catalase test, an umbrella-like zone of growth in motility media at 22°C, growth at 4°C, a positive esculin hydrolysis test, and a negative H₂S reaction.QUESTIONS
What organism is likely to have caused Stephanie's premature labor and infection of the neonate?