Reference no: EM133418275

Case Study

A 33-year-old pregnant woman, Stephanie D., reported to the emergency department with premature labor. She stated that she had been feeling a little "under the weather" for the past week with slight fever, some back pain, and headache. She explained that she began to feel"some occasional crampiness" over the previous 24 hours but did not think this could be contractions because she was only 30 weeks pregnant. She was surprised with membrane rupture about 2 hours ago and had experienced an increase in frequent of the contractions, which were ow approximately 3 minutes apart. She was taken to the delivery room and eventually delivered a 950-gram boy. The infant was in severe respiratory distress and was intubated immediately. Gross examination of the placenta revealed ischemic areas and samples of the tissue were sent to pathology and microbiology. Cerebrospinal fluid and blood cultures were also collected from the baby

Direct Gram's stain of the CSF revealed many neutrophils and short gram-positive coccobacilli. The pathology examination showed multiple abscesses approximately 1 to 3 inches in diameter. Upon microscopic evaluation, the abscesses revealed neutrophilic infiltration and aggregates of necrotic villi. Placental tissue, CSF, and blood cultures were all positive within 24 hours. The colonies on blood agar plate were small, translucent, and grey with a very narrow zone of beta hemolysis (see image). Further testing included a positive catalase test, an umbrella like zone of growth in motility media at 22° C, growth at 4° C, and a positive esculin hydrolysis test, and a negative H2S reaction.

Questions

1. What organism is likely to have caused Stephanie's premature labor and infection in the neonate?

2. The causative agent of this infection can be confused with Streptococcus agalactiae, which can also be a pathogen in this setting. How are these two organisms similar and what laboratory tests are helpful in distinguishing the two?

3. No history was presented that elucidated the source of Stephanie's infection. How might one become infected with the causative organism?

4. Why is the ability of this organism to grow at 4°C important to its pathogenicity?

5. What measures should be taken to avoid infection with this organism?

6. Pregnant woman are predisposed to infection with this organism. What other groups are at high risk?

7. What are some of the virulence factors this organism possesses?