A 23-year-old man had complained of right lower quadrant abdominal pain for approximately one week. Initially the pain was sharp and localized to a small area just above the right iliac crest. The pain subsided for approximately two days, but then recurred more diffusely over the lower abdomen, accompanied by cramping and mild diarrhea. The onset of fever and vomiting prompted a visit to the emergency room. His temperature was101 F, pulse was 90 per minute, and palpation of the right lower abdomen elicited severe pain. The white blood count was 23,000/mm with a distinct left shift, including 5% meta-myelocytes. Emergency surgery was performed for a large peri-appendiceal abscess. During surgery, multiple abscesses were noted in the spleen, which was removed (see image).Recovery was uneventful following five days of adjuvant clindamycin therapy.
Following 24-hour incubation, tiny pinpoint colonies were recovered from one of the splenic abscesses. Colonies produced wide zones of beta hemolysis after 36 hours of incubation. Gram stain showed Gram-positive coccid.
Questions:
1. Which test should be performed at this time on the colonies and why?
2. Which organism should be suspected?
3. Name and discuss the test that will presumptively identify this organism
4. Discus the pathogenicity of the organism