Case Studies:

Case-1:

An 18-month old boy was rushed to the emergency room by ambulance after his mother found him unresponsive. When he did not wake up at his usual time form a nap, she became concerned. When she tried to wake him, he would not respond and is currently lethargic and listless. His mother reported that he had had a fever for 2 days and had been cranky and irritable. The mother stated, "I think he might have an earache, because he started pulling at his ear yesterday". The family is from an extremely rural area and does not have medical insurance or easy access to health clinics. The boy had not had any routine pediatric well-care visits or immunizations.

His temperature was 39.5C. a lumbar puncture was performed and revealed the following: CSF protein, 989 mg/dl (normal, 15 to 45 mg/di); glucose, 12 mg/dl (normal, 40 to 80 mg/di); 20,000wbc/mm3 with 90% polymorphonuclear cells. Gram stain of the CSF showed gram-negative pleomorphic coccobacilli and many neutrophils. Culture yielded abundant growth on chocolate agar after overnight incubation. The colonies are small, round, and translucent with glistening/wet appearance. The microbiologist working up the culture recognized a familiar mousy odor to the culture.

Questions:

1. What organism is most likely causing the boy's infection?

2. What special growth requirements does this organism exhibit, and how can these be used to help identify the organism?

3. What 3 methods might be used to test for these growth requirements? Comment on each.

4. Even without the Gram stain or culture, how do the CSF parameters point toward a bacterial disease? (do some research)

5. What other bacteria (name at least two) commonly cause this disease in this age group?

6. How can infection with this organism be prevented?

Case-2:

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 cocci.

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 pathogen city of the organism