Question

Case Study #1: A Common Opportunistic Infection

Ben, a seven-year-old second grader, quickly finished his homework after school so he could play outside with his friend form next door. Since Ben had started coughing the day before, his mother insisted he wear his jacket. At bedtime, Ben was exhausted from his busy day. When kissing his forehead goodnight, Ben’s mother noted that he felt a little warm. To help Ben sleep more comfortably since he was likely getting a cold, his mother gave him a dose of pediatric Tyenol, “Poor Ben,” she thought. “Three weeks ago he had the flu and now a cold is starting. He could really use a break.”

In the morning, Ben didn’t come to the breakfast table when called. His mother found Ben still in bed, barely responsive, and extremely feverish. She immediately drove him to the walk-in clinic in their neighborhood. Ben’s oral temperature was 40.8C (105.4F). IV fluids were started and an ambulance transported Ben to the nearest hospital.

In the hospital emergency room, Ben presented with the following viral signs: temperature = 41.9C (107.4F), pulse = 162 bpm, pulse ox = 90%, respirations = 24/minutes and labored, BP = 62/54 mmHg. Ben was completely unresponsive. His physical exam was remarkable for rales or “crackles” heard over both right and left lower lung fields. Bilateral chest radiographs were ordered and revealed infiltrates in the lower lobes of both lungs.

Preliminary lab results yielded a white blood cell count of 16,200 cells/mm^3 and a differential count with 74% neutrophils, including 18% bands. Respiratory acidosis was indicated by an arterial blood pH of 7.2. These results were immediately called from Ben’s local hospital to his new facility and broad-spectrum IV antibiotic therapy was initiated.

9. Approximately 6 hours later, the clinical microbiologist examined the BAP and chocolate agar plates. What morphological features did she likely observe on the plates? Why were these two media types selected for culturing?

10. What results would you predict from the following tests?

Optochin

Catalase

Bacitracin

Bile solubility

Quellung reaction

11. What is the significance of the following laboratory results?

The WBC

High neutrophil count with elevated bands

Respiratory acidosis

Automated identification and sensitivity testing were initiated and the presumptive microbe identification called to the other facility to aid in treatment. Ben’s attending physician was relieved to find that the CSF was sterile, as she had just initiated prophylactic antibiotic treatment of Ben’s caregivers. Unfortunately, she reported that Ben’s condition had continued to decline and he has been pronounced dead earlier that hour. She requested that identification/sensitivity data be forwarded upon completion so Ben’s record could be finalized.

12. Why was Ben’s physician relieved that the CSF was sterile? What possible infection was she considering?

13. Assuming Ben was receiving broad-spectrum IV antibiotic therapy that was effective against his infection, what reasons can you give to explain his rapid deterioration and eventual death when receiving an appropriate empiric therapy?

Within 6 hours, the Virek analyzer confirmed the identity of this microbe and indicated its sensitivity to penicillin, cephalosporins, and fluoroquinolones. While Ben’s attending physician was pleased that her staff had not been exposed to a resistant microbe, she was frustrated to have lost a young patient to one so sensitive to standard antibiotics.

14. Were there any predisposing factors that put Ben at greater risk for this infection?