Case Study #1: A Common Opportunistic Infection Ben, a seven-year-old second gra
ID: 206950 • Letter: C
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.
1. What does crackling on auscultation suggest?
2. Is this confirmed by the radiographs? Explain.
3. Name four common infectious agents for this condition.
4. Does this diagnosis account for all of Ben’s extreme symptoms?
Blood was drawn for hematology and metabolic panels. Two sets (1 set = 1 aerobic bottle and 1 anaerobic bottle) of blood cultures were also drawn and a lumbar puncture performed to collect CSF. Ben was air lifted to a major medical facility for treatment.
5. Indicate two reasons why two sets of blood cultures were ordered.
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.
6. What is the likely causative agent of Ben’s infection?
7. Where is this microbe typically found?
8. How did it end up in his blood if Ben’s initial problem was respiratory?
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?
Explanation / Answer
Answer 1:-
Crackling sound or rales occur if lung infection is present. When the lung infection causes secretion of excessive fluids in the airways, crackling sound of auscultation can be heard. Congestive heart failure may result in transudate accumulation; however lung infections are common cause, where exudate accumulation occurs. Exudates such as increased mucus production lead to crackling sound in lungs.
Answer 2:-
The radiograph, in this case confirmed the crackling on auscultation as the infiltrates in lower lung lobes were revealed.
Answer 3:-
The lung infections that can lead to crackling on auscultation include pneumonia (Klebsheilla pneumoneae), acute viral bronchitis (influenza virus), atelectasis, pulmonary fibrosis (exposure to environmental pollution, dust, bacteria etc), bronchiectasis etc.
Answer 4:-
Ben’s extreme symptoms such as high fever, low blood pressure, lower oxygen level and hence unresponsiveness accounts for the diagnosis of lung infection. Also Ben suffered from flu previously, therefore, the lingering flu might have relapsed or the decreased immunity due to flu led to secondary infections (viral or bacterial).
Answer 5:-
The two sets of blood cultures – one aerobic and another anaerobic were ordered. The infiltrate was observed in the lower lung lobes and hence chances are there that the infection might be because of the anaerobic bacteria. Thus, to detect the exact nature of infectious agent, two sets of blood culture were ordered. The other reason for ordering two sets of blood cultures is to determine the Gram nature of the bacteria, so as to determine the broad spectrum or narrow spectrum specific antibiotic.