Chapter 117: Using Laboratory Tests in Infectious Diseases: Chief of Staph Level III

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LEARNING OBJECTIVES

After completing this case study, the reader should be able to:

• Discuss the possible etiology of bacterial disease following a viral illness such as influenza.

• Discuss the use of rapid diagnostic testing methods that help differentiate coagulase-negative staphylococci from Staphylococcus aureus.

• Design a therapeutic plan to treat a bloodstream infection due to Staphylococcus aureus based on laboratory-based information.

• Evaluate culture and sensitivity results, and determine the clinical significance of the MIC for S. aureus.

• Recommend a plan for monitoring efficacy and adverse effects of antimicrobial therapy.

PATIENT PRESENTATION

Chief Complaint

Patient’s wife states of her husband, “Lately he has not been acting like himself. He has been very dizzy, tired and has not been eating or drinking well.”

HPI

David Covey is a 72-year-old man who came to the ED via ambulance. The patient’s history is obtained from his wife. She describes a change in mental status, lethargy, and shortness of breath, along with a significant decrease in activity and nutritional intake. The symptoms started 3 days ago and have progressively worsened. Over the past 24 hours he has become very nauseated and developed a fever (39°C). She states that Mr Covey has not eaten anything over this time period. He was recently hospitalized (last week) for 4 days due to influenza A pneumonia confirmed by PCR.

PMH

• Diabetes mellitus

• Resistant hypertension

• Depression

• Influenza pneumonia

FH

Both parents are deceased (mother, aged 88, of PE; father, aged 71, of stroke). He is married without any children.

SH

Retired steel mill worker and union chief, distant history of tobacco and alcohol use with no current use

Meds

• Metformin 1000 mg PO BID

• Glyburide 5 mg PO daily

• Spironolactone 25 mg PO daily

• Lisinopril 40 mg PO Q HS

• Amlodipine 10 mg PO daily

• Paroxetine 10 mg PO daily

All

• Penicillin: hives when he was a child

• Morphine: itching

ROS

Patient’s primary complaint is of nausea and dizziness but due to current status unable to review further

Physical Examination

Gen

The patient is frail, disheveled, appearing in respiratory distress

VS

BP 108/58, P 108, RR 36, T 39°C; Wt 64.2 kg, Ht 68 in

Skin

Warm and diaphoretic

HEENT

PERRLA; EOM intact; dry mucous membranes, teeth clean and intact, pharynx negative

Neck/Lymph Nodes