Dr. Collins and the Case of the Mysterious Infection

PART II

by
Paula P. Lemons and Sarah Huber
Biology Department
Duke University

Day 3

Dr. Collins sat down at her desk. It was the time in her day designated to looking over laboratory test results. Among the pile of folders she found the report from the microbiology lab on Kayla Starnes. She had been waiting two days for this. Despite surgical drainage of the infected hip joint and administration of several doses of cefazolin, Kayla’s condition was not improving. Her fever persisted and she was beginning to complain of difficulty in breathing.

Dr. Collins ran through the protocol for antibiotic prescription in her head. Administration of cefazolin was standard therapy for the type of infection Kayla was displaying. Only patients who have specific risk factors for a special type of Staphylococcus aureus infection—hospital-acquired MRSA (methicillin resistant S. aureus)&mdashgenerally receive any other kind of treatment. These risk factors include recent hospitalization, living in a nursing home, or exposure to health care workers. Typically these patients are treated with vancomycin since MRSA tends to be resistant to all other antibiotics.

But Jenna had no risk factors for MRSA. Why wasn’t she responding to cefazolin? Dr. Collins hurriedly opened the report and searched for an explanation. As she read over the lab results, her heart sank.

Examine the data from the Microbiology Lab Report below and consider the following questions:

  1. Why has Kayla not responded to treatment with cefazolin?
  2. What are the similarities and differences between the strain of bacteria that Kayla carries and the typical hospital-acquired version of MRSA?
  3. What should Dr. Collins do now?

Microbiology Lab Report


	Date: July 15, 1997

	Patient Name:  Kayla Starnes        Doctor:  Jenna Collins

	Source of bacteria: 
        	surgical drainage fluid - right hip joint.  Obtained 7/13/97

	Species of bacteria:    
        	Staphylococcus aureus

	Strain of bacteria:
    	    Methicillin-resistant Staphylococcus aureus

	Pattern of antibiotic susceptibility:
  	      Trimethoprim-Sulfamethoxazole - susceptible
  	      Tetracycline - susceptible
  	      Methicillin - resistant
  	      Cefazolin - resistant
  	      Vancomycin - susceptible

	Analysis of chromosomal DNA by PCR:
 	       mecA positive

Go to Part III

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