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Part III

Week 5, Day 1

Dr. Collins sank into her chair. Breaking the news of a patient’s death to the patient’s family was the worst part of this job. She thought back over the past five weeks of Kayla’s hospital stay. Despite the switch to vancomycin when she discovered that Kayla was carrying MRSA, Kayla’s respiratory condition worsened, leading eventually to pneumonia.

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    ings continued to escalate until early this morning when Kayla died of hemorrhaging from the lungs. “Some things,

Dr. Collins mused aloud, “I’ll just never understand.”

She reached for the phone and dialed Dr. Kurt Blanton, one of her best friends from college and an up-and-coming researcher at the Centers for Disease Control in Atlanta. She recalled from their last conversation that Kurt was working on characterizing various MRSA isolates. Using a method known as pulsed-field gel electrophoresis, he could determine the genetic relatedness of each isolate. Perhaps he could characterize this strain and help to explain some of its oddities—similar to MRSA in its resistance to cefazolin-like antibiotics, most likely because of mecA, but dissimilar to MRSA in its susceptibility to multiple other common antibiotics and its presence in a person without any MRSA risk factors.

“So what do you think, Kurt?” Jenna asked after telling him Kayla’s story.

“Sure, I’ll characterize the strain. I’m always looking for new samples. is information adds to our database and helps us know how to advise doctors like you about prescribing antibiotics to your patients. I’ll be in touch with your hospital’s microbiology lab about the details and get back to you when our tests are complete.”

Week 10, Day 1

“Hello, Dr. Collins speaking.”

“Hi, Jenna. It’s Kurt. I’m emailing you an attachment with our pulsed-field gel electrophoresis results. I’ve included a description of things you need to know to understand what you’re looking at. I think you’ll find this interesting.”

Date: Mon, 16 Jul 2001 12:56:15 -0700 (PDT) From: Kurt Blanton, kblanton@cdc.gov To: Jenna Collins, jcollins@stlukes.org Subject: Pulsed-field gel electrophoresis results


The important thing for you to look at in the figure I’ve attached is the pattern of bands. These are bands of DNA; each band represents a piece of DNA of a specific length (see my note in the P.S.). Compare the pattern obtained from your patient’s sample with the other patterns on the gel. This will give you a clue about the genetic origin of this isolate. When comparing patterns use the following criteria: If the patterns are indistinguishable, the isolates are said to be genetically identical; if they differ by 2-3 bands they are said to genetically closely related; if they differ by 4-5 bands they are said to be possibly genetically related; and if they differ by more than 5 bands they are genetically unrelated.

We compared the isolate from your patient to various MRSA isolates. I know you were puzzled about why your patient carried an MRSA strain yet had no risk factors for MRSA infection. Look below; I think our results will shed some light on this for you.

P.S. If you’re interested in learning about pulsed-field gel electrophoresis, I’ve included a description of the technique and a diagram to help you understand on a separate page.


“Dr. Collins and the Case of the Mysterious Infection” by Lemons & Huber

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