MedicalResearch.com Interview with:
Dr. Daria Van Tyne, PhD
The Gilmore Lab
Department of Ophthalmology
Harvard Medical School
Massachusetts Eye and Ear Infirmary
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: A specific clone of E. coli, type ST131, which produces an extended-spectrum beta-lactamase (ESBL – an enzyme that inactivates many penicillin-type antibiotics), has rapidly spread around the globe to become the leading cause of multidrug-resistant, non-intestinal E. coli infection. Despite this, E. coli is a rare cause of infection of the cornea. A patient was recently seen at the Massachusetts Eye and Ear Infirmary with a severe E. coli infection of the cornea, and the large number of antibiotic resistances of this strain tipped us off to the possibility that it might be the highly virulent ST131 ESBL type. By sequencing the DNA of its genome, we found that it was indeed ST131 ESBL E. coli. Moreover, we discovered a new mutation in this strain that allows it to produce a slimy outer coating on its surface. This slime layer, or capsule, makes the bacteria more resistant to removal by phagocytic cells of the immune system. The slime layer also makes these particular colonies appear different on a special type of agar that contains the dye Congo Red.
MedicalResearch.com: What should readers take away from your report?
Response: In addition to being resistant to antibiotics of many types, this already virulent strain of E. coli seems now to have evolved additional resistance to elimination by cells of the immune system, which is a troubling development. The good news is that this slimy superbug can be easily distinguished on Congo Red agar – and we hope that this easy identification will help limit its spread.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: We are now working to understand what factors led this E. coli strain to evolve resistance to immune cell clearance – a process called phagocytosis. Every night when our eyes are closed, immune cells called neutrophils remove bacteria and other debris from the surface of the eye. We think that this exposure, along with exposure to other antimicrobial factors in the tear film, selected for this particular type of E. coli possessing the new mutation we found. We are now trying to recapitulate this idea in a carefully controlled laboratory environment, and are asking to what degree does this phagocytosis resistance allow E. coli to more easily cause corneal infections.
MedicalResearch.com: Is there anything else you would like to add?
Response: This study is the result of a collaborative effort that brought physicians and researchers together to study an unusual superbug. The physicians were able to successfully treat the infection, and the researchers figured out why this bacterium might have been found in this type of infection. It is a great example of what can be accomplished when physicians and researchers team up!
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Van Tyne D, Ciolino JB, Wang J, Durand ML, Gilmore MS. Novel Phagocytosis-Resistant Extended-Spectrum β-Lactamase–Producing Escherichia coli From Keratitis. JAMA Ophthalmol. Published online September 15, 2016. doi:10.1001/jamaophthalmol.2016.3283.
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