Antimicrobial susceptibility testing

Jen Liao,
Here are the answers to the questions you asked,

I had this as a topic for the proposed agenda for the next NE HAI/AR call, but I thought it may be more useful to have as a side conversation on here

We currently are trying to decide what AST method we would like to use at our SPHL. It is our understanding that ARLN would like a method that most clinical labs in the state aren't using, i.e. KB/disc diffusion or Etest. We have a Vitek2 that our lab is interested in doing automated AST on.
New Hampshire is currently using Kirby Bauer disk testing. In a perfect would we would also be using broth microdilution(I.E. Sensititre) but that is not possible for us budget-wise. I believe the MA state lab has validated their Sensititre system. I don’t see any harm in using your Vitek 2, but it shouldn’t be your only method. I would reach out to the ARLN or lab at Wadsworth to find out if you can use your Vitek in conjunction with a different method such as the Kirby Bauer.
For those states who do AST for CRO isolates, what method are you using and have any issues come up with this method? We've heard of discrepant interpretations between clinical and public health labs, and have also heard that clinical lab interpretations supercede the public health lab's.

NH uses Kirby Bauer testing. We frequently have discrepant results.. More often than not the hospital lab will call an isolate resistant to a carbapenem and when the PHL tests it, it will be susceptible. (sometimes intermediate). Hospital labs in NH are not confirming results that are abnormal, and in our state, CRE is not a common finding. Hospital labs should be using a secondary method to confirm any abnormal results. I believe a few will repeat the same method (Vitek, Mscan) before sending it. Another issue that we’ve had is that hospital labs think that we are confirming their results for them, when we are only performing surveillance. It’s been a challenge to communicate this.
You heard correct, and the hospital lab results should be what goes in the patient record, and what the clinicians act on.

We have gotten feedback from our facilities that it would be useful for us to bring AST on board for CRE confirmation, and wanting to anticipate any issues that may come up. I know most of the SPHL testing is done for surveillance/infection control/containment purposes, but it sounds like with this AST piece our interpretations may inform treatment decisions for some of our facilities. Since this isn't normally within our realm, we wanted to see what other folks' experience was with this.
If you aren’t doing sensi testing currently, how have you been confirming CRE? Or are you currently only testing for carbapenemase production, which is different than carbapenem resistance? I’m also under the impression that ARLN testing is not meant to confirm hospital results.. If your lab wanted to take on sensi testing as an option you might need to go through realms other than the ARLN. I could be wrong though!


Thank you,



Lisa Tibbitts, RN, BSN, MSNed, BC
Healthcare Associated Infections Program Manager
Bureau of Infectious Disease Control
New Hampshire Division of Public Health Services
Department of Health and Human Services
29 Hazen Drive
Concord, NH 03301-6504
Phone: 603-271-4706
Fax: 603-271-0545
Email: lisa.tibbitts@dhhs.nh.gov<mailto:lisa.tibbitts@dhhs.nh.gov>

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Hi Jen,

In response to your question, I consulted with Tracy Stiles our Micro Lab Director on this. Here are her comments: “Our assumption in MA is that we are not confirming results or guiding treatment in any way. We are strictly doing surveillance, and have a statement on our lab reports to that effect. We are doing the KB Disk Diffusion but have (perhaps lofty) dreams of eventually validating the sensititre. My understanding is that most of the ARLN labs are using (or will be using) the sensititre. I can’t really speak to what Maine should do if they were to decide to be a confirmatory lab for their clinical labs. In that case they’d be acting as a reference lab not as a public health or surveillance lab. They may want to use a method other than what their clinical labs are doing.”

I hope this is helpful-
Melissa

____________________________________________
Melissa A. Cumming M.S.
Epidemiologist
Antibiotic Resistance and Hemovigilance Coordinator
Epidemiology Program
Bureau of Infectious Disease and Laboratory Sciences
Massachusetts Department of Public Health
305 South Street
Jamaica Plain, MA 02130
(Tu, Th, Fri) State Lab 617-983-6817
(M, W) West Boylston Office 508-792-7880 ext. 2345
melissa.cumming@state.ma.us<mailto:melissa.cumming@state.ma.us>