Give me back my name

“There’s a name for it,
names make all the difference in the world” 

Talking Heads

A little over two years ago, I told the sad story about how a contaminated blood culture became a central-line associated bloodstream infection (CLABSI). In that case, a “coryneform” or “diphtheroid” was more precisely identified by virtue of the adoption of mass spectrometry (MALDI-TOF) for organism identification. 

As more labs adopt technologies that provide this greater precision for species ID, it becomes more important to understand how much of an impact this might have on CLABSI rates (it’s not as if anything is riding on those rates, right?). So I was happy to see this small study in ICHE that begins to examine this issue. While this particular study is too small to help estimate the extent of the problem, it confirms that variation in species ID using different methods can impact a CLABSI designation. I hope this helps spur further evaluation not only of species ID methods, but of the broader issues around how laboratory advances impact healthcare-associated infection (HAI) definitions and rates. 

What are the next steps for evaluating the impact of species identifications on CLABSI rates? First, CDC/NHSN needs to update their master organism lists to keep up with current laboratory capacity to identify organisms, and with changing nomenclature. I know they are doing this, because I’ve been involved in that ongoing effort. Second, we should be able to use NHSN data to drill down on this problem—but can only do so if we know which lab methods are being used in each hospital for organism ID. So NHSN has now added questions to their annual survey to elicit this information. My hope is that we can use that information to compare CLABSIs among those organism groups most likely to affected by more precise species ID methods (e.g. gram positive rods).

As long as HAI definitions hinge on laboratory results, HAI rates will be very sensitive to technological advances (as well as to lab ordering practices). This dynamic receives far too little attention.

Punished for precision (or, too much information (TMI) from the micro lab!)

We recently had a patient's blood culture turn positive for a Gram-positive, catalase-positive, facultative diphtheroid. In the “pre-MALDI” era, we’d have called this isolate a “diphtheroid”. Taking into account other aspects of the case, the NHSN definition would have categorized this as a contaminant (diphtheroids being on the “common commensal” list maintained by NHSN). By virtue of the wonders of mass spectrometry, we are now able to identify the organism to species-level as Actinomyces neuii, an organism previously categorized as CDC group 1-like coryneform bacteria (also on the “common commensal” list). 

Actinomyces neuii isn’t anywhere on the NHSN organism lists. However, Actinomyces species (as a group) can be found on the “all organisms” list but NOT on the “common commensal” list. The NHSN rules tell us we have to categorize any organism on the “all organisms” list that isn’t also on the “common commensals” list as a pathogen, meaning this positive blood culture now helps define a central-line associated bloodstream infection (CLABSI).

And that’s the story of how a contaminated blood culture became a CLABSI. We’ve had other similar cases since we introduced MALDI-TOF. Before the CLABSI rate became worth millions of dollars to a hospital’s bottom line and reputation, this might have been easy to navigate. Now, though, it’s a much bigger deal. 

These and other issues regarding the impact of microbiological advances on infection prevention will be discussed at SHEA 2015 (ever heard of it?). Register now!