One of the main tools we use at work to rapidly identify potential pathogens is Bruker's MALDI-TOF. In this case, Bruker's machine utilizes proteins found in bacteria for this process.
As helpful as it is, there are always limitations to what the instrument can and cannot identify. A high confidence score does not guarantee identification when the bacteria have similar proteins or time-of-flight patterns. A recent database update showed that the technology is constantly improving. Here are some recent updates:
Streptococcus peroris is not a pathogen (usually). However, it's good to know that we could take another species off the "can't tell the difference" list. The optochin disk works fine and is still the preferred method to find Streptococcus pneumoniae.
The better part of the update is the ability to identify Streptococcus pyogenes, or Group A Strep (GAS). For the most part, our department prefers the PathoDX™ Strep Grouping Kit for beta-hemolytic strep. The kit is faster and easier to use. At the same time, it's comforting to know we have a reliable alternative should we run out of our supplies of kits. We now can tell Group A apart from Group C and G Strep.
Sounds pretty good!
As we improve our tools, it's also important to remember that life is dynamic. We also had to update some of our protocols. The image above is an excerpt of those changes. While they have nothing to do with the MALDI-TOF method, I felt they were relevant.
When I started my position nine years ago, we expected Pseudomonas species to be intrinsically resistant to ertapenem only. Evolution has taken the bacteria to where they have resistance to any carbapemem drugs. Some of my colleagues, who have been in the field for over 20 years, could remember when they had to confirm ertapenem resistance.
The same could apply to imipenem resistance for the genera listed. Our instruments have yet to be updated to ignore the imipenem flag on them. Less experienced lab personnel would have to get up to speed to prevent wasting time verifying resistance that doesn't need to be.
We live in fascinating and scary times in this cat-and-mouse game against pathogens.
Posted with STEMGeeks