Microbiology at the speed of light
Contact: Mardi Ford
Written for the La Grande Observer by George R. Wettach, MD, FASCP, FCAP of Blue Mountain Pathology.
Imagine if your doctor could swab a wound, learn which infection it is, and prescribe the best antibiotic – all in a fraction of the time it usually takes.
Microbiology is one of the most time-consuming areas of the clinical laboratory. Traditionally, organisms have been identified through a variety of techniques, including observing how they interact with different chemicals as they grow. The greatest challenge is knowing which tests to apply up front. This is why microbiologists require a description of the source and prefer as much information about the patient as possible, such as age, symptoms, and history of any sick contacts.
The specimen is streaked onto one or more gelatin plates with different nutrients. Some organisms require specific sugars and proteins to grow, a fact that allows us to distinguish one from another. After several hours to even a few days, a microbiologist must then transfer small colonies to other tubes and cards to see how the organism responds to various chemicals. These patterns must then be recorded and interpreted correctly to reach the right conclusion.
Matrix-assisted laser desorption and ionization time-of flight mass spectrometry, or MALDI-TOF, will greatly shorten the time to result by eliminating the need for these biochemical tests. Once the organism is isolated on a culture plate, typically after 16 to 24 hours, a small sample is smeared onto a metallic plate with a proprietary matrix. This system uses barcodes to help minimize clerical errors, and there are cross hairs to guide a laser to the target on the plate. The laser then blasts the specimen, and the fragments are vacuumed through a column. As pieces strike a detector, the times of impact are recorded as peaks on a graph. A computer inside the instrument compares the pattern of peaks against an expanding library of known bacteria and fungi.
“For years, some have argued that there’s nothing really new in microbiology,” says Sandi Larison, MT(ASCP). “This is a total game changer.”
Currently, there are only a few such instruments in Oregon and Idaho. Nationwide, Grande Ronde Hospital is now one of only very few critical access hospitals with this technology, joining the ranks of much larger facilities, such as the Mayo Clinic, Kaiser Permanente, and ARUP.
While waiting for cultures to grow and other conventional tests to be completed, doctors often use broad-spectrum antibiotics based on a best guess of what is causing the infection. Unfortunately, these can also target “good bacteria” that help us digest food and that keep the “bad bacteria” at low numbers. More rapid identification will ensure that the right antibiotic is started earlier, potentially reducing length of hospitalization and cost. By limiting the use of broad-spectrum antibiotics, disease-causing bacteria can be eliminated before the helpful strains are killed.
Image: Microbiologist R'Chel Plank-Gryffin, MLT(ASCP), reviews data generated by the MALDI-TOF instrument recently installed at Grande Ronde Hospital.
Dr. Wettach is board certified in both anatomic and clinical pathology. A partner of Blue Mountain Pathology, he serves as medical director of multiple clinical laboratories throughout Union, Wallowa, and Baker counties