The last 18 months have truly been a watershed period in the land of science and medicine. Obviously, SARS-CoV-2 must be mentioned at least once, and this sentence serves as that obligatory acknowledgment. Moving beyond the superficial, the global accomplishment of recognizing a novel pathogen emergence, identifying the pathogen, retarding the pathogen’s progress through the human population, developing a vaccine, and finally manufacturing and distributing that vaccine on a global scale is an amazing accomplishment. When one then considers that all these significant tasks were accomplished in 12-14 months from pathogen emergence to effective vaccine distribution, the past year in science and medicine was simply incredible.
In the age of warp-speed vaccine development (and manufacture and distribution), one wonders if other components of the healthcare system are progressing as quickly.
Despite the truly awe-inspiring response from the health sciences in the face of SARS-CoV-2, the testing available proved less than ideal. In fact, depending on which test was employed and the community prevalence, the results were often equivocal at best—even in the face of fairly sophisticated interpretation.
Have clinical diagnostics kept pace with other areas of healthcare? And how about veterinary medical care? What is the current state of veterinary diagnostics for infectious diseases? And, furthermore, what is the prognosis for diagnostics in the veterinary practice?
Diagnostic tests to determine health—or causes for the lack thereof—are not new. Diagnostic testing by physicians and veterinarians alike was not always the sophisticated practice of today.
Prior to 400 BC, the oldest known test on bodily fluids was pretty straight forward. The patient’s urine was poured on the ground, and if the urine drew insects, then the patient was diagnosed with boils. Progress was made around 300 BC when Hippocrates performed a full diagnostic work-up by tasting the urine, listening to the lungs, observing skin color and other outward appearances. Bubbles on the surface of urine was readily tied to kidney disease, and chronic illness and hematuria was first documented as indicative of kidney failure circa 50 AD.
In early times, urine was certainly the key to a diagnosis; so much so that failure to examine the patient’s urine allowed for a public beating of a physician, according to the Jerusalem code of 1090. While medical advancement suffered from a severe paralysis for centuries due to the hubris of Galen, by the time the 1600’s and 1700’s rolled around, health experts had “graduated” to assessing a patient’s urine…still!
Then, in the 1800’s, came the “Golden Age” wherein the shape of a patient’s skull could predict mental health and magnets were used to treat all manners of illness. At least improvements in hygiene led to dramatic increase in survival rates overall. Indeed, the late 1800’s produced Koch’s postulates and an epiphany regarding infectious diseases. The concept of producing a pure culture of the disease-causing pathogen is still prevalent today.
While we no longer rely on horses, wagons or even steam engines for transportation, we still refer to culture as a diagnostic gold standard for many infectious agents. And while candles and lanterns are now reserved for austere and temporary events, culture remains a routine diagnostic method for many clinical conditions.
What?! Why?! Why has clinical identification of a pathologic agent not kept pace with other facets of society and medicine?
Oh, but it has!
In the early 1990’s, the world at-large was introduced to a cutting-edge laboratory process called polymerase chain reaction (PCR) via the US judicial system. Thirty years later, even PCR has evolved and advanced. But what bearing might any of this have on veterinary practice?
While culture and sensitivity remain readily available, quantitative PCR (qPCR) has now become available to veterinary practitioners, a mere five to six years after appearing in human medicine. While qPCR is certainly more sophisticated than a culture, is qPCR advantageous? Less prone to error? More sensitive and specific? The short answer is “yes” to all of these.
Consider that culture of a pathogen (bacterial, fungal or viral), at its most basic, provides the most welcoming environment and watching for the pathogen to appear. Any number of imperceptible errors can impact the results of a culture; a small temperature excursion, incorrect nutrients provided, incorrect nutrient ratio or a random contaminant that may simply outpace the growth of the actual disease-causing organism. Quantitative PCR amplifies any known pathogen present in a sample and does so in such a way as to provide relative population comparison. Thus, if a normal component of an animal’s microbiome is present in extreme numbers so as to produce pathology, that circumstance is reflected in qPCR while such growth might be routinely dismissed on interpretation of sample culture. Therefore, the huge gap in traditional PCR appears to be bridged as qPCR can determine whether the organism detected is viable.
Accurate assessment of the pathogen in question is not the only factor in effective treatment and diagnostics. In an effort to avoid a “post-antibiotic” era, veterinary medicine must begin to acknowledge the value of more routine sensitivity evaluation prior to administration. If qPCR is the cutting-edge for pathogen determination, then how is antibiotic resistance to be determined without growing a culture?
Enter the era of PCR-determined antibiotic resistance. The ability of a pathogen to resist antibiotics is based on possession of genetic codes. PCR technology can be used to determine whether or not a microbe population has the capability to express resistance. It is true that just because the gene for resistance is present, the microbe is not necessarily resistant. However, if resistance is a possibility, the engaged practitioner simply chooses an antibiotic where resistance is not known to be likely.
While the practice of veterinary medicine remains a practice, in a world of warp-speed vaccine development and administration, it seems that clinical diagnostics for infectious diseases are poised to exceed impulse power. The next big step since the introduction of antibiotics seems to have arrived.
With the introduction of molecular determination of pathogens combined with molecular determination of antibiotic sensitivity into the arsenal of the general practitioner, veterinary medicine is ready to truly enter the war on antimicrobial resistance. This veterinarian’s prognosis for diagnostics in practice is positive! +
