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Sarah Schmid, DVM, DACVIM (SAIM), is an assistant professor at the University of Tennessee whose latest publication can be found in the November issue of Vet Record. This review evaluates the impact of antibiotics and biotics—including prebiotics, probiotics, and synbiotics—on dysbiosis, a catchall term for any negative change in the gastrointestinal (GI) microbial environment. Here, she covers some of the most important points from that review on what we know about the microbiome in relation to feline and canine GI disease.
What is the most important takeaway for each of the main categories of GI disease (acute uncomplicated diarrhea, acute hemorrhagic diarrhea syndrome, chronic enteropathy, and constipation) you cover in this review article?
Dr. Schmid: Despite being commonly prescribed for the treatment of GI disease, antibiotics confer no benefit in the treatment of acute uncomplicated diarrhea and are rarely indicated for the treatment of chronic enteropathy. Antibiotic administration can be harmful as it results in altered microbial and metabolic profiles that can persist for weeks after cessation of treatment. Furthermore, the indiscriminate use of antibiotics for the treatment of GI disease can lead to the emergence of resistant bacterial strains and delayed recovery of the GI tract. Given these negative implications, antibiotics should be reserved for patients with severe GI disease in which there is suspected to be a loss of gut barrier and bacterial translocation, leading to bacteremia and/or sepsis.
The strongest indication for probiotic use is likely for the treatment of canine acute uncomplicated diarrhea. Probiotics have been shown to decrease the incidence of kennel stress-associated diarrhea in dogs and hasten the return to normal stools in dogs with acute diarrhea, including those with acute hemorrhagic diarrhea syndrome. In cases of canine chronic enteropathy, a lactic acid bacteria mixture (Visbiome) has been shown to improve intestinal epithelial barrier integrity through the upregulation of tight junction protein expression. Finally, in cats with chronic constipation or idiopathic megacolon, administration of a proprietary blend of several strains of Bifidobacterium and Lactobacillus (SLAB51) improved clinical signs.Â
However, what I found most interesting in this study by Rossi et al was that the probiotic blend resulted in restoration of the number of GI pacemaker cells (interstitial cells of Cajal) seen on histopathology after just 3 months of probiotic administration. As feline idiopathic megacolon is characterized by an enlarged colon with little to no motility that is often refractory to pharmacologic intervention, seeing an increase in the number of cells that initiate GI motility is particularly exciting.
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Acute diarrhea: Despite their widespread use, antibiotics show no benefit and should not be recommended. Probiotics, such as Enterococcus faecium (FortiFlora), have shown some benefit in cases of canine kennel stress-associated diarrhea and acute uncomplicated diarrhea.
Acute hemorrhagic diarrhea syndrome: Antibiotics (potentiated amoxicillin with or without metronidazole) fail to shorten hospitalization time, improve daily clinical scores, and reduce mortality. In contrast, probiotics, such as the lactic acid bacteria mixture Visbiome, have been shown to hasten recovery in terms of a dog’s clinical signs and dysbiosis correction.
Chronic enteropathy: Subclassified according to clinical response to diet, antibiotics, and immunomodulatory drugs, cases of chronic enteropathy are often forced to try many different treatments. Thus, empirical antibiotics are fairly common in the treatment of dogs with chronic diarrhea. However, very few dogs respond to antibiotic therapy (5% to 10%), and the majority relapse following antibiotic discontinuation. Thus, dietary management remains the therapy mainstay (50% to 65%). Because of the long-lasting detrimental effects antibiotics have on the GI tract, treatment strategies have shifted to restoring a diverse and functional microbiome through diet and biotics (prebiotics, probiotics, and synbiotics).
Constipation: A disease of poor motility, constipation is treated by the administration of prebiotics (fermentable fibers) and dietary fibers. Probiotics, particularly Visbiome SLAB51, have shown great promise in the treatment of not only constipation but also feline idiopathic megacolon.
Your study points out the importance of optimal formulation, dosage, timing, and duration of biotics. Since this review, have you changed the way in which you recommend and administer biotics?
Dr. Schmid: I have learned that the benefits of probiotics are strain specific. One probiotic might help constipation but have no effect on acute diarrhea. Thus, when selecting a probiotic, it is important to consider the patient’s type of GI disease and if scientific evidence supports its use.
Since writing this review article, I am more likely to pay attention to the bacteria strain in a probiotic and consider whether that strain or another strain is more likely to be beneficial to a specific patient. As many pet owners purchase probiotics on their own, I plan to be more diligent about reviewing the specific product they choose, including the bacteria strains in the probiotic. Knowing that many products labeled as probiotics do not meet the minimum criteria to be called probiotics, I am going to educate my clients on which probiotics they should reach for and why.
Do you have any cautionary words for primary care veterinarians on how they prescribe antibiotics for the treatment of gastrointestinal disease?
Dr. Schmid: Antibiotics are rarely indicated for the treatment of canine and feline gastrointestinal disease and are more likely to do more harm than good. As we have learned more about the gastrointestinal microbiome, we have learned just how harmful antibiotics can be. After antibiotic administration (even if only administered for a week), microbial diversity and richness decline; and those decreased levels can persist several weeks after antibiotic administration has stopped. The indiscriminate use of antibiotics contributes to the spread of antibiotic resistance, which has negative implications for human and animal health. Even patients who initially respond to antibiotic treatment often relapse as soon as antibiotic treatment is discontinued. Moreover, those patients have significant changes to their microbiome, which might lead to additional complications. Many treatment options for feline and canine GI disease are better than antibiotics, backed by scientific evidence, and carry less risk. I recommend that primary care veterinarians focus their treatment plans on diet, prebiotics, probiotics, and synbiotics to restore a diverse and functional microbiome.
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With the compilation of data in this study, did anything surprise you?
Dr. Schmid: Metronidazole has long been prescribed for the treatment of canine diarrhea, yet it was very difficult to find scientific literature investigating its use in canine GI disease. There is not a lot of scientific evidence supporting its use. In addition, when the use of metronidazole has been studied, it has been evaluated most often in combination with another treatment, making it difficult to determine any conferred benefit.
Is there anything we have not covered that you would like our readers to know from this study?
Dr. Schmid: Although our knowledge of the microbiome has grown tremendously in the past decade with the advent of molecular tools, there is still a lot we do not know. Many studies include heterogenous populations and use concurrent treatments that make it difficult to determine the sole impact of probiotics. Furthermore, optimal dose, frequency, and duration of probiotic therapy, which is likely dependent on the disease being treated, is unknown. If a study detected no benefit with probiotic administration to a small group of dogs, that does not mean that probiotic strain will not benefit another group of dogs. We are just uncovering the tip of the iceberg, and I am so excited to see what the future of probiotics holds!
It’s not emphasized in this review article, but new evidence has been released that dogs with immunosuppressant- and antibiotic-responsive chronic enteropathies are being reclassified as food-responsive chronic enteropathies. I want primary care veterinarians to recognize the importance of pursuing multiple diet trials (ideally a minimum of 3) before concluding an enteropathy is not diet-responsive. The impact of diet on the microbiome is often forgotten.
The Study:
Harnessing the microbiome: probiotics, antibiotics and their role in canine and feline gastrointestinal disease.
Schmid SM, Tolbert MK. Vet Rec. doi.org/10.1002/vetr.4915