At birth we receive a set of intestinal bacteria from our mothers, that colonize and grow in the intestinal tract and form a community of bacteria that help digest our food, protect us from pathogens, and interact profoundly with our immune system. This community of bacteria shifts a bit when we start to take in solid foods, and again when we go through puberty. But other than that it stays roughly the same throughout our lives. There is a daily circadian rhythm to these bacteria: they sense nutrients; some of them bind to our intestinal lining, and then trigger through the immune system antimicrobial proteins to protect us from foreign bacteria and keep the flora balanced and in check. An ebb and a flow throughout the day, in balance.
This is true for dogs, and for cats, also.
What if the puppy, still a baby really, now is weaned and adopted by their forever family, and either develops loose stools from all this change or is found to have a parasite that integrates into the microbiome such as Giardia or Coccidia?
In days gone by it was automatic to reach for metronidazole, or flagyl to correct the loose stools or to do away with the parasite. Metronidazole is an antibiotic effective specifically in the intestinal tract. It does kill foreign bacteria. But it also kills the normal microbiome community.
This community will be forever altered and never function normally. This puppy will be forever prone to imbalances in their microbiome and have a strong tendency to develop loose stools.
The imbalance in the microbiome will alarm the immune system leading to increased reactivity and a tendency to allergy, and the absence of certain bacteria in the colon will lead to damage of the intestinal lining and chronic colitis. The repercussions are profound and only beginning to be understood.
Later in life, can antibiotic therapy do the same to the established intestinal flora? It stands to reason that antibiotics do not just affect the bacterial infection at which they are targeted but can truly damage and alter the intestinal microbiome leaving the patient vulnerable to intestinal pathogens and activating immune responses leading to chronic inflammation in the body.
We can help with live probiotics to try to fill in the gaps of what is missing in the microbiome. However the probiotics, however beneficial, are usually a Lactobacillus species that really aren’t part of the nascent and normal microbiome of the puppy. Will it stay and colonize? No one really knows. So it can be helpful to give a potent live probiotic to fill in the gaps in the microbiome but there is no guarantee that these bacteria will stay and provide lasting benefit.
Be very cautious then with metronidazole prescribed to your puppy and really consider the risk:benefit from using an antibiotic later in life. There are times and cases when these medications are absolutely necessary but the decision to use them should be made with care.
