Funny you should ask that.
I am sitting here wondering how much the state of modern society's gut bacteria variation/illhealth is due to all those antibiotics we have been fed like sweets for the past 70(?) years.
I mean, time out of mind, gut bacteria populations in humans have been tailored by evolution, diet and cross contamination from lack of hygiene. Then along come antibiotics and whoops, a diabetic epidemic.
Yes, I know, there are thousands of other factors from Vit D deficiency to plastics leaching into the water supplies, to sugar and high fructose corn syrup, to takeaways on every corner and genetics. I am purely speculating here.
But bacteria are opportunists. And if you blast a digestive tract with strong antibiotics, it kills off all the bugs, both good and bad. The first bacteria to repopulate are the ones that flourish the best in the barren, convalescent environment of that particular gut. They are not necessarily the bugs that will most benefit the long term health of the gut owner.
How many courses of antibiotics have YOU (aimed at everyone, not just pleinster) had in your life? I am guessing I have had around 7, but only 1 as an adult.