«So John went back to the hospital and spent a month on powerful antibiotics pumped directly into a vein near his heart.»

This is not «extremely common».

Sure, but if you want to water the claim down to the idea that only extreme doses of antibiotics have noticeable effect sizes then its not a relevant claim to 99.99% of the population.

No it is not, but ignoring the part about the severe infection require extended hospitalization and trying to reduce it all to “antibiotics” is extremely disingenuous.

Given that antibiotics are common but extreme infections and extended hospitalizations are not, why would anyone focus on the antibiotics as the root cause?

Not all antibiotics are created equal nor do they affect gut bacteria the same. There isn’t a singular scale for antibiotic power. Often, antibiotics are given via vein because they aren’t absorbed from the gastrointestinal tract, for example. This doesn’t tell us anything about the magnitude of impact on gut bacteria relative to an antibiotic that actually starts its journey in your gut.

This is a complicated case. Reducing the entire complicated episode to “it was the antibiotics” is extremely reductionist.

Antibiotics refer to a group of drugs. Eating food from the supermarket will expose a child to antibiotics. Different classes of antibiotics have a lifelong effects while common ones are quickier to recover from.