This excellent article by Carl Zimmer gives a brief history of the development of antibiotics. It makes the usual points that the microbes within us improve our health and killing them (with antibiotics) can have bad effects. One study found that children given antibiotics had a higher risk of developing inflammatory bowel disease (IBD) later in life. Giving antibiotics to a child younger than one year was especially dangerous — the risk of IBD increased by a factor of 6.
The article makes the minor mistake of taking seriously what researchers say about number of species:
Each of us is home to several thousand [bacterial] species. . . . My own belly button, I’ve been reliably informed, contains at least 53 species.
Counting the number of species inside us is like measuring the length of the coast of England. The more closely you look (in the case of coastlines, the shorter the ruler you use), the larger the number you will arrive at. I’d be surprised if the researchers who count bacterial species adjust for this.
What I found most interesting about the article is it says nothing about fermented foods. Apparently the connection is not so obvious.