Vagina MuseumToday, we'd like to show you what is probably the most deadly object in our collection: a tampon. Specifically, a Rely brand tampon, on sale between 1975 and 1980 in the USA.
In the 1970s, a combination of new synthetic materials and huge market competition led to an arms race among tampon manufacturers. There was a drive to be the most absorbent, the most leak-proof. Rely tampons, manufactured by Procter & Gamble, were highly absorbent, and expanded wide to prevent leaks. They quickly became a market leader owing to the innovative design and super absorbency.
Meanwhile, in the late 1970s, something else happened: a new syndrome was identified and named. Paediatrician James K. Todd reported an illness among childen aged 8-17. The childen had developed a condition after infection with Staphylococcus Aureus. He suspected toxins caused by the bacteria. He called the disease Toxic Shock Syndrome (TSS)
Once TSS was named and described, physicians across the USA began to notice it. And they spotted something unusual: the vast majority of cases were recorded in women, and onset of symptoms tended to take place within a few days of their periods.
An investigation was launched in 1980, and identified that menstruation-related TSS was caused by tampons. And a September 1980 report by the CDC identified that up to 75% of these cases were caused by one specific brand of tampon: Rely.
The thing about Rely brand tampons is that the manufacturers had inadvertently designed the perfect medium for helping S. aureus proliferate, and get its toxins into the bloodstream. A number of factors contributed to this.
An important thing to know about S. aureus is that it is frequently found in the vagina in small quantities. This isn't an infection, per se. The population is kept in check by the vaginal microbiome, and it lives there reasonably harmlessly. However, something very absorbent going into the vagina can shift the balance of the natural moisture of the vagina, which affects vaginal flora.
Rely brand tampons were *incredibly* absorbent. They could reportedly hold 20 times their own weight in fluid. They also had a unique design which essentially prevented anything getting out of the vagina while wearing it. (image from Rely's own leaflet)
The high absorbency of Rely tampons dried the vagina out fairly comprehensively, and due to dryness and the girth and flared tip of the tampons when expanded, this caused small abrasions in the vaginal walls - the perfect entrance for toxins produced by S. aureus to get into the bloodstream.
In addition, Rely's unique design consisted of a gel-like substance called carboxymethylcellulose and beads of polyester. It later turned out that the gel-like substance acted like a plate of agar jelly for S. aureus to grow, and the beads provided increased surface area for bacterial growth.
Bacteria can't proliferate quite so well if the tampon doesn't stay in for too long. However, given its super absorbency (and being reportedly very uncomfortable to remove), these tampons likely weren't changed very frequently.
Rely's own information leaflet suggested changing "at least once a day", i.e. leaving it in for up to 24 hours.
Kevin Karhan 
@vagina_museum and now realize that bacteria under ideal conditions have a "Generation Time" (aka. average time until they double) of 5-30 minutes, and if we assume 30 minutes for example, we get 2 generations per hour or a 4x increase.
- Which means 24x2=48 generations per 24 hours = 248 bacteria ( or 281.474.976.710.656 to be precise) from a single one.
Making TSS a statistical inevitability worse than shoving uncleaned, repeatedly used anal toys into a vagina. (Which noone should do!)
- This is also why there are hygenic stickers espechally on underwear aiming at women!
Jesse McClure 
Did you misplace a trillions indicator and / or powers of 10?
Using your numbers of (unchecked) doubling every 30 minutes would, after 24 hours, result in 248 TRILLION times as many bacteria.
[NB bacterial overpopulation would make the conditions not "ideal" for the bacteria itself, and thus this doubling rate probably wouldn't continue throughout a full day.]
@jmcclure @vagina_museum thanks for picking that up.
Granted, that number of bacteria could not exist within a tampon as they'd exceed the volume of it and the very finite amount of "growth media" and increasing amount of toxic metabolic products of said bacteria will naturally impose caps on their population.