Antibiotics

"What medicines do you have?"
"Three of the neosulfas and verdomycin"
"Give him all three and pray."
"He might be allergic to one of them!"
"He'll be more allergic to dying."

Like other Heinlein Juveniles, Tunnel in the Sky appears to be in a postwar period of exploration and discovery. The "tunnel" refers to a technological advance ("Gates") that allow you to walk literally from Earth to another planet. It has opened up possibilities for colonization across the galaxy. The characters here are high school seniors taking their final exam in Advanced Survival:  Gated onto an uninhabited planet with minimal supplies, they pass if they can get to safety.

(Anyone who wants to become a colonist is required to take the normally college-level class. Earth is becoming crowded enough that leading a colony on uncharted worlds is what the cool kids want to do.)

This quote from the 1955 novel shows some fascination in the availability of cheap and effective antibiotics. The students, who are trying to save a fellow student with a high fever, mention evidently new and improved versions of sulfa drugs and a bacterially derived aminoglycoside. This fascination could be because the first antibiotics were only about 20 years old at the time.

Some of the initial important discoveries were:

1928: Alexander Fleming notices that one of his bacterial cultures has been contaminated by a penicillium mold that inhibits further growth. He conjectures that an antibacterial substance is being produced by the mold.

1931: Bayer chemists begin trials on Prontosil, the first of the sulfa drugs. It is found to be very effective at combatting bacterial infections.

1935: Scientists at the Pasteur Institute determine the active ingredient in Prontosil, sulfanilamide. The compound had been discovered almost 30 years before, making any patents worthless, and removing any hope of massive profits away from Bayer. Soon after, generic sulfas are mass-produced.

1942: The Cocoanut Grove fire in Boston kills 492 people. Survivors are among the first people treated with penicillin, in order to avoid infection in skin grafts.

1943: Streptomycin is first isolated at Rutgers university. Also, a new strain of the penicillium mold - one that yields superior results to Fleming's - is found....on a moldy cantaloupe.

1944: Mass production of penicillin means millions of units are available for the Allied invasion of Normandy.

1946-47: Tuberculosis is shown to be curable using streptomycin, although some side effects are noted.

If you are using The Grid for any of this ... well, you probably aren't, because it hasn't been updated to this point yet....you will see that that the starting point (1928) is between 1927 (Unraveling: Lindbergh and the Spirit of St. Louis) and 1933 (Crisis: The Securities Act of 1933). The Cocoanut Grove fire was not quite a year after Pearl Harbor,  so much of this is happening before World War II. Still, a lot of advancement occurs during this short period.  One could also note that Alexander Fleming is about the only well-known person here, and he shows up during the Third Turning - once the Fourth takes hold, it's all corporations and governments taking a hand.