Never mind medical knowledge- if you don’t have someone who can tell the diference between edible and non-edible plants and fungi you are going to have major issues.
A LOT of medication came about through trial and error- error in this case being synonymous with death. Sure willow bark will give you aspirin and foxgloves will give you digitalis, but extracting the drug correctly and getting the doses calibrated correctly will probably kill a few patients along the way.
Your presumably survivors won’t know how to card, spin, or weave wool, nor how to tan leather and fur or turn flax or cotton into usable thread. Dying of exposure might be a more pressing issue if they can’t make new clothes or blankets (I can’t see a situation where libraries and pharmacies are hit but the clothes shops survive unscathed).
I think the first of your survivors who delivers a baby is going to have problems- 10% of women in some countries today die in pregnancy or during childbirth.
If your survivors can’t do much more than simple first aid they aren’t going to be able to deliver and resuscitate a newborn, repair a perineal tear or stop a post-partum bleed.
I was thinking about this a while ago…imho, what you need is simple plot-driven luck. When they need to do something, it miraculously happens. When you are trying to build drama, they fail. Think about how/when the Millennium Falcon decided to work, when it didn’t, and how it helped move the plot along.
I would suggest that the basic thing to retain would be the Scientific Method. A population of 150 isn’t large enough to rebuild medical science. They’re going to be too busy surviving. And by what do you mean ‘no technological equipment’? No clothes? No worked metals (knives, saws, etc)? Since there’s no paper, they’ll have to use papyrus, if there are suitable reeds nearby and they think of it. And what are they going to use for ink?
Actually, it didn’t. The Scientific Method is a very recent invention. Before that knowledge was trial and error mixed in with mythology, lore, lies, and rumour. Knowledge - often faulty - was passed down from master to apprentice.