My strategy failing me?

When I first started thinking about the Step 1, I was a bit worried about microbiology.  This was partly because I didn't need to know much as part of my coursework, and partly because microbiology was the bane of my existence during undergrad.  So, about six months ago, I spent a couple of days reading Levinson and making notes into First Aid.  At that time I felt I'd learned heaps, but I finally began revising it today.

As I was reading through, I thought, "Wow, this isn't quite as bad as I'd remembered."  Then, I started doing Kaplan questions.  Mother of god.  I got 46% correct on the first question block.  46%?!?  How can this stand?

The thoroughly abrading thing about all of this is that most of the questions I got wrong were related to things I have never before seen!  Did you know Pseudomonas aeruginosa has two elastases called LasA and LasB responsible for ecthyma gangrenosum?  I sure didn't until today.

Did my high-yield review resources let me down?  Or does Kaplan just suck?  Either way, are they preparing me adequately for the USMLE or am I being led into a dark alleyway for mental assault and battery?

Feeling crotchety, --KM