Would studying the several handouts posted on the Microbe Mission webpage of the Science Olympiad website be enough to prepare for the competition? Are there any other topics that are not in those handouts but are going to be on the test?
The training handouts are awesome, but it's a good rule of thumb to treat them as bare minimum level studying material, especially in a biology event where there's just so much content. I don't think relying on Campbell is a good idea here, either. For Cell Bio, that would have been effective, as the first however many chapters covered nearly everything in adequate detail on the RS level topics. Select sections of microbiology texts are the optimal resource here (as we may as well rename the event "Microbiology Lab".
That highlights a key difference between those two events, though: Cell Bio's topics were narrow enough where you could have confidence at a point that you know what you're doing. Here? There's far less assurance. For example, I sat through a presentation where the presenter said that the only thing you need to know about diseases are the causative agents. A)That's not how the rules are written, and, more importantly, B)that's copy-directly-from-the-cheat-sheet type stuff, which isn't exactly how SO is supposed to go. So, some tournaments will have very easy disease sections, while others will involve analyzing clinical scenarios. This sort of thing applies to other topics, too.
A consequence of this is that some supervisors are going to be unsure of what to put on a test. My B team competed at a tournament recently where the supervisor gave photographs of bacteria and asked them to identify. Yeah, no...there are a couple of causative agents that I actually think are fair game for C division to be able to identify (if only because they have very, very distinctive appearances), but I fear that that won't be the last tournament I come across this.