Itachi and Kisame should mid diff s1.
-None of the Sannin have a chance at damaging his Susanoo, so they shouldn't even try it. The only thing that will work is Frog Song, but Jiraiya and/or elder toads won't live long enough to actually get it off.
-Kisame is in the ocean, so he can just merge with Samehada (without hindering Itachi w/ Water Dome) and attack the Sannin from under the water. They won't be able to catch him due to his speed, and every single hit skewers them with his bone like appendages while absorbing their chakra at the same time, and B was finished after a few hits. None of them have chakra levels that even come close to B's.
-Depending on how hard they put on the pressure, Jiraiya might not even make it to Sage Mode, but even if he does. All his Ninjutsu is tanked by any level of Susanoo V3 and up, or Kisame just sucks it up with Samehada. Frog Call can paralyze them, but Susanoo would still protect them from anything the Sannin tried to do during that interval.
-Orochimaru's Zetsu techniques are useless except for his spores. Clones are too weak to do anything, and does Mayfly even work on the water? Doubt it. Anyway, spores. Spores aren't even as useful as they could be since Kisame has his own absorption to counter, and they can't even get Itachi past any Susanoo above a Ribcage. His regular techniques shouldn't even be mentioned here due to Itachi's presence. Susanoo fodderizes any and all summons, and then Orochimaru gets sealed away by Totsuka when the opportunity arises.
Tsunade adds little to this fight here. She can buff Jiraiya's Ninjutsu, but all she will do is give Kisame more power.
So at the end of the day, Susanoo+underwater attacks=Dead Sannin. S2 goes the same, but Kisame will have to take Jiraiya's Rasengan with Samehada since V2 might not tank without trouble, and taking Orochimaru out will be a little more annoying than usual due to lacking Totsuka, but Itachi would still easily manage. He'd just have to rely on Tsukuyomi. Tsunade, once again, adds little to nothing here.