Sure. It's hard to imagine it in the context provided. How does a frog make a "mighty swing against two adjacent enemies" with its bite attack?
I would just say it quickly snaps a fast bite at each enemy (really two bites) but still use the Swipe rules: one attack roll compared against each enemy, one damage roll applied to each enemy you hit.
Make sense? Probably not.
But what I definitely would not do is make some ruling that an Animal Totem barbarian cannot use the Swipe class feat. Don't take away players' options because the "fluff" description text seems incompatible with that character's current situation. Instead, alter that "fluff" in some way to make it plausible or, if you can't, then make it comical, and allow the ability to work:
"While raging in your frog totem, your mouth grows way, way bigger than any humanoid could possibly imagine. You open your mouth so wide that you can simultaneously bite two adjacent enemies with a single ginormous froggy bite!"