I have found that finding much of anything in an actual scientific study sort for chickens very difficult.
I do find common ideas among the many articles though.
for vent gleet getting that crop acidified, treating that bum and keeping her clean all pop up.
How to do it all is what varies.
Molasses in the water at 1/3 cup to the gallon for 24 hours to clear the system.
ACV or citric acid in the water to acidify the crop.
A flushing of the bum and a bath (yup enema time)
Metronidazole in the front and the back. Some sites say yes in the bum while others treat topically.
Personally I would treat very aggressively since these dang tough birds like to fall over on us.
https://hoovesandfeathers.wordpress...gleet-clearing-up-messy-vents-in-laying-hens/
http://www.poultrydvm.com/condition/vent-gleet
Scientific?