Model For Destruction Of Bacteria In The Midgut Of Blow Fly Maggots1

Abstract

A 5-log destruction of gram-positive and gramnegative bacteria in the acid midgut of the blow fly maggot, Calliphora vicina Robineau-Desvoidy, has been reported. This paper describes 3 different models which employ various physical and biotic factors known to be present in the maggot gut, in order to reproduce this destruction in vitro. Two of the models which simulated gut conditions by incorporating combinations of low pH, proteolytic enzymes and partial anaerobiosis failed to reproduce the kill observed in the maggot. A third model satisfies the in vivo requirement of rapid kill, broad-spectrum effect and acid-dependent activity. It consists of 3 fractions obtained from 15-day broth filtrates of Proteus mirabilis which differ in molecular size and activity. The active agents have properties which distinguish them from known bacteriocins and are named Mirabilicides. They resist proteolysis, are thermostable and are active only below pH 4.5. Their possible significance in the digestive tract of the maggot is discussed.