A Bactericidal Principle in Excretions of Surgical Maggots which Destroys Important Etiological Agents of Pyogenic Infections

Abstract

The elimination of bacteria from pyogenic infections must precede permanent healing. That such a phenomenon occurs under the influence of maggot therapy is well known. Baer, in his original report (1929), called the maggots "a viable anti-septic." Later (1931) he had the following to say: "Whatever the bacteria of the original wound, be they aerobes or anaerobes ... the amount begins to diminish from the first application of maggots." Weil and coworkers (1933) made prelimi ary bac-teriological studies of wounds before implantation of maggots, followed by subsequent cultures at each dressing, and found a marked decrease in infection as the treatment progressed. Other workers (Buchman and Blair, 1932; Livingston and Prince, 1932; Myers and Czaja, 1931; Slocum et al., 1933) have obtained the same results. How this remarkable phenomenon is accomplished however, has been only partially shown. Among the factors that contribute to wound disinfection are: 1. The mechanical washing out of bacteria through stimulation of drainage by the maggots; by a, mechanical stimulation of the viable tissue; b, enzymic liquefaction of the necrotic tissue; and c, increase of discharge through dilution by maggot excretions, or a combination of these factors. 2. The destruction of organ-isms in the alimentary tract of the maggots, as has been shown by Robinson and Norwood (1933). 3. The utilization of ne-crotic tissue as maggot food, thus rendering conditions less favor-1 Division of Insects Affecting Man and Animals, Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture. 253 S. W. SIMMONS able for bacterial growth. 4. The rapid development of vascular granulation tissue. It has also been suggested that the increase in pH is a factor. The foregoing factors, although of importance, can hardly ac-count for the almost complete sterility obtained in some infec-tions. The excretions of surgical maggots, which are continually released into the wound, have not heretofore been shown to have bactericidal properties. Livingston and Prince (1932) claimed to have demonstrated bactericidal action with filtered extracts from bodies of crushed maggots. Their work, however, was not substantiated by sufficient evidence, and several investigators (Maseritz, 1934; Robinson and Norwood, 1933; Slocum et al., 1933) have since proved their theory to be wrong. The material used in this investigation is not an extract and is entirely different from that tried by other workers. It consists of the natural elimination products of living maggots, and tests with such material have not been previously reported. The investigation has revealed that a potent bactericide is present in maggot excretions. The substance collected and used in these experiments consisted of the entire elimination products of the maggots, which included fecal matter as well as cutaneous and oral secretions. There is reason to believe, however, that the active principle is contained in the feces. Robinson and Norwood (1933) found the contents of the hind intestine of maggots to be sterile while those of the crop and stomach were heavily contaminated, and their findings have recently been confirmed by Stewart (1934). Duncan (1926) found that the feces of certain insects were sometimes sterile. The substance at present, therefore, is called "maggot excretions," for lack of a more specific name. The preliminary work, herein presented, has been confined to tests of the bactericide on seven species of bacteria, in vitro. Two of these play the principal etiological r6le in pyogenic in-fections, and another is often a dangerous and sometimes fatal secondary invader. All organisms were exposed to the material at a temperature of 370C., unless otherwise designated. The maggots used were