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The persistence of Bacillus pyocyaneus in pupae and imagines of Musca domestica raised from larvae experimentally infected with the bacillus

Published online by Cambridge University Press:  06 April 2009

A. W. Bacot
A. W. Bacot
Affiliation:
Loughton, Essex
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Extract

In the course of an inquiry into the relation between the bionomics of certain insects and epidemic disease upon which I am engaged, the following question suggested itself to me. In the event of a larva becoming bacterially contaminated by means of its food, is it possible that the resulting pupa and imago will still be infected? The only previous work bearing upon this question with which I am acquainted is that of Faichnie, who writes:

Type
Research Article
Information
Parasitology , Volume 4 , Issue 1 , March 1911 , pp. 68 - 74
Copyright
Copyright © Cambridge University Press 1911

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References

1 1Faichnie, N. (1909). Bacillus typhosus in flies. Journ. Boy. Army Med. Corps xiii. 580–585, 672–675.Google Scholar

1 Strictly speaking, the case in which the adults of the Muscidae develop is not a pupal case but a puparium. It really consists of the larval skin which is not, as usual, moulted but shrinks and becomes hardened by a secretion. The pupal skin itself is of very delicate texture. The connection between the pupa and the outer air is by way of two semicircular openings at one end of the puparium, these openings are converted into efficient filters by an elaborate series of projecting papillae and filaments that would effectively prevent the ingress or egress of fluid for some time or until some suction of air or expulsion of gas took place.

1 In all cases the growth obtained appeared both culturally and microscopically to be pure B. pyocyaneus except that some nine slides showed slight contamination with B. prodigiosus.

1 Later experiments show that if the ends of the puparia are varnished, so as to block the stigmata, that after being allowed to soak in 10% solutions of lysol or formalin for periods np to 39 hours and then in control tubes of sterile broth for further periods up to 14 hours, the pupae will still give a positive result when cracked or pierced in the culture tube. The control tube remains sterile.

1 Since this was written I have devised a simple but efficient method of examining the bacterial content of the pupal interior in M. domestica. The pupa is held lightly between the left thumb and forefinger so that its blunt extremity is free. With a small searing- iron this extremity is seared and at the same time flattened. It is then pierced by a fine capillary pipette controlled by a rubber teat. The pupal contents are stirred up by the extremity of the pipette and finally drawn up into the tube whence they are immediately squirted on to plates. The whole process takes less than a minute to perform.

Recently I have been successful in isolating B. typhosus from pupae the larvae of which have fed on this organism. The experiments will be published shortly.