The integrity of proteoliposomes targeted to a model biosurface

Surface-sterilized larvae were incubated with nutrient broth cultures of P-fimbriate E. coli. Immunofluorescence microscopy techniques employing monoclonal antibodies [mouse IgG anti-(E. coli P-fimbriae)] revealed that E. coli attach to the larval surface. Transmission electron microscopy also implied that E. coli adhere to the larval surface (Fig. 1). Further experimental work implied that surface-sterilized larvae excrete bacteria from their own intestinal tracts. This was suggested by the fact that a mixed growth of bacteria was obtained following inoculation of 'sterile' larvae onto bloodagar plates. The invasive filariform larvae do not feed, but the rhabditiform larvae in an earlier state of the parasite life cycle are ravenous feeders. Thus, if they ingest enteric bacteria while feeding in the human gut, then it could well be the case that enteric bacteria are excreted by the now transformed and disseminated filariform larvae. Septicaemia may also develop due to enteric bacteria escaping from the bowel when the invasive filariform larvae penetrate the gut wall. Such an investigation into this proposed mechanism was not feasible during this study, but there is no reason to discount it as a possibility. There have been several reports in the literature of helminths acting as vectors of microbial diseases. This has been clearly demonstrated in agriculture with plant parasite nematodes and the microflora of the rhizosphere (Poinar & Hansen, 1986). Enteric bacteria have been associated with human parasite nematodes in several instances, but a vector relationship has only been suggested (Woodruff, 1968). The frequency with which bacterial infections complicate disseminated strongyloidiasis suggests that enteric bacteria can be carried in or on the disseminated larvae, but up until now the precise mechanisms have never been elucidated. Our results suggest that the hypothesis that S . stercorulis larvae can act as vectors of enteric bacteria is indeed valid.