From curiosity to curative- developing Bdellovibrio as living antibiotics between farm and fork

Bdellovibrio are small, human-friendly, predatory bacteria which invade the cells of other pathogenic bacteria (such as ones that give humans food poisoning) and kill them. Bdellovibrio have no activities against human, animal or bird cells but they are naturally good at killing other bacteria. Pathogenic bacteria do not have simple cell surface receptors for Bdellovibrio attachment and invasion and so it is not easy for them to develop resistance to the Bdellovibrio (unlike the situation with conventional antibiotics) Bdellovibrio were discovered in the 1960s and recently we and others have been researching their genes and trying to understand how they may be useful to humans. Previous scientists have published short reports showing that Bdellovibrio has predatory activity against a range of food-borne pathogens, from farm settings, but they usually studied this on food preparation surfaces such as boards or knives, or in foods themselves. No-one has published data on Bdellovibrio treatment of food borne pathogens by Bdellovibrio in farm animals. This leaves Bdellovibrio sitting on the sidelines with much reported potential as an antibacterial agent but no real steps forward in applying it. We wish to do this in our application with human pathogenic Salmonellas including the phage type 4 Salmonella Enteritidis which causes human disease in Europe UK and USA, and in poultry and with bird pathogenic and colonizing strains including Salmonella gallinarum. We have carried out a small pilot project that shows that giving chicks that are colonized with Salmonella, some lab strain Bdellovibrio to drink, does not harm them, but does reduce the numbers of Salmonellas a lot in their intestines. Now we are asking for the funding to be able to study what the best dose of Bdellovibrio is for getting rid of the maximum amount of Salmonellas. How the Bdellovibrio do it exactly inside the chicks and what factors are important, and whether if we use Bdellovibrios we have isolated from inside chickens poultry farms, these ones are better than the lab Bdellovibrio at removing the Salmonellas without harming the chickens, or the people who may go on to cook and eat them. We will work with a mathematical modeller on all the data we collect to calculate what is going on inside each chicken's gut as the Bdellovibrio are killing the Salmonella and to work out how this might prevent infections in flocks of birds. The idea is to develop Bdellovibrio as a real new treatment for human, animal and bird disease and this is the first step.

We are applying to use predatory Bdellovibrio bacteria as a living antibiotic against Salmonella in chickens, particularly timely given recent EU Zoonoses Legislation (Directive 2003/99, Regulation 2160/2003) which requires member states to have National Salmonella in poultry control programmes operational by 2008 and by 2009 no eggs from flocks which are infected with S.Enteritidis will be allowed to be sold into the fresh egg market. We carried out a small, pilot study that proves that our concept that orally delivered Bdellovibrio do kill Salmonella colonizing the intestines of chicks; that the Bdellovibrio do survive gut passage well. We wish to extend that study to titer the efficacy of Bdellovibrio in Salmonella treatment regimen and any longer term effect of Bdellovibrio on bird health and also to test the behaviour of Bdellovibrio mutant strains that we have show to have reduced predation in vitro, in the chicks; analysing and modelling the data gathered to determine the important parameters in the Salmonella reduction process and their possible impact on flock level infections . We will also carry out parallel in vitro predation assays to see whether in vitro assays can predict in vivo predatory behaviour. In pilot isolations from 25 different birds on several different farms, we have found that Bdellovibrio and like bacteria are rare constituents of the normal flora of some, but not all chicken caeca. We will test the prey range and predatory efficiency of these Bdellovibrio-chicken isolates in vitro and if strains with enhanced anti- Salmonella properties, over our existing lab strain, are found; we will test these in vivo. It is our aim to develop predatory Bdellovibrio bacteria as true friendly bacteria, that are safe and effective on the farm for the removal of food-borne infections of birds and also later as treatments for other infections of animals birds and man. This application is the first step along that path.