A research team at St Vincent's University Hospital in Dublin is searching poultry DNA for proteins that destroy bacteria in order to improve food safety, writes Dick Ahlstrom
Unexpected guests are always a challenge over the holiday season but unwanted guests are even worse, particularly when they arrive at dinner time. Visitors such as Salmonella and Campylobacter particularly come to mind at this time of year.
A research group at St Vincent's University Hospital is studying poultry DNA as a way to keep these guests away from the table.
They are searching for naturally occurring substances that have evolved over time as an immune response to these pathogens.
The Innate Immunity Research Group focus is on chicken rather than the turkey traditionally seen at this time of year. But the choice has more to do with the fact that the chicken's entire genetic blueprint, its DNA sequence or genome, was published in February 2004, explains research team member and PhD candidate, Rowan Higgs.
The 10-strong group, led by Prof Cliona O'Farrelly, who also heads St Vincent's Education and Research Centre, trawled through the entire genome and also searched through a library of RNA rather than DNA, on the lookout for "antimicrobial peptides" - small, naturally-occurring proteins that destroy bacteria.
All species from humans to mice to fruit flies to fungi have these peptides, known as AMPs for short, explains Higgs.
"We all have these AMPs, all organisms have them." They are ubiquitous "because they are part of our innate immune system", the system that protects us from microbes, he says.
Access to the RNA library, and now the full DNA genome, allows scientists to search for the telltale DNA sequences associated with AMPs. The group managed to find 11 novel peptides of interest as a result of the trawl, Higgs explains. "We are trying to find them because they are a natural alternative to antibiotics."
The ready availability of antibiotics allowed poultry farms to increase bird densities while keeping bacterial infestation under control. Many bacterial species quickly developed resistance to these antibiotics, however, which means most chickens and turkeys are awash with unwanted microbes when we buy them.
The peptides offer an alternative to antibiotics and promise a better impact against these organisms.
"It is obvious that bacteria can't form resistance to them as quickly as antibiotics. For that reason they have great potential for use against bacteria," says Higgs.
"Using the chicken genome we identified sequences we recognise as being antimicrobial. The kind of AMPs we are looking at have a very similar structure."
They are quite small, having no more than 60 or 70 amino acids, with the active part only about 40 amino acids long.
They pack a punch, however, and are able to knock holes in the bacterial cell wall to kill the organism.
"Some are very effective and others aren't effective at all depending on the bacteria you are testing," Higgs says.
The variability in effectiveness is probably because they are currently testing against a limited number of bacteria, but it is a rogues' gallery indeed.
It includes Salmonella and Campylobacter, but also the dangerous E coli and the infamous Staphylococcus aureus. Staph aureus can cause food poisoning but has become even more dangerous as methicillin-resistant Staph aureus, the bug that causes infections in hospitals as MRSA.
The work at St Vincent's is therefore important as a way to improve food safety but also for its potential to combat infections in hospital. The small peptides are easily synthesised and could be used to kill off microbe populations without having to resort to antibiotics.
Controlling these infections in poultry production is particularly difficult, says Higgs. "It is down to the fact of the high-end density of poultry where they are kept. They are so densely packed together it is easy for infections to spread."
The good news is that because AMPs are found in all species there are plenty of places to look for new ones.
The discovery of an AMP in a fungus greatly expands the search given there are so many species of fungus to check and so much potential to find AMPs of interest.