Sheep poo and human skin the latest sources of antibiotic alternatives

13 Feb 2020

Image: © Jonas/

Researchers have discovered an arsenal of new antimicrobials not only on our own skin, but within sheep poo.

The search continues for alternatives to common antibiotics that could very soon be rendered useless due to the rise of antibiotic resistance. Now, researchers from the SFI centre APC Microbiome Ireland have published two papers to the Journal of Bacteriology revealing two new alternatives with significant potential.

The first, nisin J, is an antimicrobial produced from staphylococcal bacteria found on human skin, and the second is actifensin, which is produced by actinomycetes found in sheep faeces. Both of these new antimicrobials fall into a class of small antimicrobial proteins called bacteriocins, which represent versatile alternatives to some commonly used antibiotics.

Nisin J is a strain of bacteria found between human toes, with nisin being used commonly in the food industry as a preservative since 1988. It is also approved by the World Health Organisation as a food additive and has the e-number E234.

Tests have so far shown that nisin J is effective against a range of harmful gram-positive bacteria including MRSA and Cutibacterium acnes, which causes acne. Therefore, this new antimicrobial could be used as an effective alternative to antibiotics in the treatment of skin infections.

Rise of the resistance

“Nisin J is the first nisin to be isolated from a Staphyloccus species and the first produced from a bacterium found on human skin,” said Julie O’Sullivan, the postgraduate student who made the discovery.

“It has eight amino acid changes, compared to nisin A, and is the longest nisin variant found to date; six of these substitutions are unique to nisin J.”

Meanwhile, actifensin is another new bacteriocin found in a strain of Actinomyces ruminicola isolated from sheep faeces. It is the first bacteriocin to be discovered that is produced by Actinomyces ruminicola.

Ivan Sugrue, another postgraduate student who made this particular discovery, said: “Peptides similar to this are known to be produced by higher organisms such as fungi, ticks and even oysters but it was not known that bacteria had such a potent defence mechanism.”

The UN estimated last year that drug-resistant diseases kill approximately 700,000 people globally each year. If no new antibiotic alternatives are discovered soon, in the worst-case scenario, as many as 10m people could die each year by 2050.

Colm Gorey was a senior journalist with Silicon Republic