Antimicrobials found in sheep poo and on human skin

Wednesday, 19 February, 2020

Antimicrobials found in sheep poo and on human skin

Irish scientists have discovered two new antimicrobials: Nisin J, produced from staphylococcal bacteria found on human skin, and actifensin, produced by Actinomycetes isolated from sheep faeces.

Antimicrobial resistance poses one of the biggest threats to global health today. Globally, according to the United Nations, drug-resistant infections — caused by superbugs — result in about 700,000 deaths per year. Without effective antibiotics for the prevention and treatment of infections, many of the achievements of modern medicine such as organ transplantations, chemotherapy and surgeries such as caesarean sections become much more dangerous.

The newly discovered antimicrobials fall into a class of small antimicrobial proteins called bacteriocins, which represent versatile alternatives to some commonly used antibiotics. They were found by researchers at the University College Cork’s (UCC) APC Microbiome Ireland SFI Research Centre and Teagasc, the Agriculture and Food Development Authority, and described in two papers in the Journal of Bacteriology.

Nisin J — isolated from Staphylococcus capitis, a strain of bacteria between the human toes — is a type of nisin, commonly used in the food industry as a preservative. Nisin has been used since 1952 and was granted generally regarded as safe (GRAS) status in 1988 by the US Food and Drug Administration (FDA). It is also approved by the World Health Organization (WHO) as a food additive and has the E number E234.

Nisin J was found to have antimicrobial activity against a range of harmful gram-positive bacteria including the superbug MRSA and Cutibacterium acnes, which causes acne. As such, Nisin J and other bacteriocins could contribute to the reduction of antibiotic usage for skin infections.

“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 UCC postgraduate student Julie O’Sullivan. “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.”

Actifensin, meanwhile, is a bacteriocin found in a strain of Actinomyces ruminicola isolated from sheep faeces. It is said to be the first bacteriocin to be discovered that is produced by Actinomyces ruminicola.

“Actifensin has a broad range of antimicrobial activity against pathogens such as MRSA and vancomycin-resistant Enterococcus (VRE),” said UCC postgraduate student Ivan Sugrue. “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.”

Professor Paul Ross, co-research leader at the APC Microbiome Ireland SFI Research Centre and Teagasc, concluded, “The discovery of these latest antimicrobials forms part of the APC’s overall strategy to develop precision biological tools to control harmful bacteria and as such provide efficacious alternatives to antibiotics. As such, we plan to further develop these compounds which have important implications for human and animal health as part of the APC program ‘Microbes to Molecules’.”

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