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Immunity mutation discovered in zoonotic bacteria
The study investigated the response of Staphylococcus aureus to macrophages.
The mutation helps the bacteria survive immune responses and antibiotics.

New research has discovered a genetic mutation, which is helping zoonotic bacteria to develop a resistance to immune system defences and antibiotics.

Researchers from the Roslin Institute studied the response of Staphylococcus aureus, a major pathogen affecting both humans and animals, to immune cells known as macrophages.

The study aimed to discover how the bacteria was avoiding being killed by macrophages, and how it was adapting to immune responses.

Macrophages represent a significant component in the immune system response to S.aureus, and play a major part in disease outcomes. The researchers passaged strains of S.aureus along a macrophage cell line, where it collected mutations.

Exposure to the macrophages saw the bacteria undergo changes to its characteristics over time. Mutations meant that the bacteria developed many of its survival traits, including an ability to grow within immune cells and resist antibiotics.

However these advantages proved to be conditional, with the bacteria losing these mutations when grown in nutrient-rich conditions away from macrophages.

Further research revealed that the phenotype which was contributing to bacterial survival was a new type of small colony variant (SCV). These variants frequently contribute to more persistent, but less virulent, form of the pathogen.

These SCVs are often linked to chronic infections such as osteomyelitis and lung infections in cystic fibrosis patients. The adaptation has also led to the bacteria becoming more resistant to antibiotics, such as vancomycin.

The new model suggests that repeatedly exposing bacteria to macrophages could reveal the conditional way that bacteria adapts to specific niches.

It may also lead to a better understanding of how bacteria can evade the immune system, meaning scientists can consider potential treatment strategies for both humans and animals.

Dr Joana Alves, a research fellow at the Roslin Institute, said: “Our study uncovers a novel adaptation strategy by S. aureus in response to immune challenges, highlighting the remarkable ingenuity of pathogens in evading host defences.

“Our findings demonstrate the power of experimental models to unravel the complex mechanisms underlying bacterial adaptation during infection”

The full study can be found in the journal mBio.

Image © Shutterstock

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Free CPD announced for BVNA members

News Story 1
 Zoetis is to present a CPD event for free to members of the British Veterinary Nursing Association (BVNA).

Led by veterinary consultant Ruth Moxon, the one-hour online session is designed to help veterinary nurses discuss parasiticide options with clients. It will advise on structuring recommendations, factors for product choice and moving away from 'selling'.

'How do you recommend parasite treatments to your clients?' will be presented on Tuesday, 20 May at 7.30pm. It is free for BVNA members, with £15.00 tickets for non-members.

Veterinary nurses can email cpd@bvna.co.uk to book their place. 

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DAERA to reduce BVD 'grace period'

DAERA has reminded herd keepers of an upcoming reduction to the 'grace period' to avoid BVD herd restrictions.

From 1 May 2025, herd keepers will have seven days to cull any BVD positive or inconclusive animals to avoid restrictions being applied to their herd.

It follows legislation introduced on 1 February, as DAERA introduces herd movement restrictions through a phased approach. Herd keepers originally had 28 days to cull BVD positive or inconclusive animals.

DAERA says that, providing herd keepers use the seven-day grace period, no herds should be restricted within the first year of these measures.

Additional measures, which will target herds with animals over 30 days old that haven't been tested for BVD, will be introduced from 1 June 2025.

More information is available on the DAERA website.