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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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Charities' XL bully neutering scheme closes

News Story 1
 A scheme that helped owners of XL bully dogs with the cost of neutering has closed to new applications due to high demand.

The scheme, run by the RSPCA, Blue Cross, and Battersea, has helped 1,800 dogs and their owners after XL bullies were banned under the Dangerous Dogs Act.

In England and Wales, owners of XL bully dogs which were over one year old on 31 January 2021 have until 30 June 2024 to get their dog neutered. If a dog was between seven months and 12 months old, it must be neutered by 31 December 2024. If it was under seven months old, owners have until 30 June 2025.

More information can be found on the Defra website. 

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News Shorts
Avian flu cattle outbreak spreads to tenth US state

Cattle in two dairy herds in Iowa have tested positive for highly pathogenic avian influenza (HPAI), making it the tenth state in the USA to be affected by the ongoing outbreak of the disease in cattle.

Since March 2024, more than 80 herds across the USA have been affected by the virus and three dairy workers have tested positive. Authorities have introduced measures to limit the spread of the virus and farmers have been urged to strengthen their biosecurity protocols.

Mike Naig, Iowa secretary of agriculture, said: "Given the spread of highly pathogenic avian influenza within dairy cattle in many other states, it is not a surprise that we would have a case given the size of our dairy industry in Iowa.

"While lactating dairy cattle appear to recover with supportive care, we know this destructive virus continues to be deadly for poultry."