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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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Reporting service for dead wild birds updated

News Story 1
 The Animal and Plant Health Agency (APHA) has updated its online reporting service for dead wild birds.

The new version allows those reporting a dead bird to drop a pin on a map when reporting the location. It also includes a wider range of wild bird species groups to select from when describing the bird.

The online service, which helps APHA to monitor the spread of diseases such as avian influenza, can be accessed here

Click here for more...
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NI chief vet urges bluetongue vigilance

Northern Ireland's chief veterinary officer (CVO) has urged farmers to be vigilant for signs of bluetongue, after the Animal and Plant Health Agency warned there was a very high probability of further cases in Great Britain.

There have been 126 confirmed cases of bluetongue virus serotype 3 in England since November 2023, with no cases reported in Northern Ireland. The movement of live ruminants from Great Britain to Northern Ireland is currently suspended.

According to the Department of Agriculture, Environment and Rural Affairs (DAERA), the virus is most likely to enter Northern Ireland through infected animals or germplasm (semen or ova) being imported.

Brian Dooher, Northern Ireland's CVO, said: "Surveillance for this disease within Northern Ireland has been increased to assist with detection at the earliest opportunity which will facilitate more effective control measures."

Farmers should report any suspicions of the disease to their private veterinary practitioner, the DAERA Helpline on 0300 200 7840 or their local DAERA Direct Veterinary Office.