Milk may help bacteria survive against low levels of antibiotics

Sep 08, 2008

Milk may help prevent potentially dangerous bacteria like Staphylococcus from being killed by antibiotics used to treat animals, scientists heard today at the Society for General Microbiology's Autumn meeting being held this week at Trinity College, Dublin.

Bacteria sometimes form structures called biofilms that protect them against antibiotics and the body's natural defences. Now scientists have discovered that one of the most important micro-organisms that causes mastitis in cows and sheep, called Staphylococcus, can evade the animal's defences and veterinary medicines by forming these protective biofilms. Mastitis is an infection of the udder in cattle and sheep. It is often a painful condition for the cows and can even cause death.

"Mastitis is a difficult disease to control. It causes risks for public health if people drink infected milk and is expensive for farmers as it usually causes severe milk production losses, increased treatment costs and means the animals may have to be culled," said Dr Manuela Oliveira from the Faculty of Veterinary Medicine at the Technical University of Lisbon, Portugal. "When the staphylococci produce a biofilm, the structure protects them against host defences and antibiotic treatment, allowing the bacteria to persist in the udder."

In the past, scientists studying mastitis have conducted most of their experiments under laboratory conditions rather than mimicking the conditions found in living animals. This may mean that they have missed important contributory factors. However, Dr Oliveira and her colleagues have used realistic conditions to overcome this problem.

"We have discovered that milk may also protect bacteria against low concentrations of antibiotics – in the presence of milk, three of the five antibiotics tested, penicillin, gentamicin and sulphamethoxazole combined with trimethoprim, were less effective against Staphylococcus when compared with the same experiment performed in the absence of milk," said Dr Oliveira.

The Lisbon team is currently trying to identify the correct antibiotic concentrations needed to stop biofilms forming in the first place and also the concentrations needed to destroy a biofilm that has already formed. The scientists are also looking at the influence of the forces acting inside an udder during milking to see whether these help or hinder the bacteria in producing biofilms.

"This will allow for a better control of staphylococcal mastitis, cut disease costs and give an important improvement in the protection of consumers' health," said Dr Manuela Oliveira. "If we can get the doses right, and the animals are cured quicker, we will have less antibiotic residue in the environment and the risk of bacteria such as Staphylococcus aureus developing and spreading antibiotic resistance is lower."

Source: Society for General Microbiology

Explore further: Birds 'weigh' peanuts and choose heavier ones

Related Stories

Why does rotting food smell bad?

Dec 16, 2014

When food goes bad and starts to become pungent, it is most often due to the growth of spoilage microbes such as bacteria, yeasts and mold. Odors can come from two sources: chemicals that are released from ...

Recommended for you

Birds 'weigh' peanuts and choose heavier ones

1 hour ago

Many animals feed on seeds, acorns or nuts. The common feature of these are that they have shells and there is no direct way to know what's inside. How do the animals know how much and what quality of food ...

Q&A: Why are antibiotics used in livestock?

16 hours ago

Wal-Mart, the world's biggest retailer, is the latest company to ask its suppliers to curb the use of antibiotics in farm animals. Here's a rundown of what's driving the decision: ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.