Milk may help bacteria survive against low levels of antibiotics

September 8, 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: Novel antibiotic resistance gene in milk

Related Stories

Novel antibiotic resistance gene in milk

April 27, 2017

Researchers of the University of Bern have identified a new antibiotic resistance gene in bacteria from dairy cows. This gene confers resistance to all beta-lactam antibiotics including the last generation of cephalosporins ...

Some cows may be predisposed to subacute ruminal acidosis

April 25, 2017

Cattle with subacute ruminal acidosis suffer from a number of low-level ailments that affect productivity. A research team led by University of Illinois scientists has documented changes in pH, microbiome, and rumen epithelial ...

Raw milk advocates push to expand legalized sales

April 21, 2017

Raw milk advocates' efforts to expand availability across the U.S. have not slowed despite health officials' assertions that it's dangerous to drink milk that hasn't been heated to kill bacteria.

Recommended for you

Jupiter's complex transient auroras

May 25, 2017

Combined observations from three spacecraft show that Jupiter's brightest auroral features recorded to date are powered by both the volcanic moon Io and interaction with the solar wind.

0 comments

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.