Milk reduces effectiveness of antibiotics against bacteria
Posted Nov 21 2008 4:29pm
New research suggests that milk can prevent the protection offered by antibiotics in the treatment of dangerous bacteria such as Staphylococcus.
A study lead by Dr Manuela Oliveira from the Faculty of Veterinary Medicine at the Technical University of Lisbon, Portugal revealed that bacteria can survive antibiotic treatment of conditions like mastitis in cattle when milk is present in the udder. The discovery is important because mastitis in cows is a public health risk if people are exposed to infected milk. Dr Oliveira explained: “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,” Because the disease is very painful for the animal and can lead to death, Dr Oliveira added: “increased treatment costs means the animals may have to be culled.”
Bacteria can produce biofilm structures that form a guard against the body’s immune system and ingested antibiotics. The bacteria, staphylococcus which causes mastitis in cows and sheep may develop protective biofilms which are resistant to antibiotic treatment in the udder. Dr Oliveira said: “When the staphylococci produce a biofilm, the structure protects them against host defences and antibiotic treatment, allowing the bacteria to persist in the udder.”
He continues: “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,”
One of the areas of research focus is on what components within the udder during milking affect the production of biofilms. The research team also hope to identify the exact concentration levels of antibiotics required to prevent biofilms from forming. Their research endeavours to determine the concentrations needed to destroy existing biofilms. According to Dr Oliveira, if better control of staphylococcal mastitis can be asserted, then the cost of treating the disease will be significantly reduced, whilst also offering greater consumer protection. Dr Oliveira said: “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.”
Dr Manuela Oliveira’s research is published in Medical News Today, and was presented at the Society for General Microbiology’s Autumn conference at Trinity College, Dublin.