Forsøksdyr: Novel antimicrobial peptides to overcome drug-resistant infections in skin.

Godkjenningsdato 30.04.2018

Multidrug resistant Staphylococcus aureus, Streptococcus pyogenes, Streptococcus dysgalactiae, Trueperella pyogenes Staphylococcus pseudintermedius and Staphylococcus haemoliticus are pathogenic bacteria that can cause skin and mammary gland infections in animals and humans. Our objective is to test the effect of a newly discovered antibacterial peptides (bacteriocins) - garvicin KS and enterocin K1-EJ on infections caused by these pathogens in vivo. In vitro, these bacteriocins showed to be effective against both antibiotic resistant and sensitive bacteria, and work through different mechanisms than traditional antibiotics. Garvicin KS is isolated from a probiotic bacterial strain, and based on our preliminary results, and similarity with other non-toxic probiotics, we expect garvicin KS to be safe for treated individuals. Enterocin K1-EJ is a hybrid molecule made of enterocin K1 and enterocin EJ97 – both are common molecules in human gut. Bacteriocin K1-EJ and garvicin KS were shown to be non-cytotoxic by an independent evaluator. The bacteriocins will be applied on the skin in 20% (w/v) hydroxypropyl cellulose (HPC) – a common, non-toxic emulsion stabilizer (E463). To confirm our preliminary in vitro results, we thus seek to establish mice models to evaluate the effect of the bacteriocins on skin infections caused by pathogenic bacteria mentioned above.
If successful, we will test the bacteriocins in cows with mastitis. In principle, using bacteriocins will reduce the amount of antibiotics in veterinary and decrease the spread of antibiotic resistant bacteria. Since bacteriocins are essentially small proteins, they are not supposed to have as many side effects as antibiotics. If the treatment is successful, the bacteriocin may have a potential for use in human medicine to treat mastitis and bacterial skin infections and at least partly replace some antibiotics in human medicine.
Since immune response to bacteria varies greatly between individual animals, we will use a well established mouse strain - BALB/c female mice between 6 and 8 weeks. For the treatment of the most important skin pathogens – S. aureus and S. pyogenes we will use luminescent-tagged bacteria (transformed with a bacterial luciferase), allowing non-invasive visualization of bacterial infection of the skin during the treatment, thus obtaining better and safer data from each experimental animal. For S. dysgalactiae, T. pyogenes, S. pseudintermedius and S. haemoliticus bacterial infection severity will be measured only by spread of the lesion. No invasive sampling will be done during the experiment.
Number of animals: 78
Severity category of the experiment – moderate. During the experiment mice are likely to experience short-term localized skin pain. Less likely systemic symptoms including fever, flu-like aches. We strive to maintain a stable environment with constant temperature, humidity and light conditions. Temperature and humidity is recorded on a daily basis by using sensors in relevant rack positions. We also minimize traffic in the animal room to reduce stress to the animals. Each cage has a running wheel and house to increase their activity levels and well-being. We underline the importance of avoiding stress in the lab and housing room by e.g. high frequency sounds, sudden movements or non-gentle handling of animals.