Forsøksdyr: Novel antimicrobials to treat skin infections caused by multidrug resistant bacteria.

Godkjenningsdato 13.05.2020

Godkjenningsperiode 13.05.2020-13.05.2022

Multidrug resistant Staphylococci, Streptococci and Enterococci are pathogenic bacteria that can cause skin infections in animals and humans. We plan to test the effect of topical application of antibacterial peptides, also known as bacteriocins in a mouse model of skin infection. The bacteriocins are: enterocin K1-EJ, enterocin EJ97, garvicin KS all chemically synthesized with purity >95%, micrococcinP1 purified to 99% and semi-purified garvicin KS produced by Lactococcus garvieae by fermentation in milk. In vitro, these bacteriocins are effective against both antibiotic resistant and sensitive bacteria that will be used in the mouse model against multidrug-resistant bacteria. Preliminary results in vitro by the use of cultured skin cells also indicate that the bacteriocins are not cytotoxic and hence safe for skin treatment. We also plan to use the bacteriocins in combination with conventional antibiotics to reduce the amount of the latter in animal treatment.
If successful, we plan to test the bacteriocins in domestic animals with skin infections. Our goal, by using bacteriocins, is to reduce the amount of antibiotics needed in veterinary medicine and hence decrease the spread of antibiotic resistant bacteria. If the animal treatments are successful, these experiments may in the future be extended to human use.
For these experiments we will use a well established inbred mouse strain - BALB/c female mice between 6 and 8 weeks, where the pathogenic bacteria are inoculated onto wounds made by scraping the skin with a scalpel blade. The most important skin pathogen - Staphylococcus aureus, is tagged with luciferase to allow non-invasive visualization of severity of bacterial infection of the skin during the phase of infection and treatment. For the rest of the bacteria, treatment efficacy is assessed only by harvesting bacteria from the skin wound at the time of termination and by counting the number of colonies on agar plates (CFU counting).
Number of animals: 200 BALB/c mice
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. In our laboratory 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-necessary handling of animals.