Effect of temperature on biofilm growth in the presence of an antimicrobial peptide

The aim of this study was to investigate the effect of simulated human body temperatures, more specifically hypothermia and the febrile response, on Staphylococcus epidermidis biofilm formation in the presence of the human cathelicidin antimicrobial peptide LL-37. LL-37 has been shown to inhibit bacterial biofilm formation and also plays an important role in innate immunity. Staphylococcus epidermidis (ATCC® 35984™) causes intraveneous-catheter sepsis.

A biofilm formation solid-surface assay was performed in tissue culture-treated microtiter plates using Staphylococcus epidermidis clinical strain (ATCC® 35984™), and plates were individually incubated for 20 hours at 35°C, 37°C, and 39°C. Results indicate that LL-37 inhibits biofilm formation significantly at all temperatures, but when compared with the control, biofilms formed in the presence of LL-37 at 35°C showed the lowest percent decrease in the amount of biofilm present as LL-37 concentration increased, while 39°C showed the highest, meaning the least amount of biofilm was present at 39°C, and the most at 35°C. Furthermore at the minimal inhibitory concentration (MIC) of LL-37, biofilms formed at the other temperatures were significantly different to the hypothermic temperature in the presence of LL-37.

Reasons for this include the temperature specificity of mammalian proteins, and it can be assumed that hypothermic temperatures (35°C) are detrimental to LL-37's anti-biofilm activity.

These findings suggest possible immune system suppression and increased susceptibility to biofilm-related infections at hypothermic body temperatures. Findings also reiterate LL-37’s therapeutic potential, and its role at the peak of an immune response.