Break

Overuse and lack of novel antibiotics has led to resistant phenotypes of bacteria especially in the developing world with limited access to healthcare. Unfortunately, difficulty in innovation and minimal return on investment for development of antibiotics have caused a lack of novel antibiotics for treatment of bacterial infections. (1) Antimicrobial peptides (AMPs) synthesized by bacteria called bacteriocins hold great promise as potential scaffolds for antibiotics due to their antibacterial activity. Here we tested bacterial resistance against a novel synthetic bacteriocin with cationic properties, syn-safencin. A known resistance mechanism against cationic antibiotics in gram positive bacteria is charge modification in the cell wall through the D-alanylation of lipotechoic acids (DA – LTA) to repel cationic antibiotics. We measured the effect of this resistance mechanism against syn-safencin by monitoring the dltABCD operon encoding the genes responsible for this resistance. We were able to quantify the relative expression using a reverse transcription – real time PCR (qRT – PCR) approach. The expression fold changes of mRNA transcripts were calculated using the CT method where CT is the cycle threshold value obtained from qPCR analysis. The results did not show any significant expression fold changes when treated with syn-safencin compared with the vehicle control of 10% DMSO. These results suggest that the DA – LTA is not a mechanism of resistance of syn-safencin, and other mechanisms involving surface charge modification should be monitored for resistance. Finding the mechanisms of resistance against synthetic bacteriocins will allow for the design optimization of peptide candidates that account for known resistance mechanisms.

(1) Fischbach, M. A. 2010, 1089 (2009).