Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

Delineating the activity of a guanidine functionalized anthranilamide peptidomimetic against ESKAPEE pathogens (104583)

Shyam Mishra (Baishnab) 1 , Rajesh Kuppusamy 1 2 , MUHAMMAD YASIR 1 , Edgar Wong 3 , Alex Hui 1 4 , Mark Willcox 1
  1. Rupert Myer's Building, School of Optometry and Vision Science, UNSW Sydney, Kensington, NSW, Australia
  2. School of Chemistry, UNSW Sydney, Kensington, NSW, Australia
  3. School of Chemical Engineering, UNSW Sydney, Kensington, NSW, Australia
  4. Centre for Ocular Research & Education, School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada

Introduction:

Infections caused by antimicrobial resistant pathogens pose a significant public health challenge warranting the development of novel antimicrobials. This study explored the antimicrobial activity of RK758, a novel guanidine functionalized anthranilamide peptide mimic developed by our laboratory.

 

Methods:

ESKAPEE antibiotic resistant and susceptible pathogens were used. The minimum inhibitory concentration (MIC) of RK758 to isolates was determined by broth microdilution. The effect of RK758 on viability over time, motility, biofilm formation, morphology of cells, and ability to inhibit efflux pumps was tested. The ability of bacteria to become resistant was measured by serial passage at sub-MIC and synergy of RK758 was tested with conventional antibiotics by measuring fraction inhibitory concentrations.

 

Results:

The geometric mean MIC of RK758 was 14.5 µM. The antimicrobial effect of RK758 was time and concentration dependent, with decreases in bacterial numbers from 93% to 64% and 57% at the MIC, and 38% and 31% at 2 X MIC after 30 and 60 minutes incubation, respectively. RK758 at 1/8 of MIC caused reductions in the swimming and swarming motilities of P. aeruginosa strains (p>0.05).  The biofilm tolerance factor-prevention (the ratio of biofilm prevention concentration to MIC) of RK758 against multidrug-resistant (MDR) isolates was 2-8 while that for ciprofloxacin was 1-≥16. Under electron microscopy, the surface of bacteria showed changes in their outer layers. At 0.5XMIC, RK758 inhibited the efflux of minocycline from bacteria. Bacteria did not develop resistance to RK758 during 30-day passage at sub-MIC; however, there were 16-, 32- and 128-fold increases in MIC to ciprofloxacin, colistin and gentamicin under the same passage conditions. RK758 was able to synergise with colistin with K. pneumoniae and P. aeruginosa. There was no antagonism to a range of commonly used antibiotics in different ESKAPEE pathogens.

 

Conclusion:

RK758 showed good antimicrobial and antibiofilm activity against ESKAPEE pathogens, several of which were MDR. Bacteria did not develop resistance to RK758 on repeated challenge to it. Furthermore, it showed no antagonism with the tested conventional antibiotics while synergy was seen in certain cases.

  1. Yasir M, Dutta D, Willcox MD. Comparative mode of action of the antimicrobial peptide melimine and its derivative Mel4 against Pseudomonas aeruginosa. Scientific reports. 2019 May 8;9(1):7063.