Role of dipA and pilD in Francisella tularensis Susceptibility to Resazurin

Abstract

The phenoxazine dye resazurin exhibits bactericidal activity against the Gram-negative pathogens Francisella tularensis and Neisseria gonorrhoeae. One resazurin derivative, resorufin pentyl ether, significantly reduces vaginal colonization by Neisseria gonorrhoeae in a mouse model of infection. The narrow spectrum of bacteria susceptible to resazurin and its derivatives suggests these compounds have a novel mode of action. To identify potential targets of resazurin and mechanisms of resistance, we isolated mutants of F. tularensis subsp. holarctica live vaccine strain (LVS) exhibiting reduced susceptibility to resazurin and performed whole genome sequencing. The genes pilD (FTL_0959) and dipA (FTL_1306) were mutated in half of the 46 resazurin-resistant (RZR) strains sequenced. Complementation of select RZR LVS isolates with wild-type dipA or pilD partially restored sensitivity to resazurin. To further characterize the role of dipA and pilD in resazurin susceptibility, a dipA deletion mutant, ΔdipA, and pilD disruption mutant, FTL_0959d, were generated. Both mutants were less sensitive to killing by resazurin compared to wild-type LVS with phenotypes similar to the spontaneous resazurin-resistant mutants. This study identified a novel role for two genes dipA and pilD in F. tularensis susceptibility to resazurin.

Low Oxygen Concentration Reduces Neisseria gonorrhoeae Susceptibility to Resazurin

“…We previously showed the phenoxazine dye resazurin has antimicrobial activity against Francisella tularensis and N. gonorrhoeae [14][15][16]. Resazurin is produced from resorcinol (1,3-dihydroxybenzene), which is obtained by the distillation of Brazilwood extract.…”

Genomic Analysis of Antibiotics Resistance in Pathogens

“…This collection also gathers papers on antibiotic resistance of some of the major emerging infections pathogens such as Mycobacteroides abscessus [ 3 ], Klebsiella pneumoniae [ 4 , 5 ], Salmonella sp. [ 6 , 7 ], Francisella tularensis [ 8 ], Acinetobacter baumannii [ 9 , 10 ], or Pseudomonas aeruginosa [ 11 ] and other human pathogens such as Neisseria gonorrhoea [ 12 ], Staphylococcus aureus [ 13 ], or Escherichia coli [ 14 ]. Most of them are high-priority pathogens [ 15 ], according to the National Institute of Allergy and Infectious Diseases, and are globally and medically important pathogens.…”

“…Souder et al have identified a novel role for two genes dipA and pilD in Francisella tularensis (the etiologic agent of Tularaemia) susceptibility to resazurin [ 8 ].…”