Version 1: Antimicrobial Effect of Blue Light on Antibiotic-Sensitive and Drug-Resistant E. coli: A Novel Isotropic Optical Fiber

BACKGROUND 

Orthopaedic oncologic pelvic reconstructions have an elevated risk of infection with gram-negative bacteria. This study evaluates the bactericidal ability of a novel antimicrobial blue light (ABL)-emitting optical fiber on antibiotic-sensitive E. coli (AS-Ec) and ESBL-producing E. coli (ESBL-Ec). 

MATERIALS AND METHODS 

Time-to-kill assays used a 10 mL NaCl solution with a starting inocula of 1x105 CFU/mL for AS-Ec or ESBL-Ec; assays were repeated a minimum of 3 times per strain. Experimental tubes had either 1 optical fiber (20.1 mW/mm; low power [LP]) or 2 optical fibers (40.3 mW/mm; high power [HP]), which delivered 5 wavelengths of ABL over 60 minutes. Control tubes had no optical fibers. 50µL samples taken from each tube at 0, 10, 20, 30 and 60 min were streaked onto agar plates and incubated. CFU/mL was determined. Bactericidal reduction was defined as a 99.9% (≥3 log10) reduction in CFU/mL. One-way ANOVA were conducted. 

RESULTS 

Bactericidal effects were seen for AS-Ec under both LP-ABL and HP-ABL with a log10CFU/mL±SD difference of 3.44±0.35 (p=0.043) and 3.74±0.21 (p=0.048) at 30 min and 20 min, respectively. For ESBL-Ec, while there was a significant reduction in bacterial colony formation, the bactericidal threshold was not reached with a log10CFU/mL±SD difference of only 1.02±0.41 (p=0.034) and 2.53±0.22 (p=0.037) at 60 min for LP-ABL and HP-ABL, respectively. 

CONCLUSIONS 

A novel ABL-emitting optical fiber exhibited bactericidal effects in AS-Ec and a clinically meaningful reduction of ESBL-Ec, providing a promising avenue for the use of ABL as a potential therapy for gram-negative infections.