Is there a direct antimicrobial effect of botulinum neurotoxin type A?

Abstract

OBJECTIVE • To determine a potential direct antimicrobial effect of botulinum neurotoxin type A (BoNT/A). MATERIALS AND METHODS • A prospective study was carried out using onabotulinumtoxin A (Botox ® ) and abobotulinumtoxin A (Dypsort ® ) in agar diffusion and broth microdilution assays with various clinical urinary tract isolates ( Escherichia coli , Klebsiella pneumoniae , Enterobacter cloacae , Pseudomonas aeruginosa , Acinetobacter baumannii , Citrobacter freundii , Klebsiella oxytoca and Bacillus subtilis ). • Inhibition zones (mm) of bacteria around a disc containing 20 μ L saline with 4 IU of Botox ® were measured in the agar diffusion assay. • Minimal inhibitory concentrations (MICs, IU/mL) of both toxins for all bacteria were determined in the broth microdilution assay after overnight incubation at 35 ° C. RESULTS • There was no inhibition zone in the agar diffusion assays with any bacterial strain. • The microdilution test using Botox ® and Dysport ® showed bacterial growth in all dilutions, i.e. MICs > 20 and > 100 IU/mL for Botox ® and Dysport ® , respectively. CONCLUSIONS • BoNT/A has no direct antimicrobial effect. • The reduced frequency of symptomatic urinary tract infections (sUTIs) in patients with neurogenic detrusor overactivity (NDO) after BoNT/A intradetrusor injections seems to be caused by different indirect mechanisms, which are still not completely understood. © 2012 THE AUTHORS.