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

Several studies describe a reduction of symptomatic urinary tract infections in patients with neurogenic detrusor overactivity after intradetrusor injections of botulinum neurotoxin A (BoNT/A).

It was, however, unclear if a direct antibacterial effect of BoNT/A plays a role in this clinical observation. This is the first study to investigate a potential antibacterial effect of two frequently used BoNT/A formulations (i.e. Botox® and Dysport®), providing evidence that BoNT/A does not exert an antibacterial effect on lower urinary tract pathogens.

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 µL 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.

Written by:
Wöllner J, Schmidig K, Gregorini F, Kessler TM, Zbinden R, Mehnert U.   Are you the author?
Neuro-Urology, Spinal Cord Injury Center & Research, University of Zurich; Balgrist University Hospital Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.

Reference: BJU Int. 2012 Aug 9. Epub ahead of print.
doi: 10.1111/j.1464-410X.2012.11414.x


PubMed Abstract
PMID: 22882378

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