Gentian violet and ferric ammonium citrate disrupt Pseudomonas aeruginosa biofilms.
OBJECTIVE
Bacterial biofilms are resistant to antibiotics and may contribute to persistent infections including chronic otitis media and cholesteatoma. Discovery of substances to disrupt biofilms is necessary to treat these chronic infections. Gentian violet (GV) and ferric ammonium citrate (FAC) were tested against Pseudomonas aeruginosa biofilms to determine if either substance can reduce biofilm volume.


METHODS
The biofilm volume and planktonic growth of PAO1 and otopathogenic P. aeruginosa (OPPA8) isolated from an infected cholesteatoma was measured in the presence of GV or FAC.


METHODS
OPPA8 and PAO1 expressing a green fluorescent protein plasmid (pMRP9-1) was inoculated into a glass flow chamber. Biofilms were grown under low flow conditions for 48 hours and subsequently exposed to either GV or FAC for an additional 24 hours. Biofilm formation was visualized by confocal laser microscopy and biofilm volume was assayed by measuring fluorescence. Planktonic cultures were grown under standard conditions with GV or FAC. Statistical analysis was performed by Student t test and one-way ANOVA.


RESULTS
GV reduced PAO1 and OPPA8 biofilm volume (P < .01). GV delayed the onset and rate of logarithmic growth in both strains. FAC reduced OPPA8 biofilm volume (P < .01), but did not effect of PAO1 biofilms. FAC had no effect on planktonic growth.


CONCLUSIONS
The efficacy of GV in disrupting biofilms in vitro suggests that it may disrupt biofilms in vivo. The effect of FAC on Pseudomonas aeruginosa biofilms is strain dependent. Strain differences in response to increasing iron concentration and biofilm morphology stress the importance of studying clinically isolated strains in testing antibiofilm agents.
Department of Otolaryngology/Head and Neck Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA.
Eric W
EW
Wang
Gabriela
G
Agostini
Osarenoma
O
Olomu
Daniel
D
Runco
Jae Y
JY
Jung
Richard A
RA
Chole
D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D015169:Colony Count, Microbial; D005290:Ferric Compounds / Q000494:pharmacology*; D005840:Gentian Violet / Q000494:pharmacology*; D006801:Humans; D018613:Microscopy, Confocal; D010033:Otitis Media / Q000188:drug therapy / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification / Q000502:physiology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*
D000891:Anti-Infective Agents, Local; D005290:Ferric Compounds; D000644:Quaternary Ammonium Compounds; D005840:Gentian Violet; C013531:ferric ammonium citrate