April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Effect of biguanide on excystment, proliferation and death of Acanthamoeba strains
Author Affiliations & Notes
  • Marina Roizenblatt
    Department of Ophthalmology and Visual Sciences, Paulista School of Medicine, São Paulo Hospital, Federal University of São Paulo, São Paulo, Brazil
  • Linda C Carrijo-Carvalho
    Department of Ophthalmology and Visual Sciences, Paulista School of Medicine, São Paulo Hospital, Federal University of São Paulo, São Paulo, Brazil
  • Annette S Foronda
    Department of Ophthalmology and Visual Sciences, Paulista School of Medicine, São Paulo Hospital, Federal University of São Paulo, São Paulo, Brazil
  • Fabio R Carvalho
    Department of Ophthalmology and Visual Sciences, Paulista School of Medicine, São Paulo Hospital, Federal University of São Paulo, São Paulo, Brazil
  • Denise Freitas
    Department of Ophthalmology and Visual Sciences, Paulista School of Medicine, São Paulo Hospital, Federal University of São Paulo, São Paulo, Brazil
  • Footnotes
    Commercial Relationships Marina Roizenblatt, None; Linda Carrijo-Carvalho, None; Annette Foronda, None; Fabio Carvalho, None; Denise Freitas, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 5788. doi:
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      Marina Roizenblatt, Linda C Carrijo-Carvalho, Annette S Foronda, Fabio R Carvalho, Denise Freitas; Effect of biguanide on excystment, proliferation and death of Acanthamoeba strains. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5788.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Acanthamoeba keratitis is a sight-threating infection which can progress into the eye, causing corneal ulcer, loss of visual acuity and eventually blindness. There is a lack of a standard therapy. The treatment is based on topical instillation of biguanides and/ or diamidines at higher concentration and these compounds seems to be toxic to corneal cells. The present study was designed to investigate the antimicrobial activity of a biguanide, at a lower concentration, against Acanthamoeba cysts isolated from a severe AK case, comparing the susceptibility pattern with an avirulent strain of the protozoa.

Methods: The study was approved by the local ethics committee. The effect of polyhexamethylene biguanide (PHMB) at 0.02% was evaluated in an avirulent Acanthamoeba strain (ATCC 30011) and a clinical isolate. Induction of death, excystment and proliferation of protozoa at 12 and 72 h were evaluated by quantitative analysis. The experimental procedures were carried out in triplicate. Data were subjected to one-way ANOVA and results were considered statistically significant when p < 0.05.

Results: Our findings demonstrated a reduction of 44.5 and 61.6% in the total number of trophozoites from ATCC 30011 and clinical isolate, respectively, at the time of 12 h. After 72 h, the reduction was 94.9 and 85.4% for ATCC 30011 and the clinical isolate, respectively. Avirulent strain and clinical isolate were equally susceptible to PHMB at 12 h, while the clinical isolate showed increased resistance to PHMB action after 72 h, with a high viability rate.

Conclusions: Differential patterns of resistance against PHMB were demonstrated between Acanthamoeba strains. Data suggest the hypothesis of PHMB acts in the viability and proliferation of trophozoites and not in the inhibition of excystment of the protozoa. Our findings demonstrates the importance of an earlier and specific therapeutic profile and the key role of patient in regular usage of PHMB in order to avoid the eventual occurrence of acquired resistance strain during the treatment for AK. Finally, the results open perspectives about the dosage and frequency of PHMB 0.02% to be used in the treatment of AK.

Keywords: 402 Acanthamoeba • 480 cornea: basic science  
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