Biofilms of Candida spp. from the ocular conjunctiva of horses with reduced azole susceptibility: a complicating factor for the treatment of keratomycosis?
OBJECTIVES
This study aimed to assess the biofilm-forming ability of Candida spp. from the ocular conjunctiva of horses and to investigate the antifungal susceptibility of these biofilms.


PROCEDURES
Initially, the biofilm-forming ability of 15 strains was assessed by crystal violet staining, which reveals the fungal biomass adhered to the polystyrene plates, and scanning electron microscopy. Then, the minimum inhibitory concentrations (MICs) of amphotericin B, fluconazole, itraconazole, and caspofungin were initially determined against strains in planktonic form. Afterward, antifungal susceptibility of mature biofilms was evaluated by exposing them to 10 × MIC and 50 × MIC of the tested drugs, followed by the assessment of their metabolic activity, using the oxidoreduction indicator XTT. Results were analyzed through ANOVA and Tukey's post-test, and P-values below 5% led to significant conclusions.


RESULTS
Eight strains produced biofilms and were classified as strong (1/15), moderate (3/15) and weak (4/15) producers, according to the amount of crystal violet retained by the adhered fungal biomass. Biofilm metabolic activity of one C. tropicalis did not decrease after exposure to the tested antifungals, while biofilm metabolic activity of five strains was reduced by amphotericin B, but not the other drugs. One C. parapsilosis sensu stricto and one C. glabrata showed significant reduction in biofilm metabolic activity after exposure to fluconazole, itraconazole, and caspofungin, but not amphotericin B.


CONCLUSIONS
The results demonstrate that Candida from the ocular conjunctiva of horses can pose as a risk to animal health as they are capable of forming biofilms, which are commonly involved in fungal keratitis.
['Brilhante|Raimunda Sâmia Nogueira|RSN|', 'Bittencourt|Paula Vago|PV|', 'de Souza Collares Castelo-Branco|Débora|D|', 'de Melo Guedes|Glaucia Morgana|GM|', 'de Oliveira|Jonathas Sales|JS|', 'Alencar|Lucas Pereira|LP|', 'de Aguiar Cordeiro|Rossana|R|', 'Pinheiro|Mariana|M|', 'Nogueira-Filho|Evilázio Fernandes|EF|', 'de Aquino Pereira-Neto|Waldemiro|W|', 'Sidrim|José Júlio Costa|JJC|', 'Rocha|Marcos Fábio Gadelha|MFG|']
D000666:Amphotericin B D000818:Animals D000935:Antifungal Agents D001393:Azoles D018441:Biofilms D002175:Candida D000077336:Caspofungin D003228:Conjunctiva D054714:Echinocandins D015821:Eye Infections, Fungal D015725:Fluconazole D006734:Horse Diseases D006736:Horses D017964:Itraconazole D007634:Keratitis D055666:Lipopeptides D008826:Microbial Sensitivity Tests
biofilm Candida spp horses antifungal susceptibility microbiota yeasts