+ Models
MYCMED-499; No. of Pages 2 Journal de Mycologie Médicale (2014) xxx, xxx—xxx
Available online at
ScienceDirect www.sciencedirect.com
´DACTEUR LETTER TO THE EDITOR/LETTRE AU RE Melatonin inhibits biofilm formation in Candida parapsilosis La me ´latonine inhibe la formation du biofilm de Candida parapsilosis Sir, Candida are commensal microbial flora in human oral cavity, gastrointestinal tract and urinogenital system. However, they can turn virulent and cause both superficial and deep-seated infections (candidiasis) in immunosuppressive patients or individuals who are undergoing prophylaxis or antimicrobial chemotherapy. Severe cases of candidiasis can be lethal, with morbidity and mortality rates as high as 60% [1]. Conventional arsenal of antifungal agents includes polyenes, azoles, and echinocandins. However, they have poor pharmakinetics or severe side effects. In addition, emergence of resistant strains is frequently encountered in clinical settings [2]. Therefore, there is a dire need for novel antifungal agents. Melatonin (N-acetyl-5-methoxytryptamine) is an indole hormone that is responsible for a variety of cellular and biological processes, including natural sleeping, antiinflammation, regulation of circadian rhythms, anti-oxidation, and immunomodulation. The immune regulatory effects of melatonin on fungal infections have been demonstrated in a rat model of Candida sepsis [5]. Another study showed that melatonin reduced oxidative stress during candidiasis [3]. In light of the antifungal activity of melatonin against Candida species, the present study was designed, for the first time, to investigate the in vitro effects of melatonin against Candida parapsilosis biofilms. C. parapsilosis ATCC 22019, obtained from the archival collection of Oral BioSciences, Faculty of Dentistry, was routinely grown on YPD agar (1% yeast extract, 2% peptone, 2% dextrose, 2% agar) overnight at 30 8C. Fungal cells were harvested, washed twice with phosphate-buffered saline (PBS), and resuspended in yeast nitrogen base (YNB) medium at 107 cells/mL (standard cell suspension). Melatonin (Sigma—Aldrich) was dissolved in dimethyl sulphoxide (DMSO). The final concentration of DMSO in all assays was 1%. Candida biofilms were prepared by adding 200 mL of the standard cell suspension
into pre-sterilized, polystyrene, flat-bottomed 96-well microtitre plates (Iwaki), and incubated at 37 8C with agitation (80 rpm) for 1.5 h. After adhesion, the wells were washed twice with PBS to remove unattached fungal cells, followed by addition of 200 mL of fresh YNB medium containing different concentrations of melatonin (from 0.1 mM to 200 mM). The plates were incubated at 37 8C with agitation for an additional 24 h. YNB medium containing 1% DMSO was included as control. The viability of the fungal cells was assessed semi-quantitatively by a colorimetric XTT reduction assay [4] using spectrophotometric measurement at 492 nm (SpectroMax 340, Molecular Devices). All assays were performed in duplicates in two independent occasions. We found that melatonin inhibited biofilm formation in C. parapsilosis by 48% at 12.5 mM (P < 0.05). Biofilm formation is one of the important virulent traits of Candida for host invasion. Fungal cells embedded in the highly organized biofilm architecture are less susceptible to antifungal agents [1,2]. The potent anti-biofilm effects of melatonin against C. parapsilosis suggest this compound would be promising in treating biofilm-related fungal diseases. Further studies are warranted to investigate the anti-biofilm effects of melatonin using in vivo models of candidiasis with indwelling catheters.
Disclosure of interest The authors declare that they have no conflicts of interest concerning this article.
References [1] Ghannoum MA, Rice LB. Antifungal agents: mode of action, mechanisms of resistance, and correlation of these mechanisms with bacterial resistance. Clin Microbiol Rev 1999;12: 501—7. [2] Morschhäuser J. Regulation of multidrug resistance in pathogenic fungi. Fungal Genet Biol 2010;47:94—106. [3] Terrón MP, Paredes SD, Barriga C, Ortega E, Rodriguez AB. Comparative study of the heterophil phagocytic function in young and old ring doves (Streptopelia risoria) and its relationship with melatonin levels. J Comp Physiol B 2004;174:421—7. [4] Tsang PWK, Bandara HMHN, Fong WP. Purpurin suppresses Candida albicans biofilm formation and hyphal development. PLoS One 2012;7:e50866.
http://dx.doi.org/10.1016/j.mycmed.2014.05.003 1156-5233/# 2014 Elsevier Masson SAS. All rights reserved.
Please cite this article in press as: Yang HP, et al. Melatonin inhibits biofilm formation in Candida parapsilosis. Journal De Mycologie Médicale (2014), http://dx.doi.org/10.1016/j.mycmed.2014.05.003
+ Models
MYCMED-499; No. of Pages 2
2 [5] Yavuz T, Kaya D, Behcet M, Ozturk E, Yavuz O. Effects of melatonin on Candida sepsis in an experimental rat model. Adv Ther 2007;24:91—100.
c
Technological and Higher Education Institute of Hong Kong, Room 412, 20A Tsing Yi Road, Tsing Yi Island, Hong Kong1 *
a
b
c*
H.P. Yang , P.C.S. Tsang , P.W.K. Tsang a Oral BioSciences, Faculty of Dentistry, The University of Hong Kong, 5/F., Prince Philip Dental Hospital, 34, Hospital Road, Sai Ying Pun, Hong Kong b Oral Diagnosis and Polyclinics, Faculty of Dentistry, The University of Hong Kong, 5/F., Prince Philip Dental Hospital, 34, Hospital Road, Sai Ying Pun, Hong Kong
Corresponding author E-mail address: [email protected] (P.W.K. Tsang) 1 Present address. Received 17 January 2014 Accepted 28 may 2014
Please cite this article in press as: Yang HP, et al. Melatonin inhibits biofilm formation in Candida parapsilosis. Journal De Mycologie Médicale (2014), http://dx.doi.org/10.1016/j.mycmed.2014.05.003
MYCMED-499; No. of Pages 2 Journal de Mycologie Médicale (2014) xxx, xxx—xxx
Available online at
ScienceDirect www.sciencedirect.com
´DACTEUR LETTER TO THE EDITOR/LETTRE AU RE Melatonin inhibits biofilm formation in Candida parapsilosis La me ´latonine inhibe la formation du biofilm de Candida parapsilosis Sir, Candida are commensal microbial flora in human oral cavity, gastrointestinal tract and urinogenital system. However, they can turn virulent and cause both superficial and deep-seated infections (candidiasis) in immunosuppressive patients or individuals who are undergoing prophylaxis or antimicrobial chemotherapy. Severe cases of candidiasis can be lethal, with morbidity and mortality rates as high as 60% [1]. Conventional arsenal of antifungal agents includes polyenes, azoles, and echinocandins. However, they have poor pharmakinetics or severe side effects. In addition, emergence of resistant strains is frequently encountered in clinical settings [2]. Therefore, there is a dire need for novel antifungal agents. Melatonin (N-acetyl-5-methoxytryptamine) is an indole hormone that is responsible for a variety of cellular and biological processes, including natural sleeping, antiinflammation, regulation of circadian rhythms, anti-oxidation, and immunomodulation. The immune regulatory effects of melatonin on fungal infections have been demonstrated in a rat model of Candida sepsis [5]. Another study showed that melatonin reduced oxidative stress during candidiasis [3]. In light of the antifungal activity of melatonin against Candida species, the present study was designed, for the first time, to investigate the in vitro effects of melatonin against Candida parapsilosis biofilms. C. parapsilosis ATCC 22019, obtained from the archival collection of Oral BioSciences, Faculty of Dentistry, was routinely grown on YPD agar (1% yeast extract, 2% peptone, 2% dextrose, 2% agar) overnight at 30 8C. Fungal cells were harvested, washed twice with phosphate-buffered saline (PBS), and resuspended in yeast nitrogen base (YNB) medium at 107 cells/mL (standard cell suspension). Melatonin (Sigma—Aldrich) was dissolved in dimethyl sulphoxide (DMSO). The final concentration of DMSO in all assays was 1%. Candida biofilms were prepared by adding 200 mL of the standard cell suspension
into pre-sterilized, polystyrene, flat-bottomed 96-well microtitre plates (Iwaki), and incubated at 37 8C with agitation (80 rpm) for 1.5 h. After adhesion, the wells were washed twice with PBS to remove unattached fungal cells, followed by addition of 200 mL of fresh YNB medium containing different concentrations of melatonin (from 0.1 mM to 200 mM). The plates were incubated at 37 8C with agitation for an additional 24 h. YNB medium containing 1% DMSO was included as control. The viability of the fungal cells was assessed semi-quantitatively by a colorimetric XTT reduction assay [4] using spectrophotometric measurement at 492 nm (SpectroMax 340, Molecular Devices). All assays were performed in duplicates in two independent occasions. We found that melatonin inhibited biofilm formation in C. parapsilosis by 48% at 12.5 mM (P < 0.05). Biofilm formation is one of the important virulent traits of Candida for host invasion. Fungal cells embedded in the highly organized biofilm architecture are less susceptible to antifungal agents [1,2]. The potent anti-biofilm effects of melatonin against C. parapsilosis suggest this compound would be promising in treating biofilm-related fungal diseases. Further studies are warranted to investigate the anti-biofilm effects of melatonin using in vivo models of candidiasis with indwelling catheters.
Disclosure of interest The authors declare that they have no conflicts of interest concerning this article.
References [1] Ghannoum MA, Rice LB. Antifungal agents: mode of action, mechanisms of resistance, and correlation of these mechanisms with bacterial resistance. Clin Microbiol Rev 1999;12: 501—7. [2] Morschhäuser J. Regulation of multidrug resistance in pathogenic fungi. Fungal Genet Biol 2010;47:94—106. [3] Terrón MP, Paredes SD, Barriga C, Ortega E, Rodriguez AB. Comparative study of the heterophil phagocytic function in young and old ring doves (Streptopelia risoria) and its relationship with melatonin levels. J Comp Physiol B 2004;174:421—7. [4] Tsang PWK, Bandara HMHN, Fong WP. Purpurin suppresses Candida albicans biofilm formation and hyphal development. PLoS One 2012;7:e50866.
http://dx.doi.org/10.1016/j.mycmed.2014.05.003 1156-5233/# 2014 Elsevier Masson SAS. All rights reserved.
Please cite this article in press as: Yang HP, et al. Melatonin inhibits biofilm formation in Candida parapsilosis. Journal De Mycologie Médicale (2014), http://dx.doi.org/10.1016/j.mycmed.2014.05.003
+ Models
MYCMED-499; No. of Pages 2
2 [5] Yavuz T, Kaya D, Behcet M, Ozturk E, Yavuz O. Effects of melatonin on Candida sepsis in an experimental rat model. Adv Ther 2007;24:91—100.
c
Technological and Higher Education Institute of Hong Kong, Room 412, 20A Tsing Yi Road, Tsing Yi Island, Hong Kong1 *
a
b
c*
H.P. Yang , P.C.S. Tsang , P.W.K. Tsang a Oral BioSciences, Faculty of Dentistry, The University of Hong Kong, 5/F., Prince Philip Dental Hospital, 34, Hospital Road, Sai Ying Pun, Hong Kong b Oral Diagnosis and Polyclinics, Faculty of Dentistry, The University of Hong Kong, 5/F., Prince Philip Dental Hospital, 34, Hospital Road, Sai Ying Pun, Hong Kong
Corresponding author E-mail address: [email protected] (P.W.K. Tsang) 1 Present address. Received 17 January 2014 Accepted 28 may 2014
Please cite this article in press as: Yang HP, et al. Melatonin inhibits biofilm formation in Candida parapsilosis. Journal De Mycologie Médicale (2014), http://dx.doi.org/10.1016/j.mycmed.2014.05.003
