Antimicrobial Blue Light Inactivation of Polymicrobial Biofilms.

Raquel Ferrer-Espada,Xueping Sharon Goh,Tianhong Dai,Xiaojing Liu

doi:10.3389/fmicb.2019.00721

Raquel Ferrer-Espada, Xueping Sharon Goh + Show 2 more

Open Access

https://doi.org/10.3389/fmicb.2019.00721

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Abstract

Polymicrobial biofilms, in which mixed microbial species are present, play a significant role in persistent infections. Furthermore, polymicrobial biofilms promote antibiotic resistance by allowing interspecies transfer of antibiotic resistance genes. In the present study, we investigated the effectiveness of antimicrobial blue light (aBL; 405 nm), an innovative non-antibiotic approach, for the inactivation of polymicrobial biofilms. Dual-species biofilms with Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) as well as with P. aeruginosa and Candida albicans were reproducibly grown in 96-well microtiter plates or in the CDC biofilm reactor for 24 or 48 h. The effectiveness of aBL inactivation of polymicrobial biofilms was determined through colony forming assay and compared with that of monomicrobial biofilms of each species. aBL-induced morphological changes of biofilms were analyzed with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). For 24-h old monomicrobial biofilms formed in 96-well microtiter plates, 6.30-log10 CFU inactivation of P. aeruginosa, 2.33-log10 CFU inactivation of C. albicans and 3.48-log10 CFU inactivation of MRSA were observed after an aBL exposure of 500 J/cm2. Under the same aBL exposure, 6.34-log10 CFU inactivation of P. aeruginosa and 3.11-log10 CFU inactivation of C. albicans were observed, respectively, in dual-species biofilms. In addition, 2.37- and 3.40-log10 CFU inactivation were obtained in MRSA and P. aeruginosa, dual-species biofilms. The same aBL treatment of the biofilms developed in the CDC-biofilm reactor for 48 h significantly decreased the viability of P. aeruginosa monomicrobial and polymicrobial biofilm when cocultured with MRSA (3.70- and 3.56-log10 CFU inactivation, respectively). 2.58-log10 CFU inactivation and 0.86-log10 CFU inactivation was detected in MRSA monomicrobial and polymicrobial biofilm when cocultured with P. aeruginosa. These findings were further supported by the CLSM and SEM experiments. Phototoxicity studies revealed a no statistically significant loss of viability in human keratinocytes after an exposure to 216 J/cm2 and a statistically significant loss of viability after 500 J/cm2. aBL is potentially an alternative treatment against polymicrobial biofilm-related infections. Future studies will aim to improve the efficacy of aBL and to investigate aBL treatment of polymicrobial biofilm-related infections in vivo.

Highlights

Microorganisms are prone to forming biofilms, surfaceassociated microbial communities that are extremely resistant to antimicrobials and the immune system (Costerton et al, 1999)
ABL Inactivation of Monomicrobial and Polymicrobial Biofilms Grown in 96-Well Microtiter Plates
We investigated the efficacy of 405 nm antimicrobial blue light (aBL) for the treatment of P. aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA), and C. albicans in monomicrobial and polymicrobial biofilms formed in 96well microtiter plates and the CDC biofilm reactor

Summary

Introduction

Microorganisms are prone to forming biofilms, surfaceassociated microbial communities that are extremely resistant to antimicrobials and the immune system (Costerton et al, 1999). Polymicrobial biofilms, in which mixed microbial species are present, are the dominant form of microbial life in nature (Harriott and Noverr, 2011; DeLeon et al, 2014). The gram-negative pathogen Pseudomonas aeruginosa is commonly found in mixed infections with the polymorphic fungus Candida albicans or the gram-positive bacterium Staphylococcus aureus (Harriott and Noverr, 2011; DeLeon et al, 2014). P. aeruginosa and S. aureus, on the other hand, have frequently been isolated from chronically infected wounds, chronic suppurative otitis media, indwelling medical devices, abnormal airways such as those in cystic fibrosis and other chronic obstructive lung diseases (Yadav et al, 2017)

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