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Volume 50, Number 1, February 2017

Effects of toluidine blue O (TBO)-photodynamic inactivation on community-associated methicillin-resistant Staphylococcus aureus isolates 

Sung-Pin Tseng, Wei-Chun Hung, Hsiao-Jan Chen, Yu-Tzu Lin, Hung-Sih Jiang, Hao-Chieh Chiu, Po-Ren Hsueh, Lee-Jene Teng, Jui-Chang Tsai


Corresponding author:

Jui-Chang Tsai, Corresponding author. Department of Surgery, Division of Neurosurgery, National Taiwan University Hospital, Room 822, 8th Floor, 7, Chung-Shan South Road, Taipei, Taiwan. 


Background and purpose: 

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized as a leading pathogen and has been shown to be genetically different from the health care-associated MRSA (HA-MRSA). Photodynamic therapy (PDT) is considered a potential alternative method for the treatment of resistant bacterial infections, but the effect of PDT on CA-MRSA is unknown. The purpose of this study was to compare the bactericidal effects of toluidine blue O (TBO) on CA-MRSA and HA-MRSA and investigate the photodynamic inactivation effects of TBO (TBO-PDI) against bacterial virulence factors. 



TBO-PDI effects were determined by measuring the survival fractions for four strains and bactericidal activities for 26 CA-MRSA isolates and 26 HA-MRSA isolates. The influences of TBO-PDI on DNA fragmentation and the activities of protease, lipase, staphylococcal α-hemolysin, and enterotoxin were studied. 



TBO-PDI has effective bactericidal activity against both CA- and HA-MRSA. However, the bactericidal activity of TBO-PDI was significantly higher against HA-MRSA than CA-MRSA isolates. In addition, TBO-PDI treatment using a sublethal TBO concentration led to reduced production of several virulence factors, including protease, lipase, staphylococcal α-hemolysin, and enterotoxin.




Although TBO-PDI is slightly less effective against CA-MRSA than HA-MRSA isolates, TBO-PDI could reduce the production of virulence factors at a sublethal TBO concentration, which would be beneficial for treating CA-MRSA infections. 


Key words:

CA-MRSA, photodynamic inactivation, virulence factors