JKAOH Journal of Korean Academy of Oral Health

ISSN(Print) 1225-388X ISSN(Online) 2093-7784


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Original Article

Journal of Korean Academy of Oral Health 2017; 41(4): 290-295

Published online December 30, 2017 https://doi.org/10.11149/jkaoh.2017.41.4.290

Copyright © Journal of Korean Academy of Oral Health.

Red fluorescence of oral bacteria is affected by blood in the growth medium

Seung-Hwa Jeong1,2, Yong-Hoon Yang1, Min-Ah Lee1, Se-Yeon Kim1,2, Ji-Soo Kim1,2

1Department of Preventive and Community Dentistry, 2BK21 PLUS Project, School of Dentistry, Pusan National University, Yangsan, Korea

Received: December 7, 2017; Revised: December 11, 2017; Accepted: December 12, 2017


Objectives: Dental plaque emits red fluorescence under a visible blue light near the ultra-violet end of the light spectrum. The fluorescence characteristics of each microorganism have been reported in several studies. The aim of this study was to evaluate changes in red fluorescence of oral microorganisms that is affected by blood in the culture media. Methods: The gram-positive Actinomyces naeslundii (AN, KCTC 5525) and Lactobacillus casei (LC, KCTC 3109) and gram negative Prevotella intermedia (PI, KCTC 3692) that are known to emit red fluorescence were used in this study. Each bacterium was activated in broth and cultivated in different agar media at 37oC for 7 days. Tryptic soy agar with hemin and vitamin K3 (TSA), TSA with sheep blood (TSAB), basal medium mucin (BMM) medium, and BMM with sheep blood (BMMB) were used in this study. Fluorescence due to bacterial growth was observed under 405-nm wavelength blue light using the quantitative light-induced fluorescence-digital (QLF-D) device. The red, green, and blue fluorescence values of colonies were obtained using image-analysis software and the red to green ratio (R/G value) and red to total RGB ratio (R/RGB value) were calculated for quantitative comparison. Results: The QLF-D images of the AN, LC, and PI colonies showed red fluorescence in all media, but the fluorescence of all bacteria was reduced in TSA and BMM media, compared with in TSAB and BMMB media. Both the R/G and the R/RGB values of all bacteria were significantly reduced in growth media without blood (P<0.001). Conclusions: Based on this in vitro study, it can be concluded that red fluorescence of oral bacteria can be affected by growth components, especially blood. Blood-containing medium could be a significant factor influencing red fluorescence of oral bacteria. It can be further hypothesized that bleeding in the oral cavity can increase the red fluorescence of dental plaque.

Keywords: QLF-D, Red fluorescence, Blood, Dental plaque, Lactobacillus casei, Actinomyces naeslundii, Prevotella intermedia