Assessment of Nosocomial Pneumonia Pathogens Using Quantitative Light-induced Fluorescence-digital

Objectives: Nosocomial pneumonia (NP) is caused by aspiration of respiratory pathogens colonising the oropharynx and upper gastrointestinal tract. Many pulmonary infections are caused by aerobic bacteria in the oral cavity, but are not related to oral diseases. If the causative bacterium is detected in the oral cavity, NP can be prevented. This study is the first attempt to observe the fluorescence of a single strain known to cause NP, induced by using a 405-nm light source.
Methods: The following bacterial strains were assessed: Staphylococcus aureus (SA), Pseudomonas aeruginosa (PA), Acinetobacter baumannii (AB), Klebsiella pneumonia (KP), Escherichia coli (EC), Enterococcus faecalis (EF), and Streptococcus mutans (SM, control group). The bacteria were cultured separately on tryptic soy agar (TSA) at 37 degrees Celsius under aerobic conditions for 72 h. Fluorescence photographs of each agar plate were taken every 12 h using a Quantitative Light-induced Fluorescence-digital (QLF-D) with fixed camera settings. The images were analysed by measuring the red and green value (R/G ratio) at a central point in the colony. The R/G ratios were analysed using One-way ANOVA.
Results: All strains were found to grow on the TSA medium. The R/G ratio of SA was significantly higher than that of other strains. The R/G ratio of SA increased steadily up to 72 h, peaking at 2.47. In addition, AB and EC showed higher red values than green values, and the R/G ratios at 72 h were 1.02 and 1.04, respectively. However, the R/G ratios of EF, KP, PA, and SM were less than 1.0 and were almost constant over 72 h.
Conclusions: In conclusion, among the NP pathogens that were cultured on TSA for 72 h, the R/G ratios of SA, AB, and EC were 1 or more, and those of EF, KP, PA, and SM were less than 1.