Real-time quantification of Staphylococcus aureus in liquid medium using infrared thermography

We previously showed that infrared thermography (IRT) could be used to quantify viable Escherichia coli, a representative gram-negative bacterium, in liquid growth media. Here, we evaluated the ability of IRT to enumerate a viable representative gram-positive organism, Staphylococcus aureus. We found that the energy content (EC) of the media was strongly positively correlated (r = 0.999) to measured viable counts of S. aureus ranging from 85 colony-forming units (CFU)/ml to ∼4 × 108 CFU/ml. The EC of S. aureus was ∼2-fold higher than that of E. coli at comparable cell concentrations suggesting that IRT may be used to distinguish genera.