Wavelength-normalized spectroscopic analysis of Staphylococcus aureus and Pseudomonas aeruginosa growth rates

Abstract

Optical density (OD) measurements are the standard approach used in microbiology for characterizing bacteria concentrations in culture media. OD is based on measuring the optical absorbance of a sample at a single wavelength, and any error will propagate through all calculations, leading to reproducibility issues. Here, we use the conventional OD technique to measure the growth rates of two different species of bacteria, Pseudomonas aeruginosa and Staphylococcus aureus. The same samples are also analyzed over the entire UV-Vis wavelength spectrum, allowing a distinctly different strategy for data analysis to be performed. Specifically, instead of only analyzing a single wavelength, a multiwavelength normalization process is implemented. When the OD method is used, the detected signal does not follow the log growth curve. In contrast, the multi-wavelength normalization process minimizes the impact of bacteria byproducts and environmental noise on the signal, thereby accurately quantifying growth rates with high fidelity at low concentrations.

Emergence of a dalbavancin induced glycopeptide/lipoglycopeptide non-susceptible Staphylococcus aureus during treatment of a cardiac device-related endocarditis

“…Growth curves were performed by OD600 measurement, using a Tecan Magellan Sunrise Spectrophotometer 49 . Bacterial cultures were grown overnight in Lennox broth (LB) to obtain saturated suspensions.…”

RE-irradiation of silver nanoparticles obtained by laser ablation in water and assessment of their antibacterial effect

“…The growth rates of this bacteria was studied by optical density (OD) measurements. This standard procedure used in microbiology, measures the optical absorbance of a sample at a specific wavelength, to obtain normalized results [34]. The different silver NPs colloids were added (in triplicate) to the wells of a sterile 96-well plate already containing the bacterial suspension in culture media (BHI).…”

“…Taking into account that this method measures the turbidity of bacterial suspensions by means of its absorbance, stablishing that the higher the absorbance, the more bacterial concentration [34]. Values were compared with a positive and a negative control (medium with bacteria but without NPs and medium without bacteria respectively).…”

Evaluation of the secretion of antimicrobial peptides and antimicrobial effect of skin wash in atopic and healthy dogs: a preliminary study

“…Negative control wells contained 100 μL of broth without bacteria and 100 μL of rinsing buffer, whereas positive control wells contained 100 μL of bacterial suspension and 100 μL of rinsing buffer instead of the test antimicrobials. Then the plates were incubated at 35°C for 18–20 h and the optical density (OD) values read at wavelengths of 450, 580 and 630 nm . All values were normalized by subtracting the absorbance of the negative control well from the absorbance of each tested well.…”