New Method for Lawsonia intracelullaris Quantification Based on Optical Density by Spectrophotometry

作者：Mirtha E. Suarez-Duarte, Ricardo P. Laub, Renato L. Santos, Carlos Pereira, Talita P. Resende, Matheus Dias Araújo, Paula A. Correia, Jessica C. R. Barbosa, Roberto Maurício Carvalho Guedes · 发表于：Microorganisms · 年份：2025 · DOI：10.3390/microorganisms13030568 · 被引用次数：2 · 研究领域：Veterinary medicine and infectious diseases、Humic Substances and Bio-Organic Studies

Studies investigating the pathogenesis of Lawsonia intracellularis often require bacterial quantification in suspension. However, due to the organism’s fastidious growth requirements—being both intracellular and microaerophilic—traditional quantification methods, such as colony-forming unit counting, are not feasible. Currently, the only widely available method for quantifying L. intracellularis is real-time quantitative PCR (RT-qPCR). Unfortunately, the time required to perform RT-qPCR is incompatible with the bacterium’s limited survival outside its intracellular and microaerophilic environment. As a result, bacterial suspensions are typically quantified subjectively, based on the researcher’s experience for immediate use, with RT-qPCR conducted afterward. Optical density (OD) spectrophotometry is a rapid, although indirect, method of estimating bacterial concentrations in suspension, and it has been applied successfully to fast-growing prokaryotic species. Therefore, the objective of this study was to determine the correlation between RT-qPCR results and the optical density of L. intracellularis suspensions, with the goal of enabling the use of spectrophotometry for immediate bacterial quantification in experimental settings. Optical densities (ODs) were measured at 405 nm and 450 nm, using either a cuvette or microplate, while RT-qPCR was employed to establish a standard curve from samples of known concentration and to quantify the concentration of L. intracellularis in t...