Estimating Bacterial Concentrations in Fibrous Substrates Through a Combination of Scanning Electron Microscopy and ImageJ

Conventional signal based micro-analytical techniques for estimating bacterial concentrations are often susceptible to false signals. A visual quantification, therefore, may compliment such techniques by providing additional information and support better management decisions in the event of outbreaks. Herein, we explore a method that combines Electron Microscopy (EM) and image analysis technique and allows both visualization and quantification of pathogenic bacteria adherent even to complex non-uniform substrates. Both the estimation and imaging parameters were optimized to reduce the estimation error (E%) close to ± 5%. The method was validated against conventional microbiological techniques such as optical density, flow cytometry and quantitative real-time PCR (qPCR). It could easily be tailored to estimate different species of pathogens such as E. coli O157, L. innocua, S. aureus, E. faecalis and B. anthracis on samples similar to real-time contamination scenarios. The present method is sensitive enou...