Field Guide: Morphometric Visualization and Characterization of Selected Foodborne Pathogens Using Advanced Imaging Techniques

This paper aims to present the phenotypic characteristics, such as length, width, circular diameter, volume, surface area to cross-sectional area ratio, surface uniformity, and surface texture, of the foodborne pathogens Salmonella enterica serovar Agona, Salmonella enterica serovar Enteritidis, Listeria monocytogenes, and Campylobacter jejuni. It is a novel “field-guide” presentation of the observable morphological characteristics of these four species in the form of a Dichotomous Key. Phenotypic values of the pathogens were measured using a high-accuracy, nano-level-resolution 3D laser confocal scanning microscope. All samples were fixed with glutaraldehyde and stained with methylene blue, ensuring morphological preservation. The images of the pathogens were captured under various imaging modes, including 3D, laser, and transmission electron microscopy resolutions. Results show that these pathogens exhibit distinct morphological and surface properties, with Campylobacter jejuni showing unique features. The dichotomous key shows a simplified way of classifying selected foodborne pathogens from their morphometric properties. The morphometric measurements, in many instances first reported in the literature, and images provide a readily observable way to identify and classify microorganisms, allowing researchers to potentially study evolutionary relationships, assess species diversity, and understand how organisms interact with their environment, especially when genetic information is limited or difficult to obtain.