A prototype biospecklemeter for microbiological analysis: a starting point for a potential digital-image laser antibiotic susceptibility test

Abstract

Abstract This work describes the design and construction of a low-cost prototype biospecklemeter. In this first report of its applications a microbiological analysis was performed. The relationship between microorganism density, motility and biospeckle activity was evaluated. The aim is to produce a device for research and for student use. The biospecklemeter was constructed on an antivibration table with low-cost materials and accessories and assayed using different microorganisms grown in Mueller–Hinton broth and/or agar as well as urine samples. Three lasers were installed (blue, green and red) as well as two webcams and a charge-coupled device camera. The samples were carried within the wells of a VDRL plate and 5–30 s videos or photographs of reflected light were taken. Video or photo processing was carried out using the method of temporal differences (ImageJ) or generalized differences (ImageDP). It was possible to establish a direct relationship between spectrophotometric absorption, the microbial count and the biospeckle intensity; changes in motility and the effect of antibiotics on bacterial laboratory samples as well as on urine samples were also detected. Finally, with this method colonies of different microorganisms on Mueller–Hinton agar were studied.