title: Noise-free accurate count of microbial colonies by time-lapse shadow image analysis.
abstract: Microbial colonies in food matrices could be counted accurately by a novel noise-free method based on time-lapse shadow image analysis. An agar plate containing many clusters of microbial colonies and/or meat fragments was trans-illuminated to project their 2-dimensional (2D) shadow images on a color CCD camera. The 2D shadow images of every cluster distributed within a 3-mm thick agar layer were captured in focus simultaneously by means of a multiple focusing system, and were then converted to 3-dimensional (3D) shadow images. By time-lapse analysis of the 3D shadow images, it was determined whether each cluster comprised single or multiple colonies or a meat fragment. The analytical precision was high enough to be able to distinguish a microbial colony from a meat fragment, to recognize an oval image as two colonies contacting each other, and to detect microbial colonies hidden under a food fragment. The detection of hidden colonies is its outstanding performance in comparison with other systems. The present system attained accuracy for counting fewer than 5 colonies and is therefore of practical importance.
authors.affiliation: Microbio Corporation, Aoba-ku, Sendai, Miyagi, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ogawa
authors.forename: Senshi
authors.initials: S
authors.lastname: Nasu
authors.forename: Motomu
authors.initials: M
authors.lastname: Takeshige
authors.forename: Hisakage
authors.initials: H
authors.lastname: Funabashi
authors.forename: Mikako
authors.initials: M
authors.lastname: Saito
authors.forename: Hideaki
authors.initials: H
authors.lastname: Matsuoka
mesh_terms: D001419:Bacteria / Q000254:growth & development* / Q000302:isolation & purification; D015169:Colony Count, Microbial / Q000379:methods*; D005516:Food Microbiology; D007091:Image Processing, Computer-Assisted; D059008:Time-Lapse Imaging / Q000379:methods* / Q000592:standards