MOLECULAR AND METABOLIC TYPING OF RESIDENT AND TRANSIENT FLUORESCENT PSEUDOMONAD FLORA FROM A MEAT MINCER

Nine spots on a meat mincer in a large catering facility were sampled four times over a three-month period after routine cleaning and disinf ection. Spot 2 carried a significantly higher average microbial load t han the other spots and was the only spot with a persistent population of fluorescent pseudomonads. The predominant type of fluorescent pseu domonads produced a yellow diffusible pigment and were always found in turkey meat. Since turkey was also the last type of meat minced on ea ch working day, it was considered the likely source of these bacteria on the mincer. Sixty-three yellow-fluorescing pseudomonad strains from unminced turkey and 17 strains from mincer spot 2 after mincing, clea ning, and disinfection were subjected to fingerprint analysis by rando m amplification of polymorphic DNA (RAPD) and by analysis of the assim ilation patterns of 95 carbon sources using the Biolog system. Cluster analysis of the RAPD and the metabolic fingerprints revealed that all the mincer strains formed a homogeneous cluster, exclusive of all the turkey strains which displayed a higher degree of heterogeneity. Six strains isolated 1 week earlier and six strains isolated 11 weeks earl ier from spot 2 were also subjected to RAPD analysis. Their fingerprin ts fell within the existing cluster of 17 spot 2 strains. These result s suggest the existence on mincer spot 2 of an endemic flora of fluore scent pseudomonads, probably in the form of a biofilm. The genetic and physiological homogeneity of this flora, as opposed to the het erogen eity of the raw meat flora, indicates that only a fraction of the raw meat population of P. fluorescens is successful in forming biofilm in this environment.