title: The use of chromogenic bacteria as coloured substitutes for pathogens: a simple strategy during design and development of a new method for sample pretreatment.
abstract: OBJECTIVE
  In the present study, chromogenic (red) bacteria were used to simulate actual target bacteria during set-up and optimization of an isolation process of bacteria, designed for food samples. Isolation of bacteria from food in the context of molecular biological detection of food pathogens is a multistep process. Development of such a separation method requires continuous monitoring of the location of the presumable targets in the sample tubes. Therefore, red-coloured pigmented bacteria were used as substitutes for the actual target bacteria, during the establishment of a new sample preparation technique.
  
  
  RESULTS
  The chromogenic bacteria Micrococcus roseus and Serratia marcescens were confirmed to withstand the physical (e.g. centrifugal forces) and chemical (e.g. lysis buffer composition) conditions required during establishment of the new technique. Furthermore, the suitability of these model bacteria to substitute for the actual target pathogens (Salmonella enterica subsp. enterica serovar Typhimurium and Listeria monocytogenes) was assured by testing the physical properties of the model bacteria with respect to the proposed separation methods.
  
  
  CONCLUSIONS
  Visibility of the pigmented bacteria within the complex sample matrices served to allocate bacterial content during the various steps necessary for finalization of the method protocol. The presumptive bacterial targets can be allocated simply by visualization of their bright red colour silhouetted against the background sample matrix.
  
  
  CONCLUSIONS
  The use of pigmented bacteria as substitutes for actual colourless target bacteria during design and development of a bacterial isolation method is a simple and inexpensive application. It saves a huge amount of time and resources, as the proof of principle of new methods is possible in rapid succession.
authors.affiliation: Christian Doppler Laboratory for Molecular Biological Food Analytics, Veterinärplatz, 1210 Vienna, Austria. peter.rossmanith@vetmeduni.ac.at
authors.forename: P
authors.initials: P
authors.lastname: Rossmanith
authors.forename: K
authors.initials: K
authors.lastname: Frühwirth
authors.forename: B
authors.initials: B
authors.lastname: Süss
authors.forename: E
authors.initials: E
authors.lastname: Schopf
authors.forename: M
authors.initials: M
authors.lastname: Wagner
mesh_terms: D005516:Food Microbiology; D005517:Foodborne Diseases / Q000382:microbiology* / Q000517:prevention & control; D008837:Micrococcus / Q000166:cytology / Q000254:growth & development*; D008954:Models, Biological; D010858:Pigmentation; D011933:Reagent Kits, Diagnostic; D012706:Serratia marcescens / Q000166:cytology / Q000254:growth & development*
chemical_list: D011933:Reagent Kits, Diagnostic