title: Sensitivity of Salmonella typhimurium TA97a to the type of agar used for preparation of Vogel-Bonner plates.
abstract: Recent problems with the supply of Difco bacto agar have forced some laboratories to evaluate alternative agars for use in the Salmonella/microsome assay. This led to the independent observation in two laboratories (Boots and Glaxo) that Salmonella typhimurium TA97a is sensitive to certain types of agar that may be used to prepare Vogel-Bonner minimal medium plates. A programme of work was, therefore, undertaken to investigate this phenomenon; 9-aminoacridine hydrochloride (at Boots) and 4-nitro-o-phenylenediamine (at Glaxo) were tested against TA1537 and TA97a using Vogel-Bonner plates prepared with a number of different agars. Three agars (Lab M, Difco Bi-tek and Beckton Dickinson granulated) were identified which, although supporting normal growth of TA1537 revertant colonies, gave much reduced control counts and responses to the mutagens with TA97a. One agar, Becton Dickinson grade A, gave poor responses with TA1537 but produced satisfactory results with TA97a. In contrast to the Vogel-Bonner plates, varying the type of agar used in the top agar overlays had little effect on the responses obtained. On the basis of these comparisons, Becton Dickinson purified agar was selected as a suitable alternative to Difco bacto and it was concluded that laboratories using agars other than these, or purchasing pre-poured plates without specifying the type of agar, should be made aware of potential problems with TA97a.
authors.affiliation: Glaxo Group Research Ltd., Ware, Hertfordshire, UK.
authors.forename: P
authors.initials: P
authors.lastname: Wilcox
authors.forename: D J
authors.initials: DJ
authors.lastname: Wedd
authors.forename: W R
authors.initials: WR
authors.lastname: Williams
authors.forename: C D
authors.initials: CD
authors.lastname: Mee
authors.forename: M R
authors.initials: MR
authors.lastname: O'Donovan
mesh_terms: D000362:Agar; D016368:Frameshift Mutation / Q000187:drug effects; D009152:Mutagenicity Tests / Q000379:methods*; D012486:Salmonella typhimurium / Q000235:genetics / Q000254:growth & development*; D013045:Species Specificity
chemical_list: D000362:Agar