title: Rapid antibiotic sensitivity testing and trimethoprim-mediated filamentation of clinical isolates of the Enterobacteriaceae assayed on a novel porous culture support.
abstract: A porous inorganic material (Anopore) was employed as a microbial culture and microcolony imaging support. Rapid Anopore-based antibiotic sensitivity testing (AST) methods were developed to assess the growth of clinical isolates, with the primary focus on testing the response of the Enterobacteriaceae to trimethoprim, but with the method supporting a wider applicability in terms of strains and antibiotics. It was possible to detect the growth of Enterobacter aerogenes after 25 min culture and to distinguish a trimethoprim-sensitive from a trimethoprim-resistant strain with 40 min incubation. MIC(90) determinations were made on Anopore; these were in good agreement with the results from the Vitek 2 and E-test methods. The Anopore method correctly identified sensitive (40/40) and resistant (17/17) strains of the Enterobacteriaceae and other Gram-negative rods within only 2-3 h culture. Additionally, a trimethoprim-resistant subpopulation (10 % of population) could be detected by microcolony formation within 2 h, and a smaller subpopulation (1 %) after 3.5 h. These results suggest that this is a viable approach for the rapid AST of purified strains, and that it may be able to deal with mixed populations. The microscopic examination of microcolonies during AST is an advantage of this method which revealed additional information. Filamentation triggered by trimethoprim was discovered in many species of the Enterobacteriaceae for which this phenomenon has not previously been reported. Filamentation was characterized by heterogeneity in terms of cell length, and also uneven nucleic acid distribution and flattening of damaged cells. The development and application of Anopore-based AST within clinical diagnostics is discussed.
authors.affiliation: Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands.|Department of Medical Microbiology and Infection Control, Jeroen Bosch Hospital, Nieuwstraat 34, 5211 NL, 's-Hertogenbosch, The Netherlands.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Ingham
authors.affiliation: Department of Medical Microbiology and Infection Control, Jeroen Bosch Hospital, Nieuwstraat 34, 5211 NL, 's-Hertogenbosch, The Netherlands.
authors.forename: Maaike
authors.initials: M
authors.lastname: van den Ende
authors.affiliation: Department of Medical Microbiology and Infection Control, Jeroen Bosch Hospital, Nieuwstraat 34, 5211 NL, 's-Hertogenbosch, The Netherlands.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Wever
authors.affiliation: Department of Medical Microbiology and Infection Control, Jeroen Bosch Hospital, Nieuwstraat 34, 5211 NL, 's-Hertogenbosch, The Netherlands.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Schneeberger
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D002516:Ceramics; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008826:Microbial Sensitivity Tests / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D014295:Trimethoprim / Q000494:pharmacology*; D014296:Trimethoprim Resistance
chemical_list: D000890:Anti-Infective Agents; D014295:Trimethoprim