title: Towards a Standardized Method for Broth Microdilution Susceptibility Testing of Haemophilus parasuis.
abstract: Currently, there is no agreed method available for broth microdilution susceptibility testing of Haemophilus parasuis, one of the most important bacterial pathogens in pig production. Therefore, the aim of this study was to develop a method that could be easily performed by diagnostic laboratories and that appears suitable for a harmonized susceptibility testing. Growth determinations using one type strain and three field isolates revealed no visible growth of H. parasuis in media which have proven to be suitable for susceptibility testing of fastidious organisms. Therefore, a new medium, cation-adjusted Mueller-Hinton broth (CAMHB) plus NADH and sterile filtered heat-inactivated chicken serum, was developed. The reproducibility of MICs obtained in this medium was evaluated and statistically analyzed, considering a model with two different variables (precondition of five identical MICs and MIC mode accepting a deviation of ±1 dilution step, respectively). No significant differences for both variables were seen between two time points investigated and between results obtained with the recently proposed test medium broth (TMB). Nearly all MICs of quality control strains were in the acceptable range. Subsequently, 47 H. parasuis isolates representing 13 serovars were tested with the newly developed medium and TMB. Statistical analysis of all isolates and 15 antimicrobial agents and antimicrobial combinations showed no significant difference between MICs obtained in supplemented CAMHB and TMB. Because of a simplified implementation in routine diagnostic and a lower chance of interference between medium components and antimicrobial agents, supplemented CAMHB is recommended with an incubation time of 24 h.
authors.affiliation: Institute for Food Quality and Food Safety, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Prüller
authors.affiliation: Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, EcoSciences Precinct, Dutton Park, Queensland, Australia.
authors.forename: Conny
authors.initials: C
authors.lastname: Turni
authors.affiliation: Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, EcoSciences Precinct, Dutton Park, Queensland, Australia.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Blackall
authors.affiliation: Department of Biometry, Epidemiology and Information Processing, WHO Collaborating Centre for Research and Training in Veterinary Public Health, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Beyerbach
authors.affiliation: Institute for Food Quality and Food Safety, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
authors.forename: Günter
authors.identifier: 0000-0003-1931-2701
authors.initials: G
authors.lastname: Klein
authors.affiliation: Department of Biometry, Epidemiology and Information Processing, WHO Collaborating Centre for Research and Training in Veterinary Public Health, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
authors.forename: Lothar
authors.initials: L
authors.lastname: Kreienbrock
authors.affiliation: Innovative Veterinary Diagnostics Laboratory, Hannover, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Strutzberg-Minder
authors.affiliation: Federal Office of Consumer Protection and Food Safety, Berlin, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Kaspar
authors.affiliation: Institute for Food Quality and Food Safety, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
authors.forename: Diana
authors.initials: D
authors.lastname: Meemken
authors.affiliation: Institute for Food Quality and Food Safety, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany corinna.kehrenberg@tiho-hannover.de.
authors.forename: Corinna
authors.initials: C
authors.lastname: Kehrenberg
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003470:Culture Media / Q000737:chemistry; D044137:Haemophilus parasuis / Q000187:drug effects*; D008826:Microbial Sensitivity Tests / Q000379:methods* / Q000592:standards*; D015203:Reproducibility of Results; D013552:Swine
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media
keywords: Haemophilus parasuis; MICs; TMB; broth microdilution; fastidious organism; supplemented CAMHB; susceptibility testing