title: Campylobacter growth rates in four different matrices: broiler caecal material, live birds, Bolton broth, and brain heart infusion broth.
abstract: BACKGROUND
  The objective of this study was to characterise Campylobacter growth in enrichment broths (Bolton broth, brain heart infusion broth), caecal material (in vitro), and in the naturally infected live broilers (in vivo) in terms of mean lag periods and generation times as well as maximum growth rates and population (cell concentration) achieved.
  
  
  METHODS
  Bolton and brain heart infusion broths and recovered caecal material were inoculated with 10 poultry strains of Campylobacter (eight Campylobacter jejuni and two Campylobacter coli), incubated under microaerobic conditions, and Campylobacter concentrations determined periodically using the ISO 10272:2006 method. Caeca from 10 flocks, infected at first thinning, were used to characterise Campylobacter growth in the live birds. Mean generation times (G) (early lag to exponential phase) were calculated using the formula: G=t/3.3 logb/B. Mean lag times and µmax were calculated using the Micro Fit(©) Software (Version 1.0, Institute of Food Research). Statistical comparison was performed using GENSTAT ver. 14.1 (VSN International Ltd., Hemel, Hempstead, UK).
  
  
  RESULTS
  The mean lag periods in Bolton broth, brain heart infusion broth, caecal material, and in the live bird were estimated to be 6.6, 6.7, 12.6, and 31.3 h, respectively. The corresponding mean generation times were 2.1, 2.2, 3.1, and 6.7 h, respectively; maximum growth rates were 0.7, 0.8, 0.4, and 2 generations h(-1) and the maximum populations obtained in each matrix were 9.6, 9.9, 7.8, and 7.4 log10 CFU/g, respectively.
  
  
  CONCLUSIONS
  This study provides data on the growth of Campylobacter in a range of laboratory media, caecal contents, and in broilers which may be used to develop predictive models and/or inform science-based control strategies such as the maximum time between flock testing and slaughter, logistical slaughter, and single-stage depopulation of broiler units.
authors.affiliation: Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland.|UCD School of Veterinary Medicine, University College Dublin, Dublin, Ireland.
authors.forename: Tara
authors.initials: T
authors.lastname: Battersby
authors.affiliation: Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland.
authors.forename: Desmond
authors.initials: D
authors.lastname: Walsh
authors.affiliation: UCD School of Veterinary Medicine, University College Dublin, Dublin, Ireland.
authors.forename: Paul
authors.initials: P
authors.lastname: Whyte
authors.affiliation: Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland; declan.bolton@teagasc.ie.
authors.forename: Declan J
authors.initials: DJ
authors.lastname: Bolton
keywords: Campylobacter; Growth rates in vivo and in vitro; flock thinning; foodborne pathogen