title: Systemic and respiratory oxidative stress in the pathogenesis and diagnosis of Rhodococcus equi pneumonia.
abstract: BACKGROUND
  Oxidative stress (OS) is most simply defined as an imbalance between oxidants and antioxidants. Oxidative stress has been suggested to play roles in various equine respiratory diseases and the significance of OS in the pathogenesis of Rhodococcus equi pneumonia is unknown.
  
  
  OBJECTIVE
  To measure and relate biomarkers of OS to lesions consistent with R. equi pneumonia.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Various OS biomarkers were measured from blood and exhaled breath condensate (EBC) samples collected from 26 foals between 1 and 2 months of age (n = 12 cases and n = 14 controls) on 2 Thoroughbred farms endemically affected by R. equi pneumonia. Foals were defined as cases (positive) or controls (negative) based on ultrasonographic evidence of pulmonary abscessation (>15 mm in diameter). Haematology and biochemistry testing was also performed on blood samples collected from the foals. Comparison of biomarkers and key haematological and biochemical markers of inflammation between the groups was performed using 2 sample t tests.
  
  
  RESULTS
  Derivatives of reactive oxygen metabolites (d-ROMs) were significantly greater in case foals than in control foals (P = 0.027) and the oxidative stress index (OSI) was higher in case foals (P = 0.014). Hydrogen peroxide (H2 O2 ) concentrations in EBC were significantly greater in case foals than in control foals (P = 0.002). Meanwhile, there were no significant differences in traditional measures of inflammation between the 2 groups.
  
  
  CONCLUSIONS
  Measuring OS in both blood and EBC provided useful information in the early diagnosis of R. equi pneumonia.
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, New South Wales, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Crowley
authors.forename: E
authors.initials: E
authors.lastname: Po
authors.forename: P
authors.initials: P
authors.lastname: Celi
authors.forename: G
authors.initials: G
authors.lastname: Muscatello
mesh_terms: D000193:Actinomycetales Infections; D000818:Animals; D016022:Case-Control Studies; D006734:Horse Diseases; D018384:Oxidative Stress; D018410:Pneumonia, Bacterial; D016929:Rhodococcus equi
keywords: EBC; H2O2; Rhodococcus equi; biomarkers; foals; horse; oxidative stress