title: Learning susceptibility of a pathogen to antibiotics using data from similar pathogens.
abstract: OBJECTIVE
  Selection of empirical antibiotic therapy relies on knowledge of the in vitro susceptibilities of potential pathogens to antibiotics. In this paper the limitations of this knowledge are outlined and a method that can reduce some of the problems is developed.
  
  
  METHODS
  We propose hierarchical Dirichlet learning for estimation of pathogen susceptibilities to antibiotics, using data from a group of similar pathogens in a bacteremia database.
  
  
  RESULTS
  A threefold cross-validation showed that maximum likelihood (ML) estimates of susceptibilities based on individual pathogens gave a distance between estimates obtained from the training set and observed frequencies in the validation set of 16.3%. Estimates based on the initial grouping of pathogens gave a distance of 16.7%. Dirichlet learning gave a distance of 15.6%. Inspection of the pathogen groups led to subdivision of three groups, Citrobacter, Other Gram Negatives and Acinetobacter, out of 26 groups. Estimates based on the subdivided groups gave a distance of 15.4% and Dirichlet learning further reduced this to 15.0%. The optimal size of the imaginary sample inherited from the group was 3.
  
  
  CONCLUSIONS
  Dirichlet learning improved estimates of susceptibilities relative to ML estimators based on individual pathogens and to classical grouped estimators. The initial pathogen grouping was well founded and improvement by subdivision of the groups was only obtained in three groups. Dirichlet learning was robust to these revisions of the grouping, giving improved estimates in both cases, while the group-based estimates only gave improved estimates after the revision of the groups.
authors.affiliation: Center for Model-based Medical Decision Support, Aalborg University, Aalborg, Denmark.
authors.forename: Steen
authors.initials: S
authors.lastname: Andreassen
authors.forename: Alina
authors.initials: A
authors.lastname: Zalounina
authors.forename: Leonard
authors.initials: L
authors.lastname: Leibovici
authors.forename: Mical
authors.initials: M
authors.lastname: Paul
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001419:Bacteria / Q000187:drug effects*; D003428:Cross Infection / Q000188:drug therapy; D019992:Databases as Topic; D024881:Drug Resistance, Bacterial; D006801:Humans; D016013:Likelihood Functions; D008826:Microbial Sensitivity Tests / Q000706:statistics & numerical data
chemical_list: D000900:Anti-Bacterial Agents