title: What are the critical steps in processing blood cultures? A prospective audit evaluating current practice of reporting blood cultures in a centralised laboratory serving secondary care hospitals.
abstract: OBJECTIVE
  To assess current procedures of processing positive blood cultures against national standards with an aim to evaluate its clinical impact and to determine the utility of currently available rapid identification and susceptibility tests in processing of blood cultures.
  
  
  METHODS
  Blood cultures from three secondary care hospitals, processed at a centralised laboratory, were prospectively audited. Data regarding processing times, communication with prescribers, changes to patient management and mortality within 30 days of a significant blood culture were collected in a preplanned pro forma for a 4-week period.
  
  
  RESULTS
  Of 2206 blood cultures, 211 positive blood cultures flagged positive. Sixty-nine (3.1%) of all cultures were considered to be contaminated. Fifty per cent of blood cultures that flagged positive had a Gram stain reported within 2 hours. Two (0.99%) patients with a significant bacteraemia had escalation of antimicrobial treatment at the point of reporting the Gram stain that was subsequently deemed necessary once sensitivity results were known. Most common intervention was de-escalation of therapy for Gram-positive organisms at the point of availability of pathogen identification (25.6% in Gram positive vs 10% in Gram negative; p=0.012). For Gram-negative organisms, the most common intervention was de-escalation of therapy at the point of availability of sensitivity results (43% in Gram negatives vs 17.9% in Gram positive; p=0.0097). Overall mortality within 30 days of a positive blood culture was 10.9% (23/211). Antibiotic resistance may have contributed to mortality in four of these patients (three Gram negative and one Gram positive).
  
  
  CONCLUSIONS
  Gram stain result had the least impact on antibiotic treatment interventions (escalation or de-escalation). Tests that improve identification time for Gram-positive pathogens and sensitivity time for Gram-negative pathogens had the greatest impact in making significant changes to antimicrobial treatment.
authors.affiliation: Department of Microbiology, Frimley Park Hospital, Frimley, UK.
authors.forename: Manjula
authors.initials: M
authors.lastname: Meda
authors.affiliation: Department of Microbiology, Royal Surrey County Hospital, Guildford, UK.
authors.forename: James
authors.initials: J
authors.lastname: Clayton
authors.affiliation: Department of Microbiology, Royal Surrey County Hospital, Guildford, UK.
authors.forename: Reela
authors.initials: R
authors.lastname: Varghese
authors.affiliation: Department of Microbiology, St. Peter's Hospital, Chertsey, UK.
authors.forename: Jayakeerthi
authors.initials: J
authors.lastname: Rangaiah
authors.affiliation: Department of Microbiology, St. Peter's Hospital, Chertsey, UK.
authors.forename: Clive
authors.initials: C
authors.lastname: Grundy
authors.affiliation: Department of Microbiology, St. Peter's Hospital, Chertsey, UK.
authors.forename: Farnaz
authors.initials: F
authors.lastname: Dashti
authors.affiliation: Department of Microbiology, Frimley Park Hospital, Frimley, UK.
authors.forename: David
authors.initials: D
authors.lastname: Garner
authors.affiliation: Department of Microbiology, Frimley Park Hospital, Frimley, UK.
authors.forename: Katherine
authors.initials: K
authors.lastname: Groves
authors.affiliation: Department of Microbiology, Frimley Park Hospital, Frimley, UK.
authors.forename: Karen
authors.initials: K
authors.lastname: Fitzmaurice
authors.affiliation: Department of Microbiology, Frimley Park Hospital, Frimley, UK.
authors.forename: E
authors.initials: E
authors.lastname: Hutley
mesh_terms: D016470:Bacteremia / Q000175:diagnosis* / Q000382:microbiology; D000071997:Blood Culture / Q000379:methods* / Q000592:standards*; D006801:Humans; D007753:Laboratories / Q000592:standards*; D008485:Medical Audit; D011446:Prospective Studies; D012107:Research Design
keywords: BACTERAEMIA; BLOOD CULTURE; GRAM STAIN; INFECTIONS