title: Transmission dynamics of gram-negative bacterial pathogens in the anesthesia work area.
abstract: BACKGROUND
  Gram-negative organisms are a major health care concern with increasing prevalence of infection and community spread. Our primary aim was to characterize the transmission dynamics of frequently encountered gram-negative bacteria in the anesthesia work area environment (AWE). Our secondary aim was to examine links between these transmission events and 30-day postoperative health care-associated infections (HCAIs).
  
  
  METHODS
  Gram-negative isolates obtained from the AWE (patient nasopharynx and axilla, anesthesia provider hands, and the adjustable pressure-limiting valve and agent dial of the anesthesia machine) at 3 major academic medical centers were identified as possible intraoperative bacterial transmission events by class of pathogen, temporal association, and phenotypic analysis (analytical profile indexing). The top 5 frequently encountered genera were subjected to antibiotic disk diffusion sensitivity to identify epidemiologically related transmission events. Complete multivariable logistic regression analysis and binomial tests of proportion were then used to examine the relative contributions of reservoirs of origin and within- and between-case modes of transmission, respectively, to epidemiologically related transmission events. Analyses were conducted with and without the inclusion of duplicate transmission events of the same genera occurring in a given study unit (first and second case of the day in each operating room observed) to examine the potential effect of statistical dependency. Transmitted isolates were compared by pulsed-field gel electrophoresis to disease-causing bacteria for 30-day postoperative HCAIs.
  
  
  RESULTS
  The top 5 frequently encountered gram-negative genera included Acinetobacter, Pseudomonas, Brevundimonas, Enterobacter, and Moraxella that together accounted for 81% (767/945) of possible transmission events. For all isolates, 22% (167/767) of possible transmission events were identified by antibiotic susceptibility patterns as epidemiologically related and underwent further study of transmission dynamics. There were 20 duplicates involving within- and between-case transmission events. Thus, approximately 19% (147/767) of isolates excluding duplicates were considered epidemiologically related. Contaminated provider hand reservoirs were less likely (all isolates, odds ratio 0.12, 95% confidence interval 0.03-0.50, P = 0.004; without duplicate events, odds ratio 0.05, 95% confidence interval 0.01-0.49, P = 0.010) than contaminated patient or environmental sites to serve as the reservoir of origin for epidemiologically related transmission events. Within- and between-case modes of gram-negative bacilli transmission occurred at similar rates (all isolates, 7% between-case, 5.2% within-case, binomial P value 0.176; without duplicates, 6.3% between-case, 3.7% within-case, binomial P value 0.036). Overall, 4.0% (23/548) of patients suffered from HCAIs and had an intraoperative exposure to gram-negative isolates. In 8.0% (2/23) of those patients, gram-negative bacteria were linked by pulsed-field gel electrophoresis to the causative organism of infection. Patient and provider hands were identified as the reservoirs of origin and the environment confirmed as a vehicle for between-case transmission events linked to HCAIs.
  
  
  CONCLUSIONS
  Between- and within-case AWE gram-negative bacterial transmission occurs frequently and is linked by pulsed-field gel electrophoresis to 30-day postoperative infections. Provider hands are less likely than contaminated environmental or patient skin surfaces to serve as the reservoir of origin for transmission events.
authors: From the *Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire; †The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire; ‡Department of Anesthesiology, University of Iowa Hospitals and Clinics, Iowa City, Iowa; and §Department of Anesthesiology, UMass Memorial Medical Center, Worcester, Massachusetts.
authors: Randy W
authors: RW
authors: Loftus
authors: Jeremiah R
authors: JR
authors: Brown
authors: Hetal M
authors: HM
authors: Patel
authors: Matthew D
authors: MD
authors: Koff
authors: Jens T
authors: JT
authors: Jensen
authors: Sundara
authors: S
authors: Reddy
authors: Kathryn L
authors: KL
authors: Ruoff
authors: Stephen O
authors: SO
authors: Heard
authors: Thomas M
authors: TM
authors: Dodds
authors: Michael L
authors: ML
authors: Beach
authors: Mark P
authors: MP
authors: Yeager
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000150:Acinetobacter; D000758:Anesthesia / Q000009:adverse effects; D000776:Anesthesiology / Q000295:instrumentation / Q000379:methods; D003428:Cross Infection / Q000517:prevention & control / Q000635:transmission; D004754:Enterobacter; D004866:Equipment Contamination; D006090:Gram-Negative Bacteria; D016905:Gram-Negative Bacterial Infections / Q000635:transmission; D006225:Hand / Q000382:microbiology; D009016:Moraxella; D015999:Multivariate Analysis; D016017:Odds Ratio; D009873:Operating Rooms; D011184:Postoperative Period; D011446:Prospective Studies; D011549:Pseudomonas; D015203:Reproducibility of Results