title: Application of quantitative microbial risk assessment for selection of microbial reduction targets for hard surface disinfectants.
abstract: BACKGROUND
  This quantitative microbial risk assessment (QMRA) included problem formulation for fomites and hazard identification for 7 microorganisms, including pathogenic Escherichia coli and E coli 0157:H7, Listeria monocytogenes, norovirus, Pseudomonas spp, Salmonella spp, and Staphylococcus aureus. The goal was to address a risk-based process for choosing the log10 reduction recommendations, in contrast to the current US Environmental Protection Agency requirements.
  
  
  METHODS
  For each microbe evaluated, the QMRA model included specific dose-response models, occurrence determination of aerobic bacteria and specific organisms on fomites, exposure assessment, risk characterization, and risk reduction. Risk estimates were determined for a simple scenario using a single touch of a contaminated surface and self-inoculation. A comparative analysis of log10 reductions, as suggested by the US Environmental Protection Agency, and the risks based on this QMRA approach was also undertaken.
  
  
  RESULTS
  The literature review and meta-analysis showed that aerobic bacteria were the most commonly studied on fomites, averaging 100 colony-forming units (CFU)/cm(2). Pseudomonas aeruginosa was found at a level of 3.3 × 10(-1) CFU/cm(2); methicillin-resistant S aureus (MRSA), at 6.4 × 10(-1) CFU/cm(2). Risk estimates per contact event ranged from a high of 10(-3) for norovirus to a low of 10(-9) for S aureus.
  
  
  CONCLUSIONS
  This QMRA analysis suggests that a reduction in bacterial numbers on a fomite by 99% (2 logs) most often will reduce the risk of infection from a single contact to less than 1 in 1 million.
authors.affiliation: Department of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, PA. Electronic address: mor23@drexel.edu.
authors.forename: Michael O
authors.initials: MO
authors.lastname: Ryan
authors.affiliation: Department of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, PA.
authors.forename: Charles N
authors.initials: CN
authors.lastname: Haas
authors.affiliation: Department of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, PA.
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Gurian
authors.affiliation: Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, AZ.
authors.forename: Charles P
authors.initials: CP
authors.lastname: Gerba
authors.affiliation: Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Panzl
authors.affiliation: Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI.
authors.forename: Joan B
authors.initials: JB
authors.lastname: Rose
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000302:isolation & purification*; D058491:Bacterial Load; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D004202:Disinfectants / Q000494:pharmacology; D004203:Disinfection / Q000379:methods*; D050456:Fomites / Q000382:microbiology*; D006801:Humans; D017053:Infection Control / Q000379:methods*; D029322:Norovirus / Q000187:drug effects / Q000302:isolation & purification*; D018570:Risk Assessment; D040242:Risk Reduction Behavior; D014481:United States; D019562:Viral Load
chemical_list: D004202:Disinfectants
keywords: Dose-response; Fomite; Microbial surface contamination