ASTM WK70427

    New Practice for Preparation of Cell Monolayers on Glass Surfaces for Evaluation of Microbicidal Properties of Non-Chemical-Based Disinfection Technologies

    (What is a Work Item?)

    Developed by Subcommittee: E35.15 | Committee E35 | Contact Staff Manager



    WK70427

    1. Scope

    1.1 This practice provides a protocol for creating bacterial cell monolayers on a flat surface. 1.2 This practice is similar to US EPA MB-06-09 except that test bacteria are applied to the carrier using an automated deposition device rather than as a suspension droplet. 1.3 The carrier inspection protocol is similar to US EPA MB-03-07 except that carrier surfaces are inspected microscopically rather than visually, unaided. 1.4 A monolayer of cells eliminates the confounding effect caused by the shadowing effect of outer layers of bacteria stacked upon other bacteria on test specimens thereby attenuating directed energy beams (that is, ultraviolet light, high-energy electron beams, or -radiation) before they can reach underlying cells. 1.5 An asperity-free surface eliminates the shadowing effect of specimen surface topology that can block direct exposure of target bacteria to non-chemical disinfectants. 1.6 This practice provides a reproducible target microbe and surface specimen to minimize specimen variability within and between testing facilities. This facilitates direct data comparisons among various non-chemical disinfection-based technologies. 1.7 This practice was validated using Staphylococcus aureus (ATCC 6538) and Pseudomonas aeruginosa (ATCC 15442) per US EPA MB-06-09. If other cultures are used, the suitability of this practice shall be confirmed by inspecting prepared surfaces or using scanning electron microscopy (SEM) or comparable high-resolution microscopy. 1.8 The specimens prepared in accordance with this practice are not meant to simulate end-use conditions. 1.9 Units--The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard. 1.10 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 1.11 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.


    Keywords

    automated inoculum deposition; bacterial inoculum; bacterial monolayer; disinfectant agent testing; ultraviolet light; non-chemical disinfectant; ultraviolet disinfection; FMUV; UVC; disinfection standard; MB-06-09; monolayer; EPA SOP; healthcare; light-based disinfectant

    Rationale

    There is no reproducible standardized method in existence that accurately measures the efficacy of ultraviolet light or other high-energy radiation disinfectant systems. Shadowing effects caused by cell stacking and surface asperities contributed to test result variability. Shadowing, blocking the energy-beam path, is a major confounding factor that makes it impossible to distinguish between bacterial resistance to the beams cidal effects and non-exposure.

    The title and scope are in draft form and are under development within this ASTM Committee.

    Citing ASTM Standards
    Back to Top
    Work Item Status

    Date Initiated:
    11-01-2019

    Technical Contact:
    Frederick Passman

    Item:
    002

    Ballot:
    E35.15 (20-03)

    Status:
    Negative Votes Need Resolution