Microbiologic Sampling of the Environment

Before 1970, U.S. hospitals conducted regularly scheduled culturing of the air and environmental surfaces (e.g., floors, walls, and table tops). By 1970, CDC and the American Hospital Association (AHA) were advocating the discontinuation of routine environmental culturing because rates of healthcare–associated infection had not been associated with levels of general microbial contamination of air or environmental surfaces, and because meaningful standards for permissible levels of microbial contamination of environmental surfaces or air did not exist. During 1970–1975, 25% of U.S. hospitals reduced the extent of such routine environmental culturing — a trend that has continued. Random, undirected sampling (referred to as “routine” in previous guidelines) differs from the current practice of targeted sampling for defined purposes. Previous recommendations against routine sampling were not intended to discourage the use of sampling in which sample collection, culture, and interpretation are conducted in accordance with defined protocols. In this guideline, targeted microbiologic sampling connotes a monitoring process that includes

a. a written, defined, multidisciplinary protocol for sample collection and culturing

b. analysis and interpretation of results using scientifically determined or anticipatory baseline values for comparison; and

c. expected actions based on the results obtained.

Infection control, in conjunction with laboratorians, should assess the health-care facility’s capability to conduct sampling and determine when expert consultation and/or services are needed. Microbiologic sampling of air, water, and inanimate surfaces (i.e., environmental sampling) is an expensive and time-consuming process that is complicated by many variables in protocol, analysis, and interpretation. It is therefore indicated for only four situations. The first is to support an investigation of an outbreak of disease or infections when environmental reservoirs or fomites are implicated epidemiologically in disease transmission. It is important that such culturing be supported by epidemiologic data. Environmental sampling, as with all laboratory testing, should not be conducted if there is no plan for interpreting and acting on the results obtained. Linking microorganisms from environmental samples with clinical isolates by molecular epidemiology is crucial whenever it is possible to do so.

The second situation for which environmental sampling may be warranted is in research. Well-designed and controlled experimental methods and approaches can provide new information about the spread of health-care associated diseases. A classic example is the study of environmental microbial contamination that compared health-care associated infection rates in an old hospital and a new facility before and shortly after occupancy.

The third indication for sampling is to monitor a potentially hazardous environmental condition, confirm the presence of a hazardous chemical or biological agent, and validate the successful abatement of the hazard. This type of sampling can be used to:

a. detect bioaerosols released from the operation of health-care equipment (e.g., an ultrasonic cleaner) and determine the success of repairs in containing the hazard,

b. detect the release of an agent of bioterrorism in an indoor environmental setting and determine its successful removal or inactivation, and

c. sample for industrial hygiene or safety purposes (e.g., monitoring a “sick building”).

The fourth indication is for quality assurance to evaluate the effects of a change in infection-control practice or to ensure that equipment or systems perform according to specifications and expected outcomes. Any sampling for quality-assurance purposes must follow sound sampling protocols and address confounding factors through the use of properly selected controls. Results from a single environmental sample are difficult to interpret in the absence of a frame of reference or perspective. Evaluations of a change in infection-control practice are based on the assumption that the effect will be measured over a finite period, usually of short duration. Conducting quality-assurance sampling on an extended basis, especially in the absence of an adverse outcome, is usually unjustified. A possible exception might be the use of air sampling during major construction periods to qualitatively detect breaks in environmental infection-control measures. In one study, which began as part of an investigation of an outbreak of health-care associated aspergillosis, airborne concentrations of Aspergillus spores were measured in efforts to evaluate the effectiveness of sealing hospital doors and windows during a period of construction of a nearby building. Other examples of sampling for quality-assurance purposes may include commissioning newly constructed space in special care areas (i.e., ORs and units for immunosuppressed patients) or assessing a change in housekeeping practice. However, the only types of routine environmental microbiologic sampling recommended as part of a quality-assurance program are

a. the biological monitoring of sterilization processes by using bacterial spores and

b. the monthly culturing of water used in hemodialysis applications and for the final dialysate use dilution.

Some experts also advocate periodic environmental sampling to evaluate the microbial/particulate quality for regular maintenance of the air handling system (e.g., filters) and to verify that the components of the system meet manufacturer’s specifications (A. Streifel, University of Minnesota, 2000). Certain equipment in health-care settings (e.g., biological safety cabinets) may also be monitored with air flow and particulate sampling to determine performance or as part of adherence to a certification program; results can then be compared with a predetermined standard of performance. These measurements, however, usually do not require microbiologic testing.

Thursday, February 9, 2023


Centers for Disease Control and Prevention (CDC)- Guidelines for Environmental Infection Control in Health-Care Facilities

Please Check out file at the following link

Cleaning Strategies for Spills of Blood and Body Substances

Cleaning Special Care Areas

General Cleaning Strategies for Patient-Care Areas – Cleaning Housekeeping Surfaces

General Cleaning Strategies for Patient-Care Areas – Cleaning of Medical Equipment

Environmental Services – Principles of Cleaning and Disinfecting Environmental Surfaces