Before 1970, regularly scheduled culturing of the air and environmental surfaces such as floors, walls, and table tops was widely practiced in US hospitals. By 1970, CDC and the American Hospital Association were advocating that hospitals discontinue routine environmental culturing, since rates of nosocomial infection had not been related to levels of general microbial contamination of air or environmental surfaces, and meaningful standards for permissible levels of microbial contamination of environmental surfaces did not exist. Between 1970 and 1975, 25% of US hospitals reduced the extent of such routine environmental culturing, and this trend has continued.

In the last several years, there has also been a trend toward reducing routine microbiologic sampling for quality control purposes. In 1982, CDC recommended that the disinfection process for respiratory therapy equipment should not be monitored by routine microbiologic sampling. Moreover, the recommendation for microbiolgic sampling of infant formulas prepared in the hospital has been removed from this Guideline, since there is no epidemiologic evidence to show that such quality control testing influences the infection rate in hospitals.