Ward floors and other surfaces as reservoirs of hospital infection

G.A.J.AYLIFFE, B.J.COLLINS, E.J.L.LOWBURY, J.R.BABB, H.A.LILLY

Introduction

The floors of hospital wards become contaminated with large numbers of bacteria, including Staphylococcus aureus, and are commonly assumed to be important reservoirs of hospital infection. To prevent the dispersal of bacteria from floors into the air, various improvements in methods of cleaning have been introduced, notably oiling of floors, the use of oiled mops and, with most success, the use of special vacuum cleaners (van den Ende, Lush & Edward, 1940; Bate, 1961; Babb, Lilly & Lowbury, 1963). Efforts are also commonly made to reduce the numbers of bacteria on the floors by manual or mechanical scrubbing or disinfection, but the results of such treatment have been disappointingly small (Finegold et al. 1962; Vesley & Michaelson,1964). Ayliffe, Collins & Lowbury (1966) found that areas of floor protected against recontamination lost about 80% of their bacterial flora after mopping or mechanical scrubbing, and a significantly larger proportion (about 99 %) after treatment with certain disinfectants. Since areas which were not protected against recontamination were often as heavily contaminated 1 hr. after scrubbing or disinfection as they were before such treatment, there appeared to be litle or no advantage in cleaning floors. On the other hand, frequent scrubbing or the use of disinfectants might be expected to keep the mean level of bacterial contamination lower that that which ispresent on an uncleaned surface. Even if regular disinfection of floors reduces the mean level of contamination, such treatment cannot be considered useful in preventing infection unless pathogens on the floor are transferred either by air or by contact to patients in the ward.

In this paper we describe studies on the equilibrium levels of floor contamination and the influence of various factors,including disinfection, on these levels. We also describe experiments on the redispersal by air movements of settled dust containing Staph. aureus and discuss floor bacteria as a source of infection in the light of the results obtained.