Question

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Data in this study indicate that staphylococci and entero- cocci can survive for days to months after drying on commonly used hospital fabrics and plastic. It should be noted that sur- vival in this study could result from a single microorganism or from many microorganisms viable at the time the sample was taken. In the future, more precise survival data could be ob- tained by quantitating the number of bacteria in the medium, rather than simply assessing the presence of growth versus nongrowth in that medium. Despite this methodological vari- ation, our findings for E. faecalis and E. faecium viability on polyethylene plastic agree with the work of Wendt et al. (16) on survival of these species on polyvinyl chloride. In addition, we found extended survival for two other species, E. gallinarumand E. casseliflavus, on fabrics and plastic. Viability of entero- cocci on fabrics tended to be longer than their reported sur- vival on other hospital surfaces. Specifically, Noskin et al. (8) recovered enterococci from countertops after 5 to 7 days and from bed rails at 1 day. The shorter survival times may be caused by the different surfaces tested and/or the different inocula used (Noskin et al. used 104 CFU, while we used 105CFU). There is a report of at least 2-month survival of one VRE dried on a countertop at an undesignated concentration (3).

For staphylococci, our results are consistent with those of Wilkoff et al. (17), who reported that one S. aureus isolate lived 1 week on cotton and 2 weeks on terry. In contrast, Scott and Bloomfield (12) showed S. aureus surviving only 4 to 24 h on cloth; however, their inocula were low (102 CFU). Our limited study with CNS suggests that inoculum size can affect survival (Table 2). This conclusion is consistent with a study showing a dose-response effect on the survival of a S. aureus and an E. faecalis on aluminum foil (5). Mechanistically, the effect of inoculum concentration on cell viability is consistent with the concept of cryptic growth in which bacteria in a starving or nutrient-limiting condition can live on nutrients from dying cells nearby (15). Hence, with higher bacterial inocula, there would be more dying cells to sustain the few living bacteria longer. 2 5

Howourinoculasizes(10 and10)relatetothenumbersof bacteria encountered by health care workers probably depends upon the health care worker and the particular task they are conducting. Rutala et al. (11) counted the number of MRSA on elevated surfaces, such as countertops, in rooms of patient.

In conclusion, data in this study indicate that staphylococci and enterococci can survive for extended periods of time on materials commonly worn by patients and health care workers and on various other fabrics in the hospital environment. While most previous studies have tested survival of principally staphylococci using cotton as a representative fabric (2, 12, 17), the present study examined the survival of enterococci, includ- ing VRE, and staphylococci, on a number of different fabrics. Most of the bacteria tested in this study survived longer on polyester than on cotton. Hence, fabric type may influence survival. The length of survival of these organisms on the various materials may have significant infection control impli- cations. For example, the polyester tested in this study is the material used at our hospital for privacy drapes, which are handled by both patients and staff when they are drawn around the patient’s bed. Staphylococci and enterococci survived for days to months on this fabric, thereby suggesting that such drapes could act as reservoirs for these bacteria.

Answer 1

In this data it has been found that staphylococci and entero- cocci can survive for days to months after drying on commonly used hospital fabrics and plastic. Viability of entero- cocci on fabrics tended to be longer than their reported sur- vival on other hospital surfaces. Specifically, Noskin et al. recovered enterococci from countertops after 5 to 7 days and from bed rails at 1 day. The effect of inoculum concentration on cell viability is consistent with the concept of cryptic growth in which bacteria in a starving or nutrient-limiting condition can live on nutrients from dying cells nearby. So, the survival depends upon the type of the fibres. This is the reason why some of the bacteria survive for a longer period of time as compared to the other fibres.