The Role of Contaminated Surfaces in the Transmission of Nosocomial Pathogens - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 40

clinical cultures that matched the pulsotype of the index case among contacts
(either roommates, neighbors or subsequent room occupants of index cases)
correlated with the intensity of environmental contamination, suggesting that the
transmission risk was related to the intensity of contamination.
Several studies have investigated the impact of switching to bleach for disinfec-
tion on the incidence of CDI [ 15 , 97 , 98 , 100 , 101 ]. For example, Mayfield
et al. showed that switching from quaternary ammonium compounds (QAC) to
bleach disinfection reduced the incidence of CDI for high risk bone marrow
transplant patients [ 97 ]. However, no significant reduction in infection rates
occurred for lower risk patient groups and environmental contamination was not
quantified. Wilcox et al. conducted a cross-over study in elderly care wards to
compare the impact of detergent cleaning versus bleach disinfection, and demon-
strated a significant reduction in infection rates on one ward [ 15 ]. No significant
reduction was demonstrated on the other ward and the frequency of environmental
contamination was not reduced in either study arm, suggesting that other factors
were involved. Boyce et al. found that the use of HPV to decontaminate rooms
following the discharge of patients with C. difficile reduced the incidence of CDI on
five high-incidence wards [ 61 ]. The hospital-wide incidence of CDI was also
reduced, but this was only statistically significant when the analysis was limited
to the months when the epidemic NAP1 C. difficile strain was known to be present.
Meanwhile, a before-and-after study by Manian et al. found that improved terminal
disinfection using a combination of multiple rounds of bleach disinfection and HPV
significantly reduced hospital-wide incidence of C. difficile [ 102 ].
Evidence from an in vitro model provides proof of concept that C. difficile spores
can be transmitted via environmental surfaces [ 66 ]. Mice exposed to an experi-
mentally contaminated enclosure became colonized in a dose-dependent manner
and oxidizing agents including a chlorine-containing liquid disinfectant and HPV
reduced effectively the level of contamination and blocked transmission. A recent
study found that prior room occupancy by patients with CDI increased the risk of
C. difficile acquisition, providing evidence that the in vitro concept translates into
the clinical setting [ 95 ].
3.7.2 Vancomycin-Resistant Enterococci (VRE)
Evidence from several studies suggests that the acquisition of VRE is associated
with environmental contamination. Huang et al. found that admission to a room
previously occupied by a patient with VRE significantly increased the risk of
acquiring VRE [ 94 ]. In this study, other routes of transmission (which may involve
contaminated surfaces indirectly) accounted for the majority of nosocomial trans-
mission. Drees et al. found that VRE acquisition was associated with a positive
room culture prior to admittance to the room, a prior room occupant positive for
VRE or any VRE-positive room occupants within the 2 weeks prior to admission
[ 39 ]. A study from Boston, USA, showed that enhanced cleaning reduced overall
transmission of VRE on an ICU, but did not mitigate the increased risk from the