An Overview of the Options for Antimicrobial Hard Surfaces in Hospitals - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 139

Fig. 7.2 How the increased
risk of acquiring VRE from
the prior room occupant
changes due to patient
and environmental factors
(Data extracted from
Drees et al. [ 13 ])
The fact that subsequent occupants of a room vacated by a previously colonised
or infected patient are at an increased risk of infection indicates that conventional
terminal disinfection does not reduce contamination sufficiently to prevent trans-
mission in these cases [ 2 , 13 - 16 ]. Further, one of the studies demonstrating that
admission to a room previously occupied by a patient with vancomycin resistant
enterococci (VRE) increases the chances of VRE acquisition identified some-
thing amounting to a 'dose response' [ 13 ]. The greatest increased risk was for
patients admitted to a room with an environmental culture positive for VRE, and
being admitted to a room where the immediate prior room occupant was colonized
with VRE carried a greater increased risk than being admitted to a room where any
patient in the 2 weeks prior to admission was VRE colonized (Fig. 7.2 ).
Another strand of evidence suggesting a causal relationship between contami-
nation burden and the risk of transmission comes from the finding that improving
the level of terminal disinfection mitigates or eliminates the increased risk from the
prior room occupant [ 19 , 21 ]. Improving terminal disinfection by modifying con-
ventional methods (the use of UV markers, immersing the cloth in the disinfectant
and education of cleaners) resulted in a significant mitigation of the increased risk
for MRSA but not for VRE [ 21 ]. Whereas in another study, the introduction of
hydrogen peroxide vapour (HPV) 'no-touch' automated room disinfection resulted
in an elimination of the increased risk, to the extent that patients admitted to rooms
disinfected using HPV were less likely to acquire an MDRO even than patients
admitted to rooms where the prior occupant was not known to be infected or
colonized with an MDRO [ 19 ]. Both studies demonstrate that interventions to
enhance the level of reduction in environmental burden result in reduced patient
acquisition, and thus suggest a causal relationship between the level of contamina-
tion and transmission. Furthermore, since HPV is associated with an elimination of
Fig. 7.1 Studies correlating environmental contamination burden and transmission.
(a) Correlation between the number of patients infected with Acinetobacter spp. and the number
of positive Acinetobacter spp. environmental cultures per calendar month during an outbreak on a
neurosurgical intensive care unit (ICU) [ 25 ]. (b) Correlation between microbial burden and the
number of patients who acquired a hospital acquired infection in ICUs [ 31 ]. (c) Correlation
between the number of hygiene failures and the number of patients who acquired an infection
on a surgical ICU each week [ 32 ]