The Role of Contaminated Surfaces in the Transmission of Nosocomial Pathogens - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 42

risk factor for the acquisition of these pathogens. This was the first evidence from
an endemic setting that contaminated surfaces contribute to the transmission of
GNRs [ 93 ].
Numerous outbreaks of A. baumannii have been associated with contaminated
inanimate fomites, which resolve once the common source was identified and
removed, replaced or adequately disinfected [ 4 ]. Several outbreaks, where
environmental surfaces were contaminated but a common source was not identi-
fied, offer limited evidence that surface contamination also plays a role in
continued transmission [ 48 , 112 , 113 ]. For example, during an outbreak of
A. baumannii in the UK affecting 19 patients on a neurosurgical unit, 53 % of
51 surfaces in the unit were contaminated with the outbreak strain and monthly
screens showed that the frequency of contamination correlated with the number
of affected patients on the unit [ 48 ]. Crucially, failure to maintain low levels
of contamination resulted in increases in patient colonization, suggesting that the
contamination was contributing to the outbreak. However, it was not possible to
prove causality because neither molecular epidemiological analysis nor hand
cultures were performed.
Further evidence for the role of contaminated surfaces in such transmission
comes from an investigation of a multi-institutional outbreak of A. baumannii
among war-wounded US soldiers [ 114 ]. In this study, outbreak strains of
A. baumannii were cultured from 21 % of 175 surfaces in seven field hospitals
but a very low frequency of contamination was identified in soil samples and on
healthy soldiers' skin.
3.7.4.2 Enterobacteriaceae
Two recent studies have shown that admission to a room previously occupied by
extended spectrum beta-lactamase (ESBL) producing Enterobacteriaceae did not
increase the risk of acquisition for incoming patients, suggesting that the environ-
ment may have a less important role in the transmission of Enterobacteriaciae than
for non-fermenting GNRs (Fig. 3.3 )[ 93 , 115 ]. This is supported by laboratory
findings that Enterobacteriaceae tend to survive less well on dry surfaces than
non-fermenters, Gram-positive bacteria and bacterial endospores [ 73 , 116 ]. How-
ever, several recent studies have identified environmental contamination with
ESBL and carbapenemase-producing Enterobacteriaceae (CPE) on hospital sur-
faces [ 42 , 43 ]. Resistant Enterobacteriaceae are shed into the hospital environment
and do have the capacity to survive on dry surfaces, so surfaces may be involved in
their transmission [ 1 , 117 ]. The major concern with CPE relates to K. pneumoniae
[ 117 , 118 ], which seems to be more closely associated with environmental con-
tamination than other Enterobacteriaceae; [ 42 , 43 ] thus, environmental contamina-
tion may be more important with CRE than ESBL carriers.