The Role of Contaminated Surfaces in the Transmission of Nosocomial Pathogens - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 33

Large variations in survival times in different reports is partly due to species
and strain variation but also to differences in experimental conditions, including
inoculum size, humidity, the suspending medium and the surface material [ 73 ].
3.5 Limitations of Cleaning and Disinfection
Cleaning is the removal of soil and contaminants from surfaces whereas disinfec-
tion relates to the inactivation of pathogens by using a disinfectant [ 8 ]. Microor-
ganisms vary in their resistance to disinfectants, so agents must be chosen carefully
for their effectiveness, particularly for C. difficile spores and norovirus [ 74 ].
Furthermore, the hospital environment is complex and often difficult to clean and
the use of a cleaning agent that is not effective against the target organism can
spread pathogens to other surfaces [ 74 - 76 ].
Liquid disinfectants may damage equipment, especially electronics, and
chlorine-containing materials may corrode metals [ 77 ]. Disinfectants can poten-
tially harm users and the discharge of waste biocides into the environment may
encourage the development of both biocide and antibiotic resistance and have other
more general environmentally damaging effects [ 77 ]. For these reasons some
authorities have questioned the use of routine disinfectant decontamination of the
hospital environment and favor instead the use of only detergents [ 77 ]. There has
been a tendency for disinfectants to be used in the USA and detergents in Europe
[ 77 , 78 ]. Recently, UK and European workers have moved more towards the use of
disinfectants to control MRSA and C. difficile , but the debate continues while
awaiting more evidence for the effective use of particular agents.
Cleaning and disinfection does not always eliminate pathogens from surfaces.
This is illustrated by a study from St. Louis, USA, showing that one or more site
remained contaminated with either MRSA of A. baumannii in 26.6 % of more than
300 rooms sampled following four consecutive rounds of bleach disinfection
[ 79 ]. In other studies, C. difficile was cultured from 44 % of 54 surfaces after
bleach disinfection in 9 rooms [ 32 ] and from 16 % of 243 cultures after bleach
disinfection implemented during an outbreak [ 50 ]. VRE was cultured from 71 % of
102 samples after bleach disinfection in 17 rooms [ 32 ] and it took an average of 2.8
bleach treatments to eradicate VRE in another study [ 80 ]. MRSA was cultured from
66 % of 124 surfaces in MRSA patient rooms after cleaning with a detergent
sanitizer [ 17 ], from 16 % of 65 sites following bleach and steam cleaning during
an outbreak on a surgical ward [ 49 ] and was found at a concentration of 0.7 CFU
per plate following phenolic disinfection during an outbreak on a burns unit [ 62 ].
Norovirus RNA was identified on 31 % of 239 surfaces after bleach disinfection,
and 16 % of surfaces remained contaminated after double bleach disinfection [ 45 ].
Contamination has been identified on apparently clean surfaces during outbreaks
due to Acinetobacter spp [ 81 ]. and viruses [ 47 ]. The frequent finding of conta-
mination in empty rooms and rooms occupied by patients unaffected by
pathogens suggests residual contamination from previous occupants [ 39 , 82 ].