Biomedical Engineering Reference
In-Depth Information
The following findings are based on this review; however, knowledge on
persistence of microorganisms on inanimate surfaces is now expanded by addi-
tional findings published after 2005/2006.
2.3.1 Persistence of Bacteria
In most reports, persistence was studied on dry surfaces using artificial contamina-
tion of a standardized type of surface in a laboratory. Bacteria were prepared in
broth, water or saline.
Most Gram-positive bacteria, such as
Enterococcus
spp. including VRE,
S. aureus
including MRSA, or
Streptococcus pyogenes
survive for months on dry
surfaces (Table
2.2
). In general, there is no observable difference in survival
between multi-resistant and susceptible strains of
S. aureus
and
Enterococcus
spp. [
78
]. Only in one study [
118
] a difference of survival time between antibiotic
resistant and susceptible bacteria was suggested, yet, the susceptible strains dem-
onstrated only a non-significant shorter survival time on surfaces. The factors why
the same bacteria may persist more or less on a surface (i.e. from hours to days as
detailed in Table
2.2
) will be discussed later in Sect.
2.3.5
.
Many Gram-negative species, such as
Acinetobacter
spp.,
Escherichia coli
,
Klebsiella
spp
.
,
Pseudomonas aeruginosa
,
Serratia marcescens
,or
Shigella
spp.
can survive on inanimate surfaces even for months (Table
2.2
). These species are
found among the most frequent isolates from patients with HAI [
64
,
65
]. However,
a few others Gram-negative bacteria, such as
Bordetella pertussis
,
Haemophilus
influenzae
,
Proteus vulgaris
,or
Vibrio cholera
persist only for days (Table
2.2
).
Mycobacteria, including
Mycobacterium tuberculosis,
and spore-forming bac-
teria, such as
C. difficile,
can survive for many months on surfaces (Table
2.2
).
Because paper still is omnipresent in healthcare settings worldwide today,
H
ยจ
bner et al. [
56
] have analysed the persistence of various Gram-positive and
Gram-negative bacteria including
E. coli
,
S. aureus
,
P. aeruginosa
, and
Enterococ-
cus hirae
on office paper after contamination with standardised inocula of bacterial
suspensions in the range of 2.8
10
7
cfu/mL. Opposite to
E. coli
, all other organ-
isms were more stabile at room conditions and were reduced on paper only by
3 log
10
after 7 days, whereas
E. coli
was reduced by 5 log
10
within
24 h. Furthermore, the transmissibility of bacteria from hands to paper and back
could be demonstrated for all bacteria strains. Similar investigations showed that
paper money notes could harbour and transmit pathogens [
62
,
111
,
115
].
2.3.2 Persistence of Viruses
In order to estimate the persistence of viruses on inanimate surfaces, usually cell
culture media are prepared [
64
,
65
]. Most viruses from the respiratory tract such as
Corona-, Coxsackie-, or Influenza virus, SARS, or rhinovirus can persist on surfaces
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