Original Research: Survival of Bacterial Pathogens on Paper and Bacterial Retrieval from Paper to Hands: Preliminary Results

Abstract

Paper is omnipresent on hospital units, but few studies have examined the possible role of paper in the spread of nosocomial pathogens.
To determine by laboratory investigation how long bacterial pathogens can survive on office paper and whether bacteria can be transferred from hands to paper and back to hands in a "worst-case scenario."
Samples of four bacterial pathogens (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus hirae) were prepared according to standard laboratory procedures. Sterile swatches of office paper were inoculated with the pathogens and bacterial survival was tested over seven days. To test the transmission of bacteria from one person's hands to paper and back to another person's hands, the fingertips of volunteers were inoculated with a nonpathogenic strain of E. coli; these volunteers then pressed the inoculum onto sterile paper swatches. Another group of volunteers whose hands had been moistened pressed their fingertips onto the contaminated paper swatches. Bacteria transferred to the moistened fingertips were cultivated according to standard laboratory procedures.
The four tested organisms showed differences in length of survival depending on environmental room conditions, but were stable on paper for up to 72 hours and still cultivable after seven days. Test organisms were transferred to paper, survived on it, and were retransferred back to hands.
Paper can serve as a vehicle for cross-contamination of bacterial pathogens in medical settings if current recommendations on hand hygiene aren't meticulously followed.

Full text

Survival of Bacterial Pathogens on
Paper and Bacterial Retrieval from
Paper to Hands: Preliminary Results
Continuing Education
2.1
hours
original research
By Nils-Olaf Hübner, MD, Claudia Hübner, PhD, Axel Kramer, MD, PhD, and Ojan Assadian, MD, DTMH
While electronic medical records and
in formation systems are increasingly
found in hospitals and other clinical set-
tings, paper may still be one of the most
common materials on any hospital unit.
Paper is used as a recording medium in medical and
nursing charts, patient files, notes, and reports, and
may be introduced into the clinical setting by patients
and visitors in the form of books, newspapers, maga-
zines, and other items. Paper documents are used every
day and in every way, not only by nurses and physicians,
but by many other people involved in patient care.
Disinfection of paper, unlike most other equipment,
is not an easy task because of its porous surface and
incompatibility with liquid disinfectants. Evidence is
abundant from studies of paper money that paper can
transmit pathogens in nonclinical settings.1-3
Much research has been conducted on the trans-
mission of pathogens from hands to inanimate sur-
faces. However, it remains unclear how long bacteria
can survive on paper and how many organisms may
be transferred in a full hand-to-paper-to-hand trans-
mission cycle.1, 4-10 Paper documents could be an im-
portant vehicle for cross-c ontamination and infection
in clinical settings, but data are scarce. The aim of our
study was to investigate how long bacterial pathogens
can survive on regular office paper and to quantify the
proportion of pathogens transferred from hand to
paper and back to another hand.
METHODS
Design. We performed a two-s tep experimental study
of bacterial survivability and transmission under labo-
ratory conditions simulating a “worst- case scenario” (a
high number of colony-forming units [CFU] per cm2,
and optimal transmission by wet finger and pressure
against paper) for the spread of pathogens.
Preparation of paper swatches. One-centimeter-
square swatches were cut from white all-purpose print-
ing paper (80 g/m2, Future multitech, UPM, Helsinki,
Finland) and steam sterilized. The paper was shown
to be free of antibacterial properties in an agar diffu-
sion assay in accordance with standard DIN 58940-
2-3 of the German Institute for Standardization.11, 12
Test of organism survivability on paper. To test
the survival of bacterial organisms on paper, we used
standard procedures for preparing bacterial cultures.
Four organisms—Escherichia coli, Staphylococcus
aureus, Pseudomonas aeruginosa, and Enterococcus
hirae—were cultured overnight in tryptic soy broth
(TSB, a growth medium commonly used in the cultiva-
tion of aerobic bacteria) and prepared to 109 CFU/mL.
For each strain, 18 swatches were inoculated with
0.25 mL of test suspension and air dried at room tem-
perature. Immediately after drying, each sample was
placed in a vortexer (a device used to agitate microbial
samples in solution) with 10 mL of 0.9% saline solution.
Volumes of 0.1 mL of undiluted sampling solution and
0.1 mL from 1:10 and 1:100 dilutions in TSB were plated
PaPer medical records can be a source for
transmission of bacteria.
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AJN1211.Hubner.CE.2nd.indd 2 10/29/11 7:16 PM

onto Columbia blood agar plates (Becton Dickinson,
Hei delberg, Germany), incubated at 36±1°C for 24 hours,
and plate counted. Samples were stored, while protect ed
from direct sunlight and contamination, under standard
room conditions (23±2°C, 55±5% relative air humidity).
They were then sampled and plate counted after 48, 72,
96, 144, and 168 hours, to test for bacterial growth.
Tests for bacterial growth were repeated three times.
Test of bacterial transmissibility. To test the trans-
missibility of bacteria from one hand to paper and back
to another hand, we adapted the classic finger-pad
method developed by Ansari and Sattar and specified in
the American Society for Testing and Materials (ASTM)
Standards E-1838-96 and E-1838-02 for testing viru-
cidal activity of hand antiseptics.5, 13-15 The nonpatho-
genic E. coli strain NCTC 10538 (from the National
Collection of Type Cultures [NCTC], a part of the
Health Protection Agency of the United Kingdom)
was used as the test organism. Volunteers washed their
hands in tap water without soap, dried them with single-
use paper towels, and waited 10 minutes to ensure that
they were dry.16 The tip of each volunteer’s index finger
was inoculated with 25 microliters of test suspension
(109 CFU/mL) and air dried.
After drying, volunteers pressed the inoculated finger-
tips on paper swatches for 30 seconds. The index finger-
tips of another group of volunteers were then irrigated
with sterile 0.9% saline (to simulate the common bad
habit of licking the finger before turning pages or going
through files) and pressed on the contaminated swatches
for 30 seconds to simulate cross-contamination. A ster-
ile Eppendorf tube filled with 1 mL of saline solution
was then pressed to the fingertip of each of the second
volun teers and shaken for one minute; volumes of 0.1 mL
of this undiluted sampling solution were plated onto
Columbia blood agar and incubated as described above.
Tests were repeated six times.
RESULTS
Survival of test organisms on paper over time. All
test strains survived on the inoculated paper. Figure 1
shows the changes in recoverable organisms for each
individual organism. There were notable differences in
the survival of different pathogens over time. E. coli
was reduced by almost 5 log10 in 24 hours (a reduction
abstract
Background: Paper is omnipresent on hospital units, but
few studies have examined the possible role of paper in the
spread of nosocomial pathogens.
Objective: To determine by laboratory investigation how
long bacterial pathogens can survive on office paper and
whether bacteria can be transferred from hands to paper
and back to hands in a “worst-case scenario.”
Methods: Samples of four bacterial pathogens (
Esch-
erichia coli
,
Staphylococcus aureus
,
Pseudomonas aeruginosa
,
and
Enterococcus hirae
) were prepared according to stan-
dard laboratory procedures. Sterile swatches of office paper
were inoculated with the pathogens and bacterial survival
was tested over seven days. To test the transmission of bac-
teria from one person’s hands to paper and back to another
person’s hands, the fingertips of volunteers were inoculated
with a nonpathogenic strain of
E. coli
; these volunteers then
pressed the inoculum onto sterile paper swatches. Another
group of volunteers whose hands had been moistened pressed
their fingertips onto the contaminated paper swatches. Bac-
teria transferred to the moistened fingertips were cultivated
according to standard laboratory procedures.
Results: The four tested organisms showed differences
in length of survival depending on environmental room con-
ditions, but were stable on paper for up to 72 hours and still
cultivable after seven days. Test organisms were transferred
to paper, survived on it, and were retransferred back to
hands.
Conclusion: Paper can serve as a vehicle for cross-
contamination of bacterial pathogens in medical settings if
current recommendations on hand hygiene aren’t meticu-
lously followed.
Keywords: cross-contamination, disinfection, finger pad
method, hand antisepsis, hand hygiene, hospital-acquired
infection, infection control, nosocomial infection, spread of
pathogens, survival on inanimate surfaces
ajn@wolterskluwer.com AJN ▼ December 2011 ▼ Vol. 111, No. 12 3
Bacteria can be transferred to paper,
survive on it, and subsequently
contaminate hands.
AJN1211.Hubner.CE.2nd.indd 3 10/29/11 7:16 PM

of 5 log10 is equivalent to a 99.999% reduction in re-
coverable organisms, the minimum reduction re-
quired for a surface in a clinical setting to be considered
dis infected). Other organisms, including P. aerugi-
nosa and E. hirae, were quite resistant to room condi-
tions and were reduced by 3 log10 (99.9%) only after
seven days; there fore the paper wasn’t disinfected
within the test period, and was still a potential source
of in fection.
Transmissibility of bacteria from hand to paper
and back. We demonstrated that test organisms were
transferred from hands to paper and back to hands
(see Table 1). A transmission was detected in all six ex-
periments. Although the mean bacterial transfer rate
(from one volunteer’s finger to the next volunteer’s fin-
ger) was relatively low (0.009%), quantities of bacteria
sufficient to cause infection or disease were resampled
from the second volunteer’s fingertip. (An inoculum
of 5 log10 organisms—that is, an inoculum containing
100,000 organisms—would still be enough for cross-
contamination. The initial quantity of bacteria in the
inoculum was 2.75 × 107 CFU/mL, corresponding to
a total of 7.44 log10 or 74,400,000,000 bacteria in the
sample solution.)
DISCUSSION
Because of paper’s omnipresence on hospital units,
the question if and to what extent it can play a role
as a vehicle for bacterial pathogens and promote cross-
infection is of great importance. It has been re peatedly
shown that medical records can be heavily contami-
nated with pathogens, including multidrug-resistant
bacteria like methicillin-resistant S. aureus (MRSA),
extended-spectrum β-lactamase (ESBL)–producing
enterobacteria, or vancomycin-resistant Enterococcus
(VRE).17, 18 However, data on the survival of bacteria
on pa per and other porous surfaces are scarce.
We demonstrated that bacteria not only survive on
paper but can also be transferred from one person’s
hands to paper and back to another person’s hands.
This is congruent with the results of studies of bacte-
rial growth and survival on other inanimate surfaces
and observational evidence.10, 19-21 Interestingly, the trans-
mission rate found in a full hand-to-paper-to-hand cy-
cle fits well with published data on transmission rates
to and from other inanimate surfaces.19
Organisms show differences in resistance to room
conditions, but most of the tested pathogens were quite
stable on paper for up to 72 hours and still cultivable
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Reduction in CFU/mL (log10/mL)
E. coli
(NCTC 10538)
S. aureus
(ATCC 6538)
P. aeruginosa
(ATCC 15442)
Inoculum 24 hoursAfter
drying
168 hours144 hours72 hours48 hours
E. hirae
(ATCC 10541)
0.00
-6.00
-5.00
-4.00
-3.00
-2.00
-1.00
CFU = colony-forming units.
a Initial quantity of bacteria in the inoculum was 2.75 × 107 CFU/mL, corresponding to a total of 7.44 log10 organisms.
b Specic bacterial strains are identied by the alphanumeric designations in parentheses. The American Type Culture Collection
(ATCC) and the National Collection of Type Cultures (NCTC) are repositories and distributors of standard reference microorganisms,
cell lines, and other biological materials.
figure 1.
Survival of Test Organisms on Paper Over Timea, b
AJN1211.Hubner.CE.2nd.indd 4 10/29/11 7:16 PM

after seven days. Thus, hands can become contami-
nated by these pathogens when paper is handled.
Limitations. Our study has several limitations. De-
signed as a pilot study, we wanted to assess whether
paper can promote cross-infection. We therefore cre-
ated conditions that are considered “worst case” in terms
of hygiene and optimal in terms of pathogen transmis-
sion (high inoculum, wet finger) but with a very small
con taminated spot (just one fingertip) to test transmis-
sibility, as previously described by other authors.19 This
may not well represent real-world conditions, but our
results are supported by those of other studies.18
The uncoated paper used in this study bound most
of the bacterial suspension by adsorption and absorp-
tion, thus reducing transfer. Coated paper, on the other
hand, which is often used for printed material includ-
ing paper currency, adsorbs and absorbs less bacterial
suspension, implying a higher transmission rate. Fur-
ther research should be focused on whether our results
are reproducible under real-world conditions. More
investigation is also needed to explore whether hand-
washing with soap and water or hand disinfection
with alcohol-based hand rubs (hand sanitizers) more
effectively decreases transmission from hand to paper
and vice versa in health care settings.
Conclusions. Our research shows that bacteria can
be transferred to paper, survive on it, and subsequently
contaminate hands. Paper, therefore, can serve as a
ve-
hicle for the cross-contamination of bacterial pathogens
if current recommendations on hand hygiene aren’t
meticulously followed. Once contaminated, paper is
hard to disinfect, because it cannot be disinfected by
chemical means, as other inanimate surfaces can. Thus,
the best way to minimize the spread of pathogens is
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table 1.
Transmissibility of
Escherichia coli
(NCTC 10538)a from Hand to Paper to
Another Handb
Test Number Recovered Bacteria (CFU/mL)cAverage Bacterial Transfer Rate, %d
1 1.91E+03 [1,910] 0.007
2 4.00E+02 [400] 0.001
3 5.07E+03 [5,070] 0.018
4 3.87E+03 [3,870] 0.014
5 9.20E+02 [920] 0.003
6 3.44E+03 [3,440] 0.013
Mean 2.60E+03 [2,600] 0.009
SD 1.82E+03 [1,820] 0.007
CFU = colony-forming units; NCTC = National Collection of Type Cultures.
a Designates a nonpathogenic strain of
E. coli
from the National Collection of Type Cultures.
b Initial quantity of bacteria in the inoculum was 2.75 × 107 CFU/mL, corresponding to a total of 7.44 log10 organisms.
c Quantities of bacteria recovered at the end of the transmission cycle, expressed in (scientific) E notation, with whole number quantities
in brackets.
d Designates the rate of transmission in a full hand-to-paper-to-hand transmission cycle.
The best way to minimize the spread of pathogens is proper
hand hygiene, because the transiently contaminated hands of health
care workers are known to be the most important route of
transmission of pathogenic bacteria.
AJN1211.Hubner.CE.2nd.indd 5 10/29/11 7:16 PM

proper hand hygiene, because the transiently contami-
nated hands of health care workers are known to be the
most important route of transmission of pathogenic
bacteria.22-24 Alcohol-based hand rubs have repeatedly
been shown to help improve compliance with hand
hygiene and reduce transmission of pathogens25-27 and
could therefore help to reduce bacterial transfer from
hands to inanimate surfaces. Paper should also be con-
sidered as a possible reservoir for cross-contamination
of resistant organisms, especially in outbre ak sit uatio ns
that involve different hospital units and floors, and
whenever routes of transmission are unclear. Intro-
duction of electronic health records, while re ducing the
use of paper, doesn’t reduce the need for hand hygiene,
as computer keyboards and terminals can also become
contaminated. Further research should focus on the
question of whether and how paper documents are a
part of transmission routes in clinical settings. t
Nils-Olaf Hübner is consultant, infection control, Claudia Hüb-
ner is clinical staff member, and Axel Kramer is director, all
at the Institute for Hygiene and Environmental Medicine of
the Ernst Moritz Arndt University of Greifswald, Greifswald,
Germany. Ojan Assadian is consultant, clinical microbiology,
and consultant, infectious diseases and tropical medicine, at the
Clinical Institute for Hospital Hygiene of the Medical Univer-
sity of Vienna, Vienna, Austria. Contact author: Nils-Olaf
Hübner, nhuebner@uni-greifswald.de. The authors have dis-
closed no potential conflicts of interest, financial or otherwise.
REFERENCES
1. Khin Nwe O, et al. Contamination of currency notes with
enteric bacterial pathogens. J Diarrhoeal Dis Res 1989;
7(3-4):92-4.
2. Uneke CJ, Ogbu O. Potential for parasite and bacteria trans-
mission by paper currency in Nigeria. J Environ Health 2007;
69(9):54-60.
3. Vriesekoop F, et al. Dirty money: an investigation into the
hy giene status of some of the world’s currencies as obtained
from food outlets. Foodborne Pathog Dis 2010;7(12):1497-
502.
4. Abad FX, et al. Survival of enteric viruses on environmental
fomites. Appl Environ Microbiol 1994;60(10):3704-10.
5. Ansari SA, et al. Rotavirus survival on human hands and
transfer of infectious virus to animate and nonporous inani-
mate surfaces. J Clin Microbiol 1988;26(8):1513-8.
6. Basavarajappa KG, et al. Study of bacterial, fungal, and par-
asitic contamination of currency notes in circulation. Indian
J Pathol Microbiol 2005;48(2):278-9.
7. El-Dars FM, Hassan WM. A preliminary bacterial study of
Egyptian paper money. Int J Environ Health Res 2005;15(3):
235-9.
8. Gwaltney JM, Jr., Hendley JO. Transmission of experimen-
tal rhinovirus infection by contaminated surfaces. Am J Epi-
demiol 1982;116(5):828-33.
9. Sattar SA, et al. Survival of human rhinovirus type 14 dried
onto nonporous inanimate surfaces: effect of relative humid-
ity and suspending medium. Can J Microbiol 1987;33(9):
802-6.
6 AJN ▼ December 2011 ▼ Vol. 111, No. 12 ajnonline.com
10. Scott E, Bloomfield SF. The survival and transfer of micro-
bial contamination via cloths, hands and utensils. J Appl
Bacteriol 1990;68(3):271-8.
11. German Institute for Standardization (DIN). DIN 58940-3
beiblatt 1: medical microbiology: susceptibility testing of
pathogens to antimicrobial agents—part 3: Agar diffusion
test; data for the interpretation of inhibition zone diameters.
Berlin 2000.
12. German Institute for Standardization (DIN). DIN standard
58940-2 beiblatt 2: medical microbiology: susceptibility
testing of pathogens to antimicrobial agents, part 2. Active
substance carriers for the agar diffusion test; carrier loads
and values required for drawing a standard curve. Berlin
2002.
13. American Society for Testing and Materials. Historical stan-
dard: ASTM E1838-02 standard test method for determining
the virus-eliminating effectiveness of liquid hygienic hand-
wash and handrub agents using the fingerpads of adult vol-
unteers [superseded]. West Conshohocken, PA; 2002.
14. American Society for Testing and Materials. ASTM E1838-
10: standard test method for determining the virus-eliminat-
ing effectiveness of hygienic handwash and handrub agents
using the fingerpads of adults. West Conshohocken, PA;
2010.
15. Sattar SA, Ansari SA. The fingerpad protocol to assess hygienic
hand antiseptics against viruses. J Virol Methods 2002;103(2):
171-81.
16. Hubner NO, et al. Effect of a 1 min hand wash on the bacte-
ricidal efficacy of consecutive surgical hand disinfection with
standard alcohols and on skin hydration. Int J Hyg Environ
Health 2006;209(3):285-91.
17. Panhotra BR, et al. Contamination of patients’ files in inten-
sive care units: an indication of strict handwashing after en-
tering case notes. Am J Infect Control 2005;33(7):398-401.
18. Teng SO, et al. Bacterial contamination of patients’ medical
charts in a surgical ward and the intensive care unit: impact
on nosocomial infections. J Microbiol Immunol Infect 2009;
42(1):86-91.
19. Harrison WA, et al. Bacterial transfer and cross-c ontamination
potential associated with paper-towel dispensing. Am J Infect
Control 2003;31(7):387-91.
20. Kramer A, et al. How long do nosocomial pathogens persist
on inanimate surfaces? A systematic review. BMC Infect Dis
2006;6:130.
21. Neely AN, Maley MP. Survival of enterococci and staphylo-
cocci on hospital fabrics and plastic. J Clin Microbiol 2000;
38(2):724-6.
22. Farrington M, et al. Outbreaks of infection with methicillin-
resistant Staphylococcus aureus on neonatal and burns units
of a new hospital. Epidemiol Infect 1990;105(2):215-28.
23. Laborde DJ, et al. Effect of fecal contamination on diarrheal
illness rates in day-care centers. Am J Epidemiol 1993;138(4):
243-55.
24. Mermel LA, et al. Outbreak of Shigella sonnei in a clinical
microbiology laboratory. J Clin Microbiol 1997;35(12):
3163-5.
25. Boyce JM, Pittet D. Guideline for hand hygiene in health-
care settings. Recommendations of the Healthcare Infection
Control Practices Advisory Committee and the HICPAC/
SHEA/APIC/IDSA Hand Hygiene Task Force. Society for
Healthcare Epidemiology of America/Association for Profes-
sionals in Infection Control/Infectious Diseases Society of
America. MMWR Recomm Rep 2002;51(RR-16):1-45.
26. Hübner NO, et al. Effectiveness of alcohol-based hand disin-
fectants in a public administration: impact on health and
work performance related to acute respiratory symptoms
and diarrhoea. BMC Infect Dis 2010;10:250.
27. Kampf G, Kramer A. Epidemiologic background of hand
hygiene and evaluation of the most important agents for
scrubs and rubs. Clin Microbiol Rev 2004;17(4):863-93.
For 23 additional continuing nursing educa-
tion articles on research topics, go to www.
nursingcenter.com/ce.
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