Quantification and identification of aerobic bacteria
in holy water samples from a German environment
Christoph König, Stephanie Tauchnitz, Heike Kunzelmann, Christian Horn,
Frithjof Blessing, Matthias Kohl and Markus Egert
ABSTRACT
Despite its frequent use in many religious institutions, the microbiological quality of holy water is
clearly underinvestigated. We analyzed the microbial load of 54 holy water samples, repeatedly taken
in five Roman Catholic churches in the greater area of Villingen-Schwenningen, Germany, by means of
aerobic colony counting and Matrix-Assisted Laser Desorption/Ionization (MALDI) Biotyping of
representative isolates. Over all samples, colony counting indicated an average aerobic microbial load
of 5.85 ± 3.98 × 10
3
colony forming units (CFU) ml
1
(average ± standard error of the mean (SEM)).
Urban churches showed significantly higher contaminations than rural churches, probably owing to a
greater number of visitors. Out of 145 bacterial isolates, 63 (43%) were identified to genus level and
39 (27%) to species level. The majority of the identified bacteria were typical human skin commensals,
mainly affiliated with the genus Staphylococcus. Ten out of 20 (50%) of the identified species were
classified as potential pathogens. Appropriate hygiene measures should be taken to control microbial
contamination of holy water, e.g., regular water exchange, particularly in highly frequented churches.
Christoph König
Stephanie Tauchnitz
Heike Kunzelmann
Frithjof Blessing
Matthias Kohl
Markus Egert (corresponding author)
Faculty of Medical and Life Sciences, Institute of
Precision Medicine,
Furtwangen University,
Jakob-Kienzle-Str. 17,
78054 Villingen-Schwenningen,
Germany
E-mail: markus.egert@hs-furtwangen.de
Christian Horn
Frithjof Blessing
Institute for Laboratory Medicine,
Virchowstr. 10c,
78224 Singen,
Germany
Key words | aerobic bacteria, bacterial load, holy water, hygiene, MALDI Biotyping
INTRODUCTION
Holy water is regarded as a symbol of blessing and purifi-
cation and plays an important role in many ceremonies
and customs in Christianity and other religions. For
instance, Roman Catholic believers wet their fingers with
holy water when entering a church and make the sign of
the cross; occasionally they also cross themselves on the
forehead, lips and chest. In addition, holy water is used to
bless items, food or persons by sprinkling them. Maybe
also owing to its religious importance, only a few studies
have addressed the microbiological and hygienic properties
of holy water so far.
Holy water was first recognized as a source for potentially
pathogenic microorganisms in 1992, when Pseudomonas
aeruginosa was isolated from infected wounds of a hospital
patient after sprinkling with holy water (Greaves & Porter
). In two other cases, nosocomial infections with Acineto-
bacter baumanii were traced back to contact with holy water
(Rees & Allen ; Michel et al. ). Daschner ()
reported massive contamination with Pseudomonas spp. in
holy water samples from churches and hospitals in Freiburg,
Germany. In several Buddhist temples in Thailand, holy
water was examined for microbiological contamination,
and the presence of Escherichia coli was demonstrated
(Phatthararangrong et al. ). High contaminations with
coliform bacteria and members of the Enterobacteriaceae
family, including a considerable diversity of potentially
pathogenic bacteria, were also reported from Spain ( Jurado
et al. ). Recently, a landmark study by Kirschner et al.
() reported contaminations of holy water fonts and holy
springs in Vienna, Austria, with cell counts of up to 10
7
colony forming units (CFU) ml
1
, and the presence of fecal
indicator bacteria such as enterococci and E. coli.
Aiming at a deeper understanding of the hygienic rel-
evance of holy water, the goal of our study was to
823 © IWA Publishing 2017 Journal of Water and Health | 15.5 | 2017
doi: 10.2166/wh.2017.026
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