processes used, and because season and rainfall may also impact
on findings. Proia et al. (2016) demonstrated that WWTP
effluent favors the persistence and spread of antimicrobial
resistance in aquatic microbial communities.
10
A meta-analysis
of previous research in this area reveals that WWTP processing
appears to increase the proportion of resistant bacteria (odds
ratio of 1.60, 1.33, and 1.19 for multiple antimicrobial-resistant
bacteria, single antimicrobial-resistant E. coli, and quinolone-
or fluoroquinolone-resistant bacteria, respectively).
5, 11
This
may suggest that antimicrobial-resistant bacteria are better able
to survive the wastewater treatment process, although analytical
data from the same study indicates unequivocally that the total
number of antimicrobial-resistant E. coli is greatly reduced
by wastewater treatment, even if the proportion is somewhat
increased.
5
There is a need for further research to understand
how the secondary wastewater treatment process may impact
the development of antimicrobial resistance — in particular,
what drives the development of resistance in effluent and what
helps to maintain it.
Emerging Contaminants
In addition to antimicrobial agents and antimicrobial-resistant
bacteria, other emerging contaminants of concern include
microplastics and engineered nanomaterials (ENMs). Microplastics
and ENMs have a wide range of potential applications, from
everyday uses (such as improvements in fabrics, paints, cosmetics,
packaging, etc.) to medical applications, water and soil remediation,
and renewable energy production.
12
Whereas significant benefits
are claimed for their use, there are concerns regarding the potential
for adverse impacts on human health and the environment. Based
on current available information, it is difficult to predict likely
environmental discharges. There is inadequate data on persistence/
transformation in the environment, and such parameters are
likely to vary with the nature of the microplastic or ENM and its
application. There is no consensus regarding optimal methods for
detection of such contaminants in the environment; therefore it is
difficult to ascertain to what extent microplastics and ENMs are
distributed in aquatic and other environments, to what extent they
persist or undergo transformation, and what impact wastewater
treatment systems and other processes have on their removal. An
ongoing project funded by the Irish EPA is currently examining
some of these issues. n
References:
1 World Health Organization. 2015. Global Plan on Antimicrobial Resistance. http://
apps.who.int/iris/bitstream/10665/193736/1/9789241509763_eng.pdf?ua=1
2 European Centre for Disease Prevention and Control (2009) The Bacterial Challenge:
Time to React. http://ecdc.europa.eu/en/publications/Publications/0909_TER_The_
Bacterial_Challenge_Time_to_React.pdf
3 Review on Antimicrobial Resistance. Antimicrobial Resistance: Tackling a Crisis for the
Health and Wealth of Nations. 2014. http://amr-review.org/sites/default/files/AMR%20
Review%20Paper%20-%20Tackling%20a%20crisis%20for%20the%20health%20
and%20wealth%20of%20nations_1.pdf
4 Vellinga, A., Cormican, S., Driscoll, J., Furey, M., O'Sullivan, M., Cormican, M. 2014.
Public practice regarding disposal of unused medicines in Ireland. Science of the Total
Environment. 478, p. 98-102.
5 Morris, D., Harris, S., Morris, C., Cummins, E., Cormican, M. 2016. Hospital Effluent,
Impact on the Microbial Environment and Risk to Human Health. [Available from:
http://www.epa.ie/pubs/reports/research/water ].
6 Harris, S., Cormican, M. and Cummins, E. 2013. Risk ranking of antimicrobials in
the aquatic environment from human consumption: an Irish case study. Human and
Ecological Risk Assessment, 19, 1264–1284.
7 Harris, S., Morris. C., Morris, D., Cormican, M., and Cummins, E. 2013. Simulation model
to predict the fate of ciprofloxacin in the environment after wastewater treatment.
Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances and
Environmental Engineering,
48, 675–685.
8 Rodriguez-Mozaz, S., Chamorro, S., Marti, E., Huerta, B., Gros, M., Sáanchez-Melsió, A.,
Borrego, C.M., Barceló, D., Balcázar, J.L. 2015. Occurrence of antibiotics and antibiotic
resistantce genes in hospital and urban wastewaters and their impact on the receiving
river. Water Research, 69, p. 234-242.
9 Ludden, C. Cormican, M., Vellinga, A., Johnson, J.R., Austin, B., Morris, D. 2015.
Colonization with ESBL-producing and carbapenemase-producing Enterobacteriaceae,
vancomycin-resistant enterococci, and meticillin-resistant Staphylococcus aureus in
a long-term care facility over one year.BMC Infect Diseases Apr 1;15:168. doi: 10.1186/
s12879-015-0880-5.
10 Proia, L., von Shiller, D., Sánchez-Melsió, A., Sabater, S., Borrego, C.M., Rodríguez-
Mozaz, S., Blacázar, J.L. 2016. Occurrence and persistence of antibiotic resistance genes
in river biofilms after wastewater inputs in small rivers. Environmental Pollution. 210. P.
121-128.
11 Harris, S., Cormican, M. and Cummins, E., 2012a. The effect of conventional
wastewater treatment on the levels of antimicrobial-resistant bacteria in effluent: a
meta-analysis of current studies. Environmental Geochemistry and Health, 34, 749–762.
12 European Environmental Bureau. 2009. http://www.eeb.org/?LinkServID=540E4DA2-
D449-3BEB-90855B4AE64E8CE6
10
wateronline.com
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Water Innovations
EMERGINGCONTAMINANTS
Escherichia coli (E. coli) bacteria
Dearbháile Morris, B.Sc., PhD, is lecturer in the School of Medicine,
director of the Antimicrobial Resistance and Microbial Ecology
Group, and codirector of the Centre for Health from Environment
at the National University of Ireland Galway. Dearbháile has over
18 years' experience in the study of antimicrobial resistance and
waterborne pathogens.
About The Authors
Martin Cormican, MB, BCh, BAO, MD, is Chair of Bacteriology,
and director of the Centre for Health from Environment at the
National University of Ireland Galway; consultant microbiologist
at Galway University Hospitals, director of the National Salmonella
Shigella and Listeria Reference Laboratory, and director of the
National Carbapenemase Producing Enterobacteriaceae Reference
Laboratory. Martin has over 20 years' experience of research on
antimicrobial resistance and waterborne organisms of public health
concern.
