Page 6 - Healthcare

/ Infection control

Stages in the development CONTROLLING BIOFILM LEGIONELLA
of biofilm on a surface

Naturally present in mixers, taps and pipework, biofilm This bacteria lives naturally in fresh water
is a collection of microorganisms (bacteria, algae, and man-made water features.
fungi, etc.) adhering to each other and to surfaces For optimal development Legionella requires 2 main
that are generally in contact with water, and which elements:
is characterised by the secretion of a protective - water at a temperature between 25°C and 45°C.
and adhesive matrix (slime). - stagnant water and the presence of other
Various studies have shown that, regardless of microorganisms capable of providing nutrients
the material used (copper, CPVC, stainless that its own metabolism is unable to
1: Cell attachment steel, polypropylene, etc.), biofilm forms produce, in addition to scale or corrosion.
systematically after several weeks or 517 Human contamination occurs via the
months even on biocidal materials. cases of Legionnaire’s respiratory route (inhaling contaminated
disease in the UK water in aerosol format) and can lead
99.5% of bacteria found in these to a serious pulmonary infection:
Source: ECDC (European Centre
installations are trapped in the biofilm, for Disease Prevention legionellosis.
and Control), 2019
which provides the ideal environment
(water, temperature and nutritional
conditions) for them to proliferate.
If the conditions are favourable, the bacteria multiply MONITORING FOR LEGIONELLA
and form aggregates that can easily become detached
2: Irreversible cell attachment and contaminate the water supply.
Biofilm is impossible to eradicate, but its The United Kingdom, France, Germany and the
development can still be controlled. majority of the European countries have specific
requirements for monitoring for bacteria in the water
Bacteria in the BIOFILM Free-floating bacteria distribution system.
BIOFILM
99.5% 0.5%
These regulations have a common premise (circulating
loops, hot water temperatures, etc.) but they also have
specific aspects that could provide inspiration for
other countries.
In the majority of European countries there is a legal
obligation to safeguard the bacteriological quality
3: Biofilm maturation phase I
of the water in the system by regular monitoring,
sampling and analysis. However, the methods and
subsequent follow-up action differ.
THE FIGHT AGAINST
WATERBORNE BACTERIA In France, the search for Legionella is obligatory.
The Directive of 1st February, 2010 identifies three
st
Infection control must be the priority for healthcare levels of monitoring and sampling protocols. Since 1
facilities, which shelter many germs such as viruses January, 2012, monitoring has been extended to all
and bacteria. buildings open to the public.
There are two types of waterborne bacteria which are Germany has adopted the same threshold levels
responsible for healthcare acquired infections as France, while the United Kingdom is stricter: it
4: Biofilm maturation phase II in hospitals: conducts additional testing at levels over 100 Colony
- bacteria in the system which develop when in contact Forming Units per litre (CFU/L) and initiates curative
with water e.g. Legionella spp. procedures above 1,000 CFU/L.
- bacteria at the point-of-use (water controls)
which develop when in contact with air/water e.g. Monitoring levels for Legionella spp.:
Pseudomonas aeruginosa, Mycobacterium avium,
Mycobacterium xenopi, etc. Alert level < 100 CFU/L
Since these two types of bacteria are very different, Remedial action > 100 CFU/L
bacteriological monitoring must be appropriate up to 1,000 CFU/L
for both types. Unacceptable level > 1,000 CFU/L
CFU/L: Colony forming units/Litre
5: Cell dispersion
For severely immunocompromised high-risk patients
Source: Chinks in the Armor in hospitals the draw-off at the point-of-use should
of Bacterial biofilms Monroe always be free from Legionella spp. bacteria.
D PLoS Biology Vol. 5, No. 11,
e307 doi: 10.1371/journal.
pbio.0050307/D. Davis.

4 Hospital solutions