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Biofilms in Infection
Dr.T.V.Rao M D
Beginning of Microbes

Bacteria first appeared on
earth about 3.6 billion
years ago, long before
the appearance of Homo
sapiens around 100,000
years ago.. Van
Leeuwenhoek was the
first person to visualize,
graphically illustrate, and
label "animalcules"
(bacteria) that he found
in plaque scraped from
his own teeth.
Bio film constitutes

A biofilm is an aggregate of
microorganisms in which cells are stuck to
each other and/or to a surface. These
adherent cells are frequently embedded
within a self-produced matrix of
extracellular polymeric substance (EPS).
Biofilm EPS, which is also referred to as
"slime," is a polymeric jumble of DNA,
proteins and polysaccharides.
Biofilm is a complex substance.

A biofilm is a complex
aggregation of
microorganisms growing
on a solid substrate.
Biofilms are characterized
by structural
heterogeneity, genetic
diversity, complex
community interactions,
and an extracellular
matrix of polymeric
substances.
Biofilms found in Nature everywhere
where is there is moisture

More properly known as biofilm, slime
cities thrive wherever there is water - in
the kitchen, on contact lenses, in the gut
linings of animals. When the urban sprawl
is extensive, bio films can be seen with
the naked eye, coating the inside of water
pipes or dangling slippery and green from
plumbing." (Coghlan 1996)
Biofilm supports the Bacterial
growth

Biofilm are a common mode of bacterial growth
in nature and their presence has an enormous
impact on many aspects of our lives, such as
sewage treatment, corrosion of materials, food
contamination during processing, pipe collapse,
plant-microorganisms interaction in the
biosphere, the formation of dental plaque, the
development of chronic infections in live tissue
(mastitis, Otitis, pneumonia, urinary infections,
osteomyelitis) or problems related to medical
implants.
Formation of Biofilms

Biofilms may form
on living or nonliving surfaces, and
represent a
prevalent mode of
microbial life in
natural, industrial
and hospital
settings
Biofilms increases Antibiotic
resitance
With
microorganisms
are highly resistant
to antimicrobial
treatment and are
tenaciously bound
to the surface
Mechanisims of Biofilm formation

Formation of a biofilm
begins with the
attachment of free-floating
microorganisms to a
surface. These first
colonists adhere to the
surface initially through
weak, reversible van der
Waals forces. If the
colonists are not
immediately
separated from the
surface, they can
anchor themselves
more permanently
using cell adhesion
structures such as pili
Factors Influencing Rate and Extent
of Biofilm Formation

Indwelling medical device when contaminated
with microorganisms, several variables
determine whether a biofilm develops. First the
microorganisms must adhere to the exposed
surfaces of the device long enough to become
irreversibly attached. The rate of cell attachment
depends on the number and types of cells in the
liquid to which the device is exposed, the flow
rate of liquid through the device, and the
physicochemical characteristics of the surface
Technology understands
Biofilms better…

Technological progress in
microscopy, molecular
genetics and genome
analysis has significantly
advanced our
understanding of the
structural and molecular
aspects of biofilms,
especially of extensively
studied model organisms
such as Pseudomonas
aeruginosa.
Steps in Biofilm Development

Biofilm development can
be divided into several
key steps including
attachment, micro colony
formation, biofilm
maturation and
dispersion; and in each
step bacteria may recruit
different components and
molecules including
flagella, type IV pili, DNA
and exo polysaccharides.
Stages of biofilm development.
Steps in Biofilm formation
Bacteria associated with
Biofilms differ

Bacteria living in a biofilm can have
significantly different properties from freefloating bacteria, as the dense and
protected environment of the film allows
them to cooperate and interact in various
ways. One benefit of this environment is
increased resistance to detergents and
antibiotics, as the dense extracellular
matrix and the outer layer of cells protect
the interior of the community.
Biofilms major cause of Nosocomial
infections

Microbial biofilms,
which often are
formed by
antimicrobial-resistant
organisms, are
responsible for 65%
of infections treated
in the developed
world.
Biofilms a Great threat to
Implants

A significant number of people are
affected by biofilm infections which
develop on medical devices implanted in
the body such as catheters (tubes used to
conduct fluids in or out of the body),
artificial joints, and mechanical heart
valves. When implanted material becomes
colonized by microorganisms, a slow
developing but persistent infection results.
Biofilms a Grwoing concern in
Modern Medicine

Prosthetic device infections, such as those
involving artificial heart valves,
intravascular catheters, or prosthetic
joints, are prime examples of biofilmassociated infections. With the increasing
use of such devices in the modern practice
of medicine, the prevalence of these
infections is expected to increase.
Dental plaque

Dental plaque is a
yellowish biofilm that
build up on the teeth.
If not removed
regularly, it can lead
to dental caries.
Dental plaques

The formation of
dental plaque bio
films includes a series
of steps that begins
with the initial
colonization of the
pellicle and ends with
the complex
formation of a mature
bio film.
Formation of Dental Biofilms

Additionally, through the
growth process of the
plaque bio film, the
microbial composition
changes from one that is
primarily gram-positive
and streptococcus-rich to
a structure filled with
gram-negative anaerobes
in its more mature state.
Cell-cell signaling (ex. quorum sensing),
and communication with different bacteria
enhance Biofilm formation
Biofilms everywhere

They're everywhere: on
your shower curtain, on
medical devices
implanted in patients, on
rocks in rivers and
streams, and in your
nose. While the sheer
number of different
organisms a biofilm may
contain makes it a
challenge to study,
CDC – on Biofilms

Biofilms form on the surface of catheter
lines and contact lenses. They grow on
pacemakers, heart valve replacements,
artificial joints and other surgical implants.
The CDC (Centers for Disease Control)
estimate that over 65% of Nosocomial
(hospital-acquired) infections are caused
by biofilms.
Biofilms interfere in Antibiotic
Therapy

Bacteria growing in a
biofilm are highly
resistant to antibiotics, up
to 1,000 times more
resistant than the same
bacteria not growing in a
biofilm. Standard
antibiotic therapy is
often useless and the
only recourse may be to
remove the contaminated
implant.
Biofilm and Antibiotic resistance

A key property of bio
films is that individual
microorganisms are
bound together by a
polymeric substance
excreted by the
microorganisms.. This
protective encapsulation
is believed to play a role
in some antibioticresistant infection.
Bacterial resitance and Biofilms

Another area of great importance from a
public health perspective is the role of
biofilms in antimicrobial-drug resistance.
Bacteria within biofilms are intrinsically
more resistant to antimicrobial agents
than plank tonic cells because of the
diminished rates of mass transport of
antimicrobial molecules to the biofilm
associated cells or because biofilm cells
differ physiologically from plank tonic cells
Biofilms in Cystic fibrosis

Biofilms are involved
in numerous diseases.
In cystic fibrosis
patients have
Pseudomonas
infections that often
result in antibiotic
resistant biofilms.
Endocarditis and Biofilms

Microorganisms may attach and develop biofilms
on components of mechanical heart valves and
surrounding tissues of the heart, leading to a
condition known as prosthetic valve
endocarditis. The primary organisms responsible
for this condition are S. epidermidis, S. aureus,
Streptococcus spp., gram-negative bacilli,
diphtheroids, enterococci, and Candida spp.
These organisms may originate from the skin,
other indwelling devices such as central venous
catheters, or dental work.
Eye and Biofilms

The presence of bacterial
biofilms has been
demonstrated on many
medical devices including
intravenous catheters, as
well as materials relevant
to the eye such as
contact lenses, scleral
buckles, suture material,
and intraocular lenses.
Many ocular infections
often occur when such
prosthetic devices come
in contact with or are
implanted in the eye.
Biofilms and Contact lenses

Bacterial biofilm
formation on contact
lenses and contact lens
storage cases may be a
risk factor in contact lensassociated corneal
infections. Studies have
shown that contamination
of lens cases by bacteria,
fungi, and amoebae is
common with 20% to
80% of lens wearers
having a contaminated
lens case.
Urinary catheters and Biofilms

Urinary catheters are tubular latex or silicone
devices, which when inserted may readily
acquire biofilms on the inner or outer surfaces.
The organisms commonly contaminating these
devices and developing biofilms are
S. epidermidis, Enterococcus faecalis, E.
coli, Proteus mirabilis, P. aeruginosa, K.
pneumoniae, and other gram-negative
organisms. The longer the urinary catheter
remains in place, the greater the tendency of
these organisms to develop biofilms and result in
urinary tract infections.
Biofilms and indwelling medical
devices

Biofilms on indwelling medical devices may be
composed of gram-positive or gram-negative
bacteria or yeasts. Bacteria commonly isolated
from these devices include the gram-positive
Enterococcus faecalis, Staphylococcus aureus,
Staphylococcus epidermidis, and Streptococcus
viridians; and the gram-negative Escherichia
coli, Klebsiella pneumoniae, Proteus mirabilis,
and Pseudomonas aeruginosa.
Indwelling catheters and
Biofilms*

Central venous catheters, the reference method
for quantification of biofilms on catheter tips is
the roll-plate technique, in which the tip of the
catheter is removed and rolled over the surface
of a nonselective medium. Quantification of the
biofilm depends on the number of organisms
recovered by contact with the agar surface.
Biofilm-associated cells on the inner lumen of
the device are not detected with this method,
which has low diagnostic sensitivity and low
predictive value for catheter-related
bacteraemia.
Indwelling catheters and Biofilms*

In addition, this method cannot detect
more than 1,000 colony-forming units
(CFU) per tip. A method that used
sonication plus vortexing as a means of
quantifying biofilms on catheter tips
showed that a level of 104 CFU per tip is
predictive of catheter-related septicaemia
* Biofilms and Device-Associated Infections
Rodney M. Donlan Centers for Disease Control and Prevention Atlanta,
Georgia, USA
Antibiotic therapy alone may not
cure ?

Antimicrobial agents are
administered during valve
replacement and
whenever the patient has
dental work to prevent
initial attachment by
killing all microorganisms
introduced into the
bloodstream. As with
biofilms on other
indwelling devices,
relatively few patients
can be cured of a
biofilm infection by
antibiotic therapy
alone
Biofilms a concern in Antimicrobial
Therapy

Microbial biofilms may pose a public health
problem for persons requiring indwelling medical
devices. The microorganisms in biofilms are
difficult or impossible to treat with antimicrobial
agents; detachment from the device may result
in infection. Although medical devices may differ
widely in design and use characteristics, specific
factors determine susceptibility of a device to
microbial contamination and biofilm formation.
Biofilms need higher concentration
of Antibiotics

Biofilms are remarkably difficult to treat
with antimicrobials. Antimicrobials may be
readily inactivated or fail to penetrate into
the biofilm. In addition, bacteria within
biofilms have increased (up to 1000-fold
higher) resistance to antimicrobial
compounds, even though these same
bacteria are sensitive to these agents if
grown under plank tonic conditions.
Biofilms help Gene transfer

Biofilms increase the
opportunity for gene
transfer
between/among
bacteria.. Gene
transfer can convert a
previous a virulent
commensals organism
into a highly virulent
pathogen.
Biofilms –Quorum sensing

Certain species of
bacteria communicate
with each other within
the biofilm. As their
density increases, the
organisms secrete low
molecular weight
molecules that signal
when the population has
reached a critical
threshold. This process,
called quorum sensing,
is responsible for the
expression of virulence
factors.
Quorum sensing helps the
survival of pathogens
Biofilms contribute for new
phenotypes

Bacteria express new, and sometimes
more virulent phenotypes when growing
within a biofilm. Such phenotypes may not
have been detected in the past because
the organisms were grown on rich nutrient
media under plank tonic conditions. The
growth conditions are quite different
particularly in the depths of biofilms,
Biofilms protects from Immune
responses

Bacteria embedded within biofilms are
resistant to both immunological and nonspecific defence mechanisms of the body.
Contact with a solid surface triggers the
expression of a panel of bacterial enzymes
which catalyze the formation of sticky
polysaccharides that promote colonization
and protection.
Biofilms – Protects from
Phagocytosis

Phagocytes are unable to effectively
engulf a bacterium growing within a
complex polysaccharide matrix attached to
a solid surface. This causes the phagocyte
to release large amounts of proinflammatory enzymes and cytokines,
leading to inflammation and destruction of
nearby tissues.
Current objectives on Biofilm
research

o Development of improved imaging of biofilms
in situ;
o Development of improved clinically relevant in
vitro and in vivo models of biofilms under
specific in vivo conditions such as flow rate,
nutrient content, and temperature;
o Development of better probes (genetic,
metabolic, and immunological) for real- time
analysis;
o Studies of quorum sensing/signaling
molecules;
Current objectives on Biofilm
research

o Further characterization of biofilm-specific
gene expression;
o Studies of the exchange of genetic material
within biofilms;
o Studies of organic contaminants on substrata,
and their influence on biofilm structure;
o Development of novel approaches to control
pathogenic bacteria by, for example, devising
strategies to favour growth of non-pathogenic
microorganisms in biofilm communities;
Current objectives on Biofilm
research

o Studies of pathogenic
mechanisms of microbes
growing in biofilms;
o Elucidation of
mechanisms of resistance
of biofilms to
antimicrobial agents;
o Studies of host
immune responses,
both innate and
adaptive to biofilms;
Current objectives on Biofilm
research

In studies of infectious lung disease in cystic
fibrosis;
o Studies on the potential of diagnostic
procedures such as Bronchoalveloar lavage and
bronchoscopy to disturb local biofilm flora and
inoculate distant locations;
o Development of mathematical models and
computer simulations of biofilms;
o Development of the methodology for the
prevention and control of biofilms from
catheters, water unit lines, and other clinically
important solid surfaces;.
Searching for alternatives – Tissue
engineering

Role of biofilms in multiple pathologies and the
difficulty in resolving these pathologies speaks to
the importance of developing means of replacing
or enhancing the therapies already in use. The
use of synthetic materials in the body ranges
from catheters to mesh to stents to heart valves
and beyond. Until the development of viable and
practical tissue engineering, then number and
types of applications in which synthetic materials
are used will continue to increase.
Emerging Methods

Several researchers are
finding solutions for the
cure of Biofilms , yet it is
experimental, with
advances in molecular
biology better model
treatments can be
identified to reduce the
problem of Biofilm
interference in Antibiotic
therapy.
Created for Dr.T.V.Rao MD’s ‘e’
learning series.
Email
[email protected]