Biofilms ABC

8/6/2019 Biofilms ABC

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BIOFILMS


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Introduction to Biofilms :

A biofilm is a complex aggregation of

microorganisms, which is usually slimy innature, and is covered by a protective andadhesive matrix.


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S ingle-celled organisms generally exhibit two distinct

modes of behavior.

The first is the familiar free floating, or planktonic,form in which single cells float or swim independentlyin some liquid medium.

The second is an attached state in which cells are

closely packed and firmly attached to each other andusually a solid surface.


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Formation

Formation of a biofilm begins with the attachment of free-floating microorganisms to a surface. These first

colonists adhere to the surface initially throughweak, reversible van der Waals forces. If the

colonists are not immediately separated from thesurface, they can anchor themselves morepermanently using cell adhesion molecules such aspilli.


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*1 ,2 The first colonists facilitate the arrival of other cells byproviding more diverse adhesion sites and begins to build

the matrix that holds the biofilm together.

Biofilms can contain many different types of microorganism,e.g. bacteria, archaea, protozoa and algae. Biofilms are

present on the teeth of most animals as dental plaque,where they may become responsible for tooth decay.


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Biofilms and infectious diseases

Biofilms have been found to be involved in a wide varietyof microbial infections in the body, by one estimate 80%of all infections. Infectious processes in which biofilms

have been implicated include common problems suchas urinary tract infections, middle-ear infections,formation of dental plaque, gingivitis, coating contactlenses, and less common but more lethal processes

such as endocarditis, infections in cystic fibrosis, andinfections of permanent indwelling devices such as jointprostheses and heart valves.


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Biofilms in Dentistry

D ental Unit Waterline ( D UWL) Contamination :

The current problem with the water quality used indental clinical setups, primarily centre on the

formation of microbial biofilm along the walls of the long , narrow-bore tubing that provides coolingand irrigating water to dental hand instruments.

Levels of microbial contamination as high as1 0,000 to 1 0,000,000 (colony forming units)CF Us/ml have been documented.


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DUWL Contamination Dynamics

Input: Water qualityInput: Water quality

Waterline: BiofilmWaterline: Biofilm

Output:Output:Retraction and BackflowRetraction and Backflow


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Copyright 2003, Elsevier S cience (U S A). All rights reserved.

Close up of dental tube opening.Close up of dental tube opening.

Fig. 24-1Fig. 24-1


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A cross-section of a dental unit waterline illustrating the formation of biofilmon the inside wall of a dental tube. A cross-section of a dental unit waterline illustrating the formation of biofilmon the inside wall of a dental tube.

Fig. 24-2Fig. 24-2


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M agnification of biofilm formation on the walls of the tube . M agnification of biofilm formation on the walls of the tube .

Fig. 24-3Fig. 24-3


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*3 E nvironmental Infection Control

Both water-borne and human oral microbeshave been found in dental unit water, indicatingthat both incoming community water andpatients mouths are sources of these microbes.

Most of the microbes detected are of very lowpathogenicity or are opportunistic pathogens that

cause harmful infections only under specialconditions or in immunocompromised people.


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The Center for D isease Control, U S A (C D C) hasrecommended that :

-- High-speed hand-pieces should be flushed todischarge water and air for a minimum of 20 to 30seconds after use on each patient ;

-- Use of a high-velocity evacuation should beconsidered to minimize the spread of spray, splatter and aerosols generated during treatmentprocedures;


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-- Overnight or weekend microbial accumulation in

water lines can be reduced substantially byremoving the hand-piece and allowing water linesto run and discharge water for several minutes atthe beginning of each clinic day ; and

-- S terile saline or sterile water should be used as acoolant/irrigator when surgical procedures involvingthe cutting of bone are performed.


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Hard surfaces disinfection :

Potentially infective patients must be seen at the end of theday. All instruments must be autoclaved. All hard surfacesshall be cleaned and disinfected with a disinfectant.

Protection :

CD C recommends that all high-risk areas (eg., bracket table,light handles , X-ray unit heads, counter tops, etc., ) areprotected by disposable covers or cloths, which are washedprior to reuse. The protection should be removed by glovedhands and safely discarded, after each patient.


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Special Considerations :

D ental hand-pieces and other devices attached to air and water lines : S ince there is a tendency that fluids and materials fromthe patients oral cavity may flow back into the hand-piece andwater lines , anti-retraction valves (one-way flow check valves)should be installed to prevent cross-infection. Routine

maintenance of anti-retraction valves is necessary to ensureeffectiveness ; the dental unit manufacturer should be consultedto establish an appropriate maintenance routine.


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Other reusable intraoral instruments attached to, but

removable from, the dental unit air or water lines(such as ultrasonic scaler tips and component partsand air/water syringe tips) :

These should be cleaned and sterilized after treatment of each patient in the same manner ashand-pieces.

Manufacturers directions should be followed toensure effectiveness of the process as well aslongevity of the instruments.


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S ingle-use disposable instruments (eg., prophylaxis

cups and brushes ; saliva ejectors) should be usedfor one patient only and discarded appropriately.These items are neither designed nor intended to becleaned, disinfected, or sterilized for reuse.


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Preprocedural mouth rinse with an antimicrobialproduct (ie., chlorhexidine gluconate, povidoneiodine) can reduce the level of microorganisms inaerosols and splatter generated during routinedental procedures with rotary instruments (ie., dentalhandpieces, ultrasonic scalers).


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Biofilms ABC