legion ella and dental water lines

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Legionnaires’ Disease Outbreak

June 21 to July 4, 2011

6 cases of Legionnaires’ Disease reported

Sent letters to guests who stayed at the Ariaduring this 2-week period

High levels of Legionella bacteria detected

in water supplying several guest rooms

Follow-up testing did not detect the bacteriashould you be tested, did you develop symptom, who is at risk, could you be infected, could you transmit.



Legionnaires’ Disease

Epidemic of pneumonia at the Pennsylvania State

American Legion convention 1976

221 people affected, 34 died

An upscale hotel , the Bellevue-Stratford, closed due to

the publicity

Causative mo not identified until 1977 (6 months

later) – fastidious gram-negative bacillus

Prior outbreaks (1940s, 1950s, 1960s)

Unsolved epidemic of nonpneumonic febrile illness

in Pontiac, Michigan (1960s)

pontiac fever



2010 Selfridge Air National

Guard Base Outbreak July 12-24 – at least 31 people with an URT

illness

6 people diagnosed with Legionnaires’disease



Legionella pneumophila

Gram negative aerobic bacillus

Single polar flagellum, multiple pili

Nutritionally fastidiousMedium: charcoal yeast extract pH 6.9

Usually find as intracellular organisms

In nature, found inside protozoa

In vivo replicates inside macrophages



Ecology: Legionella pneumophila

Natural habitat: rivers, lakes, streams,

thermally polluted waters

Survives water treatment process

Chlorine tolerant

Proliferate in man-made habitats

Cooling towers, water distribution systems



Transmission: Legionella pneumophila

Aerosolization

Aspiration

Instillation into lung

Not transmissible person to person



Diseases

Legionnaires’ disease

Non-specific clinical presentation

Early flu-like symptoms

Mild cough early, slightly productive

Pontiac fever

Acute self-limiting flu-like illness

Common



Pontiac Fever

>90% exposed develop symptoms

acute, self-limiting flu-like illness

IP = 24-48 hrs

malaise, myalgia, fever, chills, headache

only symptomatic tx necessary

complete recovery within 1 week




Pneumonia is most prominent finding

Spectrum of illness from mild cough to

stupor with multi-system failure

IP = 2-10 days

L. pneumophila one of 3 most common

etiologic agents of community-acquired

pneumonia




Risk factors

Cigarette smoking

Chronic lung disease

Advanced age

Immunosuppression

Treatment: erythromycin, doxycycline,

azithromycin



Outbreak of legionellosis in

Wayne Co., Michigan in 1985

Early May of 1985

14 cases of pneumonia with high fever

occurred in 380 persons who attended a

church banquet at a hotel on April 27

3 cases fatal

Washings from the cooling coils of the A/C

units supplying the banquet hall positive for Legionella pneumophila



Outbreak in Ohio automotive

plant, 2001

March 12-15, 2001

4 cases of Legionnaires’ disease

Exposure to aerosol-producing devicesFinishing area



L. pneumophila and dentistry

Legionella associated with biofilms in

dental unit water lines (DUWLs)

Also Pseudomonas

DCWs shown to have an increased level of

antibodies to Legionella

DUWLs require treatment procedures to

control biofilm and reduce #s of mo’s



Dental Unit Waterlines (DUWL)

Bacteria in DUWL first noted in 1963 byDr. G.C. Blake

Large numbers of bacteria present in water

and aerosols associated with dental watersystems.

Biofilms form in DUWLs and can harbor a

variety of microorganisms.

Most of the microbes recovered from dental

water systems are gram-negative noncoliform

bacteria.



Safe Drinking Water Act

Sets standard for noncoliform bacteria in

drinking and recreational water at 500

CFU/ml.

DUWL contamination in untreated systems

often exceeds 1000 CFU/ml

Range of 10,000 to 100,000 CFU/ ml

commonplace ADA in 1996 established a goal for dental

water to contain no more than 200 CFU/ml



Why the high numbers in DUWL?

Surface colonization

Materials commonly used to deliver water to

dental handpieces, etc., provide excellent

substrates for colonization.Minerals in water, esp. calcium carbonate,

deposited.

Organic molecules attach & promote adhesion of

bacteria suspended in water Individual cells multiply to form microcolonies

Ultimately these coalesce and form a mature biofilm



Why the high numbers?

Laminar flow

Fluids moving through narrow-bore tubing

assume a hydrodynamic pattern known as

laminar flow.Frictional forces slow the movement of fluids at the

tubing surface, creating an environment conducive

to formation of biofilm

Flushing can eliminate suspended microbes butnot biofilm.



Why the high numbers? continued

Surface:volume ratio

As the diameter of a cylinder (waterline)

decreases, an increasingly larger surface area

becomes available for colonization.This is the biggest factor. Water moves from a

10 inch water main to a 0.5 inch pipe in the

dental office to dental water system tubing that

is 1/16 in. in diameter.



Water retraction

Older dental units designed to retract water

(to prevent water dripping from handpieces

and air/water syringes)

Could also retract oral fluids

Anti-retraction valves installed to prevent

retraction of oral fluids



What organisms present?

Biofilm is hospitable environment for fungi,

protozoa, and other organisms

Legionella pneumophila

Pseudomonas aeruginosa

Nontubercular Mycobacterium spp.

Mostly noncoliform gram-negatives but

coliforms have been isolated — especiallywith careless handling of bottles and feeder

tubes.



Improving the quality of dental

water

Waterline flushing

Efficacy not established as a stand alone tx

Does not remove biofilm but can remove

suspended organisms

Independent reservoirs

Allows control of water quality

Also best combined with chemical agents




water Chemical treatment – no ideal agent

Intermittent or continuous chemical release

Intermittent usually uses biocidal concentrations of

germicides that also remove biofilm

• Active agent purged prior to patient care

Continuous tx uses lower concentrations of

chemicals

Chlorine cpds (sodium hypochlorite)

Several dental unit manufacturers recommendweekly tx of DUWL with 1:10 dilution of

household bleach




water

Other chemical agents proposed or

evaluated:

Chlorhexidine gluconate

Hydrogen peroxide

Iodophors

Commercial mouthrinses




water Automated treatment devices

Ozone and silver germicide

Sterisil straw/cartridge contains a cation exchange

resin and silver (highest concentration 3 ppm) as a

germicide

Periodic treatment regimens

Several of these including DentaPure iodinated resin

cartridges which release 2-6 ppm free iodine into

treatment water to control biofilm

Water source controls - reservoirs




water

Filtration

Remove suspended bacteria but no effect on

biofilm formation in pretreatment areas of lines

DentaPure filter includes 0.22 m filter



Bottom Line – Infection control

dilemma

Potential source of infection of

immunocompromised patients

CDC recommendations:

Sterile irrigating solutions should be used when

surgical procedures involve cutting of bone.

All dental instruments that use water should be

run 20-30 seconds after each patient and for

several minutes before the start of each clinic

day.



UDMSD Procedures 1

Before first patient:

Fill water reservoir and attach to dental unit.

Turn on master switch, wait a few seconds for

system to pressurize.

Flush waterlines for at least 1 minute.

Between patients:

Flush lines 20-30 seconds.



UDMSD Procedures 2

At the end of the day:

Flush lines for 30 seconds.

Turn off master switch.

Remove all handpieces.

Remove and empty water bottle and place on

bracket tray.

legion ella and dental water lines

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