Enterococcus faecalisJose J. Ferrari D.D.S.

Graduate Endodontic DepartmentCase Western Reserve University

E. faecalis CharacteristicsEnterococcus faecalis formerly classified as Group

D Streptococcus.

Gram-positive cocci that occur singly, in pairs, or in short chains.

Facultative anaerobes.

They catabolize a variety of energy sources including carbohydrates, glycerol, lactate, malate, citrate, arginine, agmatine, and many α keto acids.

Displays gamma hemolysis on sheep’s blood agar

Cont. Characteristics• E. faecalis can cause life-threatening infections in humans,

especially in the nosocomial (hospital) environment.

• Major nosocomial pathogens causing bacteremia, endocarditis, bacterial meningitis, urinary tract, and various other infections

Live in vast quantities in the human intestinal lumen.

They are common in environments contaminated by human and animal faecal materials (e.g. urban sewage, recipient water, and soil receiving fertilizers of animal origin), as well as in food products derived from animals

Present in human female genital tract and oral cavity in lesser numbers.

Virulence Factors Aggregation Substance

− Biofilm formation helps resist Ca(OH)2

• Surface Adhesins– Adhesins that facilitate specific binding of enterococci to intestinal

epithelium, renal epithelial cells, human neutrophils, and macrophages

Superoxide formation– Tissue destruction– Neutrophil chemo-attractant

Gelatinase formation (GelE)

− Can hydrolyse gelatin, casein, haemoglobin, and other bioactive peptides.

Virulence factorsHyaluronidase

− Destroys CT

Cytolysin– Targets erythrocytes

AS-48– An antibiotic-like peptide found in some strains of

E. Faecalis– Competition with other bacteria

Virulence FactorsLTA (lipoteichoic acid) is involved in

inflammatory responses and sepsis syndrome biofilm formation and adhesion to teeth because of its absorptive activity to hydroxyapetite

Scanning Electron Microscope

Primary Endodontic Infections Polymicrobial

Dominated by Gram-negative Anaerobic Rods

E. faecalis is found in 4to 40% of primary endodontic infections

− et al Rocas, Siqueira JOE 2004

Secondary Endodontic Infections• Compose of one or a few bacterial species

Predominantly Gram-positive microorganisms

9 times more likely to contain E. faecalis than primary endodontic infections

Primary Endodontic Infection

Secondary Endodontic Infection

Persistence of Periapical Lesion

Why in Endodontic Reinfection?

E. faecalis and Endodontic failures

E. faecalis is mostly associated with asymptomatic cases

Despite making up a small proportion of the flora in untreated canals, plays a major role in the etiology of persistent periradicular lesions after root canal treatment.

It is commonly found in a high percentage of root canal failures and it is able to survive in the root canal as a single organism or as a major component of the flora

E. faecalis: Endodontic RE-infections

Very seldom found in primary root canal infections– Sundqvist, JOE, 1992

VERY frequently found in endodontic RE-infections that have signs of chronic apical periodontitis– Engstrom, 1964, Moller, 1966

Can often occur as a monoculture in infected and treated root canals– Sundqvist, 1998

EcologyEnterococci have been described as extremely

hardy organisms capable of living in many mediums that would certainly kill other bacteria.

Capable of survival at 60 degrees Celsius for 30 minutes.

Enterocoocus faecalis is able to grow in 6.5% NaCl. Enterococci can also grow in 40% bile salts and over a broad range of pH.

Enterococci also have a large amount of natural antibiotic resistance.

E. faecalis Survival Within The Root Canal System

It exhibits widespread genetic polymorphisms

It possesses serine protease, gelatinase, collagen-binding proteins (ACE), help to bind to dentin

It can invade and live within dentinal tubules (250-400 microns)

It has the capacity to endure prolonged periods of starvation

Once nutritional supply become available starved cells are able to recover by utilizing serum

Penetrance of E. faecalis in the dentinal tubules

Penetrates 250 m in the tubules– Siren et al, 1997

Bovine model penetrates 300-400 m – Haapasalo, 1987

Penetrance of bacteria is retarded with keeping of the smear layer– Haapasalo, 1987– Case for keeping the smear layer?

E. faecalis Survival Within The Root Canal System

E. faecalis is able to form a biofilm that helps it resist destruction by enabling the bacteria to become 1000 times more resistant to phagocytosis, antibodies and antibacterials

In dentinal tubules it can resist intracanal dressings of calcium hydroxide for over 10 days

E. faecalis is less dependent upon virulence factors, it relies more upon its ability to survive and persist as a pathogen in the root canals of teeth.

Growth Phases of E. Faecalis

Longitudinal growth vs. starvation phase

When in the starvation phase, it can be 10,000 times more resistant to medicaments than when in its longitudinal growth phase– Portenier et al, 2005

More resistant to UV radiation, heat, NaOCl, H2O2, EtOH, and acid.– Giard et al, 1996

This viable but non-cultivable (VBNC) state may explain how it is a monoinfection in obturated canals

Return when the environment is more favorable for growth

Growth Phases cont...This starvation phase is poorly understood

Is not a spore forming bacteria

Synthesizes a myriad of genes in order to cope with its harsh environment and make energy– Giard et al, J Bacteriol, 2000

Quick review on Calcium Hydroxide

Is the most commonly used intracanal medicament

Calcium hydroxide releases hydroxyl ions in aqueous solutions, resulting in a high alkaline environment where most bacteria cannot survive

Is antimicrobial by raising the pH of the root canal environment

Dissolves tissue– Wadaki, Araski, Suda, Hasselgren

pH needed to kill E. Faecalis

At pH of 10.5 to 11.0, growth of E. faecalis was inhibited– McHugh et al, 2004

pH can only reach up to 10.3 because of the buffering effect of dentin.

pH gradient decreases deeper in the dentinal tubules

11.5 was necessary to eradicate

Adapts to the environmentE. faecalis has a functioning proton pump that

actually pumps hydrogen ions to acidify the cytoplasm in highly alkaline conditions– McHugh, Evans, 2002

Calcium Hydroxide and LTA

Calcium hydroxide inactivation of LTA appears to occur immediately (within 5 minutes) at a relatively low calcium hydroxide concentration (2.5 mg/mL).

Currently, the mechanism for inactivation of LTA by calcium hydroxide is unknown.

− deacylation of LTA

et al Baik, Kum JOE 2008 (November)

Therefore, E. faecalis is resistant to Ca(OH)2 intracanal/interappointment treatments

Current Strategies forEradication

Preparing the apical portion of the root canal to a larger size will help eliminate intracanal microorganisms

Full strength NaOCl is still effective against E. faecalis– Needs to be in contact– No substantivity

Need to be able to penetrate the tubules where they like to hide

Chlorhexidine is effective against E. faecalis– Smear layer prevents its contact– Has substantivity

Remove the Smear Layer!NaOCL to remove the ORGANIC component of

the smear layer

17% EDTA to remove the INORGANIC component of the smear layer

Final rinse with 2% CHX in the canal now that the tubules are opened up

Good technique for primary NSRCT’s

A MUST for NS RETX

Steps to Eliminate E. faecalis