Gram-Negative Anaerobic Bacteria

Chapter VII

ANTIMICROBIAL PROPERTY

Primary root canal infections are polymicrobial, typically dominated by obligatory anaerobic bacteria. The most commonly isolated microorganisms before root canal treatment include Gram-negative anaerobic rods, Gram-positive anaerobic cocci, Gram-positive anaerobic and facultative rods, Lactobacillus species and Gram-positive facultative Streptococcus species.83 The obligate anaerobes are rather easily eradicated during root canal treatment. In contrast, facultative bacteria such as non-mutans Streptococci, Enterococci, and Lactobacilli, once established, are more likely to stay alive even after chemo-mechanical instrumentation and root canal medication.84 In particular Enterococcus faecalis has gained attention

Enterococci can survive in monoculture, but cause only minor lesions. The outer membrane of Gram-negative bacteria contains endotoxin, which is present in all necrotic teeth with periapical lesions, and is able to trigger an inflammatory response even in the absence of viable bacteria. Furthermore, the levels of endotoxin in necrotic root canals are positively correlated to clinical symptoms such as spontaneous pain and tenderness to percussion.85 Virulent Gram-negative anaerobic rods rely on the presence of other bacteria in their environment to survive and establish their full pathogenic potential. Such collections of microorganisms in an extracellular polysaccharide matrix associated with a surface (the inner root canal wall) are called biofilms. There is convincing evidence that microorganisms organized in this manner are far less susceptible to antimicrobial agents than their planktonic counterparts, which have been used by tradition to check the antimicrobial efficacy of substances in

Results demonstrated that all substances showed bactericidal effect on all studied microorganisms at all concentrations and after a short contact period.90

Sen B H et al (1999) assessed the antifungal properties of 1% NaOCl, 5% NaOCl, and 0.12% chlorhexidine against Candida albicans using cylindrical dentine tubes and found C. albicans to be more resistant in the presence of smear layer than in the absence of smear layer. When smear layer was absent, NaOCl started to display antifungal activity after 30 minutes