Antimicrobial effect of an oxazolidinone, lantibiotic and calcium hydroxide against Enterococcus faecalis biofilm: An in vitro study

Aims: The aim was to evaluate and compare the antimicrobial efficacy of an oxazolidinone (linezolid [LZ]), lantibiotic (nisin), and calcium hydroxide against Enterococcus faecalis biofilm formed on tooth substrate after 2 and 7 days. Methods: Single rooted human mandibular premolars were decoronated, biomechanically prepared, and vertically sectioned along the midsagittal plane to obtain a standardized tooth substrate. Standardized suspension of E. faecalis and tooth substrate was incubated for 3 weeks to allow growth of biofilm. At the end of 3 weeks, the grouping was done according to the medicament used – Group I - LZ, Group II - nisin, Group III - calcium hydroxide, Group IV - negative treatment. Disk of the medicaments used were prepared and placed upon Petri dishes along with bacterial emulsion on Mueller-Hinton agar. The zones of inhibition were checked after 2 and 7 days. Statistical Analysis Used: The scores were statistically analyzed using Tukey honest significant difference test and one-way analysis of variance. Results: Zone of inhibition obtained with LZ was widest followed by nisin and calcium hydroxide after a period of 2 days (P < 0.001). The size of the zone of inhibition remain unchanged for LZ and nisin group after 7 days (P > 0.001) unlike calcium hydroxide group where the zone decreased (P < 0.001). Conclusion: LZ showed maximum antimicrobial potential against E. faecalis biofilm followed by nisin and calcium hydroxide after 2 and 7 days. The antimicrobial effect of LZ and nisin was not affected with the lapse of time, but that of calcium hydroxide significantly decreased.