title: Impact of growth conditions on susceptibility of five microbial species to alkaline stress.
abstract: The effects of different growth conditions on the susceptibility of five taxa to alkaline stress were investigated. Enterococcus faecalis ATCC 29212, Streptococcus sobrinus OMZ 176, Candida albicans ATCC 90028, Actinomyces naeslundii ATCC 12104, and Fusobacterium nucleatum ATCC 10953 were grown as planktonic cells, allowed to adhere to dentin for 24 hours, grown as monospecies or multispecies biofilms on dentin under anaerobic conditions with a serum-enriched nutrient supply at 37 degrees C for 5 days. In addition, suspended biofilm microorganisms and 5-day old planktonic multispecies cultures were used. Microbial recovery upon direct exposure to saturated calcium hydroxide solution (pH 12.5) for 10 and 100 minutes was compared with control exposure to physiologic saline. Planktonic microorganisms were most susceptible; only E. faecalis and C. albicans survived in saturated solution for 10 minutes, the latter also for 100 minutes. Dentin adhesion was the major factor in improving the resistance of E. faecalis and A. naeslundii to calcium hydroxide, whereas the multispecies context in a biofilm was the major factor in promoting resistance of S. sobrinus to the disinfectant. In contrast, the C. albicans response to calcium hydroxide was not influenced by the growth condition. Adherence to dentin and interspecies interactions in a biofilm appear to differentially affect the sensitivity of microbial species to calcium hydroxide.
authors.affiliation: Institute of Preventive Dentistry and Oral Microbiology, University of Basel, Basel, Switzerland.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Brändle
authors.forename: Matthias
authors.initials: M
authors.lastname: Zehnder
authors.forename: Roland
authors.initials: R
authors.lastname: Weiger
authors.forename: Tuomas
authors.initials: T
authors.lastname: Waltimo
mesh_terms: D000190:Actinomyces / Q000187:drug effects / Q000254:growth & development; D000468:Alkalies / Q000494:pharmacology; D000818:Animals; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development*; D001422:Bacterial Adhesion / Q000187:drug effects*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D002126:Calcium Hydroxide / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects / Q000254:growth & development; D002417:Cattle; D015169:Colony Count, Microbial; D003470:Culture Media; D019551:Dental Disinfectants / Q000494:pharmacology; D003786:Dental Pulp Cavity / Q000382:microbiology; D003804:Dentin; D013293:Enterococcus faecalis / Q000187:drug effects / Q000254:growth & development; D016967:Fusobacterium nucleatum / Q000187:drug effects / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D012387:Root Canal Filling Materials / Q000494:pharmacology*; D016986:Streptococcus sobrinus / Q000187:drug effects / Q000254:growth & development
chemical_list: D000468:Alkalies; D003470:Culture Media; D019551:Dental Disinfectants; D012387:Root Canal Filling Materials; D002126:Calcium Hydroxide