title: In vitro study of the properties of Streptococcus mutans in starvation conditions.
abstract: OBJECTIVE
  The present study is to assess Streptococcus mutans survivability in different starvation conditions and to determine the resistance of starved S. mutans to lethal acid and two common anti-caries agents, sodium fluoride (NaF) and chlorhexidine acetate (CHX).
  
  
  METHODS
  S. mutans survival rates in sterile water, PBS, sterile saliva, 1/5 strength BHI and BHI were determined at a given time by plate count of viable cell. The resistance of starved S. mutans and control S. mutans to four times the minimal bactericidal concentration (MBC) of NaF, two times the MBC of CHX and acid (pH 2.8) was evaluated and compared respectively. Furthermore, field emission scanning electron microscope (FE-SEM) was used to observe the morphologic characteristics of the starved S. mutans cells.
  
  
  RESULTS
  S. mutans showed starvation tolerance under five different starvation conditions, but the bacterial survival rates were different at the same time points. The starved S. mutans exhibited significantly higher resistance (p<0.05) to challenge by anti-caries agents and acid than the control S. mutans. Additionally, starvation resulted in the morphologic modification of S. mutans, and the disruptive degree depended on the change in time.
  
  
  CONCLUSIONS
  The present study indicates that S. mutans displays starvation tolerance, and starvation decreased the susceptibility of S. mutans to NaF, CHX and acid.
authors.affiliation: Department of Operative Dentistry & Endodontics, School of Stomatology, Fourth Military Medical University, 145 Changle West Road, Xi'an 710032, Shaanxi, China.
authors.forename: Zhongchun
authors.initials: Z
authors.lastname: Tong
authors.forename: Rui
authors.initials: R
authors.lastname: Tao
authors.forename: Wenkai
authors.initials: W
authors.lastname: Jiang
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Zhou
authors.forename: Yu
authors.initials: Y
authors.lastname: Tian
authors.forename: Longxing
authors.initials: L
authors.lastname: Ni
mesh_terms: D002327:Cariostatic Agents / Q000494:pharmacology*; D002710:Chlorhexidine / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D006851:Hydrochloric Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D008855:Microscopy, Electron, Scanning / Q000379:methods; D012969:Sodium Fluoride / Q000494:pharmacology; D013295:Streptococcus mutans / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D013312:Stress, Physiological
chemical_list: D002327:Cariostatic Agents; D012969:Sodium Fluoride; D006851:Hydrochloric Acid; D002710:Chlorhexidine