title: Effect of the Biofilm Age and Starvation on Acid Tolerance of Biofilm Formed by Streptococcus mutans Isolated from Caries-Active and Caries-Free Adults.
abstract: Streptococcus mutans(S. mutans) is considered a leading cause of dental caries. The capability ofS. mutansto tolerate low pH is essential for its cariogenicity. Aciduricity ofS. mutansis linked to its adaptation to environmental stress in oral cavity. This study aimed to investigate the effect of biofilm age and starvation condition on acid tolerance of biofilm formed byS. mutansclinical isolates.S. mutansclinical strains isolated from caries-active (SM593) and caries-free (SM18) adults and a reference strain (ATCC25175) were used for biofilm formation. (1) Both young and mature biofilms were formed and then exposed to pH 3.0 for 30 min with (acid-adapted group) or without (non-adapted group) pre-exposure to pH 5.5 for three hours. (2) The mature biofilms were cultured with phosphate-buffered saline (PBS) (starved group) or TPY (polypeptone-yeast extract) medium (non-starved group) at pH 7.0 for 24 h and then immersed in medium of pH 3.0 for 30 min. Biofilms were analyzed through viability staining and confocal laser scanning microscopy. In all three strains, mature, acid-adapted and starved biofilms showed significantly less destructive structure and more viable bacteria after acid shock than young, non-adapted and non-starved biofilms, respectively (allp< 0.05). Furthermore, in each condition, SM593 biofilm was denser, with a significantly larger number of viable bacteria than that of SM18 and ATCC25175 (allp< 0.05). Findings demonstrated that mature, acid-adapted and starvation might protect biofilms of all threeS. mutansstrains against acid shock. Additionally, SM593 exhibited greater aciduricity compared to SM18 and ATCC25175, which indicated that the colonization of high cariogenicity of clinical strains may lead to high caries risk in individuals.
authors.affiliation: Department of Endodontics and Operative Dentistry, School and Hospital of Stomatology, Fujian Medical University, 246 Yangqiao Zhong Road, Fuzhou 350002, China. kqshanj@163.com.
authors.forename: Shan
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Department of Endodontics and Operative Dentistry, School and Hospital of Stomatology, Fujian Medical University, 246 Yangqiao Zhong Road, Fuzhou 350002, China. drchenshuai@163.com.
authors.forename: Shuai
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Endodontics, Comprehensive Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China. zhangcf@hku.hk.
authors.forename: Chengfei
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Endodontology, Tianjin Stomatological Hospital of Nankai University, 75 North Dagu Road, Heping District, Tianjin 300000, China. xingfu_108@126.com.
authors.forename: Xingfu
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Department of Endodontics and Operative Dentistry, School and Hospital of Stomatology, Fujian Medical University, 246 Yangqiao Zhong Road, Fuzhou 350002, China. hxiaoj@163.com.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Huang
authors.affiliation: Department of Oral and Maxillofacial Surgery, Fujian Medical University Union Hospital, Fuzhou 350001, China. caizhiyu2007@126.com.
authors.forename: Zhiyu
authors.initials: Z
authors.lastname: Cai
mesh_terms: D000143:Acids / Q000494:pharmacology*; D000222:Adaptation, Physiological; D000328:Adult; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013295:Streptococcus mutans / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*
chemical_list: D000143:Acids
keywords: Starvation; Streptococcus mutans; aciduricity; biofilm formation; confocal laser scanning microscopy