The enhancement of biofilm formation in Group B streptococcal isolates at vaginal pH

Yueh Ren Ho, Chien Ming Li, Chen Hsiang Yu, Yuh Jyh Lin, Ching Ming Wu, I. Chen Harn, Ming Jer Tang, Yi Ting Chen, Fang Chi Shen, Chien Yi Lu, Tai Chun Tsai, Jiunn Jong Wu

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)


Group B streptococcus (GBS) is a common asymptomatic colonizer in acidic vagina of pregnant women and can transmit to newborns, causing neonatal pneumonia and meningitis. Biofilm formation is often associated with bacterial colonization and pathogenesis. Little is known about GBS biofilm and the effect of environmental stimuli on their growth along with biofilm formation. The objective of this study was to investigate the survival and biofilm formation of GBS, isolated from pregnant women, in nutrient-limited medium under various pH conditions. Growth and survival experiments were determined by optical density and viable counts. Crystal violet staining, scanning electron microscopy, and atomic force microscopy (AFM) were used to analyze the capacity of biofilm production. Our results showed that GBS isolates proliferated with increasing pH with highest maximum specific growth rate (μmax) at pH 6.5, but survived at pH 4.5 for longer than 48 h. Biofilm formation of the 80 GBS isolates at pH 4.5 was significantly higher than at pH 7.0. This difference was confirmed by two other methods. The low elastic modulus obtained from samples at pH 4.5 by AFM revealed the softness of biofilm; in contrast, little or no biofilm was measured at pH 7.0. Under acidic pH, the capability of biofilm formation of serotypes III and V showed statistically significant difference from serotypes Ia and Ib. Our finding suggested that survival and enhanced biofilm formation at vaginal pH are potentially advantageous for GBS in colonizing vagina and increase the risk of vaginosis and neonatal infection.

Original languageEnglish
Pages (from-to)105-115
Number of pages11
JournalMedical Microbiology and Immunology
Issue number2
Publication statusPublished - 2013 Apr

All Science Journal Classification (ASJC) codes

  • Immunology and Allergy
  • Immunology
  • Microbiology (medical)


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