The enhancement of biofilm formation in Group B streptococcal isolates at vaginal pH.
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.
Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Yueh-Ren
YR
Ho
Chien-Ming
CM
Li
Chen-Hsiang
CH
Yu
Yuh-Jyh
YJ
Lin
Ching-Ming
CM
Wu
I-Chen
IC
Harn
Ming-Jer
MJ
Tang
Yi-Ting
YT
Chen
Fang-Chi
FC
Shen
Chien-Yi
CY
Lu
Tai-Chun
TC
Tsai
Jiunn-Jong
JJ
Wu
D000328:Adult; D018441:Biofilms; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011247:Pregnancy; D011446:Prospective Studies; D012703:Serotyping; D013292:Streptococcus agalactiae / Q000302:isolation & purification / Q000502:physiology* / Q000648:ultrastructure; D014621:Vagina / Q000382:microbiology*