CsrRS and environmental pH regulate group B streptococcus adherence to human epithelial cells and extracellular matrix - PubMed (original) (raw)

CsrRS and environmental pH regulate group B streptococcus adherence to human epithelial cells and extracellular matrix

Su Eun Park et al. Infect Immun. 2012 Nov.

Abstract

Streptococcus agalactiae (group B Streptococcus or GBS) is a common colonizer of the gastrointestinal and genital tracts and an important cause of invasive infections in newborn infants and in adults with predisposing chronic conditions or advanced age. Attachment to epithelial surfaces at mucosal sites is a critical step in the successful colonization of a human host, and regulation of this process is likely to play an important role in both commensalism and dissemination to cause invasive disease. We found that inactivation of the CsrRS (or CovRS) two-component system increased GBS adherence to epithelial cells derived from human vaginal, cervical, and respiratory epithelium, as well as increasing adherence to extracellular matrix proteins and increasing biofilm formation on polystyrene. Neutral (as opposed to acidic) pH enhanced GBS binding to vaginal epithelial cells and to fibrinogen and fibronectin, effects that were partially dependent on CsrRS. The regulatory effects of CsrRS and environmental pH on bacterial adherence correlated with their effects on the expression of multiple surface adhesins, as assessed by quantitative reverse transcription-PCR. We conclude that GBS adherence to epithelial and abiotic surfaces is regulated by the CsrRS two-component system and by environmental pH through their regulatory effects on the expression of bacterial surface adhesins. Dynamic regulation of GBS adherence enhances the organism's adaptability to survival in multiple niches in the human host.

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Figures

Fig 1

Adherence of GBS strains to human epithelial cells. (A) Adherence to VK2 cells was compared among GBS strains 2603, 2603Δ_csrR_ (a Δ_csrR_ mutant), 2603Δ_csrS_ (a Δ_csrS_ mutant), and 2603rep (in which the csrR deletion mutation was repaired). (B) Adherence of strain 2603 to three types of epithelial cells, ME180, A549, and VK2. Adherence is shown as a percentage of the initial inoculum (mean ± SD). Each assay was performed at least three times in triplicate. NS, P > 0.05; ****, P < 0.0001; ***, P < 0.001.

Fig 2

Effect of pH on GBS adherence to vaginal epithelial cells. The influence of pH on GBS adherence to VK2 cells was compared between strains 2603 and 2603Δ_csrR_ (a Δ_csrR_ mutant) after exposure to pH 5.0 or 7.4. Adherence is shown as a percentage of the initial inoculum (mean ± SD). Each assay was performed at least three times in triplicate. **, P < 0.01; NS, _P_ > 0.05.

Fig 3

Adherence of GBS strains to immobilized human ECM proteins. (A) Relative adherence to immobilized human fibrinogen, fibronectin, or laminin by GBS strains 2603, 2603ΔPI-1 (a ΔPI-1 mutant), 2603Δ_csrR_ (a Δ_csrR_ mutant), and 2603Δ_csrR_/ΔPI-1 (a Δ_csrR_/ΔPI-1 double mutant). (B) Influence of pH on GBS adherence to immobilized human fibrinogen, fibronectin, or laminin by strain 2603 or 2603Δ_csrR_ after exposure to pH 5.0 or 7.4. Adherence is shown as a percentage of the initial inoculum (mean ± SD). Each assay was performed at least three times in triplicate. ****, P < 0.0001; ***, _P_ < 0.001; **, _P_ < 0.01; *, _P_ < 0.05; NS, _P_ > 0.05.

Fig 4

Biofilm formation by GBS strains. Biofilm formation was compared among GBS strains 2603, 2603ΔPI-1 (a ΔPI-1 mutant), 2603Δ_csrR_ (a Δ_csrR_ mutant), and 2603Δ_csrR_/ΔPI-1 (a Δ_csrR_/ΔPI-1 double mutant). GBS strains were grown in liquid medium in 96-well polystyrene plates. Wells containing growth medium but no GBS were included as a negative control (Ctr). (A) Photograph of a microtiter plate after adherent bacteria were stained with crystal violet. (B) Quantification of biofilm by measurement of _A_540 after the release of biofilm and bound crystal violet from each well using glacial acetic acid. ****, P < 0.0001; NS, _P_ > 0.05.

Fig 5

Regulation by CsrR of the expression of adhesin genes in GBS. Pairs of bars represent the ratios of transcript abundance in strains 2603Δ_csrR_ (black bars) and 515Δ_csrR_ (gray bars) to that in wild-type strains 2603 and 515, respectively. Each qRT-PCR experiment was performed at least three times in duplicate.

Fig 6

Modulation by pH of the expression of adhesin genes in GBS. Differential regulation of gene expression in GBS strain 2603 (black bars) versus that in isogenic mutant strains 2603Δ_csrR_ (gray bars) and 2603Δ_csrS_ (white bars) after exposure to pH 7.4 or 5.0. Values represent the ratio of transcript abundance at pH 7.4 to that at pH 5.0. Each qRT-PCR experiment was performed at least three times in duplicate.

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CsrRS and environmental pH regulate group B streptococcus adherence to human epithelial cells and extracellular matrix - PubMed (original) (raw)