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Identification and characterisation of an iron-responsive candidate probiotic.

Bailey JR, Probert CS, Cogan TA - PLoS ONE (2011)

Bottom Line: The isolate of S. thermophilus selected was able to reduce epithelial cell death as well as NF-κB signalling and IL-8 production triggered by pathogens.It was capable of crossing an epithelial cell barrier in conjunction with E. coli and downregulating Th1 and Th17 responses in primary human intestinal leukocytes.Therefore, we offer an alternative paradigm which considers that probiotics should be able to be competitive during periods of intestinal bleeding, trauma or stress.

View Article: PubMed Central - PubMed

Affiliation: Mucosal Microbiology, School of Veterinary Sciences, University of Bristol, Bristol, United Kingdom.

ABSTRACT

Background: Iron is an essential cofactor in almost all biological systems. The lactic acid bacteria (LAB), frequently employed as probiotics, are unusual in having little or no requirement for iron. Iron in the human body is sequestered by transferrins and lactoferrin, limiting bacterial growth. An increase in the availability of iron in the intestine by bleeding, surgery, or under stress leads to an increase in the growth and virulence of many pathogens. Under these high iron conditions, LAB are rapidly out-competed; for the levels of probiotic bacteria to be maintained under high iron conditions they must be able to respond by increasing growth rate to compete with the normal flora. Despite this, iron-responsive genera are poorly characterised as probiotics.

Methodology/principal findings: Here, we show that a panel of probiotics are not able to respond to increased iron availability, and identify an isolate of Streptococcus thermophilus that can increase growth rate in response to increased iron availability. The isolate of S. thermophilus selected was able to reduce epithelial cell death as well as NF-κB signalling and IL-8 production triggered by pathogens. It was capable of crossing an epithelial cell barrier in conjunction with E. coli and downregulating Th1 and Th17 responses in primary human intestinal leukocytes.

Conclusions/significance: We propose that an inability to compete with potential pathogens under conditions of high iron availability such as stress and trauma may contribute to the lack of efficacy of many LAB-based probiotics in treating disease. Therefore, we offer an alternative paradigm which considers that probiotics should be able to be competitive during periods of intestinal bleeding, trauma or stress.

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Translocation of bacteria through a T84 (A) or Caco-2 (B) epithelial cell monolayer.Results are shown from 3 replicates and are expressed as means. * p≤0.05, ** p≤0.01 and *** p≤0.001.
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pone-0026507-g003: Translocation of bacteria through a T84 (A) or Caco-2 (B) epithelial cell monolayer.Results are shown from 3 replicates and are expressed as means. * p≤0.05, ** p≤0.01 and *** p≤0.001.

Mentions: To determine the effect of our probiotic strains on epithelial barrier integrity, Caco-2 and T84 cells were grown in a Transwell system and challenged with E. coli K12 or AIEC HM615 in combination with each of the potential probiotics; TEER and bacterial translocation were measured. Both Caco-2 and T84 cells formed stable monolayers after 8–10 days. Neither L. acidophilus ASF360 nor S. thermophilus NCIMB 41856 had any effect on TEER alone. However, S. thermophilus NCIMB 41856 blocked the passage of E. coli K12 through the monolayer, a phenomenon not seen with L. acidophilus ASF360 which enhanced the passage of E. coli K12 across the barrier (Figure 3). In addition, S. thermophilus NCIMB 41856 reduced the response to E. coli K12, by increasing TEER, in a way that L. acidophilus ASF360 did not; when S. thermophilus NCIMB 41856 and E. coli K12 were added to the monolayer simultaneously, an increase in TEER was seen (peaking at 33% in Caco-2 cells at 6 hours and 30% in T84 cells at 10 hours compared to K12 stimulated cells), whereas L. acidophilus ASF360 and E. coli K12 together caused a decrease in TEER (peaking at 56% in Caco-2 cells at 8 hours and 11% in T84 cells at 6 hours compared to K12 stimulated cells) (Figure S1). While AIEC HM615 alone slowly migrated through the monolayer, both L. acidophilus ASF360 and S. thermophilus NCIMB 41856 appeared to interact with this strain and facilitate its migration across the epithelial monolayer. In this situation, translocation of L. acidophilus ASF360 and S. thermophilus NCIMB 41856 was increased until these probiotic strains were present in equal numbers to the pathogenic strain (Figure 3). The potentially probiotic E. coli strain Nissle 1917, similarly to L. acidophilus ASF360 and S. thermophilus NCIMB 41856, had no effect on TEER (Figure S1) but it was able to translocate quickly without the need to interact with pathogenic E. coli strains (Figure 3).


Identification and characterisation of an iron-responsive candidate probiotic.

Bailey JR, Probert CS, Cogan TA - PLoS ONE (2011)

Translocation of bacteria through a T84 (A) or Caco-2 (B) epithelial cell monolayer.Results are shown from 3 replicates and are expressed as means. * p≤0.05, ** p≤0.01 and *** p≤0.001.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198401&req=5

pone-0026507-g003: Translocation of bacteria through a T84 (A) or Caco-2 (B) epithelial cell monolayer.Results are shown from 3 replicates and are expressed as means. * p≤0.05, ** p≤0.01 and *** p≤0.001.
Mentions: To determine the effect of our probiotic strains on epithelial barrier integrity, Caco-2 and T84 cells were grown in a Transwell system and challenged with E. coli K12 or AIEC HM615 in combination with each of the potential probiotics; TEER and bacterial translocation were measured. Both Caco-2 and T84 cells formed stable monolayers after 8–10 days. Neither L. acidophilus ASF360 nor S. thermophilus NCIMB 41856 had any effect on TEER alone. However, S. thermophilus NCIMB 41856 blocked the passage of E. coli K12 through the monolayer, a phenomenon not seen with L. acidophilus ASF360 which enhanced the passage of E. coli K12 across the barrier (Figure 3). In addition, S. thermophilus NCIMB 41856 reduced the response to E. coli K12, by increasing TEER, in a way that L. acidophilus ASF360 did not; when S. thermophilus NCIMB 41856 and E. coli K12 were added to the monolayer simultaneously, an increase in TEER was seen (peaking at 33% in Caco-2 cells at 6 hours and 30% in T84 cells at 10 hours compared to K12 stimulated cells), whereas L. acidophilus ASF360 and E. coli K12 together caused a decrease in TEER (peaking at 56% in Caco-2 cells at 8 hours and 11% in T84 cells at 6 hours compared to K12 stimulated cells) (Figure S1). While AIEC HM615 alone slowly migrated through the monolayer, both L. acidophilus ASF360 and S. thermophilus NCIMB 41856 appeared to interact with this strain and facilitate its migration across the epithelial monolayer. In this situation, translocation of L. acidophilus ASF360 and S. thermophilus NCIMB 41856 was increased until these probiotic strains were present in equal numbers to the pathogenic strain (Figure 3). The potentially probiotic E. coli strain Nissle 1917, similarly to L. acidophilus ASF360 and S. thermophilus NCIMB 41856, had no effect on TEER (Figure S1) but it was able to translocate quickly without the need to interact with pathogenic E. coli strains (Figure 3).

Bottom Line: The isolate of S. thermophilus selected was able to reduce epithelial cell death as well as NF-κB signalling and IL-8 production triggered by pathogens.It was capable of crossing an epithelial cell barrier in conjunction with E. coli and downregulating Th1 and Th17 responses in primary human intestinal leukocytes.Therefore, we offer an alternative paradigm which considers that probiotics should be able to be competitive during periods of intestinal bleeding, trauma or stress.

View Article: PubMed Central - PubMed

Affiliation: Mucosal Microbiology, School of Veterinary Sciences, University of Bristol, Bristol, United Kingdom.

ABSTRACT

Background: Iron is an essential cofactor in almost all biological systems. The lactic acid bacteria (LAB), frequently employed as probiotics, are unusual in having little or no requirement for iron. Iron in the human body is sequestered by transferrins and lactoferrin, limiting bacterial growth. An increase in the availability of iron in the intestine by bleeding, surgery, or under stress leads to an increase in the growth and virulence of many pathogens. Under these high iron conditions, LAB are rapidly out-competed; for the levels of probiotic bacteria to be maintained under high iron conditions they must be able to respond by increasing growth rate to compete with the normal flora. Despite this, iron-responsive genera are poorly characterised as probiotics.

Methodology/principal findings: Here, we show that a panel of probiotics are not able to respond to increased iron availability, and identify an isolate of Streptococcus thermophilus that can increase growth rate in response to increased iron availability. The isolate of S. thermophilus selected was able to reduce epithelial cell death as well as NF-κB signalling and IL-8 production triggered by pathogens. It was capable of crossing an epithelial cell barrier in conjunction with E. coli and downregulating Th1 and Th17 responses in primary human intestinal leukocytes.

Conclusions/significance: We propose that an inability to compete with potential pathogens under conditions of high iron availability such as stress and trauma may contribute to the lack of efficacy of many LAB-based probiotics in treating disease. Therefore, we offer an alternative paradigm which considers that probiotics should be able to be competitive during periods of intestinal bleeding, trauma or stress.

Show MeSH
Related in: MedlinePlus