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Lactobacilli reduce cell cytotoxicity caused by Streptococcus pyogenes by producing lactic acid that degrades the toxic component lipoteichoic acid
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
2011 (English)In: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 55, no 4, 1622-1628 p.Article in journal (Refereed) Published
Abstract [en]

Lactobacilli are known to prevent colonization by many pathogens; nevertheless, the mechanisms of their protective effect are largely unknown. In this work, we investigated the role of lactobacilli during infection of epithelial cells with group A streptococci (GAS). GAS cause a variety of illnesses ranging from noninvasive disease to more severe invasive infections, such as necrotizing fasciitis and toxic shock-like syndrome. Invasion of deeper tissues is facilitated by GAS-induced apoptosis and cell death. We found that lactobacilli inhibit GAS-induced host cell cytotoxicity and shedding of the complement regulator CD46. Further, survival assays demonstrated that lactic acid secreted by lactobacilli is highly bactericidal toward GAS. In addition, lactic acid treatment of GAS, but not heat killing, prior to infection abolishes the cytotoxic effects against human cells. Since lipoteichoic acid (LTA) of GAS is heat resistant and cytotoxic, we explored the effects of lactic acid on LTA. By applying such an approach, we demonstrate that lactic acid reduces epithelial cell damage caused by GAS by degrading both secreted and cell-bound LTA. Taken together, our experiments reveal a mechanism by which lactobacilli prevent pathogen-induced host cell damage.

Place, publisher, year, edition, pages
2011. Vol. 55, no 4, 1622-1628 p.
National Category
Microbiology
Research subject
Molecular Bioscience
Identifiers
URN: urn:nbn:se:su:diva-63672DOI: 10.1128/AAC.00770-10ISI: 000288594600038PubMedID: 21245448OAI: oai:DiVA.org:su-63672DiVA: diva2:451667
Available from: 2011-10-26 Created: 2011-10-26 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Interplay between bacteria and host epithelial cells
Open this publication in new window or tab >>Interplay between bacteria and host epithelial cells
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacterial pathogens have developed multiple ways of manipulating host cell functions to exploit the host environment. We found that interactions with epithelial cells increase the resistance of the human pathogen Neisseria meningitidis to the antimicrobial peptide LL-37. This resistance was dependent on host cell cholesterol-rich microdomains and RhoA/Cdc42-dependent signalling.

At mucosal surfaces, pathogenic bacteria compete with the resident microbiota. Lactobacillus inhibits the adherence of a wide range of pathogens, however, the mechanisms of inhibition are still largely unknown. We demonstrate that certain lactobacilli interfere with host cell signalling pathways used by pathogenic bacteria during initial colonisation. Inhibitory lactobacilli blocked the pathogen-induced activation of Src, increases of host cytosolic [Ca2+] and upregulation of Egr1, in a TLR2-dependent fashion. We further identify Egr1 as a host factor crucial for efficient pathogen adherence. The pathogens used in these studies were N. meningitidis, Helicobacter pylori and Streptococcus pyogenes.

In summary, these studies highlight that the interplay between bacteria and host cells is a critical determinant of pathogenesis and bacterial co-existence in the host.

Place, publisher, year, edition, pages
Stockholm: Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 2013. 96 p.
Keyword
Microbial-cell interaction, Adherence, Infection, Lactic acid bacteria, Antimicrobial peptides
National Category
Microbiology
Research subject
Molecular Bioscience
Identifiers
urn:nbn:se:su:diva-92692 (URN)978-91-7447-735-1 (ISBN)
Public defence
2013-09-20, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Epub ahead of print. Paper 3: Submitted. Paper 4: Manuscript.

Available from: 2013-08-29 Created: 2013-08-14 Last updated: 2013-08-19Bibliographically approved

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