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Front. Microbiol. | doi: 10.3389/fmicb.2018.03328

Intestinal Microbiota as a Host Defence Mechanism to Infectious Threats

 Simona A. Iacob1, 2,  Diana G. Iacob2* and Luminita M. Luminos1, 2
  • 1Carol Davila University of Medicine and Pharmacy, Romania
  • 2The National Institute of Infectious Diseases prof.dr Matei Bals, Romania

Intestinal microbiota is a complex microbial community, with diverse and stable populations hosted by the gastrointestinal tract from birth. This ecosystem holds multiple anti-infectious, anti-inflammatory and immune modulating roles decisive for intestinal homeostasis.
The antagonistic interactions between commensals and pathogenic flora are extremely dynamic and involve multiple mechanisms referred to as colonization resistance. Thus, gut bacteria compete for the same intestinal niches and substrates while also producing antimicrobial substances such as bacteriocines or changing the environmental conditions. Short chain fatty acids generated in anaerobic conditions prompt epigenetic regulatory mechanisms towards a tolerogenic immune response. In addition, comensal flora is involved in the synthesis of bactericidal products namely secondary biliary acids or antimicrobial peptides such as cathellicidin-LL37, an immunomodulatory, antimicrobial and wound healing peptide. Gut microbiota is protected through symbiotic relations with the hosting organism and by quorum sensing, a specific cell-to-cell communication system. Any alterations of these relationships favour the uncontrollable multiplication of the resident pathobionts or external entero-pathogens, prompting systemic translocations, inflammatory reactions or exacerbations of bacterial virulence mechanisms (T6SS, T3SS) and ultimately leading to gastrointestinal or systemic infections.
The article describes the metabolic and immunological mechanisms through which the intestinal microbiota plays a protective role as an ally of the organism but also their limits that favour the development of infections.

Keywords: intestinal microbiota, Infection, commensal flora, colonization resistance, bacterial enteropathogens, mucosal immunity, Short Chain Fatty Acids

Received: 20 Sep 2018; Accepted: 21 Dec 2018.

Edited by:

Learn-Han Lee, Novel Bacteria and Drug Discovery Research Group (NBDD), Monash University Malaysia, Malaysia

Reviewed by:

Bei Han, Xi'an Jiaotong University, China
Claucia F. Volken De Souza, University of Taquari Valley, Brazil
Amélia M. Sarmento, Fernando Pessoa University, Portugal  

Copyright: © 2018 Iacob, Iacob and Luminos. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: MD. Diana G. Iacob, The National Institute of Infectious Diseases prof.dr Matei Bals, Bucharest, 021105, Romania,