Deciphering mechanisms of staphylococcal biofilm evasion of host immunity
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, USA
Biofilms are adherent communities of bacteria contained within a complex matrix. Although host immune responses to planktonic staphylococcal species have been relatively well-characterized, less is known regarding immunity to staphylococcal biofilms and how they modulate anti-bacterial effector mechanisms when organized in this protective milieu. Previously, staphylococcal biofilms were thought to escape immune recognition on the basis of their chronic and indolent nature. Instead, we have proposed that staphylococcal biofilms skew the host immune response away from a proinflammatory bactericidal phenotype toward an anti-inflammatory, pro-fibrotic response that favors bacterial persistence. This possibility is supported by recent studies from our laboratory using a mouse model of catheter-associated biofilm infection, where S. aureus biofilms led to the accumulation of alternatively activated M2 macrophages that exhibit anti-inflammatory and pro-fibrotic properties. In addition, relatively few neutrophils were recruited into S. aureus biofilms, representing another mechanism that deviates from planktonic infections. However, it is important to recognize the diversity of biofilm infections, in that studies by others have demonstrated the induction of distinct immune responses during staphylococcal biofilm growth in other models, suggesting influences from the local tissue microenvironment. This review will discuss the immune defenses that staphylococcal biofilms evade as well as conceptual issues that remain to be resolved. An improved understanding of why the host immune response is unable to clear biofilm infections could lead to targeted therapies to reverse these defects and expedite biofilm clearance.
Keywords: S. aureus, S. epidermidis, biofilm, macrophage, neutrophil, immune evasion, alternative macrophage activation, fibrosis
Citation: Hanke ML and Kielian T (2012) Deciphering mechanisms of staphylococcal biofilm evasion of host immunity. Front. Cell. Inf. Microbio. 2:62. doi: 10.3389/fcimb.2012.00062
Received: 02 February 2012; Paper pending published: 09 March 2012;
Accepted: 20 April 2012; Published online: 08 May 2012.
Edited by:David Heinrichs, University of Western Ontario, Canada
Reviewed by:Jeffery A. Hobden, LSU Health Sciences Center New Orleans, USA
Pietro Speziale, University degli Studi di Pavia, Italy
Copyright: © 2012 Hanke and Kielian. This is an open-access article distributed under the terms of the Creative Commons Attribution Non Commercial License, which permits non-commercial use, distribution, and reproduction in other forums, provided the original authors and source are credited.
*Correspondence: Tammy Kielian, Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE 68198-5900, USA. e-mail: email@example.com