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Inactivation of the rhlA gene in Pseudomonas aeruginosa prevents rhamnolipid production, disabling the protection against polymorphonuclear leukocytes
Author(s) -
VAN GENNIP MARIA,
CHRISTENSEN LOUISE DAHL,
ALHEDE MORTEN,
PHIPPS RICHARD,
JENSEN PETER ØSTRUP,
CHRISTOPHERSEN LARS,
PAMP SÜNJE JOHANNA,
MOSER CLAUS,
MIKKELSEN PER JENSEN,
KOH ANDREW Y.,
TOLKERNIELSEN TIM,
PIER GERALD B.,
HØIBY NIELS,
GIVSKOV MICHAEL,
BJARNSHOLT THOMAS
Publication year - 2009
Publication title -
apmis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.909
H-Index - 88
eISSN - 1600-0463
pISSN - 0903-4641
DOI - 10.1111/j.1600-0463.2009.02466.x
Subject(s) - pseudomonas aeruginosa , microbiology and biotechnology , rhamnolipid , biofilm , in vivo , quorum sensing , virulence , immune system , in vitro , pathogen , chemistry , biology , gene , immunology , bacteria , biochemistry , genetics
Many of the virulence factors produced by the opportunistic human pathogen Pseudomonas aeruginosa are quorum‐sensing (QS) regulated. Among these are rhamnolipids, which have been shown to cause lysis of several cellular components of the human immune system, e.g. monocyte‐derived macrophages and polymorphonuclear leukocytes (PMNs). We have previously shown that rhamnolipids produced by P. aeruginosa cause necrotic death of PMNs in vitro . This raises the possibility that rhamnolipids may function as a ‘biofilm shield’ in vivo , which contributes significantly to the increased tolerance of P. aeruginosa biofilms to PMNs. In the present study, we demonstrate the importance of the production of rhamnolipids in the establishment and persistence of P. aeruginosa infections, using an in vitro biofilm system, an intraperitoneal foreign‐body model and a pulmonary model of P. aeruginosa infections in mice. Our experimental data showed that a P. aeruginosa strain, unable to produce any detectable rhamnolipids due to an inactivating mutation in the single QS‐controlled rhlA gene, did not induce necrosis of PMNs in vitro and exhibited increased clearance compared with its wild‐type counterpart in vivo . Conclusively, the results support our model that rhamnolipids are key protective agents of P. aeruginosa against PMNs.