Multidrug efflux systems play an important role in the invasiveness of Pseudomonas aeruginosa.
Pseudomonas aeruginosa is an important opportunistic human pathogen. Certain strains can transmigrate across epithelial cells, and their invasive phenotype is correlated with capacity to cause invasive human disease and fatal septicemia in mice. Four multidrug efflux systems have been described in P. aeruginosa, however, their contribution to virulence is unclear. To clarify the role of efflux systems in invasiveness, P. aeruginosa PAO1 wild-type (WT) and its efflux mutants were evaluated in a Madin-Darby canine kidney (MDCK) epithelial cell monolayer system and in a murine model of endogenous septicemia. All efflux mutants except a deltamexCD-oprJ deletion demonstrated significantly reduced invasiveness compared with WT. In particular, a deltamexAB-oprM deletion strain was compromised in its capacity to invade or transmigrate across MDCK cells, and could not kill mice, in contrast to WT which was highly invasive (P < 0.0006) and caused fatal infection (P < 0.0001). The other mutants, including deltamexB and deltamexXY mutants, were intermediate between WT and the deltamexAB-oprM mutant in invasiveness and murine virulence. Invasiveness was restored to the deltamexAB-oprM mutant by complementation with mexAB-oprM or by addition of culture supernatant from MDCK cells infected with WT. We conclude that the P. aeruginosa MexAB-OprM efflux system exports virulence determinants that contribute to bacterial virulence.
Hirakata
Yoichi
Y
Division of Infectious and Immunological Diseases, Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, V5Z 4H4 Canada. hirakata@net.nagasaki-u.ac.jp
Srikumar
Ramakrishnan
R
Poole
Keith
K
Gotoh
Naomasa
N
Suematsu
Takashi
T
Kohno
Shigeru
S
Kamihira
Shimeru
S
Hancock
Robert E W
RE
Speert
David P
DP
D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D018988:Bacterial Translocation / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004195:Disease Models, Animal; D018450:Disease Progression; D004285:Dogs; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004847:Epithelial Cells / Q000166:cytology / Q000382:microbiology / Q000648:ultrastructure; D005839:Gentamicins / Q000494:pharmacology; D007668:Kidney / Q000166:cytology; D026901:Membrane Transport Proteins; D051379:Mice; D008826:Microbial Sensitivity Tests; D009154:Mutation; D011552:Pseudomonas Infections / Q000382:microbiology / Q000473:pathology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000472:pathogenicity* / Q000502:physiology; D018805:Sepsis / Q000382:microbiology / Q000473:pathology; D015996:Survival Rate; D013997:Time Factors; D014774:Virulence / Q000187:drug effects / Q000235:genetics*
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D005839:Gentamicins; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; C118597:MexB protein, Pseudomonas aeruginosa