Flagellum-mediated biofilm defense mechanisms of Pseudomonas aeruginosa against host-derived lactoferrin.
Chronic infection with the gram-negative organism Pseudomonas aeruginosa is a leading cause of morbidity and mortality in human patients, despite high doses of antibiotics used to treat the various diseases this organism causes. These infections are chronic because P. aeruginosa readily forms biofilms, which are inherently resistant to antibiotics as well as the host's immune system. Our laboratory has been investigating specific mutations in P. aeruginosa that regulate biofilm bacterial susceptibility to the host. To continue our investigation of the role of genetics in bacterial biofilm host resistance, we examined P. aeruginosa biofilms that lack the flgK gene. This mutant lacks flagella, which results in defects in early biofilm development (up to 36 h). For these experiments, the flgK-disrupted strain and the parental strain (PA14) were used in a modified version of the 96-well plate microtiter assay. Biofilms were challenged with freshly isolated human leukocytes for 4 to 6 h and viable bacteria enumerated by CFU. Subsequent to the challenge, both mononuclear cells (monocytes and lymphocytes) and neutrophils, along with tumor necrosis factor alpha (TNF-alpha), were required for optimal killing of the flgK biofilm bacteria. We identified a cytokine cross talk network between mononuclear cells and neutrophils that was essential to the production of lactoferrin and bacterial killing. Our data suggest that TNF-alpha is secreted from mononuclear cells, causing neutrophil activation, resulting in the secretion of bactericidal concentrations of lactoferrin. These results extend previous studies of the importance of lactoferrin in the innate immune defense against bacterial biofilms.
Leid
Jeff G
JG
Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona 86001, USA. Jeff.Leid@nau.edu
Kerr
Mathias
M
Selgado
Candice
C
Johnson
Chelsa
C
Moreno
Gabriel
G
Smith
Alyssa
A
Shirtliff
Mark E
ME
O'Toole
George A
GA
Cope
Emily K
EK
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms / Q000254:growth & development*; D002352:Carrier Proteins / Q000494:pharmacology*; D015169:Colony Count, Microbial; D005407:Flagella / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D006801:Humans; D007781:Lactoferrin; D007962:Leukocytes / Q000276:immunology; D050296:Microbial Viability; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; C088595:FlgK protein, Bacteria; C490098:LTF protein, human; D014409:Tumor Necrosis Factor-alpha; D007781:Lactoferrin