Effect of laparotomy on clearance and cytokine induction in Staphylococcus aureus infected lungs.
BACKGROUND
Staphylococcus aureus is a major pathogen complicating postsurgical care.


OBJECTIVE
To test the effect of sterile laparotomy (LAP) on pulmonary clearance of S. aureus in a murine model.


METHODS
Control and LAP mice were infected intranasally with 10(8) cfu of S. aureus. Microbial clearance, pulmonary leukocyte recruitment, and cytokine profiles were compared between the groups. Antibody neutralization or cytokine gene knockout mice were used to evaluate the role of cytokines.


RESULTS
Laparotomy resulted in a 10-fold increase in S. aureus lung colony-forming units on Days 2 and 3 postinfection. Both groups cleared the infection by Day 4. No defect in leukocyte recruitment into the lungs was observed in infected LAP animals; however, an increase in the number of Mac-3-positive cells and a significant decrease of cells with high surface expression of Fc-gammaR suggest suboptimal activation of leukocytes in the lungs of infected LAP animals. Infected LAP mice had decreased expression of interferon (IFN)-gamma and increased expression of mRNA for IL-13 in the lungs on Day 1 postinfection and decreased levels of IL-6, keratinocyte-derived chemokine (KC), and macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage at Day 2 postinfection. Neutralization of IFN-gamma mimicked the effect of LAP with impaired clearance on Day 2.


CONCLUSIONS
Sterile LAP induced temporary deactivation of innate immune responses to pulmonary S. aureus challenge. Impaired microbial clearance was accompanied by altered cytokine expression and suboptimal activation of pulmonary leukocytes. Lack of early IFN-gamma induction in the infected lungs of LAP animals is a likely mechanism contributing to the observed phenotype.
Olszewski
Michal A
MA
The Veterans Administration Ann Arbor Healthcare System, Ann Arbor, Michigan 48105-2303, USA. olszewsm@umich.edu
Falkowski
Nicole R
NR
Surana
Rishi
R
Sonstein
Joanne
J
Hartman
Anne
A
Moore
Bethany B
BB
Huffnagle
Gary B
GB
Toews
Galen B
GB
D000818:Animals; D002634:Chemotaxis, Leukocyte / Q000502:physiology; D015169:Colony Count, Microbial; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D007113:Immunity, Innate / Q000502:physiology*; D007813:Laparotomy; D051379:Mice; D008807:Mice, Inbred BALB C; D010586:Phagocytes / Q000502:physiology; D011023:Pneumonia, Staphylococcal / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D011183:Postoperative Complications; D012333:RNA, Messenger / Q000378:metabolism
D016207:Cytokines; D012333:RNA, Messenger