Background: Infection in humans has been linked with altered cytokine gene transcription. It is unclear whether this phenomenon is a consequence of an established disease process or precedes the infective process. The primary end point of this study was to determine whether hospital-acquired pneumonia (HAP) was associated with differential gene expression of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and IL-23p19. The secondary end point was to identify whether alteration in gene expression preceded the clinical onset of infection.
Methods: Sixty consecutive patients undergoing elective thoracic surgery were recruited. HAP was diagnosed as per National Nosocomial Infection Surveillance guidelines. Messenger RNA (mRNA) and protein levels were analyzed preoperatively and 24 h and 5 days postoperatively.
Results: Forty-one patients had an uncomplicated recovery. Nineteen patients developed HAP. IL-6, IL-10, IL-12p35, IL-23p19, IL-27p28, TNF-α, and IFN-γ mRNA and protein levels of IL-6, IL-23, and IFN-γ in peripheral blood leukocytes were analyzed before surgery and 24 h and 5 days postsurgery. IL-23p19 mRNA levels were reduced in the pneumonia group (median, 4.19; 10th-90th centile range, 3.90-4.71) compared with the nonpneumonia group (4.50; 3.85-5.32) day 1 postsurgery (P=02). IFN-γ mRNA levels were reduced in the pneumonia group (2.48; 1.20-3.20) compared with nonpneumonia group (2.81; 2.10-3.26) (P=03) day 5 postsurgery. Results are expressed as log to base 10 copy numbers of cytokine mRNA per 10 million β-actin mRNA copy numbers. All values are given as median and 10th to 90th centile range.
Conclusions: Cytokine gene expression is altered immediately following surgery in patients with postoperative HAP.