Acute pancreatitis in mice impairs bacterial clearance from the lungs, whereas concurrent pneumonia prolongs the course of pancreatitis

Abstract

Objective: Nosocomial pneumonia is a feared complication in the critically ill patient. Serious acute pancreatitis is frequently complicated by infections. The objectives of this study were to determine the influence of acute pancreatitis on host defense against Pseudomonas pneumonia and to determine the influence of Pseudomonas pneumonia on the severity of concurrent pancreatitis.

Design: A controlled, in vivo laboratory study.

Setting: Research laboratory of a health sciences university.

Subjects: Female C57Bl/6 mice.

Interventions: Pancreatitis was induced by 12 hourly intraperitoneal injections of cerulein (pancreatitis) or saline (sham) immediately followed by intranasal administration of Pseudomonas aeruginosa (to induce pneumonia) or saline (controls). Mice were killed 24 hrs later. Hence, four groups were studied: sham/control, pancreatitis/control, sham/pneumonia, and pancreatitis/pneumonia mice.

Measurements and main results: When compared with sham/pneumonia mice, pancreatitis/pneumonia mice demonstrated exaggerated lung inflammation, higher bacterial counts in lungs and pancreas, and enhanced dissemination of the infection. Concurrently, pneumonia prolonged the course of pancreatitis, as reflected by histopathology and higher plasma amylase and relative pancreas weights (all p < .05 for the difference between pancreatitis/pneumonia and pancreatitis/control mice), which was associated with the localization of Pseudomonas in the pancreas.

Conclusions: Acute pancreatitis impairs host defense against Pseudomonas pneumonia, whereas pneumonia prolongs the course of pancreatitis.