[A model of multiple organ injury induced by Klebsiella pneumoniae pneumonia in aged rats].

Objective: To reproduce a model of bacterial multiple organ injury (MOI) in aged rats.

Methods: Male Sprague-Dawley (SD) rats were used. The young rats were divided into young control group (YCG, n=10) and young model group (YMG, n=15), and the elderly, aged control group (ACG, n=10) and aged model group (AMG, n=25). The model of rats with Klebsiella pneumoniae pneumonia was produced by tracheal instillation of the bacteria, and injury to various organs was observed and evaluated with changes in biochemical parameters, pathological pictures and mortality.

Results: Between YMG and AMG, the mortality rates were 33.33% (5/15) and 60.00% (15/25), respectively, at 24 hours after instillation of the bacteria. Compared with YCG and ACG, the neutrophil percentage and white blood cell (WBC) counts in peripheral blood increased significantly in YMG and AMG groups (all P<0.01), the rates of dysfunction of the lungs, the heart and the liver, were 60%-100%. The respiratory dysfunction was evidenced by an increase in the arterial partial pressure of carbon dioxide (PaCO(2), P<0.01), and a decrease in the arterial partial pressure of oxygen (PaO(2), P<0.05 or P<0.01). Myocardial dysfunction was shown by a the sharp increase in creatine kinase (CK), creatine kinase isoenzyme MB (CK-MB) and lactate dehydrogenase (LDH), and that of the liver by changes in alanine aminotransferase (ALT) and aspartate aminotransferase (AST, P<0.05 or P<0.01). The pathological changes under light and electronic microscopy were obvious, and the main feature was infiltration of the inflammatory cells. Compared with YMG, PaO(2) in AMG dropped significantly, PaCO(2) increased, CK, CK-MB, LDH, ALT and AST also increased significantly (P<0.05 or P<0.01). The scores of pathological injury in the lungs, the heart and the small intestine in the AMG were obviously higher than that in YMG group (all P<0.05), and the same was trend in the liver and the kidney.

Conclusion: The model of bacterial MOI in aged rats is reproduced successfully, and it mimics the pathogenesis of multiple organ dysfunction syndrome (MODS) which initiates from infection in the lungs. The model is simple and convenient to replicate with a high success rate. The MOI in the aged rats is characterized by the severity of the organ injury and a high mortality rate.