Acinetobacter baumannii pneumonia increases surfactant proteins SP-A, SP-B, and SP-D levels, while decreasing SP-C level in bronchoalveolar lavage in rats

Abstract

Acinetobacter baumannii is an opportunistic pathogen which causes nosocomial infections and high mortality. It is one of the most isolated microorganisms from patients with nosocomial pneumonia. Lung surfactant proteins (SP) are crucial for lung functions, and levels of SP-A, SP-B, SP-C, and SP-D change in the presence of infection. How they are affected in A. baumannii pneumonia, however, has not been conclusively researched. Therefore, the aim of the present study is to investigate the effect of A. baumannii pneumonia on surfactant proteins. 54 six-to-seven-month-old Sprague–Dawley rats were divided into two groups: sham and A. baumannii. The rats were administered 100 μl 0.5 McFarland A. baumannii or sterile saline intratracheally according to their group. Following the inoculation, lung and bronchoalveolar lavage fluids (BALF) were collected on the 3rd, 24th, and 48th hours of instillation. The lungs were examined histopathologically and the SP-A, SP-B, SP-C, and SP-D levels in BALF were measured with ELISA. The rats challenged with A. baumannii had significantly higher SP-A, SP-B, and SP-D levels while having a significantly lower SP-C level compared to their sham equivalents. Furthermore, a strong positive correlation between SP-A and SP-D, and a moderate negative correlation between SP-B and SP-C were observed.