The effect of acinetobacter baumannii pneumonia on lung surfactant proteins SP-A, SP-B, SP-C, AND SP-D on rats

Acinetobacter baumannii is an opportunistic pathogen which causes nosocomial infections, mainly pneumonia, and it causes high mortality. Lung surfactant proteins (SP) are crucial for lung functions. The level of surfactant proteins A, B, C, and D changes in the presence of infection, however how they are affected in A. baumannii pneumonia is not known. The aim of the study is to investigate the effect of A. baumannii pneumonia on surfactant proteins. 54 6-7 months old Sprague-Dawley rates were divided into two main groups: Sham (SH) and A. baumannii (AB). 3rd, 24th and 48th hour groups were added in both main groups. Rats in SH were administered 100 µl sterile saline, whereas rats in AB received 100 µl 0.5 McFarland A. baumannii intratracheally. After the inoculation, lungs and bronchoalveolar lavage fluids (BALF) were collected on 3rd, 24th, and 48th hour. Lungs were examined histopathologically, and SP-A, SP-B, SP-C, and SP-D levels were measured in BALF with ELISA. Statistically significant differences were found between SH and AB groups in polymorphonuclear leukocyte infiltration, lymphocyte around bronchi, hemorrhage, congestion, bronchoalveolar proliferation, and macrophage accumulation. BALF concentrations; SP-A levels on every hour, SP-B on 24th, and SP-D on 3rd and 24th hours were higher, and SP-C on 24th hour was lower in AB group compared to SH group. A strong, positive correlation between SP-A and SP-D, and a moderate, negative correlation between SP-B and SP-C were found. This is the first study to demonstrate that the A. baumannii pneumonia on rats increases SP-A, SP-B, SP-D while decreasing SP-C levels, and there are correlations between surfactant proteins.