Biomarkers of early-stage Mycoplasma pneumoniae pneumonia

Abstract

Abstract Background Early recognition of Mycoplasma pneumoniae infection and the severity of M. pneumoniae pneumonia (MPP) are difficult to ascertain because early signs of infection are atypical, with no obvious clinical manifestations or imaging characteristics. The inability to diagnosis early-stage MPP delays treatment and increases risks of progression to refractory MPP or severe pneumonia. Methods Here, we used a mouse model of MPP to investigate whether levels of S100 proteins or inflammatory factors in serum and bronchoalveolar lavage fluid (BALF) could be useful biomarkers of M. pneumoniae infection or MPP severity. The contents of S100A8, S100A9, Interleukin (IL)-6, and TNF-α in serum and BALF obtained from M. pneumoniae-infected mice were measure using enzyme-linked immunosorbent assays. Hematoxylin-eosin staining used to judge the severity of MPP showed lung tissue with obvious lesions. TUNEL staining indicated apoptosis in lung tissue of M. pneumoniae-infected mice. Results The serum levels of S100A8 in the high-dose group were higher on days 3 and 5 than those in the low-dose group. The serum levels of S100A9 in the infection group were higher on days 1 and 3 than those in the control group. Serum levels of TNF-α and IL-6 in the M. pneumoniae-infected groups than those in the control group. S100A8/A9 levels in BALF derived from mice receiving the high dose of M. pneumoniae were significantly higher than those in the control group.The BALF levels of TNF-α in the high-dose group were higher on days 1 and 3 than those in the control group.The levels of IL-6 in the high-dose group were higher than those in the control group and those in the low-dose group. The degree of apoptosis in both high- and low-dose groups was higher than that in the control groups, the degree of apoptosis in the high-dose group was higher on day 3 than that in the low-dose group. Conclusion These finding suggest that serum and BALF S100A8/A9 and TNF-α levels may be useful for early diagnosis of MPP and for differentiating MPP severity.