Abstract:ObjectiveTo investigate the changes in serum procalcitonin (PCT) levels in patients with different bacterial infections and to evaluate the significance of PCT levels for differentiating grampositive and gramnegative bacterial infection. MethodsTwo hundren and sixtysix intensive care unit(ICU)patients infected with severe bacterial infections were divided into 2 groups (grampositive bacteria group and gramnegative bacteria group) according to the bacterial culture results, and serum PCT, Creaction protein(CRP), white blood cell(WBC) and neutrophil ratio(Neu%) were detected, and data of two groups were analysed statiscally. ResultsSerum levels of PCT in patients with severe bacterial infection significantly rose. When defined by the value of PCT ≥2 ng/mL as positive, the positive rate of PCT in gramnegative bacteria group (92.36%) was significantly higher than that of grampositive bacteria group (76.23%)(χ2=13.45, P<0.001); When the value of PCT ≥10 ng/mL, the possibility of gramnegative bacterial infection was great. The routine infection markers, including CRP,WBC and Neu% , were not significantly different between grampositive bacteria group and gramnegative bacteria group( both P>0.05). ConclusionPCT levels can be used as indicator for differentiating grampositive and gramnegative bacterial infection, and may provide valuable information for sensitive antimicrobial selection.