Elevated serum procalcitonin predicts Gram-negative bloodstream infections in patients with burns

Many studies have suggested that procalcitonin can predict bloodstream infection and also distinguish between Gram-negative, Gram-positive and fungal infections after burn. However, up to now, there is no literature on serum procalcitonin level of multidrug-resistant pathogens and non-multidrug-resistant pathogens among Gram-negative bloodstream infections after burn. The purpose of this study is to explore the value of serum procalcitonin in identifying Gram-negative bloodstream infection in patients with febrile critical burn and then to investigate the difference of serum procalcitonin level between multidrug-resistant pathogens and non-multidrug-resistant pathogens among Gram-negative bloodstream infections after burn.

Patients with febrile critical burn admitted to the burn department of our hospital from 1 January 2014 to 1 August 2018 were retrospectively analysed. Patients with positive blood culture whose blood samples were collected for simultaneous blood culture and procalcitonin testing were enrolled. All strains were identified by an automatic microorganism analyser, and procalcitonin was analysed by an automatic electrochemiluminescence immunoassay.

Overall, a total of 119 patients with positive blood culture met the inclusion criteria. There were 64 Gram-negative bacilli, 38 Gram-positive bacteria, 8 C. albicans and 9 polymicrobial bloodstream infections. The median procalcitonin value in Gram-negative bloodstream infections (2.67 ng/mL, interquartile range (IQR) 1.58-6.08) was significantly higher than that in Gram-positive bloodstream infections (1.04 ng/mL, IQR 0.35-1.60, P < 0.01), or C. albicans bloodstream infections (1.09 ng/mL, IQR 0.82-2.30, P < 0.05). Receiver operating characteristic curve (ROC) analysis showed that in addition to polymicrobial bloodstream infections, the area of procalcitonin under the curve distinguishing Gram-negative bloodstream infections from all other blood culture-positive bloodstream infections was 0.761, the best critical value was 1.73 ng/mL, the sensitivity was 73%, the specificity was 74%, the positive predictive value was 80%, the negative predictive value was 67%, The level of procalcitonin was significantly higher in multidrug-resistant Gram-negative bacilli (A. baumannii, Klebsiella pneumoniae and Pseudomonas aeruginosa) (2.76 ng/mL, IQR 2.01-7.76) than in non-multidrug-resistant bacilli (1.01 ng/mL, IQR 0.58-1.56, P < 0.01).

Elevated serum procalcitonin can identify Gram-negative bloodstream infections in patients with febrile critical burn. In Gram-negative bloodstream infections, high procalcitonin levels may be associated with multidrug-resistant Gram-negative bacilli (A. baumannii, K. pneumoniae and P. aeruginosa).