Procalcitonin (PCT) is a protein composed of 116 amino acid with a molecular mass of 13 kDa.1 The definite source of serum PCT is uncertain, but it has been speculated that PCT is produced by liver cells, monocytes
cells, and macrophage cells in response to infection.2 Serum PCT levels increase rapidly during various bacterial infection, especially Gram-negative bacterial infections.3 The outer membrane component of Gram-negative bacteria (i.e. endotoxin or lipopolysaccharides) has been shown to be a strong inducer of PCT
during bacterial infection. These bacteria cause the host to produce pro-inflammatory cytokines,
which leads to increased PCT production.3,4 Elevated cytokines levels also cause the host to
increase production of leucocyte and neutrophils cells. The lipopolysaccharides component plays
a large role in the severity of Gram-negative infections. In clinical settings, PCT together with
leucocyte and neutrophil counts are commonly used as markers of infection.5
Salmonella species, a cause of typhoid fever, are also Gram-negative bacteria that contain endotoxin on their cell surface. Binding of salmonella endotoxin to CD14/Toll-like receptor (TLR)4 on macrophage cells activates
nuclear factor kappa B (NFκB) to produce pro-inflammatory cytokine and increase inflammatory cytokines, resulting in elevated PCT levels.6,8 In clinical practice, leucocyte and neutrophil counts can be used as a marker of bacterial infection.9 In addition, several studies have reported that serum PCT levels are useful
in distinguishing Gram-negative bacteremia from Gram-positive bacteremia.3,10 However,
there have been no studies comparing laboratory markers of bacterial infection in Gram-negative
and Salmonella bacteremias. Therefore, we conduct this study to investigate the differences
in leucocyte and neutrophil cell counts and PCT levels among Salmonella and Gram-negative


Published: 2017-12-05