Biomarkers in respiratory tract infections: diagnostic guides to antibiotic prescription, prognostic markers and mediators

Abstract

Used appropriately, biomarkers improve the assessment of respiratory tract infections and sepsis. Most prominently, circulating procalcitonin levels increase by a factor of several tens of thousands during sepsis. Using a sensitive assay, procalcitonin safely and markedly reduces antibiotic usage in respiratory tract infections and nonbacterial meningitis. Procalcitonin is the protopye of hormokine mediators. The term ''hormokine'' encompasses the cytokine-like behaviour of hormones during inflammation and infections. The concept is based on a ubiquitous expression of calcitonin peptides during sepsis. Adrenomedullin, another member of the calcitonin peptide superfamily, was shown to complement and improve the current prognostic assessment in lower respiratory tract infections. Other peptides share some features of hormokines, e.g. natriuretic peptide and copeptin. Hormokines are not only biomarkers of infection but are also pivotal inflammatory mediators. Like all mediators, their role during systemic infections is basically beneficial, possibly to combat invading microbes. However, at increased levels they can become harmful for their host. Multiple mechanisms of action were proposed. In several animal models the modulation and neutralisation of hormokines during infection was shown to improve survival, and thus might open new treatment options for severe infections, especially of the respiratory tract.

Frequent respiratory pathogens of respiratory tract infections in children attending daycare centers

“…As crianças são mais suscetíveis a infecções respiratórias devido a características anatômicas, fisiológicas e imunológicas 4 . Essas infecções respiratórias têm um impacto significativo na área da saúde em todo o mundo, sendo predominantemente de origem viral 5 .…”

Procalcitonin in sepsis and bacterial infections

“…This makes PCT a more specific marker for bacterial infection. 13 Thus, during severe bacterial infections, the level of PCT may rise several hundred-folds and may even reach a level of 1000 ng/mL without any change in serum calcitonin level. 11,14 However, it is important to keep in mind the following situations while interpreting PCT reports: (i) Gram negative bacteraemias cause higher elevation of PCT than those caused by Gram positive pathogens; 15 (ii) there is a low or negligible rise in PCT levels in localized infections, and in infections caused by viruses or intracellular bacteria; 16,17 and (iii) in the neonatal period, particularly in the first 48-72 hours of life, serum PCT levels increase to a high level and then gradually fall during the first week.…”

Economic evaluation of procalcitonin-guided antibiotic therapy in acute respiratory infections: a US health system perspective

“…Biomarkers have shown to be very effective in aiding diagnosis and management of hospital patients with suspected systemic bacterial infections, including community-acquired pneumonia (CAP) and sepsis [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Procalcitonin (PCT) is a novel and effective marker of assumed bacterial infections that safely helps guide antibiotic therapy in acute respiratory tract infections (ARI) and sepsis in hospitals [5,[29][30][31][32][33][34][35][36][37][38][39][40].…”