Biology of procalcitonin and its potential role in veterinary medicine

Molecularly imprinted polymers as effective capturing receptors in a pseudo-ELISA immunoassay for procalcitonin detection in veterinary species

In this study, a new sandwich-type immunoenzymatic assay, based on a molecularly imprinted polymer (MIP) as an artificial antibody (pseudo-ELISA), was developed for the determination of procalcitonin (PCT) in veterinary species. The quantification of PCT in human medicine represents the state of the art for the diagnosis of sepsis; instead the clinical studies on the relevance of PCT as a sepsis predictor in veterinary patients are few, likely due to the total absence of validated assays. MIPs have been widely used as antibody mimics for important applications, and MIP-based sandwich assays have emerged as promising analytical tools for the detection of disease biomarkers. Herein, a polynorepinephrine (PNE)-based imprinted film was directly synthesized on the well surface of a 96-well plate. Subsequently, based on a commercial ELISA kit, the PCT quantification was accomplished via a colorimetric sandwich assay by replacing the capture antibody of the kit with the PNE-based MIP. This method was performed to detect canine and equine PCT in buffer and in plasma samples. Under optimal conditions, the results obtained in plasma samples showed a limit of detection (LOD) of 5.87 ng mL^-1 and a reproducibility (CV_av%) of 10.0% for canine samples, while a LOD = 4.46 ng mL^-1 and CV_av% = 7.61% were obtained for equine samples.

Use of serum procalcitonin (PCT) level and PCT mRNA expression as a potential clinical biomarker in cats with bacterial and viral infections

OBJECTIVES

The aim of this study was to investigate the use of procalcitonin (PCT) as a biomarker in differentiating bacterial infections from viral infections in cats. In addition, the relationship between PCT and mortality rate was also examined.

METHODS

Forty-five cats were included in the study. The cats were categorised into two groups: bacterial (n = 20) and viral (n = 25) infection. Serum PCT level and PCT mRNA expression were analysed from blood samples collected before treatment.

RESULTS

Serum PCT level and PCT mRNA expression of the cats with presumed bacterial infection were higher than those with viral infection (P = 0.001 and P = 0.001, respectively). The receiver operating characteristic (ROC) curve analysis revealed an area under the ROC curve value of 0.888 for serum PCT and 0.850 for PCT mRNA expression. There was no statistically significant difference among respiratory, urinary and gastrointestinal tract infections regarding serum PCT level and PCT mRNA expression in the presumed bacterial infection group (P = 0.741 and P = 0.141, respectively). In the presumed bacterial infection group, serum PCT level and PCT mRNA expression in the non-surviving cats were higher than those of the surviving cats (P = 0.021 and P = 0.026, respectively).

CONCLUSIONS AND RELEVANCE

Serum PCT level and PCT mRNA expression were considered efficient biomarkers in cats to distinguish a bacterial infection from a viral infection. Moreover, ROC curve analysis was highly accurate in the discriminative capacity of these two parameters. PCT level and PCT mRNA expression offer substantial assistance in an efficient therapeutic approach and in avoiding unnecessary antibiotic use in feline clinical practice, particularly in emergency patients and those with non-specific clinical signs, decreasing the mortality rate. However, it should be noted that these data are only research data. More detailed future studies are needed.

Biomarkers of sepsis in pigs, horses and cattle: from acute phase proteins to procalcitonin

Sepsis is a complex clinical syndrome triggered by an inflammatory host response to an infection. It is usually complicated to detect and diagnose, and has severe consequences in human and veterinary health, especially when treatment is not started early. Therefore, efforts to detect sepsis accurately are needed. In addition, its proper diagnosis could reduce the misuse of antibiotics, which is essential fighting against antimicrobial resistance. This case is a particular issue in farm animals, as antibiotics have been traditionally given massively, but now they are becoming increasingly restricted. When sepsis is suspected in animals, the most frequently used biomarkers are acute phase proteins such as C-reactive protein, serum amyloid A and haptoglobin, but their concentrations can increase in other inflammatory conditions. In human patients, the most promising biomarkers to detect sepsis are currently procalcitonin and presepsin, and there is a wide range of other biomarkers under study. However, there is little information on the application of these biomarkers in veterinary species. This review aims to describe the general concepts of sepsis and the current knowledge about the biomarkers of sepsis in pigs, horses, and cattle and to discuss possible advances in the field.

Measurement of procalcitonin in saliva of pigs: a pilot study

Background

Procalcitonin (PCT) is a widely used biomarker of sepsis in human medicine and can have potential applications in the veterinary field. This study aimed to explore whether PCT could be measured in the saliva of pigs and whether its concentration changes in sepsis. Therefore, a specific assay was developed and analytically validated, and changes in PCT concentration were evaluated in two conditions: a) in an experimental model of sepsis produced by the administration of lipopolysaccharide (LPS) to pigs (n = 5), that was compared with a model of non-septic inflammation induced by turpentine oil (n = 4), and b) in healthy piglets (n = 11) compared to piglets with meningitis (n = 20), a disease that usually involves sepsis and whose treatment often requires large amounts of antibiotics in farms.

Results

The assay showed coefficients of variation within the recommended limits and adequate linearity after serial sample dilutions. The method's detection limit was set at 68 μg/L, and the lower limit of quantification was 414 μg/L. In the LPS experiment, higher concentrations of PCT were found after 24 h in the animals injected with LPS (mean = 5790 μg/L) compared to those treated with turpentine oil (mean = 2127 μg/L, P = 0.045). Also, animals with meningitis had higher concentrations of PCT (mean = 21515 μg/L) than healthy pigs (mean = 6096 μg/L, P value < 0.0001).

Conclusions

According to these results, this assay could be potentially used as a tool for the non-invasive detection of sepsis in pigs, which is currently a topic of high importance due to antibiotic use restriction.

Neopterin, procalcitonin, clinical biochemistry, and hematology in calves with neonatal sepsis

This study aims to determine how neopterin, procalcitonin, biochemical and hematological parameters change during treatment of calves with neonatal sepsis. A total of 25 calves divided into two groups. Sepsis group was composed of 15 newborn calves aged 0–10 days which met neonatal sepsis criteria, but did not receive any treatment. Control group included 10 healthy calves aged 0–10 days. Clinical examinations (respiratory rate, rectal temperature, heart rate, capillary refill time, sucking reflex) were performed at certain times before (0th h) and during (12th, 24th, 48th, and 72th h) the treatment. The blood was taken from the jugular vein from the sepsis group before (0th h) and during the treatment (12th, 24th, 48th, and 72nd h) and once from the control group. Procalcitonin pretreatment (0th h) and control group concentrations were found as 178.08 ± 2.4 (pg/mL) and 42.78 ± 1.25 (pg/mL), respectively (p < 0.001). Neopterin pretreatment (0th h) and control group concentrations were determined as 14.44 ± 0.30 (ng/mL) and 3.63 ± 0.29 (ng/mL), respectively (p < 0.001). As a result, neopterin and procalcitonin concentration decreased along with the treatment, confirming the presence of sepsis in calves and suggesting that sepsis could be a prognostic indicator. Therefore, both procalcitonin and neopterin can be prognostic and diagnostic in calves with sepsis.

The use of inflammatory markers as a diagnostic and prognostic approach in neonatal calves with septicaemia

The objective of this study was to evaluate the usefulness of inflammatory markers as a diagnostic and prognostic approach in neonatal calves with septicaemia. The study material consisted of 13 neonatal calves with septicaemia (septicaemic calves, SC) and ten healthy neonatal calves (control calves, CC). Blood samples were collected for biochemical, haematological and microbiological analyses. In addition, faecal samples were collected for microbiological and virological analyses. Three of neonatal calves with septicaemia were positive for E. coli (E. coli O157 serotype) by microbiological examination, but all neonatal calves with septicaemia were negative for rota- and coronaviruses. By haematological examination, there were no significant differences between SC and CC for white blood cell (WBC) and neutrophil (NEU) counts (P > 0.05). NEU counts were higher on day 0 than on day 15 in SC (P < 0.05). Red blood cell (RBC) counts and packed cell volume (PCV) values were higher on day 0 in the SC than in the CC (P < 0.05). By biochemical analyses, tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), procalcitonin (PCT), haptoglobin (Hp), and fibrinogen (Fb) concentrations were higher on day 0 in the SC than in the CC (P < 0.05). After treatment (on day 15), the serum IL-6, PCT, Hp, and Fb concentrations were significantly decreased in the SC compared to the CC (P < 0.05). The serum iron (Fe) concentrations were lower on day 0 in the SC than in the CC (P < 0.05), and were higher on day 15 than on day 0 in the SC (P < 0.05). The study revealed that inflammatory markers could be used for determining the diagnosis and prognosis in neonatal calves with septicaemia.