Diagnostic usefulness of serum procalcitonin in patients with bacterial sepsis

Background

The Sequential Organ Failure Assessment (SOFA) score is used for the diagnosis of sepsis and involves clinical and laboratory parameters that may not be readily and/or timely available in most resource-poor settings. Procalcitonin (PCT) has its level changed in response to bacterial sepsis and its measurement costs only a fraction of the total cost of investigations required to calculate SOFA score. This study aims to determine the diagnostic usefulness of PCT in bacterial sepsis.

Materials and Methods

Ninety-nine participants were studied, divided into three groups: apparently healthy volunteers, those with bacterial infection without sepsis (SOFA score <2), and patients with bacterial sepsis (positive culture and SOFA ≥2). PCT level of each participant was measured and median group levels compared. Pearson's correlation was used to determine the correlation between serum PCT levels and SOFA scores in the sepsis group using a significance level of 5 percent (P < 0.05). Diagnostic usefulness of PCT was assessed using receiver operating characteristic (ROC).

Result

Positive correlation was found between serum PCT levels and SOFA scores among patients with sepsis r = 0.42, P = 0.016. At a concentration of ≥4.25 ng/ml, serum PCT as a surrogate for SOFA score had a sensitivity and specificity of 57.60% and 84.80%, respectively, for indicating sepsis. The area under the ROC curve (AUC) was 0.74 (95% CI {0.62 to 0.86}, P = 0.001).

Conclusion

Serum PCT concentration was significantly higher in bacterial sepsis compared to bacterial infection without sepsis and healthy state. PCT concentration demonstrated positive correlation with SOFA score in bacterial sepsis and can be used as surrogate for sepsis screening/monitoring in resource-poor settings.

Phosphomonoesterases of Leishmania mexicana mexicana and other flagellates

Amastigotes and log-phase promastigotes of Leishmania mexicana mexicana contained distinct acid phosphatase, 3'-nucleotidase and 5'-nucleotidase activities, distinguishable by their response to pH and inhibitors. Both tartrate-sensitive and tartrate-resistant acid phosphatase were present in the two forms, amastigotes possessed less tartrate-resistant acid phosphatase than promastigotes. A tartrate-sensitive acid phosphatase was secreted into the medium in large amounts during the growth in vitro of L. m. mexicana promastigotes. The 5'-nucleotidase activity of both parasite forms was inhibited by ammonium molybdate, sodium tartrate and, to less extent, by sodium fluoride whereas 3'-nucleotidase was inhibited by EDTA. All three activities were shown to be present on the external surface of both amastigotes and promastigotes. The three phosphomonoesterase activities were also detected in extracts of L. m. amazonensis, L. donovani, L. tarentolae, Crithidia fasciculata, Herpetomonas muscarum muscarum, H.m. ingenoplastis and Trichomitus batrachorum whereas 5'-nucleotidase was not detected in Trypanosoma brucei brucei extract and 3'-nucleotidase was absent from extracts of Trichomonas vaginalis and Tritrichomonas foetus.

Purine-metabolizing enzymes in Babesia divergens

Extracts of Babesia divergens were examined for the enzymes which catalyse purine salvage. Adenosine deaminase (EC 3.5.4.4), guanine deaminase (EC 3.5.4.3), inosine phosphorylase (EC 2.4.2.1), purine phosphoribosyltransferases (EC 2.4.2.7, EC 2.4.2.8, EC 2.4.2.22) and nucleoside kinases (EC 2.7.1.15, EC 2.7.1.20, EC 2.7.1.73) were all detected at relatively high activities, whereas nucleotide interconverting enzymes were not detected. Coformycin and 4-amino-5-imidazolecarboxamide were found to be potent inhibitors of adenosine deaminase and guanine deaminase, respectively. The results suggest that B. divergens is capable of synthesizing purine nucleotides via two routes, one involving purine phosphoribosyltransferases and the other employing nucleoside kinases.

Purine-metabolising enzymes in Entamoeba histolytica

The enzymes that catalyse the salvage of purines in Entamoeba histolytica trophozoites have been surveyed. Adenine deaminase (EC 3.5.4.2), adenosine deaminase (EC 3.5.4.4), guanine deaminase (EC 3.5.4.3), adenine phosphoribosyltransferase (PRTase) (EC 2.4.2.7), xanthine PRTase (EC 2.4.2.22) and hypoxanthine PRTase (EC 2.4.2.8) were all detected in cell homogenates but only at low activities, whereas AMP deaminase (EC 3.5.4.6) and guanine PRTase (EC 2.4.2.8) were not found. Phosphorylases (EC 2.4.2.1) active in both anabolic and catabolic directions were present and all nucleosides tested were phosphorylated by kinases (EC 2.7.1.15, EC 2.7.1.20, EC 2.7.1.73). 3'-Nucleotidase (EC 3.1.3.6) and 5'-nucleotidase (EC 3.1.3.5) were found, the former being mainly particulate. Nucleotide interconversion enzymes (adenylosuccinate lyase, EC 4.3.2.2; adenylosuccinate synthetase, EC 6.3.4.4; IMP dehydrogenase, EC 1.2.1.14; GMP synthetase, EC 6.3.5.2 and GMP reductase, EC 1.6.6.8) were not detected. The results suggest that in E. histolytica the main route of nucleotide synthesis is from the individual bases through the actions of phosphorylases and kinases.

Leishmania mexicana: purine-metabolizing enzymes of amastigotes and promastigotes

Cultured promastigote and isolated amastigote forms of Leishmania mexicana mexicana have been surveyed for the presence of enzymes involved in purine metabolism. Quantitative but not qualitative differences between the enzymes of two forms were discovered. There were found to be significant differences between the enzyme content of L. m. mexicana and that reported for L. donovani. Extracts of both parasite forms of L. m. mexicana were found to have higher levels of adenine deaminase (EC 3.5.4.2) and guanine deaminase (EC 3.5.4.3) than adenosine deaminase (EC 3.5.4.4). There appeared to be two distinct nucleosidases (EC 3.2.2.1), one active on nucleosides, the other on deoxynucleosides. Phosphorylase (EC 2.4.2.1) could be detected only in the catabolic direction. Nucleotidases were present, but were more active on 3' (EC 3.1.3.6)- than 5' (EC 3.1.3.5)-nucleotides. Phosphoribosyltransferase (EC 2.4.2.7,.8 and .22) and nucleoside kinase (EC 2.7.1.20) activities were detected in both forms. Nucleotide-interconverting enzymes were found to be present, with IMP dehydrogenase (EC 1.2.1.14) being the most active. Cell fractionation experiments revealed that, in the promastigote, enzyme separation within the parasite may play an important part in regulating cellular purine metabolism.

Purine phosphoribosyltransferases of Leishmania mexicana mexicana and other flagellate protozoa

Amastigotes and cultured promastigotes of Leishmania mexicana mexicana and L. m. amazonensis, cultured promastigotes of L. donovani and L. tarentolae, and the culture forms of Crithidia fasciculata, Herpetomonas muscarum muscarum and H. m. ingenoplastis all possessed four phosphoribosyltransferase (PRTase) activities: adenine PRTase, hypoxanthine PRTase, guanine PRTase and xanthine PRTase. The enzymes of L. m. mexicana required divalent cations for activity; Mn2+ or Co2+ produced maximal activity in most cases. Hypoxanthine PRTase, guanine PRTase and xanthine PRTase from all organisms were sedimentable in part, suggesting that they may occur within glycosomes. The enzymes of L. m. mexicana cultured promastigotes were inhibited by a range of purine analogues.

Subcellular localisation of purine-metabolising enzymes in Leishmania mexicana mexicana

Leishmania mexicana mexicana cultured promastigotes were fractionated by isopycnic centrifugation on linear sucrose gradients. Guanine, hypoxanthine and xanthine phosphoribosyltransferase activities were found to be associated with glycosomes, whereas adenine phosphoribosyltransferase was cytosolic. 3'- and 5'-nucleotidases and IMP dehydrogenase were shown to be particulate, the former two possibly being associated with the plasma membrane, IMP dehydrogenase with the endoplasmic reticulum. Nucleosidases and deaminases were found to be cytosolic. The results demonstrate that intracellular separation of enzymes could play a part in the regulation of the parasite's purine metabolism.