[A preliminary study on the measurement of (1,3)-ß-D-glucan in bronchoalveolar lavage for the diagnosis of pulmonary fungal infections].

OBJECTIVE: To explore the measurement of (1,3)-ß-D-glucan bronchoalveolar lavage fluid (BALF) for the diagnosis of pulmonary fungal infections. METHODS: A total of 135 patients in the General Hospital of Tianjin Medical University from February 2010 to February 2011 were enrolled. There were 34 cases of confirmed or clinically diagnosed pulmonary fungal infections, 53 cases of bacterial pneumonia, and 48 cases of non-infection diseases. All patients underwent BAL and the BALF samples were obtained. (1,3)-ß-D-glucan content (G test), in BALF and plasma were tested and the data were analyzed statistically by Mann-Whitney while the receiver operating characteristic curve (ROC curve) was established, from which the best threshold of the 2 G tests was derived. RESULTS: The median of BALF G test in the fungal infection group, pneumonia group and non-infection group was 281, 28 and 10 ng/L, respectively; the level in the fungal infection group being significantly higher than those of the other 2 groups (P < 0.001), but no significant difference being observed between the pneumonia group and the non-infection group (P > 0.05). The median of plasma G tests in the fungal infection group, the pneumonia group and the non-infection group was 27, 10, and 5 ng/L, respectively; the level in the fungal infection group being significantly higher than those in the other 2 groups (P < 0.001), but there was no significant difference between the pneumonia group and the non-infection group (P > 0.05). The best threshold of BALF G test was 67 ng/L, while the best threshold of G test of plasma was 17 ng/L. CONCLUSION: As compared to G test of plasma, G test of BALF may be more accurate, and have a higher clinical value for the earlier diagnosis of pulmonary fungal infections.

[Cloning and expression of N-acetyl-D-neuraminic acid aldolase in Escherichia coli].

OBJECTIVE: To obtain the Escherichia coli strains expressing N-Acetyl-D-neuraminic acid aldolase (Neu5Ac aldolase). METHODS: The gene (nanA) coding Neu5Ac aldolase was cloned from Escherichia coli C600, and the recombinant plasmid was sequenced and expressed in Escherichia coli. RESULTS: Sequencing data revealed that the open reading frame was 894 bp and predicted to encode a protein consisting of 298 amino acids. The patterns of SDS-PAGE showed that the purified enzyme protein as a single protein band with a molecular weight of 33 kD, which was consistent with those reported in the reference. In the recombinant plasmid pRY1, the expression of nanA gene was controlled by the lac promoter with the induction of IPTG or lactose. The plasmid pRY3 was constructed, in which the nanA gene ws controlled by the tac promoter. The protein of Neu5Ac aldolase was constitutively expressed using the recombinant strain, E.coli DH5 alpha/pRY3 without induction of IPTG or lactose. The crystal was finally obtained with the efficiency of 90.2% of Neu5Ac. The HPLC indicated that the Neu5Ac crystal prepared in this experiment was same as Simga product. CONCLUSION: The protein products expressed by two recombinant strains E.coli BL21(DE3)/pRY1 and DH5 alpha/pRY3 has the characteristics of Neu5Ac.