Diagnosis of Strongyloides stercoralis by morphological characteristics combine with molecular biological methods.

Strongyloidiasis is one of the neglected tropical diseases caused by infection with the nematode Strongyloides genus and distributed worldwide. Strongyloidiasis can be fatal in immunosuppressed patients induced hyperinfection or disseminated strongyloidiasis. Unfortunately, until now, due to the unspecific clinical symptom in infected individuals and the low sensitivity diagnosis of strongyloidiasis, many patients were misdiagnosed every year. Furthermore, the larvae of the Strongyloides stercoralis (S. stercoralis) is similar to other nematodes such as hookworm, Trichostrongylus increased the difficulty of diagnosis. In this case, the patient is a 63-year-old male person, who had a nearly 30 years medical history of asthma and emphysema, and 4-5-year medical history of diabetes. The sputum examination found some parasite larvae, then we identify the larvae using clinical observation and morphological characteristics combine with examined cytochrome oxidase subunit 1 (COX1) and 18S rRNA genes by PCR, sequence analysis and finally classified by phylogenetic analysis, the larvae were diagnosed as S. stercoralis. Our results showed that diagnosis with strongyloidiasis by morphological characteristics combine with molecular biological methods can improve the sensitive of diagnosis and provide a final diagnosis for the disease in the clinics.

Cloning, molecular characterization of a 13-kDa antigen from Schistosoma japonicum, Sj13, a putative salivary diagnosis candidate for Schistosomiasis japonica.

Saliva has been suggested as an easily accessible and a noninvasive diagnostic alternative for detection of antibodies. To identify and characterize Schistosoma japonicum (S. japonicum) antigens that are recognized by saliva of infected host, we have used a pool of saliva from infected patients to immunoscreen an egg cDNA library of S. japonicum. The open reading frame of the isolated two clones encodes same protein of 116 amino acids exhibiting 100% identity to an amino acid sequence (AY222893) of S. japonicum in NCBInr database. The protein encoded is inferred a secretory protein with a molecular mass of 13 kDa (Sj13) and shares no homology to any entries in the NCBInr database, demonstrating that Sj13 might be a schistosome-specific protein. Reverse transcriptase polymerase chain reaction, Western blotting, and immunolocalization analysis revealed Sj13 could be detected in cercaria, adult, and egg and was localized to forehead and tegument of cercaria, cell body ("cytons") of adult worm, egg shell, and epidermal plate of miracidium. Furthermore, Sj13 showed a good antigenicity when reacted with saliva or serum from schistosomiasis patients. The recombinant Sj13 (rSj13) expressed and purified from Escherichia coli was applied to detect its specific salivary antibody for schistosomiasis diagnosis by an indirect enzyme linked immunosorbent assay (ELISA). Preliminary laboratory test of 116 subjects, 40 with parasitologically proven S. japonicumm infection, 46 with other infectious diseases, and 30 negative controls exhibited 92.50% sensitivity with saliva/rSj13 and 95.00% with serum/SWAP (P > 0.05). The specificity of the ELISA using saliva/rSj13 was 92.11% versus 85.53% with serum/SWAP (P < 0.05). No direct correlations of anti-Sj13 IgG levels with egg counts in stool were observed in saliva detection. These results suggest that Sj13 specific salivary antibody detection may be useful as an antigen for the salivary diagnosis of schistosomiasis japonica and contribute to epidemiological study of schistosomiasis infection in endemic areas.