The neuraminidase gene is present in the non-toxigenic Vibrio cholerae Amazonia strain: a different allele in comparison to the pandemic strains

The neuraminidase gene, nanH, is present in the O1, non-toxigenic Vibrio cholerae Amazonia strain. Its location has been assigned to a 150 kb NotI DNA fragment, with the use of pulsed-field gel electrophoresis and DNA hybridization. This NotI fragment is positioned inside 630 kb SfiI and 1900 kb I-CeuI fragments of chromosome 1. Association of the pathogenicity island VPI-2, carrying nanH and other genes, with toxigenic strains has been described by other authors. The presence of nanH in a non-toxigenic strain is an exception to this rule. The Amazonia strain nanH was sequenced (Genbank accession No. AY825932) and compared to available V. cholerae sequences. The sequence is different from those of pandemic strains, with 72 nucleotide substitutions. This is the first description of an O1 strain with a different nanH allele. The most variable domain of the Amazonia NanH is the second lectin wing, comprising 13 out of 17 amino acid substitutions. Based on the presence of nanH in the same region of the genome, and similarity of the adjacent sequences to VPI-2 sequences, it is proposed that the pathogenicity island VPI-2 is present in this strain.

Study of proteases and other enzymes of Vibrio cholerae 01 E2 Tor and 0139 serotypes isolated in Yavatmal (Maharashtra).

V. cholerae 01 E1 Tor isolated during Cholera epidemic of 1994 and V cholerae 0139 serotype isolated during 1993 epidemic were subjected to the study of proteases and other enzymes. Out of 26 strains of V. cholerae 01 studied, gelatinase and caseinase activity was seen in 100 and 69.23 percent strains respectively. All strains showed catalase and oxidase activity. Of the other enzymes studied 19.23, 65.38 and 57.69 percent strains were positive for DNAse, lipase and phosphatase respectively. None of the strains showed lecithinase activity. Similar findings were observed in 22 strains of V. cholerae 0139 except all strains were positive for phosphatase activity. Role of enzymes in virulence is suggested.

Effect of Vibrio cholerae-L-asparaginase on surface structure of splenic lymphocytes.

The surface ultrastructure of splenic lymphocytes and rosetting properties of lymphocytes of Swiss mice were studied under scanning electron microscope following transplantation of Dalton's lymphoma and ascites fibrosarcoma tumour cells and administration of Vibrio cholerae-L-asparaginase. The results were compared to those obtained with the standard Escherichia coli-L-asparaginase. The surface structure of the lymphocytes (T cells) following L-asparaginase administration was not so different from that of normal lymphocytes. V. cholerae-L-asparaginase did not cause higher number of rosette formation in T cells as compared to the normal group. The study thus revealed that V. cholerae-L-asparaginase did not have a significant stimulatory or non-immunosuppressive effect on the lymphocyte functions.