Biomedical subjects
Publications and source records attributed to M S Kalra.
A 39 kD phospholipase-A was purified from Salmonella typhi. The enzyme was efficiently concentrated by precipitation with ammonium sulphate and purified by sequential use of column chromatography on DEAE-Sephacel and Sephadex G-100. Humoral and cellular immune responses were determined against both crude and purified phospholipase-A. Crude fraction was found to be more immunogenic than purified fraction.
The effect of various physico-chemical factors on the production of intra and extracellular phospholipase A by Salmonella typhi was investigated. Maximum intracellular enzyme levels were observed when cells were grown in brain heart infusion broth, after 16h of incubation at 37 degrees C. Highest level of extracellular phospholipase A was also seen in the same medium (pH 7.0), but after 24 h of incubation at 37 degrees C. Agitation during incubation enhanced the enzyme synthesis. Addition of surfactants to the growth media significantly decreased both intra and extracellular phospholipase A production.
Eight clinical isolates of Y. enterocolitica were tested for various pathogenicity and virulence markers. Seven of the eight strains gave positive results for Congo red magnesium oxalate (CRMOX) agar test and autoagglutination test at 37 degrees C. Seven strains bound crystal violet (CV) completely at 37 degrees C but not at 25 degrees C. One strain (Y1) bound CV partially. None of the strains showed pyrazinamidase activity indicating these strains to be virulent. Cells of all but one strains were aggregated by 1.8 M and 3.2M concentration of ammonium sulphate. A good correlation between these tests and virulence was observed.
Protease-deficient mutants of Pseudomonas aeruginosa obtained by ethyl methane sulphonate treatment were found to show pleiotropic effect on various extracellular toxin activities. Of eight mutants five were completely deficient in lecithinase and four in collagenase activity. The decreased hemolytic activity was obtained in five mutants and enterotoxin activity in seven mutants as compared to parent strain.
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Streptococcus faecalis has been reported to cause food poisoning. Six strains of S. faecalis were tested for Sherman's criteria. These strains were non-hemolytic, DNase+ and Ent+. The enterotoxin was purified on Sephadex G-200 column and maximum activity was observed at 37 C and pH 7.0. Enterotoxin treated with trypsin and papain elicited very poor response to fluid accumulation. The sensitivity of all the strains against different antibiotics was determined. Strain 53 M was treated with acridine orange and ethidium bromide and a total of 44 Amps Strr and 3 Amps Strs mutants were tested for toxin production. Out of these only 4 were toxin negative, amongst which 3 were also DNase negative and 1 showed partial DNase activity.
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Six starter cultures were examined for their ability to induce beta-D-Galactosidase activity. The maximum (713 x 10(-4) units/ml) and minimum (140 x 10(-4) units/ml) enzyme activity was shown by Lactobacillus bulgaricus and Streptomyces thermophilus, respectively. The maximum inhibition by aflatoxin B1 of induction and activity of enzyme in vitro was observed at 60 micrograms/ml in all cultures. However, low levels of the toxin stimulated induction of the enzyme in Streptococcus lactis and S. thermophilus.
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