Biomedical subjects

D Ferrazza

Publications and source records attributed to D Ferrazza.

3 recordsLinked to original sources

PubMed1993

Chlorine injury and the comparative performance of Colisure (TM), ColiLert (TM) and ColiQuik (TM) for the enumeration of coliform bacteria and E.coli in drinking water.

Several factors have stimulated interest in recently developed substrate specific media for the detection of coliform bacteria in water. This study compared the performance of Colisure (TM) (Millipore), ColiLert (TM) (Environetics) and ColiQuick (TM) (Hach) with accepted membrane filtration and MPN methodologies for the enumeration of total coliforms and E. coli in chlorinated water. The performance of all three media was compared, in MPN configuration, with LTB/MPN (confirmed) using a variety of drinking and source water samples, both with and without chlorination. The Cochran-Mantel-Haenszel test yielded statistical correlations between results obtained with each of the three new enzyme detection media and accepted reference methods for the detection of low numbers of total coliforms. Another series of tests compared the performance of Colisure with accepted methods (LTB/MPN confirmed with BGLB and EC-MUG) in the detection of total coliforms and E. coli in sewage-spiked samples simulating contaminated drinking water, using an USEPA/AWWA test protocol. The results demonstrated that Colisure detected these indicator bacteria with greater sensitivity than the accepted methods and that this difference increased between 24 and 28 hours of incubation. The results of this study collectively support the validity of the new enzyme detection method for the detection of low levels of coliform bacteria and E. coli in source water and contaminated drinking water.

Chlorine↗

PubMed1980

Biosynthesis of a plasmid-encoded outer membrane surface exclusion protein involves processing from a precursor polypeptide.

MRB is a major R222 plasmid-encoded outer membrane protein previously described by this laboratory which is immunologically identical with F plasmid traTp. We have detected an apparent precursor polypeptide of MRB in Escherichia coli minicells which reacts with specific anti-MRB serum. In the presence of proteolytic inhibitors, immunologically reactive precursor MRB polypeptides are found in whole cells and minicells containing R222 or F plasmids. When R222-containing minicells were incubated for short periods of time with [35S]methionine, the precursor was predominantly labeled but was shown to be converted into MRB during subsequent incubation in media containing nonradioactive methionine. This conversion was inhibited in the presence of the proteolytic inhibitor tosyllysylalanyl chloramethyl ketone. These studies show that at least one plasmid-encoded membrane protein is processed in its E. coli host in a way resembling that of host cell membrane proteins.

Antigens, Surface↗

PubMed1980

Biochemical and immunological characterization of an R plasmid-encoded protein with properties resembling those of major cellular outer membrane proteins.

MRB, a major R222 plasmid-encoded protein previously described by us, is synthesized in large amounts in host Escherichia coli cells, where it is located principally in the outer membrane. Most of this protein is also bound to the peptidoglycan layer in a form which is trypsin resistant. Its monomeric molecular weight is about 29,000, but it is isolated from cell membranes in aggregate molecular weights of more than 100,000. These properties demonstrate a strong similarity between MRB and porins, major outer membrane proteins of host E. coli cells. They suggest that MRB may have an as-yet unidentified transport function, as do cellular outer membrane proteins with similar biochemical properties. By using antiserum specific for MRB, we demonstrated identity between MRB and the product of the traT gene, one of the surface exclusion proteins on the F plasmid. The synthesis of MRB was found to be constitutive, in contrast to other tra genes, which appear to be under more rigid regulation by the tra operon. These findings suggest that on R222 and other F-like R plasmids this protein has its own promoter.

Bacterial Proteins↗