Mutations in the staphylococcal virulence regulator gene agr frequently occur during Staphylococcus aureus infection. Whether agr-defective strains are fit for colonization, an important prerequisite for infection, is unknown. Screening by means of assays to detect delta-hemolysin activity and agr autoinducing peptide production indicated that 15 ( approximately 9%) of 160 healthy human subject...

1. Normal serum, used in cultures for preparation of the streptolysin, modifies the properties of the streptolysin, causing delayed hemolysis, increased filterability, resistance to oxidation or reduction, and absence of antigenicity. 1. Streptolysin prepared without serum is an active antigen. 3. Similar temperatures are required to destroy the antigenic activity of serum-free streptolysin and...

1. The presence of a natural anti-human hemolysin, only active against Group I and Group II cells, was demonstrated in over 50 guinea pigs, obtained from different sections of the surrounding country. It was shown that, in a majority of the sera tested, this hemolysin would be a contributing factor to an excess of amboceptor in the reaction, in the quantities of complement used in an antihuman ...

Strains of streptococci whose virulence has been increased for any one species of animal do not produce greater concentrations of hemolysin than the original strain. Furthermore, there is a tendency for the original culture to grow more rapidly than the more pathogenic form, and to reach the height of hemolysin production at an earlier stage during the growth of the culture. These conclusions c...

A mutant, Vp-MX02, having a deletion in the gene (trh) for the thermostable direct hemolysin-related hemolysin (TRH) was constructed by double-crossover gene conversion from a TRH-producing Vibrio parahaemolyticus strain, TH3996. The deleted region was the upstream half of trh. Hemolysis was completely lost, and TRH antigen was undetectable in the mutant. Administration of the mutant into ligat...

Selective media for Vibrio parahaemolyticus, BTB-Teepol agar and modified arabinose-ammonium sulfate-cholate agar, were modified for use in immunological detection of the thermostable direct hemolysin produced by this organism. The modified BTB-Teepol agar and modified arabinose-ammonium sulfate-cholate agar were both found to be useful for the modified Elek test and immunohalo test with antise...

From January to December 2006, 92 Escherichia coli isolates from 25 diarrheic dogs were analyzed by screening for the presence of adhesin-encoding genes (pap, sfa, afa), hemolysin and aerobactin genes. Virulence gene frequencies detected in those isolates were: 12% pap, 1% sfa, 10% hemolysin and 6.5% aerobactin. Ten isolates were characterized as extraintestinal pathogenic E. coli (ExPEC) strai...

INVESTIGATIONS OF THE INDUCTION PERIOD OF AN IN VITRO HEMOLYSIN RESPONSE TO SHEEP ERYTHROCYTE ANTIGEN REVEALED THE FOLLOWING: 1. After antigen stimulation precursors of plaque-forming cells rapidly maturate to the point of hemolysin production. 2. Initial maturation probably occurs in the absence of cell division. 3. After initial maturation, a latent period of about 12 hr occurs before the fir...

Protoplast fractionation techniques were used to prepare subcellular fractions of three strains of Staphylococcus aureus for the analysis of alpha-hemolysin activity. More than 90% of the cellular hemolytic activity was localized in the periplasm, only a trace was detected in the cytoplasm, and none was found in either plasma membranes or mesosomes. This cellular portion constituted approximate...