The gram-positive bacterium Listeria monocytogenes is a facultative intracellular pathogen. The only known property of L. monocytogenes which has been shown to be involved in virulence is a hemolysin, listeriolysin (J. L. Gaillard, P. Berche, and P. Sansonetti, Infect. Immun. 52:50-55, 1986; S. Kathariou, P. Metz, H. Hof, and W. Goebel, J. Bacteriol. 169:1291-1297, 1987). Using our previously o...

Human diploid embryonic lung fibroblasts and HeLa cells were cultivated in Eagle minimaĺ essential medium supplemented with 10% calf serum. Monolayer cultures were labeled with (3)H-uridine and treated with highly purified staphylococcal alpha-, beta-, delta-, or gamma-hemolysin. The release of soluble radioactive substances into the medium was used as an indicator of damage to the cell membran...

Flow cytometry was developed as a method to assess the conformation of erythrocyte-bound Escherichia coli hemolysin polypeptide (HlyA). Topology of membrane-associated hemolysin (HlyA(E)) was investigated by testing surface accessibility of HlyA regions in lytic and nonlytic bound states, using a panel of 12 anti-HlyA monoclonal antibodies (MAbs). Hemolysin associates nonlytically with erythroc...

The ability of Edwardsiella tarda to hemolyse red blood cells was investigated. Most E. tarda strains (> 80%) produced a hemolysin when assayed by either an agar overlay or contact-dependent hemolysis technique. This activity was cell-associated (CAH) and not released into the culture supernatant under routine conditions. When quantified, E. tarda strains significantly produced 30-40-fold highe...

Livestock associated methicillin-resistant Staphylococcus aureus (LA-MRSA) draws concern from the public health community because in some countries these organisms may represent the largest reservoir of MRSA outside hospital settings. Recent studies indicate LA-MRSA strains from swine are more genetically diverse than the first reported sequence type ST398. In the US, a diverse population of LA...

The hemolytic Escherichia coli strain 536 (O6) propagates spontaneous hemolysin-negative mutants at relatively high rates (10(-3) to 10(-4)). One type of mutant (type I) lacks both secreted (external) and periplasmic (internal) hemolysin activity (Hlyex-/Hlyin-) and in addition shows no mannose-resistant hemagglutination (Mrh-), whereas the other type (type II) is Hlyex-/Hlyin+ and Mrh+. The ge...

One hundred clinical isolates of Pseudomonas pseudomallei from humans were tested for their ability to produce extracellular, biologically active substances which are thought to contribute to the virulence of Pseudomonas species. All isolates produced at least on extracellular enzyme; 91 strains were positive for lecithinase, lipase, and protease; but none was positive for elastase. Ninety-thre...

Secreted hemolysins were extremely common among clinical isolates of Proteus mirabilis, Proteus vulgaris, and Morganella morganii, and hemolytic activity was either cell associated or cell free. Southern hybridization of total DNA from hemolytic isolates to cloned regions of the Escherichia coli alpha-hemolysin (hly) determinant showed clear but incomplete homology between genes encoding produc...