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V A Fischetti

Publications and source records attributed to V A Fischetti.

137 records · Page 8Linked to original sources
PubMed1974

Cellular reactivity studies to streptococcal antigens. Migration inhibition studies in patients with streptococcal infections and rheumatic fever.

The question of whether hypersensitivity to streptococcal antigens plays a role in the pathogenesis of the nonsuppurative sequelae of streptococcal infections remains at present unclear. As a first step in the approach to this question, the degree of cellular reactivity of peripheral blood leucocytes to streptococcal antigens was investigated in a number of rheumatic fever patients, patients with uncomplicated streptococcal infections, as well as normal healthy subjects. Using the in vitro technique for the inhibition of capillary migration of peripheral blood leucocytes as an index of the degree of sensitivity to streptococcal antigens, the results indicate that patients with acute rheumatic fever exhibit an exaggerated cellular reactivity to these antigens and in particular to streptococcal cell membrane antigens. This abnormal response to streptococcal membrane antigens appears to persist in rheumatic subjects for at least 5 yr after the initial attack of rheumatic fever. Only Group A streptococcal membrane antigens elicited this unusual response in rheumatic subjects, since the cellular reactivity to Group C and D streptococcal membranes was the same in all groups. Patients with evidence of valvular disease exhibited the same degree of cellular reactivity to these antigens as did patients without clinical evidence of rheumatic heart disease. The nature of the antigens responsible for the observed cellular response remains unknown. Enzymatic treatment of streptococcal cell walls and membranes designed to remove type-specific M proteins did not alter the observed cellular reactivity to the streptococcal antigens. The finding that an abnormal cellular response to certain streptococcal antigens is present only in rheumatic patients suggests that cell-mediated factors may play an important role in the disease process.

Animals↗
PubMed1971

Purification and physical properties of group C streptococcal phage-associated lysin.

A purification procedure for the Group C phage-associated lysin is described utilizing tetrathionate to protect the enzyme's -SH group(s) from thiol-inactivating agents. A 652-fold purification has been accomplished yielding a solution in which the enzyme activity corresponds to essentially a single band on polyacrylamide gel which accounts for 70% of the total protein in the preparation. A molecular weight of 101,000 and frictional ratio of 1.526 was determined for the lysin utilizing experimentally determined values for its Stokes radius and sedimentation coefficient.

Acrylates↗
PubMed1968

Studies on streptococcal bacteriophages. I. Burst size and intracellular growth of group A and group C streptococcal bacteriophages.

Evidence has been presented that the burst size in the Group A and Group C streptococcal phage-host systems are in general similar producing approximately 13 phage particles per infected coccus. The exception was the C1 phage which produced 10 times more virus particles than all the other phages tested. The eclipse period for the A25 phage-host system was found to extend for 34 min, while the C1 phage were found as early as 10 min after infection. Conclusive evidence has been presented indicating that mercuric ions at 2.5 x 10(-6)M concentration have the ability to halt intracellular phage production at any point during the infective cycle of A25 bacteriophages. This blocking action can then be quickly reversed with the addition of reduced glutathione with subsequent completion of the viral cycle.

Bacteriophages↗
PubMed1968

Studies on streptococcal bacteriophages. II. Adsorption studies on group A and group C streptococcal bacteriophages.

Evidence has been presented that Group C bacteriophages differ as to their inactivating site on the streptococcal cell wall. While all three phages adsorb to isolated cell walls, only the C1 phage was inactivated by enzymatically prepared group-specific carbohydrate. None of the Group C phages were inactivated by chemically extracted group-specific carbohydrate. In contrast, all virulent Group A streptococcal bacteriophages adsorbed only to living Group A streptococci. However, Group A temperate phages were able to adsorb to isolated cell walls but not to group-specific carbohydrate. While it has not been possible to identify the specific inactivating substance for the Group A virulent phages, certain pieces of evidence indirectly implicate the group-specific carbohydrate, specifically the N-acetylglucosamine moiety. The fact that Group A virulent phages failed to adsorb to heat-killed Group A streptococcal cells suggests that additional factors produced by the living cell are needed for complete viral inactivation.

Adsorption↗
PubMedDate not supplied

Structure, function, and genetics of streptococcal M protein.

Streptococcal M protein is a coiled-coil fibrillar structure extending about 60 nm from the cell wall. From DNA sequencing of the M6 protein gene, it has been determined that the C-terminal end contains a membrane anchor and an adjacent cell wall stabilization domain, both of which are similar to C-terminal regions of surface proteins in other gram-positive organisms. Studies with monoclonal antibodies revealed that the C-terminal half of the protein is conserved among M proteins of different serotypes, whereas the N-terminal half varies. The M protein contains tandem repeats, which, through homologous recombination, are responsible for the observed size variation of the M proteins from different streptococcal strains. M protein size mutants occur in a laboratory-grown culture at a frequency of 1/2,000 colony-forming units. DNA sequence analysis of the M gene in size mutants derived from a single strain suggests that sequence changes which result from homologous recombination may play a role in the antigenic variation of M protein.

Antigenic Variation↗
PubMedDate not supplied

Identification of a new toxin from a strain of Staphylococcus aureus isolated from a patient with nonmenstrual toxic shock syndrome.

The extracellular products of a toxic shock syndrome toxin 1 (TSST-1)-negative isolate of Staphylococcus aureus (strain D4508) from a patient with nonmenstrual toxic shock syndrome were shown to possess toxic activity capable of producing shock and death when injected into rabbits. Fractionation of the extracellular products and the production of polyclonal antibodies to individual polypeptides identified the toxin as a single polypeptide of molecular weight 26,000. Immunoblot analyses showed the toxin to be antigenically related yet distinct from enterotoxins A, B, C, D, and E and unrelated to TSST-1.

Animals↗
PubMedDate not supplied

Role of air in growth and production of toxic shock syndrome toxin 1 by Staphylococcus aureus in experimental cotton and rayon tampons.

Rayon and cotton fibers of the type used in the manufacture of tampons were extracted for 6 hours in isopropyl alcohol in a soxhlet apparatus to remove all finishes from the fiber surface. The fibers were used to produce experimental tampons of commercial design. Using a syringe method, the tampons were saturated with diluted staphylococci in brain-heart infusion medium and incubated at 37 degrees C. Spent medium was expressed from the tampons and analyzed for growth of staphylococci and production of toxic shock syndrome toxin 1 (TSST-1). Results revealed no statistical difference in the production of TSST-1 by cells grown in rayon or cotton. However, a significant increase in TSST-1 production was observed in tampon cultures when compared with medium controls. When similar experiments were performed with tampons saturated with nitrogen, a significant decrease in TSST-1 production was observed when compared with air-saturated tampons. The results indicate that the oxygen normally present in tampons plays a significant role in modulating the production of TSST-1.

Aerobiosis↗