Academic literature on the topic 'Lancefield (Vic )'

During the second World War, and even almost a decade later at the conclusion of the Korean Conflict during the 1950s, infections caused by the Group A beta hemolytic streptococcus and their nonsuppurative sequelae were major problems for practicing physicians as well as for public health authorities. Epidemics of scarlet fever were ever present; quarantine signs could be seen prominently displayed in the windows of the homes of schoolchildren. Many schoolchildren had at least one schoolmate who was homebound and bedridden for months with rheumatic fever. The perceived threat of Group A streptococcal infections was of concern to the lay public, especially to parents of schoolchildren. For the medical community the presence of rheumatic fever hospitals in many cities, institutions like the Harriet Lane Home in Baltimore, the Irvington House in New York, the House of the Good Samaritan in Boston, and La Rabida Hospital in Chicago, served to reinforce the need for increasing the understanding and control of these infections. If those facts about Group A streptococci and children were not sufficiently impressive, the large numbers of individual cases and even outbreaks occurring in military troops during the second World War and during the Korean Conflict further emphasized the issue. In fact, before the second World War, relatively little was understood about the epidemiology and pathogenesis of these infections and their sequelae. The laboratory studies of Rebecca Lancefield and others, which allowed more precise identification and characterization of Group A streptococci, and the accompanying clinical observations provided the foundation for early control measures.

Purulent pericarditis is a life-threatening disease that usually manifests following bacteraemia or through spreading from an intrathoracic focus. Only a few cases of this disease have been reported with Lancefield group C streptococci as aetiological agents, and the primary focus in these infections remains unknown. We report a case of purulent pericarditis with septic and cardiogenic shock, caused by Streptococcus equi subsp. zooepidemicus (group C) in a 51-year-old patient. The pathogen was possibly contracted through contact with horses. Most probably, it caused initially pneumonia before spreading to the pericardium, either directly or via the bloodstream. A combined therapeutic approach, consisting of antibiotic therapy and repeated pericardial drainage, was necessary to ensure a clinical cure. After discharge, long-term follow-up for development of constrictive pericarditis is considered mandatory.

Viridans streptococci are a grouping of multiple streptococcal species which do not possess Lancefield antigens, are alpha-hemolytic, and result in infective endocarditis. Despite intensive care with antimicrobial therapy, the mortality has remained high for these infections and post infection squeal. All the pathways of complement system culminate in the formation of C3 convertase enzymes that mediate deposition of C3b on foreign surfaces. The goal of this study, to assay interferes between alkaline protease (AprA) of viridans streptococci and complement activation. Our data found that alkaline protease potently blocked phagocytosis of viridans streptococci by neutrophils the AprA specifically blocked C3b deposition via 2-pathways; the classical and lectin pathways. Serum degradation assays revealed that AprA degrades both human C1s and C2. However, repletion assays demonstrated that the mechanism of action for complement inhibition is cleavage of C2. These results suggest a novel viridans streptococci mechanism, through AprA interferes with complement system pathway activation via cleavage of C2.

S. dysgalactiae subsp. equisimilis (SDSE) is infrequently associated with maternal infections during delivery in pregnant women. A rare case is presented of a woman with intrauterine infection and surgical-site infection due to SDSE after cesarean section, which had colonized her genital tract and, via the ascending pathway, reached her intact fetal membrane. All isolates were identified as Streptococcus Lancefield group G, and their emm genes that coded M protein belonged to stG6.1. The isolates tested negative for a series of streptococcal superantigen virulence genes but positive for nonsuperantigenic virulence genes. In particular, molecular typing using pulsed-field gel electrophoresis analysis disclosed that the three isolates from the different infection sites had identical profiles. Furthermore, multilocus sequence typing indicated that the three isolates belonged to a new sequence typing. Our results indicated that SDSE is potentially pathogenic for pregnant women and newborns if colonized.

AbstractThe cell wall of the human bacterial pathogen Group A Streptococcus (GAS) consists of peptidoglycan decorated with the Lancefield group A carbohydrate (GAC). GAC is a promising target for the development of GAS vaccines. In this study, employing chemical, compositional, and NMR methods, we show that GAC is attached to peptidoglycan via glucosamine 1-phosphate. This structural feature makes the GAC-peptidoglycan linkage highly sensitive to cleavage by nitrous acid and resistant to mild acid conditions. Using this characteristic of the GAS cell wall, we identify PplD as a protein required for deacetylation of linkage N-acetylglucosamine (GlcNAc). X-ray structural analysis indicates that PplD performs catalysis via a modified acid/base mechanism. Genetic surveys in silico together with functional analysis indicate that PplD homologs deacetylate the polysaccharide linkage in many streptococcal species. We further demonstrate that introduction of positive charges to the cell wall by GlcNAc deacetylation protects GAS against host cationic antimicrobial proteins.

ABSTRACT Streptococcus pyogenes (Lancefield group A Streptococcus [GAS]) is a β-hemolytic human-selective pathogen that is responsible for a large number of morbid and mortal infections in humans. For efficient infection, GAS requires different types of surface proteins that provide various mechanisms for evading human innate immune responses, thus enhancing pathogenicity of the bacteria. Many such virulence-promoting proteins, including the major surface signature M protein, are translocated after biosynthesis through the cytoplasmic membrane and temporarily tethered to this membrane via a type 1 transmembrane domain (TMD) positioned near the COOH terminus. In these proteins, a sorting signal, LPXTG, is positioned immediately upstream of the TMD, which is cleaved by the membrane-associated transpeptidase, sortase A (SrtA), leading to the covalent anchoring of these proteins to newly emerging l-Ala–l-Ala cross-bridges of the growing peptidoglycan cell wall. Herein, we show that inactivation of the srtA gene in a skin-tropic pattern D GAS strain (AP53) results in retention of the M protein in the cell membrane. However, while the isogenic AP53 ΔsrtA strain is attenuated in overall pathogenic properties due to effects on the integrity of the cell membrane, our data show that the M protein nonetheless can extend from the cytoplasmic membrane through the cell wall and then to the surface of the bacteria and thereby retain its important properties of productively binding and activating fluid-phase host plasminogen (hPg). The studies presented herein demonstrate an underappreciated additional mechanism of cell surface display of bacterial virulence proteins via their retention in the cell membrane and extension to the GAS surface. IMPORTANCE Group A Streptococcus pyogenes (GAS) is a human-specific pathogen that produces many surface factors, including its signature M protein, that contribute to its pathogenicity. M proteins undergo specific membrane localization and anchoring to the cell wall via the transpeptidase sortase A. Herein, we explored the role of sortase A function on M protein localization, architecture, and function, employing, a skin-tropic GAS isolate, AP53, which expresses a human plasminogen (hPg)-binding M (PAM) Protein. We showed that PAM anchored in the cell membrane, due to the targeted inactivation of sortase A, was nonetheless exposed on the cell surface and functionally interacted with host hPg. We demonstrate that M proteins, and possibly other sortase A-processed proteins that are retained in the cell membrane, can still function to initiate pathogenic processes by this underappreciated mechanism.