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Biomedical subjects

P Gemski

Publications and source records attributed to P Gemski.

16 recordsLinked to original sources
PubMed1992

The K1 capsule is the critical determinant in the development of Escherichia coli meningitis in the rat.

Although Escherichia coli strains possessing the K1 capsule are predominant among isolates from neonatal E. coli meningitis and most of these K1 isolates are associated with a limited number of 0 lipopolysaccharide (LPS) types, the basis of this association of K1 and certain 0 antigens with neonatal E. coli meningitis is not clear. The present study examined in experimental E. coli bacteremia and meningitis in newborn and adult rats whether or not the K1 capsule and/or O-LPS antigen are critical determinants in the development of meningitis. Rats received subcutaneously at K1 E. coli strain (018+K1+) or mutants lacking either the K1 capsule (018+K1-) or 0 side-chain (018-K1+). 12-24 h later, blood and cerebrospinal fluid (CSF) specimens were obtained for quantitative cultures. The isolation of E. coli from CSF was observed in both newborn and adult rats infected with K1+ strains regardless of LPS phenotype (018+ or 18-) who also developed a high degree of bacteremia (e.g., greater than 10(4) CFU/ml of blood). In contrast, none of the newborn and adult rats infected with 018+K1- and developing bacteremia of greater than 10(4) were found to have positive CSF cultures. These findings indicate that the presence of the K1 capsule and a high degree of bacteremia are key determinants in the development of E. coli meningitis, suggesting that there may be specific binding sites present in the brain which have an affinity for the K1 capsule and thus may be responsible for the entry of K1-encapsulated E. coli into the meninges.

Animals↗
PubMed1979

Shigellosis and Escherichia coli diarrhea: relative importance of invasive and toxigenic mechanisms.

Shigellae and dysentery-like Escherichia coli must invade the epithelium of the colon to cause disease which can present as dysentery, diarrhea, or both. This paper addresses the possible role of a Shigella dysenteriae-like (Shiga-like) toxin in the pathogenesis of shigellosis and E. coli diarrheal diseases. The possibility for such a role is suggested by the following observations: 1) diarrhea, considered to be a result of secretion of water by the small bowel, is frequently observed in shigellosis, a large bowel disease. 2) Even though shigellae do not invade the jejunum of monkeys fed Shigella flexneri, jejunal secretion is seen in animals with diarrhea. 3) The Shiga toxin of S. dysenteriae has enterotoxic activity and other serotypes of shigellae produce Shiga-like toxins. 4) E. coli 015 RDEC-1 causes a diarrheal disease and frequently death in young rabbits. This organism neither produces E. coli enterotoxins nor is it invasive, but it may produce low levels of a Shiga-like toxin.

Animals↗
PubMed1978

lambdaimm P22dis: a hybrid of coliphage lambda with both immunity regions of Salmonella phage P22.

Genetically marked lambda and P22 phages were recombined in Escherichia coli-Salmonella typhimurium hybrid WR4028, a host sensitive to infection by both of these phages. Hybrid phages that acquired the immC region of P22, but retained the genes for the lambda protein coat were selected on WR4027 (lambda), a lambda-immune, P22-resistant derivative of WR4028. In these lambdaimmP22 hybrids, at least the c through P genes of lambda were replaced with functionally related P22 genes. Phage recombinants with more extensive regions of the P22 genome were selected on the double lysogen WR4027 (lambda, lambdaimmP22). One such hybrid, lambdaimmP22dis, was determined by heteroduplex analysis to contain approximately 40% of the P22 genome. Genetic studies established that lambdaimmP22dis possesses the two widely separated immunity control regions of P22 (immC and immI) and that these loci are expressed in E. coli K-12 lysogenic for lambdaimmP22dis. In addition, lambdaimmP22dis contains the P22 a 1 locus responsible for somatic 0--1 antigen conversion in Salmonella. Although the lambdaimmP22dis phage particle has the lambda head and tail, the phage genome also carried P22 tail gene 9 as evidenced by the production of free P22 tails. It also has the P22 att site as indicated by the integration of the lambdaimmP22dis prophage near the proA locus on the bacterial chromosome.

Antigens, Bacterial↗
PubMed1978

Cellular release of heat-labile enterotoxin of Escherichia coli by bacteriophage induction.

Treatment of some enterotoxigenic Escherichia coli strains with the antibiotic mitomycin C resulted in lysis of the bacteria. Heat-labile enterotoxin (LT) activity of culture filtrates, determined by means of the Y-1 adrenal cell assay, increased dramatically as lysis of the culture proceeded. Further studies with E. coli strains 263 and B21-4 revealed that lysis is due to mitomycin C induction of vetetative development of a temperature bacteriophage. These findings suggest that the elevated levels of LT detected after mitomycin C treatment reflect the lytic release of cell-bound LT rather than the induction by mitomycin C of de novo toxin biosynthesis. Comparable increases in LT activity also resulted from thermal induction of a phage P1Cm lysogen of strain 263 or from sonic disruption of enterotoxigenic strains.

Bacterial Toxins↗
PubMed1978

Interaction between bacteriophage Sf6 and Shigella flexner.

The Shigella flexneri phage Sf6 has an isometric head with hexagonal symmetry 53nm in diameter. The noncontractile tails in 16 nm long and terminates with a base plate containing six spikes. Sf6 is typical of the C phages in the morphological classification of Bradley. Phage Sf6 processes alpha-1,3-endorhamnosidase activity as demonstrated by methylation and reducing end group sugar analyses of the products obtained on interaction with the O-polysaccharide chain of S.flexneri strains which have the O-group 3,4 antigen. The major end product was an octasaccharide with the following structure: Rha III-GlcNAc-Rha I-Rha II-Rha III-GlcNAc-Rha I-Rha II. Acetylation of 0-2 of rhamnose III of the O-polysaccharide chain, either brought about by Sf6 lysogenization or found in wild-type S. flexneri (3b) strains, prevented enzymatic hydrolysis. O-deacetylation of the polysaccharide chain again made it susceptible to the S6f endorhamnosidase.

Antigens, Bacterial↗
PubMed1977

Genetic studies of hybrids between coliphage lambda and salmonella phage P22: genetic analysis of the P22-lambda hybrid class.

P22-lambda hybrids which retain the protein coat of P22 have been isolated and characterized into two types. Type 1 hybrids which have the c through O-P genes of lambda are unable to grow lytically on Salmonella typhimurium. On the other hand, type 2 hybrids which contain only the c region of lambda, plated on S. typhimurium. Both hybrid types retained the generalized transducing and antigenic conversion capabilities of P22.

Antigens, Viral↗
PubMed1977

Studies with a new generation of oral attenuated shigella vaccine: Escherichia coli bearing surface antigens of Shigella flexneri.

In an attempt to develop a safe, proliferating, oral, attenuated vaccine against shigellosis, genes that control the synthesis of group- and type-specific somatic antigens of Shigella flexneri 2a were transferred via conjugation to a recipient strain of Escherichia coli. The resultant hybrid (E. coli expressing shigella surface antigens) vaccine strain, PGAI 42-1-15, believed to have a complete (smooth) lipopolysaccharide, was given to volunteers in two vaccination-challenge studies. The vaccine was well tolerated and gave evidence of intestinal proliferation. In trial no. 1, volunteers given two doses of vaccine one month apart were challenged after eight weeks with 10(4) virulent S. flexneri 2a. Attack rates were comparable in vaccinees (50%) and controls (40%). In trial no. 2, vaccinees were given three weekly doses of vaccine and were challenged four weeks later with a small inoculum (10(2)) of S. flexneri 2a. Again, attack rates among vaccinees (47%) and controls (39%) were similar. It is unclear why this theoretically ideal, live shigella vaccine failed to protect against S. flexneri 2a.

Administration, Oral↗
PubMed1977

Biological properties of Shigella flexneri 2A toxin and its serological relationship to Shigella dysenteriae 1 toxin.

A toxin extracted from heat-inactivated, alkaline-treated Shigella flexneri 2a showed biological properties similar to those of Shigella dysenteria 1 toxin. The S, flexneri 2a toxin was lethal to mice, enterotoxic for ileal loops of rabbits, and cytotoxic for HeLa cells. A serological relationship between S. flexneri 2a and S. dysenteriae 1 toxin was shown with cross neutralization tests.

Antigens, Bacterial↗
PubMed1976

Studies on the pathogenesis of enteric infections caused by invasive bacteria.

Salmonellae, shigellae and some Escherichia coli must invade the intestinal epithelial cell and multiply within the mucosa to cause disease. Although the bacterial cell most likely possesses several properties essential to this invasive ability, the nature of the cell envelope complex is at present the only characteristic which has been implicated in this process. While a number of pathophysiological events result from invasion, some of our recent efforts have concerned the site and mechanism of intestinal fluid loss in salmonellosis and shigellosis. In both these disorders, bacterial invasion of the colonic mucosa, associated with an acute inflammatory reaction and mucosal damage, is regularly seen and colonic salt and water transport is abnormal. These defects may account for mild diarrhoea in salmonellosis and the dysenteric stools of shigellosis. However, in salmonella-infected animals with severe watery diarrhoea and in shigella-infected animals with diarrhoea alone or in combination with dysentery, the jejunum is in a net secretory state. This secretion occurs in the absence of bacterial invasion or morphological abnormalities. Thus, the diarrhoea caused by invasive bacteria may result from the inability of the colon to reabsorb the increased volume of fluid entering it from the small intestine. Although colonic mucosal damage is a feature of invasive-type diarrhoeas, the permeability of both the colon and small intestine to small molecules, mannitol and erythritol, is not altered. Thus intestinal fluid loss cannot be ascribed to transudation. In addition, the results of our Ussing chamber experiments, employing salmonella-infected rabbit ileum, reveal that salt and water secretion is an active process. Since secretion occurs in the jejunum in the absence of bacterial invasion, this might suggest the participation of an enterotoxin. Shigella dysenteriae I is the best-studied invasive organism in which an enterotoxin has been found, yet mutant strains which do not invade but retain the ability to elaborate enterotoxin fail to cause disease in either monkeys or man. Thus, the physiological relevance of Shiga enterotoxin and the mechanism of jejunal secretion in these disorders remain unclear. Recent data suggest that invasive enteropathogens, like the enterotoxin-producing bacteria, activate the mucosal adenylate cyclase-cyclic AMP system and that this activation may play a role in intestinal fluid secretion.

Animals↗
PubMed1975

Extensive segments of the Escherichia coli K12 chromosome in Proteus mirabilis diploids.

Various Escherichia coli K12 Hfr donors transfer at low frequency portions of the E. coli genome to Proteus mirabilis. By remating such Proteus hybrids with the same or a different E. coli Hfr strain, other genetic characters could be added to yield diploid Proteus hybrids which contained more than 30 percent of the E. coli genome. The extent of the E. coli genetic material in these unstable Proteus diploid hybrids included segments with the following selected markers: gal, lac, ara, mel, mtl, and malA. Unselected markers known to map throughout this region of the chromosome were also detected in these hybrids. Among the markers expressed in Proteus hybrids with the E. coli malA region was the receptor site for coliphage lambda. Although plaques were not seen, lambda was adsorbed by the Proteus hybrids. Examination of DNA from the various Proteus hybrids by CsCl density gradient centrifugation showed a satellite component of E. coli DNA with a size that corresponded to the extent of the E. coli genome present as determined by genetic analysis.

Centrifugation, Density Gradient↗
PubMed1975

Phage conversion of Shigella flexneri group antigens.

A temperate phage, designated Sf6, has been isolated from Shigella flexneri 3a. Characterization of Sf6 revealed that it possesses the capacity for converting the S. flexneri 3,4 group antigen complex to group factor 6. Serological studies and chemical analysis of lipopolysaccharide from converted strains suggest that group factor 6 is a reflection of an acetylation of the preexisting 3,4 antigen complex. Evidence is provided that the 3,4 group antigen complex functions, at least in part, as a cell surface receptor site for Sf6 adsorption.

Absorption↗