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Biomedical subjects

A Sutton

Publications and source records attributed to A Sutton.

At least 91 records · Page 5Linked to original sources
PubMed1979

Form variation in Escherichia coli K1: determined by O-acetylation of the capsular polysaccharide.

The chemical basis for the alternating antigenic change called form variation noted for the Escherichia coli K1-capsular polysaccharide has been shown by 13C nuclear magnetic resonance to be a result of random O-acetylation of C7 and C9 carbons of the alpha-2-8-linked sialic acid homopolymer. A serologic method (antiserum agar) was developed to identify and isolate the form variants. The O-acetyl positive and O-acetyl negative K1 polysaccharides had unique biochemical and immunologic properties. The O-acetyl-positive variants resisted neuraminidase hydrolysis in contrast to the susceptibility of the O-acetyl negative variant to this enzyme. In addition, O-acetylation altered the antigenicity of the O-acetyl polysaccharides. When injected as whole organisms, O-acetyl positive organisms produced anti-K1 -antibodies in rabbits specific for this polysaccharide variant. O-acetyl negative organisms were comparatively less immunogenic; however, antibodies induced by these organisms reacted with both K1 polysaccharide variants. Burros, injected with either variant, produced antibodies reactive with both K1 polysaccharides.

Acetylation↗
PubMed1979

Comparative immunogenicity of vaccines prepared from capsular polysaccharides of group C Neisseria meningitidis O-acetyl-positive and O-acetyl-negative variants and Escherichia coli K92 in adult volunteers.

Three structurally and antigenically similar capsular polysaccharides, two derived from group C Neisseria meningitidis (O-acetyl-positive and O-acetyl-negative variants) and one from Escherichia coli K92, which cross-reacts with polysaccharide from group C N. meningitidis, were compared for their ability to induce anticapsular and bactericidal antibodies to group C N. meningitidis in adult volunteers. All three vaccines elicited group C-specific serum antibodies. The vaccine derived from the O-acetyl-negative variant was the most immunogenic of the three vaccines. With use of radiolabeled O-acetyl-positive group C N. meningitidis polysaccharide antigen, the geometric mean titers of antibody in serum were 41.7 microgram/ml to the O-acetyl-negative variant, 22.8 microgram/ml to the O-acetyl-positive variant, and 7.1 microgram/ml to E. coli K92. Antibodies induced by all three vaccines were bactericidal for both of the group C N. meningitidis polysaccharide variants. An inverse relation between the comparative immunogenicity of the O-acetyl-negative polysaccharide and the virulence of group C N. meningitidis was found.

Adult↗
PubMed1977

The infant rat as a model of bacterial meningitis.

The pathogenesis of bacterial meningitis was studied in infant rats. Intranasal intoculation of greater than 10(3) Haemophilus influenzae type b resulted in an incidence of bacteremia that was directly related to the size of hte challenge inoculum. The temporal and quantitative relationship of bacteremia to meningitis indicated that bacteria spread to the meninges by the hematogenous route and that the magnitude of bacteremia was a primary determinant in the development of meningitis. In a sparate series of experiments, infant rats that were fed Escherichia coli strain C94 (O7:K1:H-) became colonized and developed bacteremia and meningitis, but invasive disease was rare when rats were fed E. Coli strain Easter (O75:K100:H5). A comparison of intranasal vs. oral challenge indicated that the nasopharynx was the most effective route for inducing H. influenzae bacteremia, whereas the gastrointestinal route was the more effective challenge route for the E. coli K1 serotype.

Animals↗
PubMed1977

Neonatal meningitis due of Escherichia coli K1.

Human neonates are uniquely susceptible to serious infections due to Escherichia coli. Investigation of the serotypes of E. coli isolated from neonates with meningitis revealed that greater than 80% of the isolates possessed the capsular polysaccharide antigen designated K1. Cultures of stool from healthy infants, children, and adults have shown that K1 organisms are commonly found in individuals of all ages. Studies of mother-infant pairs have demonstrated transmission of K1 strains from mother to infant shortly after birth. In the rare infant who develops meningitis due to E. coli K1, serotype analysis frequently reveals that the same organism was isolated from the infant's cerebrospinal fluid and from the stools of both mother and infant. Preliminary investigations of humoral immunity demonstrated an age-related acquisition of antibodies to the capsular polysaccharide of E. coli K1 in healthy infants and children. An animal model was developed in which feeding of E. coli K1 to infant rats resulted in colonization, bacteremia, and meningitis in the animals.

Adult↗
PubMed1977

Pathogenesis of neonatal Escherichia coli meningitis: induction of bacteremia and meningitis in infant rats fed E. coli K1.

Escherichia coli K1 strains, isolated from human newborns with meningitis, were fed to pathogen-free Sprague-Dawley infant rats by an oral gastric tube. Feeding of 10(3) to 10(11) organisms colonized the intestine of approximately 70% of the animals. At 5 days postfeeding of 3- to 5-day-old rats, bacteremia was detected in 60%, and meningitis occurred in 15% of bacteremic animals. Colonization and bacteremia were age-related. Rats 15 days old had only 19 colonization and 10% bacteremia, and those 30 days old were almost completely resistant to colonization and bacteremia. The intranasal route was less effective in inducing colonization and bacteremia. Intralitter transmission from E. coli K1-fed rats occurred, with 52% of water-fed controls becoming colonized and 15% become bacteremic. Colonization of mothers from their fed infants occurred, but none of five tested developed bacteremia. Other E. coli capsular polysaccharide types were studied. A K92 strain isolated from a newborn with meningitis induced a 77% colonization rate, and 8% of these developed bacteremia without detectable meningitis. An E. coli K100 strain showed a 32% colonization rate, and 2% developed bacteremia. The age relation, relatively high virulence of K1 compared with other capsular types, spontaneous appearance of colonization, bacteremia, and meningitis, and intralitter transmission of colonization and disease in newborn rats closely parellel E. coli epidemiology in human neonates.

Administration, Oral↗
PubMed1977

Absorption and endogenous faecal excretion of calcium by low birthweight infants on feeds with varying contents of calcium and phosphate.

Low birthweight infants aged 4-41 days were given from birth one of three experimental milk formulae varying widely in content of calcium and phosphate. Ca and P in feed, urine, and faeces were measured between carmine markers corresponding to a metabolic period of 48 hours. Calcium enriched in 46Ca to provide a marker for the dietary Ca was added to one feed and 46Ca measured in urine and faeces. True absorption of Ca and endogenous excretion into the bowel could then be inferred. True absorption of Ca was proportional to Ca intake and independent of P intake. Endogenous faecal excretion seemed to be independent of both Ca P intakes, and varied widely between different infants in the range 4-150 mg/day. Urine Ca was low and retention was essentially the difference between true absorption and endogenous faecal excretion. Retention of Ca tended to be much greater on a high Ca intake, but the variability in retention between infants on a given intake was large, paralleling the variability in endogenous faecal excretion. The variability in plasma Ca concentrations in newborn infants may in part be a consequence of wide individual variability in endogenous faecal excretion. The 46Ca marker technique provides a means of investigating the factors determining this variability.

Calcium↗
PubMed1977

Urinary and faecal excretion of marker calcium (46Ca) by low birthweight infants.

Low birthweight infants were given calcium enriched in 46Ca in a single feed. The specific activity of successive urine samples showed that the absorption of the marker was largely complete in about 4 hours. The rate of decrease of urinary specific activity after 3 1/2 hours was exponential and very similar in 8 sets of observations in 6 infants. Its extrapolation backwards to 1 hour may indicate the size of the exchangeable calcium pool, usually about 200 mg/kg body weight. Completeness of faecal collection for estimation of 46Ca is essential for accurate determination of true absorption and endogenous faecal excretion of natural Ca. In 5 infants examined, nor marker was detectable in faeces excreted later than 48 hours after the first stool containing marker. Nevertheless, reasons are given why a collection period limited to 48 hours may sometimes involve error.

Calcium↗
PubMed1975

Vi antigen from Salmonella typhosa and immunity against typhoid fever. 11. Safety and antigenicity in humans.

Safety and antigenicity of a purified preparation of Salmonella typhosa Vi antigen was evaluated in human volunteers. Dosages of Vi antigen at 25, 50, and 100 mug were less toxic than U.S. standard typhoid vaccine (lot 6A) containing 5 X 10(8) bacteria per dosage. Vi antigen in comparison with the standard typhoid vaccine induced higher hemagglutinating antibody but lower bactericidal antibody responses.

Antibody Formation↗