Biomedical subjects
Publications and source records attributed to W F Vann.
A method is described for typing Staphylococcus aureus capsular polysaccharides that is based on direct bacterial cell agglutination and immunoprecipitation of cell extracts with monospecific antisera. Encapsulated strains were identified by their inagglutinability with teichoic acid antisera. The typing sera reacted specifically with extracts of eight prototype strains.
The relationship of capsular types of Staphylococcus aureus to type of infection, carrier state, and phage type was studied in a collection of 477 isolates from 380 infection sites. Capsular polysaccharides were demonstrated by precipitation and agglutination with 11 monospecific antisera. When only one isolate from each infection was considered, 63% were of type 8 and 16% were of type 5. Of all the isolates tested, over 90% were encapsulated. We did not demonstrate any marked difference in the distribution of capsular types between isolates from the blood stream or purulent processes and isolates from healthy carriers or food. Most isolates from bovine mastitis milk had nontypeable capsules. The capsular type seemed stable in culture, and encapsulation had no apparent influence on susceptibility to phages. Of 27 phage-propagating strains maintained via culture transfer on artificial media over many years, 16 (59%) produced capsules. A striking association between certain phage patterns and capsular types was demonstrated.
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A capsular polysaccharide typing schema for Staphylococcus aureus, based upon the preparation of rabbit typing sera with eight prototype strains, has been reported ( Karakawa and Vann , 1982). These antisera were used to classify the capsular polysaccharides of 246 S. aureus isolates from patients in a survey of hospitals in several countries and 49 consecutive blood isolates obtained over a 17-month period in a clinical study at the Boston Veterans' Administration Medical Center. Two capsular types, 5 and 8, accounted for about 70% of these isolates; most of the remaining strains could not be typed with the available antisera. The clinical study of bacteremia identified capsular types 5 and 8 among both community-acquired and nosocomial isolates and showed that strains bearing these two types caused the patterns of disease reported for staphylococcal bacteremia. There was an association between the phage type and the capsular type of these bacteremic strains. The capsular types of the "classic" encapsulated strains of S. aureus, M (type 1) and Smith (type 2), were not observed among blood isolates in this study. The observation that most clinical isolates of S. aureus belong to two recently defined capsular types provides a new focus for investigations into the virulence of this common nosocomial pathogen and suggests the potential for protective acquired immunity against staphylococcal bacteremia.
Clinical isolates of Staphylococcus aureus have been previously classified into eight types on the basis of their capsular polysaccharide. The high prevalence of the type 8 capsular polysaccharide among bacteremic isolates suggests the importance of this capsular antigen in staphylococcal disease. The capsular polysaccharide was purified from extracts of three clinical isolates of S. aureus type 8 of different geographic and temperal origin by ion-exchange chromatography and gel filtration. Gas chromatography, gas chromatography-mass spectrometry, and 13C-nuclear magnetic resonance showed that the type 8 capsular polysaccharide is composed of O-acetyl groups, N-acetylfucosamine, and an aminouronic acid similar to N-acetylgalactosaminouronic acid. The purified polysaccharide reacted only with type 8 antiserum in double diffusion experiments. Our analysis shows that the type 8 polysaccharide is both chemically and serologically distinct from teichoic acid and previously characterized polysaccharides of S. aureus.
The plasmid pSR23, composed of a 34-kilobase E. coli chromosomal fragment inserted into the BamHI site of the pHC79 cosmid cloning vector, contains genes encoding biosynthesis of the K1 capsular polysaccharide. Deletions, subclones, and Tn5 insertion mutants were used to localize the K1 genes on pSR23. The only deletion derivative of pSR23 that retained the K1 phenotype lacked a 2.7-kilobase EcoRI fragment. Subclones containing HindIII and EcoRI fragments of pSR23 did not produce K1. Cells harboring pSR27, a subclone containing a 23-kilobase BamHI fragment, synthesized K1 that was not detectable extracellularly. Six acapsular Tn5 insertion mutants of three phenotypic classes were observed. Class I mutants synthesized K1 only when N-acetylneuraminic acid (NANA) was provided in the medium. Reduced amounts of K1 were detectable in cell extracts of class II mutants. Class III mutants did not produce detectable K1 in either extracts or when cells were provided exogenous NANA. All mutants had sialyltransferase activity. Analysis in the E. coli minicell system of proteins expressed by derivatives of pSR23 identified a minimum of 12 polypeptides, ranging in size from 18,000 to 80,000 daltons, involved in K1 biosynthesis. The 16-kilobase coding capacity required for the proteins was located in three gene clusters designated A, B, and C. We propose that the A cluster contains a NANA operon of two genes that code for proteins with apparent molecular weights of 45,000 and 50,000. The A region also includes a 2-kilobase segment involved in regulation of K1 synthesis. The B region encoding five protein species appears responsible for the translocation of the polymer from its site of synthesis on the cytoplasmic membrane to the cell surface. The C region encodes four protein species. Since the three gene clusters appear to be coordinately regulated. we propose that they constitute a kps regulon.
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After promising results were achieved with an experimental method for teaching the acquisition of psychomotor skills to dental students, a long-term follow-up study evaluated the lasting effects of that method using preclinical and clinical grades, as well as an assessment of students' clinical technical performance. Though the experimental teaching method had a significant effect on student performance in the initial preclinical activities, the differences between the control and experimental groups diminished as the students progressed through subsequent preclinical courses. No significant differences were found in measures obtained during the clinical years.
A new substrate for the deacetylase which catalyzes the removal of the N-acetyl groups from N-acetylheparosan in the course of heparin biosynthesis has been prepared. The capsular polysaccharide from Escherichia coli 010:K5:H4, which is structurally identical to N-acetylheparosan, was partially N-deacetylated by hydrazinolysis and was then radioactively labeled by N-acetylation with [3H]acetic anhydride. Upon incubation of the labeled polysaccharide with microsomes from the Furth mastocytoma, [3H]acetyl groups were released, demonstrating that the bacterial polysaccharide was a substrate for the N-deacetylase. Reaction conditions were established which permitted the quantitative assay of N-deacetylase activity; a Km of 74 mg polysaccharide/liter was determined, which corresponds to 2.1 X 10(-4) M, expressed as concentration of uronic acid; Vmax was 3.4 nmol/mg protein/liter. In confirmation of previous results, it was observed (a) that the reaction was stimulated by 3'-phosphoadenylylsulfate (up to a maximum of 45% at a concentration of 0.5 mM), suggesting that N-sulfation occurred which facilitated continued action of the N-deacetylase, and (b) that NaCl and KCl inhibited the enzyme, with 50% reduction of activity at a concentration of 25 mM. In the course of this work, a simple, single-vial assay procedure was used. Released [3H]acetate was extracted from the acidified reaction mixture with a toluene- or xylene-based scintillation fluid containing 10% isoamyl alcohol and measured directly by scintillation spectrometry.
The Escherichia coli K13, K20, and K23 capsular polysaccharide antigens are serologically related. All of these polysaccharides contain ribose and 2-keto-3-deoxyoctonate in equimolar quantities. The K13 and K20 polysaccharides are partially O-acetylated. A comparison of these polysaccharides after O-deacetylation, by nuclear magnetic resonance and permethylation analysis, showed that these polysaccharides contained the disaccharide repeat unit leads to)-beta-ribofuranosyl-(1 leads to 7)-beta-2-keto-3-deoxyoctonate. They differed in the presence and location of an acetyl moiety. The K13 polysaccharide was O-acetylated at C-4 of the 2-keto-3-deoxyoctonate. The K20 antigen was O-acetylated at C-5 of the ribose moiety. The K23 polymer was nonacetylated. The cross-reactivity of these antigens was demonstrated by tandem-crossed immunoelectrophoresis. Antibodies to K23 could be completely absorbed from OK K23 serum by K13, K20, and K23 antigenic extracts. The K13 and K20 antibodies could be completely absorbed from their respective antisera only by homologous antigenic extracts. Monoclonal antibodies were prepared against a protein conjugate of the K13 polysaccharide. Analyses of the reactions of these antibodies with the three polysaccharides suggest that the K13 polysaccharide has at least three antigenic sites, one of which is common to the K13, K20, and K23 polysaccharides.
This study sought to expand and clarify research on intra- and interexaminer reliability in preclinical pedodontic grading. Six examiners graded 30 dentoform preparations using three different evaluation methods in a design that controlled the effects of order. The three methods were global (glance and grade), checklist with criteria (analytical), and checklist only. No method resulted in superior intra- or interexaminer reliability. The three evaluation methods can be easily adapted or replicated by other clinical disciplines, and the research design offers a model for similar studies in other preclinical and clinical dental settings.
Affective assessment has been used extensively in dental education to gain valuable information from student attitudes; however, it has rarely been used as an instrument for systematically evaluating courses in order to plan instructional changes. In this investigation, affective assessment was used to plan and subsequently evaluate instructional changes in a restorative dentistry laboratory course. Affective assessment was used initially to determine attitudes concerning the laboratory course as well as the effect of an experimental program conducted during the course. Based on that assessment, changes were made in the course and the experimental program. Affective assessment was again employed the following year to determine the effect of the instructional and methodological changes. This study serves as a model for dental educators who would like to employ a systematic and practical approach to planning and evaluating instructional change through affective assessment.
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Soft tissue outlines from profile radiographs, with or without supplementary photographs, do not provide enough information to reliably assess the underlying skeletal pattern in children 8 and 12 years old. Assessment was less reliable at 8 than at 12 years of age. Prognathic patterns were not as readily identified as retrognathic patterns. Specialty training did not affect the correctness of these limited assessments.