Search PubMed⌕ Search

Biomedical subjects

S R Johnson

Publications and source records attributed to S R Johnson.

144 records · Page 8Linked to original sources
PubMed1975

The self-instructional materials project: progress and prospects.

Faculty members in the Health Sciences Consortium have developed replicable, exportable units of instruction under the direction of the Self-Instructional Materials Project. The project distributes currently 350 packages and lists 570 in it's Directory of Self-Instructional Materials. Published evaluation studies indicate improvement on national board exams with greater efficiency and savings in time when compared with other forms of instruction. One study shows similarity of results with students who use the materials in hospitals away from the university. Four basic activities are necessary to initiate and enlarge the collection of units available on each campus: training, production, tryout/revision and sharing. Analysis of trends for each set of activities is projected over a five-year period. As training activities decline, greater emphasis is placed on quality control and procedures for sharing materials that are under development.

Evaluation Studies as Topic↗
PubMedDate not supplied

Antibiotic resistance in Neisseria gonorrhoeae: genetics and mechanisms of resistance.

In recent years the emergence and spread of antibiotic resistance in Neisseria gonorrhoeae has increased markedly. Chromosomal resistance to penicillin and tetracycline is due to the effects of one or more mutations and is generally low-level. However, the effects of these mutations are additive. Thus, the level of resistance in strains with several mutations is often high enough to yield significant rates of treatment failure. Resistance to aminoglycosides (e.g., streptomycin and kanamycin) and spectinomycin, an aminocyclitol antibiotic is not due to the inactivation of the antibiotic but to an alteration in the sensitivity of the 30S ribosomal subunit to the drug. At least five beta-lactamase plasmids of N. gonorrhoeae have been described. Some of these plasmids can be mobilized by the 24.5-MDa gonococcal conjugative plasmid and transferred to other gonococcal strains. Gonococci have recently acquired high-level resistance to tetracycline due to the streptococcal tetM determinant. This determinant is located on a 25.2-MDa plasmid that possesses a considerable degree of homology with the 24.5-MDa conjugative plasmid. The 25.2-MDa plasmid has retained the ability to transfer beta-lactamase plasmids as well as to mobilize and transfer itself to suitable recipient strains.

Anti-Bacterial Agents↗
PubMedDate not supplied

Development of a polymerase chain reaction assay for the detection of Haemophilus ducreyi.

BACKGROUND AND OBJECTIVES: Haemophilus ducreyi, the causative agent of chancroid is a fastidious organism difficult to culture and identify. Consequently, culture is an insensitive method for diagnosis. The polymerase chain reaction (PCR) offers a sensitive and specific nonculture method for the detection of bacterial pathogens. STUDY DESIGN: A polymerase chain reaction (PCR) assay was developed to detect the presence of Haemophilus ducreyi. A pair of primers was selected from sequences of an anonymous fragment of DNA cloned from H. ducreyi. The primers were tested in amplification reactions with both purified DNA and lysed organisms for their ability to detect H. ducreyi, and with DNA from a variety of different bacteria for their specificity. The utility of the primers for the detection of H. ducreyi in samples taken from genital ulcers was also tested and compared with culture. RESULTS: PCR was positive for 62% of the specimens that were culture-positive, however, PCR was also positive for 49% of the culture-negative specimens. Comparison of specimens that were dark field positive for T. pallidum and PCR-positive with those that were culture-positive for herpes simplex virus and PCR positive suggested that PCR was giving true and not random positive results. Additional studies demonstrated that the failure of PCR to detect H. ducreyi in all of the culture-positive specimens probably resulted from inhibitors of the Taq DNA polymerase that were present in the nucleic acids extracted from the clinical specimen. CONCLUSION: PCR should be a useful method for the detection of H. ducreyi in genital lesions, especially where culture sensitivity is poor. However, the presence of unidentified Taq polymerase inhibitors in some ulcers specimens require the development of improved methods for specimen handling.

Chancroid↗