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Biomedical subjects

H W Engel

Publications and source records attributed to H W Engel.

31 records · Page 2Linked to original sources
PubMed1977

Drug resistance in group D streptococci of clinical and nonclinical origin: prevalence, transferability, and plasmid properties.

Group D streptococci isolated from clinical specimens and from sewage were investigated with regard to resistance to tetracycline (Tc), erythromycin (Em), and chloramphenicol (Cm). The median values of the percentages of resistant strains from sewage were: for Tc, 14%; for Em, 2.8%; and for Cm, 0.1%. For the recent isolates of clinical origin, resistance percentages found were 58% for Tc, 12% for Em, and 14% for Cm, and, in comparison to clinical isolates from 1964, the incidence of drug resistance slightly increased. In strains of both sources, the drug resistance was often found to be transferable to another group D streptococcus, probably by conjugation. Two strains were able to transfer their Em resistance to a streptococcus strain of group B. No transfer of drug resistance to a group A streptococcus and Escherichia coli was observed. All beta-hemolytic streptococci were also bacteriocinogenic, and frequently these properties were found to be transferable. The function, size, and base composition of the plasmids of two drug-resistant Streptococcus faecalis strains were investigated; strain M439 harbors at least two conjugative plasmids: pRI401, molecular weight 30 x 10(6), coding for Tc resistance, and pRI402, molecular weight 41 x 10(6), coding for Em resistance. Strain M403 carries one single conjugative plasmid species, coding for Tc resistance. The molecular weight of this plasmid, pRI404, was 37 x 10(6). The guanine plus cytosine content of these plasmids was 35 to 36%.

Chloramphenicol↗
PubMed1975

World Health Organization studies on bacteriophage typing of mycobacteria. Subdivision of the species Mycobacterium tuberculosis.

The ability of lytic mycobacteriophages to subdivide the species Mycobacterium tuberculosis reliably has been studied using a series of 100 strains isolated from cases of tuberculosis in the Netherlands. Techniques for the propagation and application of the viruses have been standardized, as have the conditions for growth and preparation of bacterial strains. On the basis of lytic results with 11 mycobacteriophages, it is proposed that the species Mycobacterium tuverculosis may be subdivided into at least 3 major phage types, A, B, and C, and into 2 subjects, Ax and A2. The reliability of the individual bacteriophage lytic result has been assessed, and the relationship between phage reliability and the degree of certainty with which a strain may be assigned to a phage type is described. The effect of rigorous standardization of techniques on the reliability of bacteriphage typing is demonstrated, and a standard protocol is proposed.

Bacteriophage Typing↗
PubMedDate not supplied

Application of pyrolysis mass spectrometry to the classification and identification of mycobacteria.

Application of modern pyrolysis techniques offers the possibility for mass spectrometric analysis of complete bacterial cells. It was shown that pyrolysis mass spectra provide fingerprints of mycobacterial cells that are characteristic on the (sub)species level. Computer-aided comparisons of the spectra for mycobacteria were used for identification of unknown strains as members of either the "tuberculosis complex" (Mycobacterium tuberculosis, Mycobacterium bovis-BCG, M. bovis) or of the group referred to as "atypical mycobacteria." Pyrolysis mass spectrometry was performed with a completely automated instrument, and spectra were evaluated by two computerized numerical methods. The first method has general applicability to mass spectrometry data, while the second was devised for the routine identification of the "tuberculosis complex." With use of the latter method, 125 strains were identified. A positive correlation of 94.4% was found between the results of this method and the results of the usual bacteriologic procedures; 1.6% of all strains were given a falsely negative identification, and 4.0% were given a falsely positive identification.

Analysis of Variance↗