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Biomedical subjects

M Goldner

Publications and source records attributed to M Goldner.

54 records · Page 3Linked to original sources
PubMed1976

Penicillin tolerance in Neisseria gonorrhoeae: evidence disallowing a penicillinase-mediated mechanism from a refined microbiological assay method.

A microbiological assay method has been developed and applied to Neisseria gonorrhoeae, for the purpose of detecting enzymatic deactivation of benzyl penicillin. Calibration of the method, using strains of Escherichia coli K-12 with previously reported penicillinase (EC 3.5.2.6.) activities, has shown that it is extremely sensitive and may be used in a quantitative manner. At the limit of sensitivity the test is able to detect penicillin breakdown in the order of 3 X 10(-3) mug in 48 h, which is equivalent to about 7 X 10(-8) mumol/min per milligram dry weight of cells. Over 100 strains of N. gonorrhoeae, most of them resistant to penicillin, were screened for their ability to deactivate penicillin during 48 h of growth in the presence of subinhibitory levels. No deactivation was detected. It is concluded, from quantitative evidence, that reduced penicillin sensitivity in N. gonorrhoeae is not due to the enzymatic deactivation of the antibiotic.

Bacteriological Techniques↗
PubMed1975

Level of redox potential as a possible contributing influence in the pathogenicity of oral anaerobes.

Dental plaque anaerobes may be associated with the etiology of periodontal disease. This has created an interest in the potential pathogenicity of oral anaerobes. We compared the metabolic activity of anaerobic corynebacteria (C. parvum, C. anaerobium) and corresponding aerobic species (C. diphtheriae, C. xerosis). The anaerobes exhibited lower levels of RNA synthesis, ranging from 5 to 10 fold over the aerobes. We further examined these anaerobes, plus Actinomyces naeslundi N16 (isolated from the anaerobic region of periodontally-diseased tissues), for the influence of redox potential on RNA level and antigenic function. Notable increases in RNA were found at specific Eh levels; the extent and direction of the changes varied with the different organisms. This environmental feature appeared to effect corresponding changes in agglutinability and PCA reactivity with antisera against the anaerobes cultured at different redox potentials. For example, while antisera against certain organisms (C. parvum, A. naeslundi) cultured under the most reuced conditions showed an intense PCA reaction, other antisera against the same organism cultured under less reduced conditions were non-reactive. Hence, alterations in redox potential may lead to alteredetabolism and to altered antigencity. Our results imply such a microbial response to environmental stress.

Actinomyces↗
PubMed1969

Effect of low pH on thiomethyl-beta-D-galactoside uptake by Streptococcus lactis.

Maximal beta-galactosidase activity in Streptococcus lactis was obtained at pH 7, but the maximal rate of thiomethyl-beta-d-galactoside uptake was observed at pH 3.6 to 4. It is concluded that the decrease in beta-galactosidase activity in intact cells at lowered pH is not due to diminished transport of beta-galactoside.

Glycosides↗
PubMed1969

Inhibition of Aerobacter cephalosporin beta-lactamase by penicillins.

Cephalosporinase (beta-lactamase) was obtained from cell washings of Aerobacter (Enterobacter) cloacae as a highly active preparation. An alkalimetric method was used to determine the enzyme activity and to estimate its inhibition by 6-amino-penicillanic acid derivatives. Their order of decreasing inhibitory effect was as follows: cloxacillin, oxacillin, methicillin, ampicillin, and penicillin G. We found that 2 to 3 ng of cloxacillin per ml was sufficient to decrease the enzyme activity by 50% in the presence of 400 mug of cephalosporin C per ml. Cloxacillin exerted a potentiating effect on the inhibition of the E. cloacae organisms by cephalosporin C.

Ampicillin↗
PubMedDate not supplied

Indication of thioglucosidase activity in extracts of Neisseria gonorrhoeae.

The recent demonstration of a host-derived inducer of gonococcal resistance to complement-mediated killing by human serum in purified serum and red blood cell fractions, which contained small glucopeptides with cysteine as one of the constituent amino acids, prompted an investigation of Neisseria gonorrhoeae for thioglucosidase activity. This involved an examination of supernatants of sonicated gonococci for thioglucoside hydrolysis by following, spectroscopically, the hydrolysis of 6-purine beta-D-glucothiopyranoside to 6-mercaptopurine and glucose. Extracts of N. gonorrhoeae were found to hydrolyse this thioglucoside. A substantial activity was present in a fraction with the same order of molecular weight as plant thioglucosidases. This led us to suspect the presence of a thioglucosidase in N. gonorrhoeae.

Glycoside Hydrolases↗