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Biomedical subjects

B J Wilkinson

Publications and source records attributed to B J Wilkinson.

81 records · Page 5Linked to original sources
PubMed1977

A new type of penicillin resistance of Staphylococcus aureus.

Penicillin--"tolerant" Staphylococcus aureus strains are resistant to the lethal action of penicillins, but are inhibited by normal (low) concentrations. They are deficient in autolytic enzyme activity which appears to be necessary for bacteriolysis and the lethal action of penicillins. This "deficiency" is caused by a large excess of an inhibitor of autolysin. Seven such tolerant strains have been isolated from blood, bone, or sputum of patients who responded poorly to penicillin treatment of endocarditis, osteomyelitis, or staphylococcal pneumonia. These isolates were of different phage-types, and most showed cross-tolerance to the killing action of cephalosporins or vancomycin, antibiotics to which they were sensitive (inhibited). They were killed at normal rates by gentamicin, cycloserine, and rifampicin. Population analysis indicated that the proportion of tolerant organisms within a resistant strain is 7% or less; their ability to inhibit autolytic activity within their own and neighbouring cells appears to account for the net decreased autolytic activity of the entire strain; 44% of the bacteraemic strains studied showed penicillin tolerance. Tolerance is thus a common, clinically important form of penicillin resistance, that differs from previously described forms of pencillin resistance, that due to beta-lactamase, and that due to "intrinsic" (e.g., methicillin resistance) mechanisms.

Adult↗
PubMed1977

A numerical taxonomic survey of Listeria and related bacteria.

A numerical taxonomic study was performed on named strains of Listeria, Erysipelothrix, Microbacterium thermosphactum, Lactobacillus, Streptococus, Propionibacterium, Kurthia and some possibly related bacteria using I43 unit characters covering a wide range of properties. The strains fell into six main clusters: (A) Listeria; (B) Microbacterium thermosphactum, Lactobacillus, Streptococcus; (C) Gemella, Erysipelothrix; (D) Kurthia and mainly aerobic corynebacteria; (E) Propionibacterium, Staphylococcus; (F) mainly Cellulomonas. The genus Listeria contained three subgroups corresponding to (I) Listeria monocytogenes, (2) Listeria grayi and (3) non-haemolytic listeria strains. Listeria murrayi did not appear to be sufficiently distinct from Listeria grayi to warrant separate species status. The genus Erysipelothrix was quite separate from the genus Listeria. Microbacterium thermosphactum was related to both the genera Listeria and Lactobacillus but formed a separate phenon that could appropriately be given generic rank. There were four distinct subgroups amongst the streptococci examined. Gemella strains appeared as a distinct phenon related to Erysipelothrix and the streptococci. The lactobacilli grouped into four phena largely corresponding to the subgenera Betabacterium, Streptobacterium and Thermobacterium and to the species Lactobacillus mali. Custers A, B, and C displayed a relatively close association to each other and it is recommended that all be included in the family Lactobacillaceae.

Culture Media↗
PubMed1975

Morphogenesis of the membrane-bound electron-transport system in sporulating Bacillus megaterium KM.

The properties of electron transport systems present in soluble and particulate fractions of spores of Bacillus megaterium KM?HAVE BEEN COMPARED WIth those of similar fractions prepared from exponential-phase vegetative cells of this organism. The timing and localization of modifications of the electron transport system occurring during sporulation have been investigated by using a system for separating forespores from mother cells at all stages during development [8]. Spore membranes contained cytochromes a + a3, and o at lower concentrations than in vegetative membranes, and in addition cytochrome c, which was not found in exponential-phase vegetative membranes. An NADH oxidase activity of similar specific activity was found in both spore and vegetative membranes but DL-glycerol 3-phosphate and L-malate oxidase activities were found only in vegetative membranes. A soluble NADH oxidase of low specific activity was found in spores and vegetative cells which probably involves a flavoprotein reaction with oxygen because the activity was stimulated by FAD or FMN and difference spectra of concentrated soluble fractions showed spectra typical of a flavoprotein. Particulate NADH oxidase was sensitive to all classical inhibitors of electron transport tested whereas soluble NADH oxidase was insensitive to many of these inhibitors. Cytochrome c was formed between stage I and II of sporulation and this coincided with a five-fold increase in NADH-cytochrome c reductase activity. Forespore membranes had lower contents of cytochromes than sporangial cell membranes but similar levels of NADH and L-malate oxidases; DL-glycerol 3-phosphate oxidase activity could not be detected in either membranes by stage III of sporulation. This characterization of spore electron transport systems provides a basis for suggestions concerning initial metabolic events during spore germination and the effect of a number of germination inhibitors.

Adenosine Triphosphatases↗
PubMed1975

Biochemical evidence for the reversed polarity of the outer membrane of the bacterial forespore.

Measurement of certain membrane-bound enzymic activities was used to study the orientation of the outer membrane of the double-membraned forespore of Bacillus megaterium KM. 2. Adenosine triphosphatase, NADH dehydrogenase and L-malate intact protoplasts, but were readily detected in intact stage II or IV forespores, consistent with reversed polarity of the outer forespore membrane relative to the mother-cell plasma membrane. 3. Measurement of NADH oxidase activity revealed that intact stage III forespores had the same high affinity for NADH as protoplast membrane preparations and protoplast lystates, consistent with ready access of NADH to oxidation sites on the outer forespores membrane. 4. Forespores and protoplasts showed osmometric behaviour in solutions of non-permanent solutes consistent with the presence of an intact permeability barrier in these structures.

Adenosine Triphosphatases↗
PubMed1972

Phospholipid composition and metabolism of Micrococcus denitrificans.

The phospholipid composition of Micrococcus denitrificans was unusual in that phosphatidyl choline (PC) was a major phospholipid (30.9%). Other phospholipids were phosphatidyl glycerol (PG, 52.4%), phosphatidyl ethanolamine (PE, 5.8%), an unknown phospholipid (5.3%), cardiolipin (CL, 3.2%), phosphatidyl dimethylethanolamine (PDME, 0.9%), phosphatidyl monomethylethanolamine (PMME, 0.6%), phosphatidyl serine (PS, 0.5%), and phosphatidic acid (0.4%). Kinetics of (32)P incorporation suggested that PC was formed by the successive methylations of PE. Pulse-chase experiments with pulses of (32)P or acetate-1-(14)C to exponentially growing cells showed loss of isotopes from PMME, PDME, PS, and CL with biphasic kinetics suggesting the same type of multiple pools of these lipids as proposed in other bacteria. The major phospholipids, PC, PG, and PE, were metabolically stable under these conditions. The fatty acids isolated from the complex lipids were also unusual in being a simple mixture of seven fatty acids with oleic acid representing 86% of the total. Few free fatty acids and no non-extractable fatty acids associated with the cell wall or membrane were found.

Autoradiography↗