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G K Best

Publications and source records attributed to G K Best.

32 records · Page 2Linked to original sources
PubMed1974

Evidence for participation of autolysins in bactericidal action of oxacillin on Staphylococcus aureus.

A comparison of the autolytic enzyme activity in Staphylococcus aureus strains that differ markedly in their rates of lysis and killing after exposure to oxacillin has been made. Log-phase cells of the clinical isolate that is tolerant to oxacillin inhibition were found to contain a level of autolytic enzyme activity comparable to that in a sensitive strain. This autolysin from log-phase cells was recovered after a single freeze-thaw cycle and assayed by using both native and penicillin (un-cross-linked) mureins. These same assays, however, revealed a significant difference in autolysin activity extractable from the two strains if the cells were inhibited by oxacillin. Under these conditions, the S. aureus strain that is susceptible to the killing and lytic effects of oxacillin had considerably more activity on penicillin murein than did the tolerant organism. These results provide evidence that hydrolytic enzymes on the cell surface are required to augment the wall damage initiated by oxacillin and other beta-lactam antibotics to produce a bactericidal effect.

Bacteriolysis↗
PubMed1973

Chemical analysis of cell walls and autolytic digests of Bacillus psychrophilus.

The amino acid composition of isolated cell walls of Bacillus psychrophilus has been determined before and after extraction of protein with ethylenediamine-tetraacetic acid at 45 C. This revealed that the peptidoglycan consists of Ala, Lys, and Glu in a molar ratio of 3:1:2. By using autolytic digests of log-phase cell walls, it was possible to detect 14 ninhydrin-positive degradation products. Chemical analyses of the seven major bands from these digests indicated that the amino acid sequence of the peptide subunit in the murein of this organism consists of muramyl-l-alanyl-gamma-d-glutamyl-l-lysyl- d-alanine, and the linkage between adjacent peptides is supplied by a second d-glutamic acid which is bound to the sigma-amino group of lysine and the carboxyl group of the d-alanine through its amino group. The nature of the solubilized wall fragments indicates that each of the peptide bonds in the murein is hydrolyzed by autolysins except the l-alanyl-gamma-d-glutamyl linkage.

Alanine↗
PubMed1972

Cell wall composition of two strains of Blastomyces dermatitidis exhibiting differences in virulence for mice.

Cell walls isolated from two strains of Blastomyces dermatitidis were examined. Whereas strain Ga-1 was practically avirulent for mice, strain KL-1 produced death by 21 days in 50% of the mice inoculated. Analyses of the trypsin-treated cell walls of the two strains revealed a higher chitin and protein content in strain KL-1, whereas a higher polysaccharide content was observed in the cell walls of strain Ga-1. Extraction of the walls with 1 n NaOH revealed a threefold difference in the amount of alkali-soluble cell wall material present. The alkali-soluble material could be further fractionated into a water-soluble and a water-insoluble fraction. Previous reports have indicated that the water-insoluble fraction of B. dermatitidis consists of an alpha-linked glucan; however, we report that in addition a phospholipid moiety is covalently bound to the polysaccharide. Furthermore, on the basis of organic phosphorus content, considerably more phospholipid is associated with the alpha-linked glucan of the more virulent KL-1 strain. These results suggest that this cell wall constituent might be one of the factors related to the virulence of this fungus.

Amino Acids↗
PubMed1972

Effect of temperature on the integrity of Bacillus psychrophilus cell walls.

Cell walls isolated from Bacillus psychrophilus autolyse at temperatures which support growth. At temperatures above the maximum growth temperature (28 C), a nonenzymatic lysis occurs. Removal of autolytic enzyme activity with 10 m LiCl had little effect on the rate or extent of lysis at elevated temperatures (37 and 45 C). Nonenzymatic lysis was characterized chemically by a decrease in the liberation of N-terminal groups, and the effects of pH, Ca(2+), and ethylenediaminetetraacetic acid suggest that ionic linkages are involved in much of the integrity of the cell wall of this psychrophile. The nonenzymatic absorbance decrease at 45 C can be reversed to the extent of 70 to 100% at 0 C. Centrifugation of a heat-lysed wall suspension separated a soluble protein component which is required for low-temperature reaggregation. Preliminary evidence indicates the insoluble residue which remains after temperature-mediated lysis is primarily peptidoglycan.

Autolysis↗
PubMed1970

Relative affinity of vancomycin and ristocetin for cell walls and uridine diphosphate-N-acetylmuramyl pentapeptide.

A determination of the relative affinity of vancomycin and ristocetin for isolated cell walls and for a peptidoglycan precursor was made. These antibiotics had previously been shown to adsorb to cell walls and to complex with peptides containing a d-alanyl-d-alanine C-terminus. By using (14)C-uridine diphosphate (UDP)-N-acetylmuramyl pentapeptide, it was shown that the complex which is formed between this peptidoglycan precursor and either vancomycin or ristocetin does not preclude adsorption of the antibiotics to cell walls of Micrococcus lysodeikticus. Complex formation between ristocetin and UDP-N-acetylmuramyl pentapeptide was assured by differential absorption spectra. However, when the complex was mixed with cell walls, the antibiotic was sedimented with the walls, and the radioactivity remained in the supernatant solution. This indication that ristocetin and vancomycin have a greater affinity for walls than for UDP-N-acetylmuramyl pentapeptide and that the complex per se does not bind to cell walls suggests that adsorption of these antibiotics to cell walls is probably responsible for the inhibition of peptidoglycan synthesis. This proposal is strengthened by the observation that complexed antibiotic is no less inhibitory for growth of Bacillus subtilis than free vancomycin or ristocetin.

Adsorption↗
PubMedDate not supplied

Passive protection of rabbits infected with toxic shock syndrome-associated strains of Staphylococcus aureus by monoclonal antibody to toxic shock syndrome toxin 1.

The effectiveness of passive immunization was assessed in an infection model of toxic shock syndrome (TSS) in which monoclonal antibody to TSS toxin 1 (TSST-1) was administered intravenously to rabbits. Previously implanted infection chambers were inoculated with Staphylococcus aureus strains RN4710 and D4508. The former strain carries the TSST-1 gene on plasmid pRN6201; the latter is a TSST-1-negative clinical isolate obtained from a patient with nonmenstrual TSS. Purified monoclonal antibody, MAb 8-5-7 (IgG), was administered in two doses of approximately 1.25 mg each 24 hours before and 24 hours after infection. MAb 8-5-7 provided complete protection against both the TSS-like syndrome and the mortality that occurred in unprotected rabbits infected with strain RN4710 but did not provide complete protection in rabbits infected with strain D4508; three of the five rabbits either displayed signs of illness or died despite treatment. Western-blot analyses of the extracellular proteins produced by strains RN4710 and D4508 that used MAb 8-5-7 as a probe revealed that only TSST-1 produced by RN4710 reacted with the antibody. Thus, if MAb 8-5-7 partially protected animals against infections with strain D4508, the protection appears to have been nonspecific.

Animals↗
PubMedDate not supplied

Endotoxin enhancement of toxic shock syndrome toxin 1-induced secretion of interleukin 1 by murine macrophages.

The purpose of this study was to determine whether endotoxin could augment toxic shock syndrome toxin 1 (TSST-1)-induced production of interleukin 1 (IL-1) by murine macrophages. Macrophages from C3H/HeJ or C57Bl/6 mice were stimulated with purified TSST-1 alone or in combination with lipopolysaccharide (LPS). A dramatic synergistic thymocyte-proliferative response was induced by supernatants from C57Bl/6 macrophages stimulated with both TSST-1 and LPS. No enhanced response was induced by supernatants from C3H/HeJ macrophages. A portion of the enhanced response induced by C57Bl/6 macrophage supernatants was attributed to synergism between IL-1 and residual TSST-1 in the thymocyte assay. The addition of monoclonal antibody to TSST-1 to the supernatants eliminated the effects of residual TSST-1 in the thymocyte assay and demonstrated a synergistic induction of IL-1. These data (1) show that LPS can enhance macrophage responsiveness to TSST-1; (2) suggest that TSST-1 not only induces IL-1 secretion but also enhances target cell responsiveness to IL-1; and (3) further support the role of IL-1 in the pathogenesis of toxic shock syndrome.

Animals↗