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W M Shafer

Publications and source records attributed to W M Shafer.

62 records · Page 4Linked to original sources
PubMed1982

Identification of a new genetic site (sac-3+) in Neisseria gonorrhoeae that affects sensitivity to normal human serum.

A previously undescribed genetic site (sac-3) affecting susceptibility of the gonococcus to normal human serum was localized on the gonococcal chromosome. The presence of the sac-3+ allele in a clinical isolate (FA889) resulted in sensitivity only to relatively high concentrations of serum (greater than or equal to 12.5%). Genetic mapping experiments demonstrated that sac-3+ was tightly linked to another genetic site (sac-1+) involved in determining susceptibility to normal human serum and to a locus (nmp-3) involved in the replacement of outer membrane protein I. The sac-1+ and sac-3+ loci resulted in phenotypically distinct levels of sensitivity to human serum. The sac-3+ serum sensitivity and sac-1+ serum sensitivity loci recombined with high frequency, resulting in serum resistance. The results show that serum sensitivity in clinical isolates may be due to different serum sensitivity loci and suggest that different antigens and immunological mechanisms could be responsible for sensitivity of different gonococcal isolates to human serum.

Blood Bactericidal Activity↗
PubMed1982

Pyocin-resistant lipopolysaccharide mutans of Neisseria gonorrhoeae: alterations in sensitivity to normal human serum and polymyxin B.

Pyocins from Pseudomonas aeruginosa were used to select several lipopolysaccharide (LPS) mutants of Neisseria gonorrhoeae strain FA19. Three classes of LPS mutans were found in the initial group selected for study. The LPS of one class lacked galactose. That of a second group lacked the typical heptose found in the parental LPS, was reduced in glucose, galactose, and N-acetylglucosamine content, appeared to contain a new unidentified sugar component, and consisted of two species of LPS separable on sodium dodecyl sulfate-polyacrylamide gels. The LPS of a third strain lacked the heptose, glucose, galactose, and N-acetylglucosamine found in the oligosaccharide portion of parental FA19 LPS. The minimal inhibitory concentration for polymyxin B of the mutant strains was 3 to 4 times that of the parental strain. The strains lacking only galactose were as resistant as the parent to the bactericidal action of normal human serum, but cells of the other two classes were quickly killed by serum. Gonococcal LPS thus appears to be important in determining phenotypic properties of the cells.

Blood Bactericidal Activity↗
PubMed1979

Genetics of staphylococcal enterotoxin B in methicillin-resistant isolates of Staphylococcus aureus.

Biophysical and genetic analysis of staphylococcal enterotoxin B (SEB) synthesis in 16 methicillin-resistant (Mecr) Staphylococcus aureus isolates demonstrated that the toxin gene (entB) can occupy either a plasmid or chromosomal locus. Biophysical analysis of the plasmid deoxyribonucleic acid content of these strains by agarose gel electrophoresis revealed the presence of a 1.15-megadalton plasmid in six isolates that appears to contain the entB gene. Genetic manipulation of SEB synthesis by transduction and elimination procedures demonstrated that this plasmid is critical for enterotoxigenesis. Nevertheless, the majority of the Mecr SEB+ isolates (62.5%) analyzed in this investigation were found to lack the 1.15-megadalton plasmid. In at least two of these strains (COL and 57-dk), transduction and elimination procedures showed that entB was chromosomal. Genetic studies involving strains harboring either a plasmid or chromosomal entB gene demonstrated that toxin synthesis was coeliminated with mec. However, analysis of the entB and mec loci by transformation or transduction showed that the genes are not closely linked. On the other hand, transduction of entB, regardless of the donor, was observed when both mec and the Tcr plasmid were jointly cotransduced. This finding suggests that, during transduction, a transient association between entB, mec, and the Tcr plasmid may exist.

Chromosomes, Bacterial↗
PubMed1978

Chromosomal locus for staphylococcal enterotoxin B.

The genetic locus of staphylococcal enterotoxin B (SEB) was investigated in the Staphylococcus aureus food-poisoning isolates, strains S6 and 277. Direct neutral sucrose gradient centrifugation analysis of sodium dodecyl sulfate-sodium chloride-mediated cleared lysates demonstrated that strain S6 contained a single 37S plasmid. Transductional analysis revealed that the 37S plasmid in S6 encoded for cadmium resistance (Cad) but not SEB. Additionally, elimination of cadmium resistance in S6 provided a plasmid-negative derivative that produced SEB at the same level as the parent. Examination of strain 277 showed two plasmids, a 37S species encoding for penicillin resistance (Penr) and a 21S species containing the gene(s) responsible for tetracycline resistance (Tetr). Elimination of the 37S, penr plasmid in 277 had no effect on SEB production, whereas introduction of the 21S tetr plasmid via transformation into strain 8325 (SEB--) did not confer enterotoxigenesis upon the transformants. The data obtained in this investigation suggest that the SEB gene(s) in these food-poisoning isolates of S. aureus is chromosomal.

Cadmium↗
PubMed1977

Regulation of staphylococcal enterotoxin B.

The effect of glucose and the glucose analogues 2-deoxyglucose and alpha-methyl-glucoside on the synthesis and regulation of staphylococcal enterotoxin B was examined. The attenuating effect of glucose on staphylococcal enterotoxin B synthesis was observed. However, when this effect was examined with analogues of glucose, contradictory responses were seen. alpha-Methylglucoside had a slight stimulatory effect on enterotoxin production and other extracellular proteins, whereas 2-deoxyglucose markedly inhibited enterotoxin production. beta-hemolysin and staphylococcal nuclease were also inhibited by 2-deoxy glucose but the synthesis of nuclease could be rescued by the addition of glucose to 2-deoxyglucose-containing cultures. Enterotoxin and beta-hemolysin synthesis were not subject to glucose rescue. The cells used in this study were permeable to cyclic 3',5'-adenosine monophosphate, but the addition of this compound did not reverse glucose repression or 2-deoxyglucose inhibition of enterotoxin B synthesis. We conclude from these data that the regulation of enterotoxin is not under catabolite control as previously reported.

Cyclic AMP↗
PubMedDate not supplied

Neutrophil killing of bacteria by oxygen-independent mechanisms: a historical summary.

The historical development of the concept of neutrophil killing of bacteria by oxygen-independent mechanisms is traced. The role of oxygen-independent microbicidal mechanisms in relationship to neutrophil management of microbes is critically evaluated. In the ultrastructural sense, oxygen-independent killing of bacteria requires the deposition of a bactericidal component (granule proteins) or the establishment of a hostile, non-physiologic environment in the phagolysosome. Accordingly, this review is concerned with the identification and cellular location of cationic proteins that participate in nonoxidative killing of gram-negative bacteria by human polymorphonucleur neutrophil granulocytes. Studies reviewed support the hypothesis that oxygen-independent mechanisms function in vivo and are important in host defense against infection. The chemistry of antimicrobial proteins, the biologically active site of each protein, and the mechanism by which the proteins trigger bacterial death all need to be determined at the molecular level.

Antimicrobial Cationic Peptides↗