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M S Gilmore

Publications and source records attributed to M S Gilmore.

63 records · Page 4Linked to original sources
PubMed1990

Genetic analysis of the pAD1 hemolysin/bacteriocin determinant in Enterococcus faecalis: Tn917 insertional mutagenesis and cloning.

Thirty-seven nonhemolytic/nonbacteriocinogenic mutations in Enterococcus (Streptococcus) faecalis plasmid pAD1 were generated by Tn917 insertion. All were found to belong to one of two complementation classes. Each class of mutants secreted either hemolysin/bacteriocin (Hly/Bac) component A or L into the culture medium. DNA encoding Hly/Bac was cloned in Escherichia coli in which both components of the hemolysin were expressed individually and collectively. The region encoding components A and L was further defined by deletion analysis and physically mapped. A total of approximately 8.4 kilobases of pAD1 DNA were observed to be required for hemolysin expression. Hly/Bac activity of the wild-type and the inactive L substance was observed to be heat stable. Active Hly/Bac resulting from incubating separately secreted components A and L was also found to be heat stable. The results indicate that component A activates component L and that activated component L possesses the Hly/Bac activity. Component A was also observed to be associated with host immunity to the Hly/Bac.

Bacteriocins↗
PubMed1990

The growth-inhibitory effect of the Enterococcus faecalis bacteriocin encoded by pAD1 extends to the oral streptococci.

Many strains of Enterococcus faecalis, a normal inhabitant of the oral cavity, elaborate a plasmid-encoded bacteriocin. The growth-inhibitory effect of this bacteriocin was observed to extend to a variety of pathogenic oral streptococci, including those that play a major role in tooth surface colonization and caries formation. These results suggest that transient colonization by bacteriocin-producing E. faecalis may effect shifts in oral colonization by susceptible organisms and that bacteriocin-producing E. faecalis may be a candidate for application in strain replacement therapy.

Bacteriocins↗
PubMed1989

Human B cell lines can be triggered to secrete an interleukin 2-like molecule.

To determine whether human B cells can be triggered to secrete interleukin 2 (IL-2), 19 tumor cell lines derived from patients with undifferentiated lymphomas of Burkitt's and non-Burkitt's types and 6 normal lymphoblastoid cell lines were tested. Cells were grown in the presence or absence of the new tumor promoter teleocidin, and culture supernatants were assayed for IL-2 activity using the standard CTLL-2 assay. Teleocidin (10 ng/ml) triggered IL-2 secretion in 7/8 (87%) EBV-negative lymphoma cell lines of American origin and in 6/6 (100%) normal lymphoblastoid cell lines, but in only 1/6 (16%) EBV-positive tumor cell lines of American origin. Teleocidin had no effect on 5/5 (0%) African Burkitt's cell lines. IL-2 secretion was not detected in control supernatants. IL-2 secretion correlated with the induction of IgM secretion and was linked to both EBV status and karyotype. The following similarities in the functional biological characteristics of T cell and B cell IL-2 suggest that B cell IL-2 is not a factor which mimics IL-2 activity in the CTLL-2 assay: (i) neutralization of IL-2 by anti-IL-2 monoclonal antibody (DMS-1); (ii) elution of IL-2 following its adsorption to CTLL-2 cells; (iii) determination of the MW of IL-2 by SDS-PAGE and Western blot analysis; and (iv) ability of B cell IL-2 to support T cell proliferation and blocking of this activity by anti-tac monoclonal antibody. cDNA probes for T cell IL-2, however, did not detect IL-2 mRNA in B cells. The cell lines were also found to constitutively express IL-2 receptors detected by anti-tac monoclonal antibody, and to secrete soluble IL-2 receptors measured by ELISA. Our results imply that under certain circumstances, B cells can be triggered to secrete IL-2 or an IL-2-like molecule and thus influence T cell activation and proliferation.

Antibodies, Monoclonal↗
PubMed1989

In vitro susceptibility studies of vancomycin-resistant Enterococcus faecalis.

Vancomycin resistance exhibited by Enterococcus faecalis isolates V583, V586, and V587 is described. The vancomycin MICs ranged from 32 to 64 micrograms/ml. Although resistant to vancomycin, the isolates were susceptible to teicoplanin (MIC, less than or equal to 0.5 micrograms/ml). Such a glycopeptide susceptibility profile has not been previously described for E. faecalis. Time kill studies showed that vancomycin resistance adversely affected the synergistic activity that vancomycin and aminoglycoside combinations usually demonstrate against enterococci. However, the ability to detect vancomycin resistance varied with the susceptibility testing method used. Whereas broth microdilution, broth macrodilution, and agar dilution methods detected resistance, disk-agar diffusion and the AutoMicrobic system Gram-Positive GPS-A susceptibility card (Vitek Systems Inc., Hazelwood, Mo.) did not. To detect vancomycin resistance reliably and establish the incidence of such E. faecalis isolates, adjustments in some susceptibility testing methods may be necessary.

Anti-Bacterial Agents↗
PubMed1989

A Bacillus cereus cytolytic determinant, cereolysin AB, which comprises the phospholipase C and sphingomyelinase genes: nucleotide sequence and genetic linkage.

A cloned cytolytic determinant from the genome of Bacillus cereus GP-4 has been characterized at the molecular level. Nucleotide sequence determination revealed the presence of two open reading frames. Both open reading frames were found by deletion and complementation analysis to be necessary for expression of the hemolytic phenotype by Bacillus subtilis and Escherichia coli hosts. The 5' open reading frame was found to be nearly identical to a recently reported phospholipase C gene derived from a mutant B. cereus strain which overexpresses the respective protein, and it conferred a lecithinase-positive phenotype to the B. subtilis host. The 3' open reading frame encoded a sphingomyelinase. The two tandemly encoded activities, phospholipase C and sphingomyelinase, constitute a biologically functional cytolytic determinant of B. cereus termed cereolysin AB.

Amino Acid Sequence↗
PubMed1981

Location of antibiotic resistance determinants, copy control, and replication functions on the double-selective streptococcal cloning vector pGB301.

The physical map of the streptococcal cloning vector pGB301 (9.8 kb) has been extended by localizing the cleavage sites of restriction endonucleases AvaII, AvaI, BclI, BstEII, and PvuII. The latter four enzymes cleaved pGB301 at unique sites. Insertion of chromosomal DNA from Staphylococcus aureus strain 3Ar-m- into the single BstEII site of pGB301 led to inactivation of the plasmid's chloramphenicol resistance determinant. Twelve deletion derivatives of pGB301 were isolated either by in vitro manipulation of pGB301 or as spontaneous deletion mutants following transformation of Challis by mixtures of recombinant plasmids. The overlapping deletions which spanned a continuous sequence of 7.7 kb ranged in size from 0.3 kb to 4.1 kb and allowed to localize the chloramphenicol and MLS-resistance determinants, the copy control function, and the replication region on the physical map of pGB301. Plasmid pGB301 together with its deletion mutants constitutes a valuable tool for further molecular cloning experiments in streptococci.

Chloramphenicol↗
PubMed1981

Plasmid pGB301, a new multiple resistance streptococcal cloning vehicle and its use in cloning of a gentamicin/kanamycin resistance determinant.

Streptococcal plasmid pGB301 is an in vivo rear ranged plasmid with interesting properties and potential for the molecular cloning of genes in streptococci. Transformation of S. sanguis (Challis) with the group B streptococcal plasmid pIP501 (29.7 kb) gave rise to the deletion derivative pGB301 (9.8 kb, copy number 10) which retained the multiple resistance phenotype of its ancestor (inducible MLS-resistance, chloramphenicol resistance). Among the eight restriction endonucleases used to physically map pGB301 were four that cleaved the plasmid at single sites yielding either sticky (HpaII, KpnI) or blunt-ends (HpaI, HaeIII/BspRI). Passenger DNA derived from larger streptococcal plasmids (pSF351C61, 69.5 kb; pIP800, 71 kb) was successfully inserted into the HpaII site and, by blunt-end cloning into the HaeIII/BspRI site. The gentamicin/kanamycin resistance gene of pIP800 was expressed by recombinant plasmids carrying the insert in either orientation. Insertion of passenger DNA into the HaeIII/BspRI site (but not the HpaII site) caused instability of adjacent pGB301 sequences which were frequently deleted, thereby removing the chloramphenicol resistance phenotype. The vector pGB301 has a remarkable capacity for passenger DNA (inserts up to 7 kb) and the property of instability and loss of a resistance phenotype following insertion of passenger DNA into the HaeIII/BspRI site should facilitate the identification of cloned segments of DNA when using this plasmid in molecular cloning experiments.

Chloramphenicol↗
PubMedDate not supplied

Multiple-drug resistant enterococci: the nature of the problem and an agenda for the future.

Enterococci, leading causes of nosocomial bacteremia, surgical wound infection, and urinary tract infection, are becoming resistant to many and sometimes all standard therapies. New rapid surveillance methods are highlighting the importance of examining enterococcal isolates at the species level. Most enterococcal infections are caused by Enterococcus faecalis, which are more likely to express traits related to overt virulence but--for the moment--also more likely to retain sensitivity to at least one effective antibiotic. The remaining infections are mostly caused by E. faecium, a species virtually devoid of known overt pathogenic traits but more likely to be resistant to even antibiotics of last resort. Effective control of multiple-drug resistant enterococci will require 1) better understanding of the interaction between enterococci, the hospital environment, and humans, 2) prudent antibiotic use, 3) better contact isolation in hospitals and other patient care environments, and 4) improved surveillance. Equally important is renewed vigor in the search for additional drugs, accompanied by the evolution of new therapeutic paradigms less vulnerable to the cycle of drug introduction and drug resistance.

Anti-Bacterial Agents↗