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Biomedical subjects

M A Melly

Publications and source records attributed to M A Melly.

7 recordsLinked to original sources
PubMed1986

Bactericidal effects of polyunsaturated fatty acids.

Bactericidal effects of polyunsaturated fatty acids were investigated by using an in vitro killing assay. All gram-positive species tested were extremely susceptible to 10(-5) M arachidonic acid as were Neisseria, Branhamella, and Haemophilus spp. Pseudomonas aeruginosa and and members of the Enterobacteriaceae were resistant. The toxicity of polyunsaturated fatty acids for Staphylococcus aureus was dependent upon time, concentration, and fatty acid unsaturation. Arachidonic acid underwent peroxidation when incubated with S. aureus, but arachidonic acid peroxidation products had low bactericidal activity. Catalase protected S. aureus, whereas superoxide dismutase was ineffective. Scavengers of hydroxyl radicals or singlet oxygen or removal of halide ions had little effect on arachidonic acid-induced killing of bacteria, whereas transition metal chelators and some thiols were highly protective. S. aureus grown in iron-supplemented broth had increased iron content and arachidonic acid susceptibility. Ascorbate also potentiated arachidonic acid-induced killing of S. aureus. These observations indicate that bactericidal effects of polyunsaturated fatty acids are mediated by a peroxidative process involving H2O2 and bacterial iron.

Arachidonic Acid↗
PubMed1986

Localization of gonococcal lipopolysaccharide and its relationship to toxic damage in human fallopian tube mucosa.

An experimental model using human fallopian tubes in organ culture was used to study the localization of purified gonococcal lipopolysaccharide (LPS). LPS was visualized by light microscopy with immunoperoxidase staining. Immediately after addition to fallopian tube organ cultures, gonococcal LPS aggregated on the tips of cilia. By 1 to 2 h after exposure, LPS could be seen distributed throughout the cytoplasm of ciliated and nonciliated cells in structures resembling vesicles. By 12 h, there were sloughed, ciliated cells present in the fallopian tube lumen, which had positive LPS stain on their surfaces as well as in their cytoplasm. By 24 h, LPS was distributed throughout the cytoplasm. Control experiments with rabbit oviduct organ cultures showed that LPS failed to attach, enter, or damage mucosal cells. These studies illustrate the initial localization of LPS on human mucosal cells and its uptake into the cells, which are coincident with toxicity for ciliated epithelial cells.

Animals↗
PubMed1986

Analysis of damage to human ciliated nasopharyngeal epithelium by Neisseria meningitidis.

We used an in vitro model of human nasopharyngeal tissue in organ culture to evaluate the effects of Neisseria meningitidis on human cilia and ciliary function. Encapsulated, viable meningococci damaged ciliated epithelium of nasopharyngeal organ cultures, whereas Neisseria subflava, a commensal species, did not. Meningococcus-induced ciliary damage was due to loss of ciliated cells to which meningococci were not attached. Damage was seen with piliated and nonpiliated meningococci and did not appear to require the presence of other specific meningococcal surface proteins. Meningococcal viability was a requirement for both ciliary damage and interactions of meningococci with microvilli of nonciliated epithelial cells. That is, filter-sterilized supernatants from meningococcus-infected organ cultures, heat-killed meningococci at high inoculum, and purified meningococcal or gonococcal lipopolysaccharide at concentrations of 100 micrograms/ml did not damage ciliary activity of nasopharyngeal organ cultures. In contrast, meningococcal lipopolysaccharide at 10 micrograms/ml markedly damaged ciliary activity of human fallopian tube organ cultures, suggesting a selective toxicity of lipopolysaccharide for specific human ciliated cells. Damage to nasopharyngeal ciliated epithelium by N. meningitidis may be an important first step in meningococcal colonization of the human nasopharynx, but meningococcal lipopolysaccharide does not appear to be directly responsible for this toxicity.

Bacterial Outer Membrane Proteins↗
PubMed1979

An electron microscopic India ink technique for demonstrating capsules on microorganisms: studies with Streptococcus pneumoniae, Staphylococcus aureus, and Neisseria gonorrhoeae.

A technique using India ink in electron microscopic preparations was used to study bacterial capsules. Capsules were demonstrated on Streptococcus pneumoniae and Staphylococcus aureus (strain M and the Smith diffuse variant) from in vitro cultures. Two types of false capsules were observed on Neisseria gonorrhoeae grown in vitro or obtained from human urethral exudates. No true capsules were definitively identified on gonococci from these sources. The technique described does not require the use of specific anticapsular antibody or specific polysaccharide stains and permits the detection of artifacts that may, by the use of light microscopic methods, be misinterpreted as capsules.

Antigens, Bacterial↗
PubMed1976

An outbreak of nosocomial infection due to multiply resistant Serratia marcescens: evidence of interhospital spread.

Interhospital spread appeared to be responsible for a large epidemic of infections due to a strain of Serratia marcescens that was resistant to all currently available parenteral antibiotics. Between April 1, 1973 and January 1, 1975, 210 patients in four geographically separate hospitals in Nashville, Tennessee, were infected with the epidemic strain; 21 patients were bacteremic and eight died. Catheter-associated urinary tract infection accounted for the majority of isolates, and broad-spectrum antibiotic exposure appeared to promote the acquisition of the epidemic strain. The serotype (O1:H7) and phage type (186) of the organism were identical in all four hospitals, but background, sensitive strains of S. marcesens yielded a variety of other serotypes. Carriage on the hands of hospital personnel was implicated as the mode of spread within the hospital and apparently was the mode of transmission between the hospitals. Antibiotic resistance was largely episomally mediated, but resistance to gentamicin, cephalothin, and colistin was not transferable.

Cross Infection↗
PubMed1975

Microbiol growth in lipid emulsions used in parenteral nutrition.

Parenteral nutrition via central venous catheterization is associated with serious risks, especially that of sepsis. Lipid emulsion (Intralipid[Sweden]), which may be administered peripherally, was evaluated for its potential to support microbial growth. Washed cultures of Staphylococcus aureus, Candida albicans, and three species of Gram-negative rods were all capable of multiplying in the emulsion at room temperature. Variations in inoculum size did not affect the growth rate. Studies comparing the emulsion to amino acid-glucose solutions (total parenteral nutrition [TPN])confirmed other reports that TPN inhibits the growth of certain bacteria but merely retards fungal multiplication. When human serum was added to the lipid emulsion in an attempt to simulate in vivo conditions at the catheter tip, Escherichia coli was inhibited while the growth of S aureus and C albicians was unaltered.

Amino Acids↗