Pyrroindomycins, novel antibiotics produced by Streptomyces rugosporus LL-42D005. II. Biological activities.

The pyrroindomycins, a complex of novel antibiotics identified in fermentation broths of "Streptomyces rugosporus" LL-42D005, demonstrated excellent in vitro activity against Gram-positive bacteria. The semisynthetic diacetyl derivative of pyrroindomycin B (pyrroindomycin B-Ac2) was bactericidal for exponential-phase cells, but not for stationary-phase cells. This compound also exhibited marginal protection against a lethal Staphylococcus aureus challenge in mice. The poor in vivo activity of this antibiotic complex may be related to binding to blood components, as suggested by elevated MICs observed in blood-containing media. Incorporation of radiolabeled precursors into DNA, RNA, and protein was inhibited in an exponential-phase culture of Bacillus subtilis within ten minutes of exposure to pyrroindomycin B-Ac2. Microscopic examinations of drug-treated cells revealed lysis within the same ten minute period. These data are consistent with an effect of pyrroindomycin B-Ac2 on the integrity of the bacterial membrane.

Glycothiohexides, novel antibiotics produced by "Sebekia" sp. LL-14E605. I. Taxonomy, fermentation and biological evaluation.

The new glycothiohexide antibiotics, which are related to nosiheptide, were identified in fermentations of an actinomycete belonging to the genus "Sebekia". Strain LL-14E605 was classified as a "Sebekia" based on the presence of both mesodiaminopimelic acid and madurose in the cell wall and the presence of pseudosporangia encasing the spores. Culture LL-14E605 was successfully fermented in 10 to 3,000 liters of a complex medium. Antibiotic activity closely followed cell mass accumulation and usually peaked after 4 to 5 days of incubation. Glycothiohexide alpha demonstrated excellent in vitro activity against Gram-positive bacteria with MICs of 0.03 to 0.06 microgram/ml against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis. However, glycothiohexide alpha failed to protect mice against a lethal challenge with Staphylococcus aureus Smith unless it was administered prior to challenge.

Invasion and lysis of HeLa cell monolayers by Salmonella typhi: the role of lipopolysaccharide.

Adhesion to and penetration of HeLa cell monolayers by Salmonella typhi Ty2 requires the presence of a complete lipopolysaccharide as demonstrated by the inability of polysaccharide-defective mutants to invade the monolayer. Lysis of HeLa cell monolayers by Salmonella typhi Ty2 is associated with intracellular bacterial multiplication and no detectable production of extracellular toxins. The ability of Salmonella typhi to invade and lyse monolayers could provide a novel system for the study of its ability to invade the bloodstream from the intestine.

Cloning, expression and characterization of the 36 KDal Salmonella typhi porin gene in Escherichia coli.

A recombinant plasmid containing the gene for the 36 KDal porin of Salmonella typhi has been identified in a cosmid library of S. typhi propagated in Escherichia coli. The recombinant clone was identified by its ability to endow E. coli with susceptibility to porin specific phages, and by the appearance in the outer membrane of E. coli containing the clone of a new protein of 36 KDal. While the porin confers upon a porinless mutant of E. coli an increased susceptibility to beta-lactam antibiotics, it does not react with serum from patients with typhoid fever in immunoblotting assays.