Louis J. Nisbet

New Genus of the Actinomycetales: Kibdelosporangium aridum gen. nov., sp. nov.

A new actinomycete genus, Kibdelosporangium, is described. Members of this genus have type IV cell walls (meso-diaminopimelic acid, D-glutamic acid, DL-alanine, muramic acid, N-acetyl-D-glucosamine, D-galactose, and arabinose) and a type A whole-cell sugar pattern (D-galactose and arabinose) plus traces of madurose (3-O-methyl-D-galactose). No mycolic acids are present. The substrate mycelium has a tendency to fragment. The aerial mycelium bears long chains of spores, as well as sporangiumlike structures with well-defined walls. These sporangiumlike structures do not contain spores but germinate directly when they are placed on agar. The type strain of K. aridum is strain SK&F-AAD-216 (= ATCC 39323).

Charge and lipophilicity govern the pharmacokinetics of glycopeptide antibiotics.

The pharmacokinetics and urinary excretion of nine glycopeptide antibiotics with diverse pIs (3.8 to 8.5) and lipophilicities were studied. The disposition of the aridicin antibiotics and their hydrolysis products were examined in male CD-1 mice after subcutaneous and intravenous administration and compared with the disposition of teicoplanin, ristocetin, and vancomycin. The total systemic clearance, half-life, volume of distribution, and urinary excretion were highly correlated with pIs. In general, as the pI decreased, the clearance, urinary recovery, and volume of distribution decreased, whereas the half-life increased. With those glycopeptides that had similar pIs, clearance decreased and half-life increased with increasing lipophilicity. The urinary recovery of the glycopeptides decreased with decreasing pI and increasing lipophilicity. Because vancomycin (pI = 8.0) is cleared by glomerular filtration, increased binding to serum is the likely mechanism of reduced renal clearance for glycopeptides with low pIs. These results are consistent with previous findings concerning the correlation of physical-chemical properties and the drug disposition of small organic molecules. Results of these studies also indicate that desirable pharmacokinetic properties can be incorporated into glycopeptides through semisynthetic modifications.

Antimicrobial activity of aridicins, novel glycopeptide antibiotics with high and prolonged levels in blood.

Three new glycopeptide antibiotics, aridicins A, B, and C, produced by Kibdelosporangium aridum have a spectrum of antimicrobial activity in vitro which is similar to that of vancomycin. The antimicrobial activities of these glycopeptides against clinical bacterial isolates were compared with those of vancomycin and other related glycopeptide antibiotics in vitro by agar dilution and microtiter broth dilution tests and in vivo in mouse protection studies. In vitro they were somewhat less effective than vancomycin against strains of Staphylococcus aureus and less active against coagulase-negative Staphylococcus spp. However, they were more active than vancomycin against strains of Streptococcus faecalis and markedly superior to vancomycin and other glycopeptide antibiotics against strains of Clostridium difficile. In experimental infections, aridicin A was effective against strains of S. aureus, S. epidermidis, Streptococcus faecalis, and Streptococcus pyogenes, although its 50% effective doses were higher than those of vancomycin when administered after infection. After subcutaneous administration, aridicin A had a higher peak level in serum and a longer half-life than vancomycin or teicoplanin. The aridicins were markedly superior to vancomycin when administered prior to infection in mouse protection tests, indicating long-acting potential.

Activity of a peptidyl prodrug, alafosfalin, against anaerobic bacteria.

Alafosfalin, an antibacterial phosphonodipeptide requiring peptide transport for activity, was tested for activity against clinical strains of anaerobic bacteria in peptide-free Roche Sensitivity Test Medium no. 5 agar. It was active against Bacteroides spp., Fusobacterium nucleatum, and Clostridium perfringens but not against Clostridium difficile. Alafosfalin activity was antagonized by appropriate peptides. Synergy was obtained with other cell wall-active antibiotics.

CHLOROCARDICIN, A MONOCYCLIC β-LACTAM FROM A STREPTOMYCES SP.

Chlorocardicin is a new monocyclic beta-lactam produced by a Streptomyces sp. It is structurally related to nocardicin A but differs in having a m-chloro substituent on the p-hydroxyphenylglycine unit. The biological activity of chlorocardicin was similar to nocardicin A but the former showed less antagonism in complex media. Moderate in vitro activity was observed against Enterobacteriaceae and Pseudomonas aeruginosa. Chlorocardicin showed low activity against Staphylococcus aureus whereas nocardicin A was inactive. Both compounds were shown to be strongly potentiated by antibiotics that inhibit peptidoglycan biosynthesis and were antagonized by selected L- and D-amino acids.

Roche Susceptibility Test (RST) medium, a defined formulation for susceptibility testing: I. Nutrient interaction and optimization studies

Roche Susceptibility Test (RST) Medium represents the most completely optimized and convenient fully defined medium described. It requires no post-autoclaving supplementation with vitamins, supports good growth of all common aerobic and anaerobic pathogens and may be used as a broth or agar gel on which the swarming of Proteus spp. is virtually eliminated. The broth as a superior buffering capacity to most complex media and an osmolality and pH close to those of human serum. RST is highly satisfactory for the susceptibility testing of commonly used antibiotics and meets the requirements of the National Committe for Clinical Laboratory Standards of the U.S.A. in almost every respect.

Analytical HPLC of the aridicin glycopeptide complex and its application to fermentation development

SummaryA gradient analytical HPLC system was developed to assay titers of the three major components of the aridicin (Ardacin) complex produced byKibdelosporangium aridum (SK&F AAD-216). The separation was performed on a Beckman Ultrasphere column using a gradient of acetonitrile (26–43%) in 0.1 M pH 3.2 phosphate buffer with UV detection at 220 nm. The gradient system was necessary to analyze all three major factors within a reasonable recycle time (14 min) without interference by front eluting impurities. The assay was linear from 12 to 200 μg/ml (multipleR2=0.998), with a standard deviation for retention time of 1.4%. A SepPAK isolation scheme was developed to assay samples in complex matrices such as fermentation broths. Using this assay as a monitor, fermentation medium optimization increased the total titers of the three factors from approximately 5 μg/ml to over 200 μg/ml. The optimal medium contained glucose, beet molasses and methyl oleate. The latter substrate was particularly effective in enhancingproducation 10-fold, presumably by enhancing the supply of acetly-CoA. This is a biosynthetic precursor of both dihydroxyphenylglycine, present in the nucleus, and the acyl side chains present on the amino-glucuronic acids.