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Biomedical subjects

M J Basker

Publications and source records attributed to M J Basker.

At least 19 recordsLinked to original sources
PubMed1991

Uptake of a catecholic cephalosporin by the iron transport system of Escherichia coli.

beta-Lactam antibiotics containing a catechol moiety show potent activity against Gram-negative bacteria, particularly organisms grown under iron-limited conditions, suggesting that the iron-regulated outer membrane proteins (IROMPs) play a role in antibiotic uptake. A catecholic C(7) alpha-formamido-substituted cephalosporin showed increased penetration into Escherichia coli cells grown in an iron-deficient medium compared with cells grown in a medium supplemented with iron. In contrast, penetration of the corresponding monohydroxyphenyl analogue was not influenced by iron concentration. Susceptibility studies with mutants of E. coli lacking one or more IROMPs suggested that the catecholic analogue was able to utilize the Fiu (83 kDa) and Cir (74 kDa) proteins, but not the enterobactin receptor FepA (81 kDa). Mutants lacking both Fiu and Cir showed a specific decreased susceptibility for catechol-containing cephalosporins. Radio-ligand binding studies with a Fe-catecholic cephalosporin confirmed an association with these proteins.

Bacterial Outer Membrane Proteins↗
PubMed1990

6-(substituted methylene)penems, potent broad spectrum inhibitors of bacterial beta-lactamase. I. Racemic 6-ethylidenepenems.

The dehydration of various 6-(1-hydroxyethyl)penems to give E- and Z-6-ethylidenepenems is described. Both isomers have been shown to be potent broad spectrum inhibitors of bacterial beta-lactamases capable of reducing the MIC values of beta-lactam antibiotics such as amoxycillin and cephaloridine against a wide range of resistant organisms.

Anti-Bacterial Agents↗
PubMed1990

Synthesis and antibacterial activity of C-2 carboxyethenylthio-carbapenem derivatives.

A number of C-2 carboxyethenylthio-carbapenem derivatives possessing either the (5R,6R,8S)- or the (5R,6S,8R)-stereochemistries have been prepared from the olivanic acids MM 22382 (1) and MM 22383 (4), respectively. Their in vitro antibacterial activities and stabilities to human kidney homogenate are superior to those of the parent compounds, particularly in the latter series.

Animals↗
PubMed1987

Studies on semi-synthetic 7 alpha-formamidocephalosporins. III. Synthesis and antibacterial activity of some 7 beta-[D-2-(aryl)-2-[(4-ethyl-2,3-dioxopiperazin-1-yl)carbonyl amino] acetamido]-7 alpha-formamidoceph-3-em-4-carboxylate derivatives.

The synthesis and antibacterial activity of 7 beta-[D-2-(aryl)-2-[(4-ethyl-2,3-dioxopiperazin-1-yl) carbonylamino] acetamido]-7 alpha-formamidocephalosporins with various substituents at the C-3 position of the cephalosporin nucleus is described. Inhibition of Gram-positive and Gram-negative bacteria including beta-lactamase producing strains was observed with phenyl as the aryl residue. The 3,4-dihydroxyphenyl group further enhanced the activity against Gram-negative organisms; in this series, the 3-[(1-methyl-1H-tetrazol-5-yl)thiomethyl] and 3-[(1-carboxymethyl-1H-tetrazol-5-yl)thiomethyl] analogues (2 and 12b) exhibited exceptional activity against Gram-negative bacteria, including Pseudomonas aeruginosa.

Cephalosporins↗
PubMed1986

BRL 20330, an oral prodrug of temocillin: bioavailability studies in man.

BRL 20330 is the o-methyl phenyl ester of temocillin which is well absorbed after oral administration and converted to temocillin in the body. BRL 20330 was administered to healthy subjects in a three-part cross-over study with single doses equivalent to 400, 600 and 800 mg of temocillin. Peak serum concentrations of temocillin were 9.8, 12.8 and 15.8 mg/l respectively and concentrations of 3.0-6.0 mg/l were measured at 12 h after dosing. High and prolonged concentrations of temocillin were measured in the urine. The mean urinary recovery was 22-25% and only 0.2% of unhydrolyzed BRL 20330 was detected in the urine. Little difference in the extent of absorption was noted when BRL 20330 was administered with food although the peak levels of temocillin were delayed and reduced slightly. Urinary concentrations of temocillin, even after 24 h, were bactericidal for a number of Gram-negative bacteria including multi-resistant strains. BRL 20330 was well tolerated and there was no evidence of gastro-intestinal adverse effects.

Administration, Oral↗
PubMed1985

Mutual pro-drugs of the olivanic acids and renal dipeptidase inhibitors.

The carbapenem antibiotics, which include the olivanic acids and thienamycin, possess potent broad spectrum antibacterial activity. They are however extensively metabolized by the renal dipeptidase enzyme, dehydropeptidase I. As a result of this degradation, only low urinary recoveries of antibiotic are obtained in vivo. The preparation of mutual pro-drugs of the olivanic acids and an inhibitor of the renal dipeptidase enzyme is described. MM 22382 and MM 13902 have been combined with Z-2-isovaleramidobut-2-enoic acid as double esters of formaldehyde hydrate. Administration of these linked esters to mice results in improved urinary recoveries of antibiotic.

Amides↗
PubMed1985

Preparation and structure-activity relationships of some 6 alpha-substituted penicillins.

The influence on the antibacterial activity of introducing a 6 alpha-methoxy group into carbenicillin, and various 6 alpha-substituents into sulbenicillin and piperacillin was examined. Further variations of the side chain aryl group were examined in the 6 alpha-methoxy substituted series. This led to the identification of disodium 6 beta-(D,L-2-carboxy-2-thien-3-ylacetamido)-6 alpha-methoxypenicillanate (5b) as a beta-lactamase stable derivative with useful activity against Enterobacteriaceae, and disodium 6 beta-[D-2-(4-aminophenyl)-2-sulfoacetamido]-6 alpha-methoxypenicillanate (6e) with slightly lower activity against the Enterobacteriaceae but more active against Pseudomonas aeruginosa.

Enterobacteriaceae↗
PubMed1979

Comparative antibacterial activity of azlocillin, mezlocillin, carbenicillin and ticarcillin and relative stability to beta-lactamases of pseudomonas aeruginosa and klebsiella aerogenes.

The antibacterial activities of two ureidopenicillins, azlocillin and mezlocillin, were compared with those of the alpha-carboxypenicillins, carbenicillin and ticarcillin, against a large number of gram-positive and gram-negative bacteria. All four penicillins were active against a wide range of bacteria including Pseudomonas aeruginosa, but there were differences in the antibacterial spectra and in the antibacterial effects demonstrated by the two classes of penicillins. In particular, the minimum inhibitory concentrations of azlocillin and mezlocillin against Klebsiella aerogenes and against P. aeruginosa were greatly influenced by the size of bacterial inoculum tested whereas there was no significant inoculum effect with carbenicillin and ticarcillin. In stability tests, the ureidopenicillins were inactivated rapidly by the beta-lactamases of K. aerogenes and P. aeruginosa whereas the alpha-carboxypenicillins were stable. It seems probable that the inoculum effect seen with azlocillin and mezlocillin in antibacterial tests with K. aerogenes and P. aeruginosa is associated with the instability of the compounds to the beta-lactamases of these bacteria.

Carbenicillin↗
PubMed1979

Comparative activities of ampicillin, epicillin and amoxycillin in vitro and in vivo.

The antibacterial activities of three aminopenicillins ampicillin, epicillin and amoxycillin were compared in vitro and in vivo. The minimum inhibitory concentrations (MIC) of the three penicillins were very similar and the compounds were active against non-beta-lactamase-producing strains of Escherichia coli, Salmonella and Shigella species, Proteus mirabilis, Haemophilus influenzae and Neisseria gonorrhoeae. Streptococci including Streptococcus faecalis, and non-beta-lactamase-producing staphylococci were also sensitive to the compounds but Pseudomonas aeruginosa, Klebsiella aerogenes, Enterobacter and indole-positive Proteus species were resistant. At concentrations close to MIC value epicillin and ampicillin showed similar bactericidal activity against E. coli and against S. typhi and both compounds caused a slower rate of kill than was seen with amoxycillin. Microscopical observation of the cells exposed to ampicillin and epicillin for 1 h showed the presence of filamentous forms which lysed slowly, whereas cells exposed to amoxycillin for the same period rapidly. Epicillin was similar to or slightly less active than ampicillin against experimental mouse infections, and against the majority of infections both compounds were significantly less effective than amoxycillin by the oral and subcutaneous routes of administration.

Administration, Oral↗
PubMed1978

beta-lactam antibiotics. II. Structure-activity relationships of 6-[alpha-(alpha'-ureido-acylamino) acylamino] penicillanic acids.

The influence on the structure-activity relationships (S.A.R.) of the stereochemistry and various alkyl, aryl, aralkyl and heterocyclic substituents at the two chiral centres in the dipeptide side-chain of a new series of penicillins was examined. In many cases the effects of these changes had a pronounced influence on the degree of activity against Gram-positive and especially Gram-negative bacteria. Several compounds indicated that the size, shape and spatial disposition of a substituent were the parameters of importance in influencing activity, rather than it lipophilic or electronic character. The most active homologues in the series provided broad-spectrum penicillins which in terms of their in vitro antibacterial properties showed improvements over certain of the marketed penicillins. Thus 6-[D-alpha(alpha'-ureidoacyl-amino)acylamino]penicillanic acids were found which had a carbenicillin-like profile, with improvements against Pseudomonas aeruginosa, Klebsiella aerogenes, sensitive and beta-lactamase-producing Gram-positive cocci.

Bacteria↗