Molecular species of phosphatidylethanolamine from continuous cultures of Saccharomyces pastorianus syn. carlsbergensis strains.

Saccharomyces pastorianus syn. carlsbergensis strain 34/70 is well known to be the most used strain for lager beer production. The difference between this strain and very closely related strain 34/78 is the latter's greater flocculating character. This single physiological trait can cause technical difficulties in beer production. The aim of this study was to determine whether lipid analysis by a combination of thin layer chromatography (TLC) with electrospray ionization mass spectrometry (ESI-MS) could be used as a strain-typing technique in order to distinguish S. pastorianus syn. carlsbergensis strain 34/70 from strain 34/78. Both strains (34/70 and 34/78) were harvested after continuous culture under standard conditions. Polar lipids were then extracted from lyophilized cultures and analysed by TLC in order to separate phospholipid families. Phosphatidylethanolamine (PE) was extracted and investigated using ESI-MS, to gain further information on individual molecular species. Using TLC analysis, lipids were separated corresponding to standards for PE, phosphatidylcholine (PC), phosphatidylglycerol (PG), cardiolipin (CL), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidic acid (PA) and sphingomyelin (SM). ESI-MS of the PE band, separated by TLC, showed that electrospray mass spectra were highly reproducible for repeat cultures. Novel findings were that both brewing strains displayed major phospholipid peaks with m/z 714, PE (34 : 2) m/z 742, PE (36 : 2) and m/z 758, PE (37 : 1). However, strain 34/78 had additional peaks of m/z 700, PE (33 : 2) and m/z 728, PE (35 : 2). Strain 34/70 had an extra peak with m/z 686 PE (32 : 2). We conclude that combined TLC/ESI-MS can distinguish between S. pastorianus syn. carlsbergensis 34/70 and 34/78 and may be a useful typing technique for differentiation of closely related yeast strains. This novel approach may aid quality assurance and could be suitable for yeast collections and larger industrial companies.

Hypolipidemic activity of rifamycin derivatives.

Series of 3-piperidinyl- and 3-piperazinylrifamycins and to a certain extent 3-hydrazonorifamycins all bearing lipophilic side chains were found to exert potent hypolipidemic activity in lowering both serum cholesterol and LDL-cholesterol in rats. Starting from 3-[N'-(2,4,6-trimethylbenzyl)-N-piperazinyl]rifamycin SV (compound 25), a series of derivatives were synthesized with the aim of dissociating the hypolipidemic from the antibacterial activity, leading to the 8-O,N-dipivaloyl derivative of 25 (compound 48), which is devoid of any antibacterial activity but shows about 50-60% reduction of LDL-cholesterol and 20-30% reduction of serum cholesterol at a dose of 10 mg/kg. Compound 48 was selected for further pharmacological evaluation.

Synthesis and biological activity of 2-lactonyl penems.

A series of potent antibacterial agents have been prepared. These agents are penems carrying a lactone ring in the C-2 position. Excellent activity against Gram-positive and Gram-negative organisms--except Pseudomonas aeruginosa--was found.

CGP 4832, a new semisynthetic rifamycin derivative highly active against some gram-negative bacteria.

CGP 4832 (5) is a new derivative of rifamycin S, showing a very high degree of activity against certain Gram-negative bacteria, with MICs as much as 400 times lower than those of rifampicin. CGP 4832 and rifampicin inhibit DNA-dependent transcription in vitro to a similar extent, which excludes any difference in their effect on the target enzyme. The most plausible explanation for the potent activity of CGP 4832 is that it penetrates into bacterial cells by way of a specific mechanism. This hypothesis is corroborated by the high rate of mutations leading to bacterial strains resistant against CGP 4832.

Papulacandins--synthesis and biological activity of papulacandin B derivatives.

A series of papulacandin B derivatives was synthesized and their in vitro and in vivo activity against Candida albicans and other fungi was established. The biological data have shown that some 10-alkyl ether and 11-acylamino derivatives exhibit an improved in vivo activity compared to papulacandin B whereas derivatization in other positions of the molecule led to less potent compounds.

[Quantitative sensitivity determination of bacteria. Indications and methods]. / Quantitative Empfindlichkeitsbestimmungen für Bakterien. Indikationen und Methoden.

The authors describe the indications for quantitative susceptibility tests and also the methods themselves (agar dilution, macrodilution, combination tests, tests for beta-lactamase production). This study forms part of a series on susceptibility methods which started with a paper on disk susceptibility testing (this journal, 1984; 114: 1079-1086).

The rate of killing of Escherichia coli by beta-lactam antibiotics is strictly proportional to the rate of bacterial growth.

Nongrowing bacteria evade the bactericidal activity of beta-lactam antibiotics. We sought to determine if slow growth rate also alters bactericidal activity. The bactericidal activity of two beta-lactams on Escherichia coli grown in glucose limited chemostats was compared for generation times ranging from 0.7 to 12 h. The degree of killing varied with drug structure and with E. coli strain. However, all killing rates were a constant function of the bacterial generation time: slowly growing bacteria became progressively more phenotypically tolerant to beta-lactam antibiotics as the generation time was extended.

Evaluation of the bactericidal activity of beta-lactam antibiotics on slowly growing bacteria cultured in the chemostat.

The bactericidal activity of 23 beta-lactam antibiotics was compared in slowly growing bacteria cultured in a chemostat. In an attempt to mimic possible in vivo conditions, slowly growing cultures were produced by limitation of iron, glucose, phosphate, or magnesium. Only select antibiotics remained effectively bactericidal against slowly growing cells. For these compounds, the rate of antibiotic-induced loss of viability was a constant when killing was expressed per generation (in contrast to absolute time) in that slowly growing bacteria were killed proportionately more slowly. Individual antibiotics differed greatly, however, in their specific bactericidal activities against slowly growing cells, i.e., in the absolute degree of killing elicited during exposure of the bacteria to MIC equivalents of the drugs. Specific bactericidal activities varied not only with drug structure but also with the bacterial strains and, to a lesser extent, with the nature of the growth-limiting nutrient. In slowly growing cultures exposure to the low drug concentrations studied here (near MIC) caused killing without detectable lysis. Antibiotics with high specific bactericidal activities were capable of rapidly killing cultures of slowly growing pathogens despite extremely long generation times approaching those reported for in vivo growth rates.

The penems, a new class of beta-lactam antibiotics. 7. Synthesis and antimicrobial activity of 2-heterocyclylmercaptoalkyl derivatives.

2-Heterocyclylmercaptoalkyl penems were synthesized and their in vitro potency was established. The compounds exhibit moderate to strong antibacterial activity against various Gram-positive and Gram-negative bacteria. Their antimicrobial activity is related to the nature of the heterocycle, the length of the hydrocarbon spacer between the 2-position of the penem nucleus and the mercapto group, and the substitution pattern of the C-6 position of the penem skeleton.

Correlation of antibacterial activities of antibiotics in vitro and in animal models of infection.

Laboratory tests of antibiotic activity in vitro, ranging from simple MIC determinations to sophisticated, computerized models for studying the effects of simulated plasma concentration-time curves of antibiotics in broth, differ inherently from tests in vivo in both the general and specific variables. There are therefore likely to be discrepancies between the results obtained. Apart from the obvious lack of host-defence mechanisms in the in-vitro tests systems, the reasons for these discrepancies have still not been fully elucidated. For the time being, it seems unrealistic to expect that in-vitro tests could be developed that would make it possible to predict the efficacy of any antibiotic against any specific infection in vivo.

Possible approaches to the simulation of antibiotic kinetics and the determination of antibacterial activity in vitro.

Various methods of determining antibacterial effects in vitro by simulation of antibiotic kinetics were investigated. MICs were determined in fluids with and without proteins. Only concentrations of free drug were antibacterially active, and these concentrations should therefore be simulated in culture media without protein. Varying drug concentrations can easily be simulated in our in-vitro system, but the question remains which of the concentrations found in the different body fluids is the most representative. Cephalosporins were more active when phagocytosis was simulated, as shown by the continuous elimination of approximately 90% of the bacteria. If phagocytosis was not simulated, the effects of long-lasting concentrations were not decreased as much as those of concentrations corresponding to short half-lives and repeated doses.

Cephalosporin antibiotics. Synthesis and antimicrobial activity of 7 beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2-oxyiminoacetamido]cephalosporin derivatives.

Cephalosporins with a 7 beta-[2-(5-amino-1,2,4-thiadiazol-3-yl) -2-oxyiminoacetamido] side chain were synthesized and their in vitro inhibitory potency was established. The compounds exhibit a strong antibacterial activity against various Gram-positive and Gram-negative bacteria. The antimicrobial activity is related to the oxime-substituent R1 and the C-3 substituent R2. Selected amino-1,2,4-thiadiazolyl-cephems 1 show a prolonged half-life in mice.

Antibacterial effects of cefroxadine, cephalexin and cephradine in a new in vitro pharmacokinetic model.

A pharmacokinetic model has been developed, by means of which all possible time courses of the concentrations of antibiotics in the plasma of treated individuals can be exactly simulated in vitro without diluting the test organism and affecting the growth curves. Equieffective concentrations in the system corresponded to the plasma concentrations in man produced by cefroxadine in a single oral dose of 250 mg and cephalexin and cephradine in a single oral dose of 500 mg.

Semisynthetic bicyclomycin derivatives: preparation and antibacterial evaluation.

A number of semisynthetic bicyclomycin derivatives have been prepared by modifications at various sites of the molecule. The preparation, characterization and antimicrobial evaluation of the new compounds is described. In contrast to bicyclomycin itself, the new derivatives 48 and 58 are also active against Proteus species. Otherwise, the antibacterial potency of the bicyclomycin molecule was found to be very sensitive to structural changes.

[Serum and joint levels of cefacetrile during its administration for septic arthritis]. / Concentrations plasmatiques et articulaires pendant l'administration de céfacétrile pour arthrite septique (6 cas).

Six patients, five of whom had normal and one impaired renal function, and all suffering from purulent arthritis caused by cephalosporin-sensitive germs, were given a seven-day course of 8 g cephacetrile daily. On the first day, 6 g were administered by continuous intravenous infusion at the rate of 500 mg/h, followed by 2 g over a further 45 min. On days 2 to 7, the patients received 2 short infusions of 4 g each at an interval of 12 h. In four patients with normal renal function, serum half-life ranged from 0.8 to 1.4 h, serum levels during continuous infusion from 19 to 31 microgram/ml, and total clearances from 265 to 434 ml/min. In one patients, these values were 1.6 h, 70 microgram/ml and 131 ml/min respectively (small volume of distribution). The concentrations in the synovial fluid varied from 2 to 29 mcirogram/ml; they were generally lower than the serum levels, but clearly exceeded the minimum inhibitory concentrations for germs commonly present in purulent arthritis. In five patients, the synovial fluid became germ-free and the arthritis was clinically cured. In the case presenting with renal insufficiency, the serum half-life was 5.8 h. During continuous administration, a steady state was not attained; peak serum levels amo9nted to 75 microgram/ml and the total clearance to 61 ml/min. The cephacetrile concentrations in the synovial fluid were very high (26 and 67 microgram/ml). In this case, in which the renal insufficiency associated with mycosis fungoides was present before the treatment, renal function deteriorated futher during treatment while the arthritis improved.

CGP 9000: a new orally active, broad-spectrum cephalosporin.

CGP 9000, (7-[D-2-amino-2-(1,4-cyclohexadienyl)-acetamido]-3-methoxy-3-cephem-4-carboxylic acid), is a new broad-spectrum cephalosporin antibiotic. Its antibacterial activity in vitro (MIC) is similar, but its bactericidal efficacy superior to that of cephalexin and cephradine. Upon oral administration to mice infected with various bacteria, CGP 9000 is, in general, 2 to 7 times more effective than either cephalexin or cephradine.