[Infectious agents : current concepts and perspectives]. / L'agent infectieux : notions actuelles et perspectives.

The authors present a detailed discussion on infectious agents and their development in the immediate future and the anti-microbial strategies which need to be developed. After describing a series of new diseases and the suspected microbial aetiology of little known syndromes, they describe the major lines of development of chemotherapy: new products which need to be developed; microbial enzyme inhibitors; selective transport. The proper use of the range of drugs already available should not be underestimated. Finally, the authors review recent developments and the prospects for the future in the immunological field: new vaccines or the improvement of existing vaccines and the immense possibilities of immunological techniques of identification.

Bioluminescence Assay for Measuring the Number of Bacteria Adhering to the Hydrocarbon Phase in the BATH Test.

A thorough validation of the bacterial adherence to hydrocarbons (BATH) test was performed by means of a bioluminescence assay. Ten different gram-negative strains were subjected to the BATH test. For the calculation of the adhesion index, several factors had to be taken into account: ATP leakage, the action of ATP-hydrolyzing enzymes, the change in the extraction efficiency of Nucleotide-Releasing Reagent for Microbial Cells (NRB; Lumac bv) after vortexing and the difference in light production after the addition of NRB. When the adhesion index values obtained by bioluminescence measurement were used as reference, the total plate count technique appeared to be unreliable in estimating the number of bacteria adhering to the hydrocarbon phase. A highly significant correlation was established, however, between those reference values and the adhesion index values obtained by the optical density reading for octane and especially for hexadecane. With xylene, no correlation was found between the optical density reading values and the total plate count or bioluminescence values.

Determination of endotoxins on hypodermic needles by means of a chromogenic Limulus amoebocyte lysate assay. Development of a test model.

A test model was developed in order to describe the determination of endotoxins on hypodermic needles in a reliable and reproducible manner. As in all in-vitro experiments one has to be very careful about extrapolating data to in-vivo situations. However by choosing a hydrophilic (Salmonella typhimurium ATCC 14028) and a hydrophobic bacterium (Acinetobacter calcoaceticus var. anitratus RR 8212/113), one could hope to obtain a quite representative idea about the extraction of contaminating gram-negative micro-organisms. Using the proposed extraction procedure and a chromogenic LAL assay as detection system, it was possible to achieve a quantitative idea about the extraction of endotoxins on hypodermic needles. Extracting needles at 19 degrees C during 83 to 98 min produced the highest yield as to the detection of endotoxins from hydrophilic strains. For the detection of endotoxins from hydrophobic strains, the highest yield values were obtained when the extraction was performed at temperatures between 64 and 80 degrees C during 96 to 120 min. However it seems necessary to perform the extractions at least three times in order to obtain reproducible results. In conclusion, using the extraction procedure as described, it is possible to measure endotoxin-like activity, on the inner and outer surface of hypodermic needles in a simple but accurate way, using water as extraction fluid and a chromogenic Limulus Amoebocyte Lysate assay as detection system.

In vitro antibacterial activity of BMY-28142, a new extended-spectrum cephalosporin.

The in vitro activity of BMY-28142 was compared with that of cefotaxime, ceftazidime, moxalactam, and imipenem against 639 clinical isolates and a number of in vitro-selected resistant mutants. BMY-28142 was the most potent compound against the members of the family Enterobacteriaceae with a MIC for 90% of the strains of 0.12 micrograms/ml. The activity against Pseudomonas aeruginosa was comparable to that of ceftazidime and imipenem. Strains of staphylococci were moderately susceptible to BMY-28142 (MIC required to inhibit 90% of strains, 4 micrograms/ml), but Streptococcus faecalis isolates were resistant. The activity of the five compounds was inoculum dependent for several gram-negative species. By a single-step selection procedure, resistant mutants were selected from strains of Citrobacter freundii, Enterobacter cloacae, and P. aeruginosa. The mutant frequencies with the cephalosporins, including BMY-28142, ranged between 10(-6) and 10(-8). BMY-28142 was the most active cephalosporin against these resistant organisms, most of them strong beta-lactamase producers. It inhibited all mutants of C. freundii and E. cloacae at 2 micrograms/ml and all mutants of P. aeruginosa at 32 micrograms/ml. Imipenem on the other hand was as active on all of these resistant organisms as on the parent strains.

Urease activity of enterobacteriaceae: which medium to choose.

Detection and intensity of urease activity in enterobacteriaceae greatly varies as a function of the media or techniques used, or both. A comparative investigation on several solid and liquid media led us to the following conclusions. (i) Detection of Proteus spp. can be adequately performed with the highly selective solid medium described by Cook (1948), as well as with the different liquid media described (Stuart standard and rapid media; Elek medium). (ii) Detection of Klebsiella should be based upon urease production on solid media with low buffer capacity (Christensen, 1946). (iii) For the identification of Yersinia, either the solid Christensen urea agar or the rapid Elek technique give optimal results.

Endotoxin testing.

Parenterals, sterile preparations intended to be injected in man or animal, should be free from pyrogenic substances which are able to raise the thermostatic setting in the hypothalamus. This article gives an up-to-date review of the principal detection and quantification methods for these agents, with special attention on the chromogenic Limulus Amebocyte Lysate assay.

In vitro activity of BL-s640 against gram-negative bacilli and Staphylococcus aureus compared with activity of four other semisynthetic cephalosporins.

The in vitro activity of BL-S640 (cefatrizine) was determined against 674 recent clinical isolates of Staphylococcus aureus and Enterobacteriaceae. Activity against S. aureus was less than that of cephapirin, cephalothin, and cefazolin, but greater than that of cephalexin. Activity against gram-negative isolates was variable: BL-S640 was slightly less potent than cefazolin against Escherichia coli and Klebsiella, but more active than the other compounds. As for the more resistant gram-negative genera, BL-S640 was significantly superior to the control cephalosporins. The effect of inoculum size on the antibacterial activity was moderate for most organisms except Enterobacter, Providencia stuartii, and indole-positive Proteus, the median minimal inhibitory concentrations of which were 6 to 27 times lower when determined with a 10(-4)-diluted culture compared with the undiluted one. The stability in aqueous solution at 37 C was remarkably high at the lower pH values, but low at the neutral point.

Selection of resistant mutants of Citrobacter freundii by second and third-generation cephalosporins and imipenem.

Using a single-step selection procedure, resistant mutants could be obtained from three clinical isolates of Citrobacter freundii with two second-generation and four third-generation cephalosporins but not with imipenem. All mutants showed a drastically increased beta-lactamase activity and were cross-resistant to all the cephalosporins examined. Combinations of cloxacillin with the cephalosporins were markedly synergistic, suggesting the principal role of the cephalosporinase in the resistance of these mutants.

In vivo comparison of two galenic forms of ampicillin-trihydrate.

In order to evaluate a new galenic form of ampicillin-trihydrate, individual blood serum levels and urine excretion of ampicillin-trihydrate were compared in a crossover study after oral absorption of 1-gram captab formulation (this being the new galenic form) versus 2x500 mg of the same product. Analyses performed by two different laboratories indicate that clinically insignificant slightly higher serum concentrations can be obtained with captabs, and that very individual absorption profiles should make one take a sceptic viewpoint as to mean serum concentrations computed from larger series of experiments. To obtain a valid blood serum level in as many patients as possible, a posology of 3-4 captabs, spaced over a 24-hour period is suggested for the treatment of infections with ampicillin-sensitive germs. For less sensitive micro-organisms, one should switch to parenteral therapy or to other antibiotics.

Investigation of the ability of newer beta-lactam antibiotics to select resistant mutants from Serratia marcescens after mutagenesis with nitrosoguanidine.

Resistant mutants could easily be selected from a nitrosoguanidine-treated culture of Serratia marcescens with piperacillin, cefotaxime, cefoxitin, cefotetan, latamoxef (moxalactam) and aztreonam. Imipenem on the other hand was significantly less effective in mutant selection. Resistant clones broadly fell into two distinct classes. Most mutants did not show increased beta-lactamase; their resistance seemed to be due to changed outer membrane proteins. Other mutants had strongly increased cephalosporinase activity, although the derepression was only partial. Piperacillin, cefotaxime and aztreonam preferentially selected the derepressed phenotype, whereas mutants selected with cefoxitin, cefotetan, moxalactam and imipenem were exclusively of the non-derepressed phenotype. There was a significant degree of cross-resistance between the beta-lactam antibiotics except imipenem which was only slightly less active against the membrane-altered mutants.

[Comparison of methods of determination of serum doxycyline assessing relative bioavailability of two commercial formulations (author's transl)]. / Vergleich der Messmethoden von Doxycyclin im Serum bei einer Prüfung der relativen Bioverfügbarkeit zweier Handelspräparate.

The present study was undertaken to evaluate the accuracy of the analytical results of an investigation of relative bioavailability of two doxycycline preparations. Six methods in four laboratories were applied: one fluorimetric, three high-pressure-liquid-chromatographic and three microbiological methods. The analyses were performed after coding the samples. In all cases the two preparations were bioequivalent. When comparing the methods, it could be shown that the fluorimetric method was slightly more accurate than the others. The HPLC-methods were almost as accurate. The results of the microbiological determinations showed the lowest accuracy. Two of the results were in good agreement with the biochemical methods, whereas the third showed such a high deviation that a comparison was no longer possible. Altogether a good agreement of all compared methods (except one) could be demonstrated.

Pharmacokinetics of amikacin in patients with renal insufficiency: relation of half-life and creatinine clearance.

The half-life of amikacin after a single intramuscular injection was determined in patients with severe renal failure who received 3.75 mg of drug/kg and in patients with various degrees of renal function who received 7.5 mg of drug/kg. The relation of the half-life of amikacin to levels of serum creatinine is practically identical to that of kanamycin. However, although concentrations of serum creatinine remained practically unchanged, rates of creatinine clearance may by considerably decreased in older subjects. This decrease may result in overestimation of the rate of glomerular filtration and subsequent overdosage. Therefore, the half-life of amikacin should be derived from values of rates of creatinine clearance or be predicted with use of a nomogram. The calculated half-life values may be used for development of appropriate dosage schedules for patients with various degrees of renal function. Such schedules would ensure therapeutic levels of drug and avoid potentially toxic accumulation of antibiotic.