A compact-rigid multi-analyser for energy and angle filtering of high-resolution X-ray experiments. Part 2. Efficiency of a single-crystal-comb

Diffraction instruments using filtering by one or several analyser crystals exist since the 1980s and 1990s at synchrotron radiation sources, but, due to its low efficiency, this filtering is little used on laboratory sources. In order to overcome this limitation, the efficiency of a small diffraction filtering multi-analyzer block (MAD block) realized with a `single-crystal-comb' curved on a rigid support is demonstrated here. The geometry of this curved surface is logarithmic spiral and is optimized to allow multi-filtering over a relatively important diffraction angular range and to be also applicable over an X-ray spectral range. The efficiency of such a small rigid-compact MAD block consisting of this single-crystal-comb generating 20-50 Si(111) single-crystal blades, associated with a block of Soller collimators, is demonstrated. The angle between each crystal is 0.1°, so the measurement range of the comb is 2-5°. The geometry of this system has been optimized for operation with a synchrotron X-ray source over an energy range of 22 keV to 46 keV and could be used with laboratory X-ray sources (Ag Kα<sub>1</sub>, 22.1 keV). This MAD block complements and exploits the qualities of the `photon-counting' detectors which have very low intrinsic noise. Their joint efficacy is supported by powder pattern measurements of a LaB₆ reference sample and of several heterogeneous samples of cultural heritage materials, carried out at 22 keV on the D2AM beamline at the ESRF. Their signal-to-noise ratio is excellent (1000/1) and allows the detection thresholds of the measurements (from 3-1% to 0.1%) to detect minor phases in the studies of `real' heterogeneous materials to be drastically improved.

Molecular Structure of a D-homoandrostanyl Steroid Derivative: Single Crystal and Powder Diffraction Analyses

The knowledge of the structure of a molecular crystal is frequently a prerequisite for the understanding of its solid state properties. Even though single-crystal diffractometry is the method of choice when it comes to crystal structure determination, methods using powder diffraction data become more and more competitive. There has been much recent interest in the development of a new generation of "direct-space" approaches that are particularly suited for molecular crystals. The crystallographic structure of a steroid derivative molecule (17,17-di-n-propyl-17a-aza-D-homo-5alpha-androstan-3beta-ol) was obtained in two independent ways: from a single crystal by laboratory X-rays and from a polycrystalline powder by high-resolution synchrotron powder diffraction. The molecule crystallizes in the orthorhombic space group P2(1)2(1)2(1) (a = 6.5346, b = 17.6006 and c = 19.6978 A). Hydrogen bonds form infinite chains of molecules parallel to the c axis.

[Chemistry of cosmetics in antiquity]

Several texts, statues and paintings denote the importance of make up and eye medicines since the earliest periods of Egyptian history. We have investigated cosmetic powders that were preserved in original alabaster and reed containers. Quantitative crystallographic and chemical analysis of the mineral and organic components revealed surprising facts. In addition to the well known galena PbS and cerussite PbCO3, two unexpected constituents have been identified: laurionite PbOHCl and phosgenite Pb2 (CO3) Cl2, which are rare halide minerals found in lead slag only in certain places where the sea water has weathered lead debris left over from silver mining operations in Antiquity. Alteration of natural lead minerals is also unlikely, given the excellent state of conservation of the reed vessels. This evidence indicates that laurionite and phosgenite were synthesised artificially. Support for this statement comes from recipes of medicinal products to be "used in ophthalmology" reported by Greco-Roman authors such as Dioscorides and Pline (1st Century B.C.): silver foam PbO is crushed and mixed with rock salt and sometimes with natron (Na2CO3). The reaction seems to be straightforward. However, our experiments in the laboratory have shown a major difficulty, arising from the concomitant production of alkali, which raises the pH and leads to different products. It follows that the Egyptians very early mastered this kind of chemical synthesis and technology, a fact of great importance in the History of Sciences. Fire-based technology had been mastered to manufacture Egyptian Blue pigments since the third millennium B.C. The present results now suggest that wet chemistry was already known 4000 years ago. This key finding provides a new insight into the chemical technology of far greater antiquity than has previously been believed. Yet, an important question remains relative to the ultimate motivation for these technological developments. If the Egyptians initially only aimed at different nuances of grey, they could use cerussite, an easily accessible mineral, crushed and mixed with galena. Thus, one should seek other motivations; we shall propose to consider a religious-ritual context, ultimately linked to a pharmaceutical aspect.

The effect of subinhibitory concentrations of some antibiotics on the hydrophobicity of gram-negative bacteria

Cell surface hydrophobicity is currently regarded as an important factor in promoting bacterial adherence to a wide variety of surfaces. This feature was investigated in some Gram-negative bacteria isolated from urinary tract infections and the extent to which their surface characteristics were affected by subinhibitory concentrations of some antibiotics was assayed. Surface properties were evaluated using the salting-out technique (SAT) and bacterial absorption to n-hexadecane (BATH). SAT showed that all except 3 Escherichia coli strains were autoaggregating. BATH detected more hydrophobic characteristics in the stationary phase of bacterial growth. Pretreatment with antibiotics generally reduced hydrophobicity and thus affected the initial reversible phase of attachment of bacteria to eukaryotic cells.

[Mixed culture of Enterococcus faecium SF 68 with pathogenic intestinal bacterial strains]

An antagonistic activity of Enterococcus faecium SF 68 towards Plesiomonas shigelloides, Aeromonas sp., enteropathogenic Escherichia coli and Yersinia enterocolitica has been studied and demonstrated.

[Evaluation of in vitro antibiotic sensitivity: critical features of the MIC]

Current methods for the "in vitro" study of antibiotic activity, as minimum inhibitory concentration, expose bacteria to constant concentrations of antibiotics. The "in vivo" situation is significantly different, since the antibiotic concentration changes with time. Pharmacokinetic models are "in vitro" experimental systems that seek to simulate conditions of exposure of bacteria to antimicrobial agents that exist in blood and tissues. All of these systems are complicated constructions. A new simple "in vitro" kinetic model, based on solid phase growth, is described.

[Combining indirect hemagglutination with the direct agglutination as a parameter for evaluating patients sent for serological verification of toxoplasmosis]

The importance that Toxoplasma gondii congenital infection may assume is still representing a stimulus for trying to improve Toxoplasmosis serological diagnosis; task, this one, which Laboratory is charged with, and that is often hard, particularly when we have to value the possibility of an infection in progress. With the purpose to complete the results obtained in a preceding work of ours, we have valued two among the most commonly used tests for Toxoplasmosis serodiagnosis, the AD (direct agglutination provided by BioMerieux) and the IHA (indirect haemoagglutination provided by Behring), together and separately, in order to make use of their coupling with major security and effectiveness, on the ground of the results obtained on two different groups of individuals, in the number of 125 for each group; for these groups it was possible to expect a different index of receptivity and a different percentage of recent or in progress infections. It was come out, as regards the IHAm a very good degree of assurance in trying to single out the past immunity, while this test wouldn't generally seem to be able to offer sufficient indications to distinguish the recent or in progress infection from past immunity, as it often declares, in fact, middle-high titres also in cases probably referable to the last mentioned situation. The AD has offered a good tribute in estimating the past immunity and it would also appear to give assurance in singling out recent or in progress infection (thanks to the possibility to determine IgM presence); while the presumed capacity of this test in revealing cases of very early infection has resulted not sufficiently assured. In substance the coupling of the two test, which in the direct comparison have shown a good correlation, but also several discordances, seems to be an useful procedure of reciprocal confirmation as regards the singling out of immunity; while the possibility of showing the recent or in progress infection--anyway, always a difficult task, above all, when, as it happened in this research, we deal with it without being able to follow the titre evolution in the time-should be entrusted with major certainty to the AD.

[Urinary infections: observations on the frequency of microbial isolation at the hospital environment and its surroundings]

Numerous studies have been carried out to specify bacterial frequencies in the urinary tract infections. In such researches the prevalence of Gram negative bacterial species has generally emerged, the most part of these ones would be Enterobatteriaceae (and among them E. coli has a special prominent position); on the other hand several Authors have often found, among other bacterial groups (Gram positive bacteria, Pseudomonas etc.) involved in such pathologies, some differences (also remarkable) in relation to various factors, among them, the hospitalizing condition, the clinical situation, the type of infection etc. In this research we have carried out a statistical analysis of the bacterial frequencies relative to 321 positive urine cultures, trying to point out their differences in relation to hospitalized or ambulatorial patients and to single are mixed infections; above all with regard to three bacterial groups: Enterobatteriaceae, Pseudomonas species and Gram positive bacteria. The most evident result has been the absolute prevalence of Enterobacteriaceae, among them the E. coli has represented, almost always, the most frequent isolated species, followed by Proteus mirabilis, in every kind of patient (hospitalized or ambulatorial) and infection, single or double (we didn't notice, in this research, infections supported by more than two species). Moreover, we noticed, but with less clearness, especially in relation to the numerical dimension of the observations and to the short comparison of the two kind of patients, some indications pointing out that hospitalized patients (in comparison with the ambulatorial) were charged with a major frequency of the two kind of patients, some indications pointing out that hospitalized patients (in comparison with the ambulatorial) were charged with a major frequency of infections supported by Gram + bacteria and Proteus mirabilis, while the Pseudomonas species presented an opposite behaviour (contrary to what several Authors generally report in literature: but a pollution problem of the specimen might have had some influence); and as regard the single infections we observed, among them, a greater frequency of the E. coli and Gram + bacteria than among the double infections, while the Pseudomonas species happened the contrary.

[Antibiotic resistance at a hospital environment. Observations from 1980 to 1986]

A total of 1659 bacteria Strains were examined for susceptibility to different drugs by the Kirby-Bauer method. The isolates came from the General Medicine ward of Castellamonte's hospital (USSL 40). The results were retrospectively studied and statistically elaborated. The study lasted from 2 to 7 years depending on the antibiotic considered. The isolates included: Escherichia coli, Klebsiella spp., Serratia spp., Citrobacter spp., Proteus mirabilis, Proteus IND+, Pseudomonas aeruginosa, Pseudomonas spp., Staphylococcus aureus, Staphylococcus spp., Streptococcus faecalis. Penicillines, Cefalosporines, Aminoglycosides, Quinolones, Tetraciclines, Nitrofurantoin, Macrolides, Rifampins, Lincosides and peptide antibiotics were tested. The results of this study can be useful for the choice of the antibiotics in non-specific therapy of infectious diseases and show the frequency of isolation of resistant strains from hospitalized patients. Furthermore it would be important to constitute a regional-epidemiological centre of Infectious Diseases.

[Aztreonam: monocenter microbiological study with prevention experience in surgery]

Aztreonam is a monobactam antibiotic active against aerobic gram-negative bacteria. The susceptibility of 127 urinary tract isolates to aztreonam, cefotaxime, cefonicid and ceftazidime was determined. Aztreonam showed good antibacterial activity even against Pseudomonas spp. Only 7 bacterial strains were resistant to aztreonam. The clinical efficacy and pharmacokinetics of aztreonam were assessed in two patients treated for urinary tract infections. The concentrations of aztreonam in serum and urine are reported. Aztreonam safety was evaluated on 20 patients given aztreonam immediately prior to an elective abdominal, urinary or gynecological operation. The results provide support for the use of aztreonam for prophylaxis.

In vitro antimicrobial activity in comparison with tonsillar tissue penetration of mezlocillin

The aim of this study was to determine the role of mezlocillin, a new acylureidopenicillin, in otorhinolaryngology. One hundred and forty-four bacterial strains were isolated from 100 patients suffering from infections of the oropharyngeal tract. Among the isolates only 10 (6.9%) resulted in being mezlocillin-resistant by the agar diffusion method. Minimum inhibitory and minimum bactericidal concentrations were also determined. Pharmacokinetic parameters e.g., diffusion in tonsillar tissue and serum concentrations, were studied. Mean mezlocillin tonsillar levels of 3.5 micrograms/g and 1.8 micrograms/g and serum concentrations of 60.2 micrograms/ml and 10.6 micrograms/ml, 1 h and 4 h respectively after administration, were found.

[Novel characteristic of the genus Campylobacter: Campylobacter-like organisms]

The first report of human infections due to Campylobacter dates back to 1947. These microorganisms, classified initially as Vibrio, had been known for many years as agents of several diseases in animals. In 1963 they were grouped in the new Genus Campylobacter belonging to Spirillaceae. Campylobacter are ever more important, particularly C. jejuni, which is an ubiquitous agent of diarrhoea in children. Other microorganisms of this Genus, the "gastric Campylobacter-like organisms" type I, otherwise known as Campylobacter pyloridis, are responsible for gastric diseases.

Adherence of Trichomonas vaginalis to cell culture monolayers

The in vitro adherence to WISH cells of a pathogenic Trichomonas vaginalis strain was studied with a method utilizing thymidine-labeled protozoa. A marked dose-related adherence was observed. Glutaraldehyde fixed trichomonads were not adherent. The presence of fetal calf serum during the assay did not influence attachment. Concanavalin A inhibited adherence of protozoa. Complete or partial inhibition of adherence was achieved by preincubating WISH cells with Lactobacillus fermentum or Streptococcus agalactiae. Finally, pretreatment of cells with alpha-estradiol, beta-estradiol, progesterone and estrone influenced attachment of protozoa, whereas estriol was ineffective. These results suggest that adherence of Trichomonas vaginalis is dependent on different factors, whose manipulation may have clinical relevance in preventing recurrence of trichomonad vaginitis.

Effect of prolonged administration of low doses of dietary retinoids on cell-mediated immunity and the growth of transplantable tumors in mice

A study was conducted on the activity exerted by prolonged dietary supplementation with progressive amounts of retinoids on cell-mediated immune responses and the growth of transplantable tumors in mice. A few groups of BALB/c mice received 0 (group C), 50 (group A 50), 200 (group A 200), 500 (group A 500), and 1,000 (group A 1000) IU retinol palmitate/mouse/day in drinking water for 150 days. At progressive intervals mice from each group were tested for proliferative responses to concanavalin A (Con A), Escherichia coli lipopolysaccharide, interleukin-2, and interferon-gamma release to Con A. Ten mice from each group were also challenged with the 90-100% tumor-inducing dose of 3 distinct transplantable tumors. At the end of the experiment the principal organs were histologically examined, and the accumulation of vitamin A was evaluated. In groups A 200, A 500, and A 1000, an increase in the proliferative responses and production of lymphokines as compared to those in group C occurred after 60-90 days, but vanished after 150 days. The takes of the 3 tumors were impaired when the challenges were performed on days 75 and 150. This enhancement of distinct functions of cellular reactivity and resistance to transplantable tumors showed a linear relationship with the amount of supplemental retinol palmitate for the first 60-90 days. After 150 days, however, these enhancement effects vanished or tended to decrease.

[Microbiological-clinical study on the efficacy of a new antibiotic: teicoplanin]

Teicoplanin is a new antibiotic isolated from the fermentation broth of Actinoplanes teichomyceticus nov. sp. It's a glycopeptide antibiotic belonging to the same family as vancomycin, active against Gram-positive bacteria. The antimicrobial activity of this drug was evaluated in 32 patients suffering from different infections due to Gram-positive bacteria. Among the 36 Gram-positive microorganisms isolated, 15 staphylococci were methicillin resistant, 10 were sensitive, 1 was intermediate and for another one the methicillin susceptibility was not evaluated. After the treatment with teicoplanin, cure and improvement occurred in 26 cases (81%), in 2 cases the therapy failed (6%), in 2 cases there was a relapse and 2 cases were not evaluable. From this clinical study Teicoplanin results safe and effective in the therapy of Gram-positive infections.

Adhesion of Proteus species to various cell types

Pathogenic and saprophytic Proteus strains from the urine of patients with urinary tract infections and healthy adults respectively were evaluated with regard to their ability to adhere in vitro to homologous cells (uroepithelial cells from urinary sediment and cultured WISH cells) and heterologous cells (RK-13 and MDCK cells). The effect on attachment of pretreating bacteria with subinhibitory concentrations of piperacillin and sagamicin was also determined for one sensitive and one resistant strain. Fifty percent of the pathogenic Proteus strains demonstrated good adherence to human urinary epithelial cells, whereas saprophytic strains did not adhere. There was a lower rate of attachment to culture cells. Piperacillin and sagamicin in subinhibitory concentrations caused a decrease in the attachment of the sensitive Proteus strain.

Natural macrophage cytotoxicity against Trichomonas vaginalis is mediated by soluble lytic factors

Mechanisms of lysis of the extracellular protozoan Trichomonas vaginalis by uninduced resident macrophages were analyzed. Supernatants obtained by culturing such macrophages with T. vaginalis were cytotoxic for the protozoa in a dose-dependent manner. Supernatants from macrophages cultured alone were cytotoxic at lower levels, whereas those obtained from T. vaginalis alone and from macrophages cultured with unrelated cells (B77) were not cytotoxic. Cytotoxic activity appeared after 4 h of contact between effectors and target cells and reached a plateau at 18 to 24 h. Microtubule disrupting agents (colchicine and vinblastine) enhanced protozoan lysis, whereas cytochalasin B, an inhibitor of microfilaments, completely blocked T. vaginalis lysis. Treatment of macrophages with protein synthesis inhibitors (cycloheximide and puromycin) impaired effector cytotoxicity. Lytic activity remained after dialysis of supernatants, treatment with 10% bovine fetal serum, and treatment at 56 degrees C for 1 h, but it was completely prevented by treatment at 90 degrees C for 10 min. In conclusion, our data show that natural cytotoxicity against T. vaginalis is performed by normal resident macrophages through the release of at least two heterogeneous soluble factors.

Comparison between five methods for the separation of IgM

Five serum fractionation methods were examined with regard to their suitability for use in the demonstration of specific IgM antibodies. It was found that Protein A - Sepharose CL - 4B chromatography leads to higher IgM recovery than absorption with whole Staphylococcus aureus (58% as opposed to 40%). It is also cheaper, since this absorbent can be reused. Contamination with 2-5% IgG and about 70% IgA is encountered with both methods. Quaternary aminoethyl (QAE) - Sephadex chromatography gives excellent IgM recovery (97%) and its cost and execution time are the lowest. IgG and IgA residues are 2% and 53% respectively. Ultrafiltration results in poorer recovery of IgM (31%). However, the sample volume can be brought back to its initial value, or concentrated still further. IgG and IgA residues are 2% and 14%. The cost of the method and the time needed for its execution are relatively high. Gel chromatography is the only method to give a completely IgG- and IgA-free IgM fraction. The percentage of IgM recovered varies in accordance with the ratio between the volume of the sample and that of the column. Very high values may be obtained, but at the expense of heavy dilution. The cost is low, but the method requires a considerable amount of time. In short, none of the five methods is clearly superior to the others. Whether or not a given method is chosen will thus depend on the relative importance attached to the percentage of IgM recovered, the presence or otherwise of IgA, sample dilution, cost, and rapidity of execution.

[Toxoplasmosis: comparative serological diagnosis (direct agglutination, complement fixation, hemagglutination inhibition tests) in order to attempt to clarify the diverse periods of infection in man]

Large diffusion of human toxoplasmotic infection and consequent injuries that, sometimes, occur in pregnancy and to the newborn, have been and are principal stimulus to study and to set several diagnostic means to specify, directly or indirectly, acute infection and acquired immunity. Serological methods are, at least till now, the best diagnostic means; among these, we have selected 3 methods: IHA (Behring), CF (I.S.M.) and DA (Bio-Mérieux); with which have been tested 125 sera (selected randomly). Obtained results have been elaborated statistically according to some interpretative perspectives which have been considered the most significant. Da test, that had a propensity to understimulation of serum-positive cases, would show a good sensibility about acute or recent infections and would be positive more difficulty about past infections. IHA test, on the contrary, that showed the greatest percentage of erroneously positive results, had, on the whole, a opposite propensity, but it would seem, with some reservations, also adaptable to the search of acute infections. CF test, rather complicated and long, would seem most versatile of three tests fitting well both to the search of past immunity and to serological diagnosis of acute infection, thanks to the new TTE antigen use.

[Assay of IgA specific anti-Trichomonas vaginalis in vaginal secretions by indirect immunofluorescence]

30 vaginal secreta of women affected by acute and chronic trichomoniasis from the Gynaecological Hospital S. Anna of Turin were examined. In the same secreta the specific IgA anti Trichomonas vaginalis were detected using indirect immunofluorescence and titered on LC-Partigen IgA immunodiffusion plates. Only in 30% of these cases a correlation between immunodiffusion and fluorescence test resulted.

[Vaginal bacterial flora under normal conditions and in frequently encountered gynecological pathologies]

The bacterial flora of the female reproductive tract is a central point for the study of infectious diseases in obstetrics and gynecology. The vaginal flora contains a large variety of bacterial species, including both aerobic and anaerobic organisms. The reading of the cultures obtained from vaginal specimens in women with genital tract infections is often hard, because some organisms which are normally present in vagina may sometimes involve infectious processes. Bacterial flora was studied in 126 healthy women, in 120 with symptoms of vaginitis, in 28 with inflammation of the cervix and in 102 women previously treated for vaginitis. Comparison among the groups shows little differences in the microbial population between healthy women and patients with genital tract infections. The use of a questionnaire and the obstetrical examination were very important. As quantitative studies are fundamental, the use of methods for semiquantitative bacteriology at least have been necessary to evaluate relationships among vaginal organisms.

[The mechanism of action of aminoglycosides]

The mechanism of action of aminoglycosides depends on the inhibition of polypeptide synthesis. In fact, some of them such as Streptomycin, Sisomicin and Gentamicin are believed to cause codon misreading, by increasing the incorporation of certain aminoacids into polypeptide in the ribosome-polyribonucleotide system. Their primary site of action seems to be located in the bacterial ribosome system. Experiments with Sisomicin showed that this antibiotic arrest cell growth, aminoacid incorporation and Beta-galactosidase synthesis, but not incorporation of uracil in ribonucleic acid in E. coli cultures. When polypeptide synthesis is directed by endogenous messenger in cell-fre extracts, the antibiotic stimulates the incorporation of some amino acids into protein.

Microbiological research on specimens (dusts) drawn from the Holy Shroud

The Holy Shroud is a relic of great historical importance that, according to catholic tradition, represents the "Sudarium" i.e. the "Sindon" of Jesus Christ. By several techniques, the most recent studies try to establish a well defined dating of the Holy Shroud. In addition an attempt is also made to find out the best mean to preserve the relic. We have to this purpose performed microbiological tests on specimens (Dusts) from the Holy Shroud establishing the microbic content in various spots. Besides few exceptions, the bacteria and fungi found on the Shroud and related objects are common and spread in all the areas examined.

[Fosfomycin, lysine-fosfomycin, arginine-fosfomycin: antibacterial activity in vitro]

The antibacterial activity of NaFosfomicin and of two of its aminoacidic derivatives -Lisin-Fosfomycin and Arginin-Fosfomycin- has been determined "in vitro" as MICs and MBCs, on different groups of Bacteria. The results obtained were then statistically analyzed - according to the "t of Student" - in a comparative evaluation of the values between NaFosfomycin-Lisin-Fosfomycin (F-LF); NaFosfomycin-Arginin-Fosfomycin (F-AF); Lisin-Fosfomycin-Arginin-Fosfomycin (LF-AF). From these comparisons, the data found demonstrated no significant differences among the three compounds, for Proteus, Coliforms and Pseudomonas groups, while Salmonella and Staphylococcus Genera showed good differences (P less than 0.05) from the comparison F-AF.

[Blood protein, iron and copper, and leukocyte alkaline phosphatase in lymphoma]

An assessment was made of the importance of certain laboratory data as diagnostic and prognostic parameters in 34 cases of Hodgkin and non-Hodgkin lymphoma. The results of other workers are referred to by way of comparison.

Variability of immune response induced by bacteria treated with subminimal inhibitory concentrations of fosfomycin

Experiments were conducted to explore the possibility that bacterial strains treated with subminimal inhibitory concentrations (sub-MICs) of fosfomycin might induce immune responses different from those induced by intact, untreated bacteria. A preliminary study was done with a strain of Salmonella wien. The immune response in rabbits immunized with bacteria that had been exposed to either the sub-MIC or the minimal inhibitory concentration (MIC) of fosfomycin was compared with that in rabbits immunized with S. wien not exposed to the drug. The titers of antibody to S. wien in rabbits immunized with abnormal, sub-MIC-treated bacteria were higher than those in rabbits immunized with either MIC-treated or untreated S. wien. This difference was seen not only with the total antigen of Salmonella but also with somatic (O) and flagellar (H) antigens.

[Antibiotic resistance transmissible in "minor" Salmonella strains recently isolated in the Piedmont region]

The presence of R factors in one hundred (100 strains of Salmonella, recently isolated in Piedmont Region, has been investigated. The resistance to 9 antibiotics has been determined for these strains. 83 proved resistant to one or more antibiotics and in particular 57 of these proved to be multiresistant. Only 18 R factors were put in evidence, 13 of these belonging to Salmonella wien. The majority of the R factors found were present in strains of Salmonella isolated from healthy carriers.

[Influence of composition of the culture media on the in vitro determination of the bacterial sensitivity to sulfonamides, trimethoprim and cotrimoxazole]

The difficulties concerning the interpretation of results of susceptibility tests to sulphonamides, trimethoprim, co-trimoxazole have been investigated. The zones of inhibition produced by discs containing these drugs are peculiar since frequently they contain a light bacterial growth and small colonies. Therefore the real sensitivity or resistance of the microorganism is questionable. Susceptibility tests performed on media of different composition, have shown that the phenomenon is chiefly due to the presence in the medium of thymidine and methionine. Both the substances are end-products of the metabolic pathway on which act sulphonamides, trimethoprim, co-trimoxazole. When they are in the medium, they can be available for the bacteria in spite of the inhibition caused by the mentioned drugs.

Genetic control of Trichomonas vaginalis infection. I. Resistance or susceptibility among different mouse strains

Susceptibility of different strains of mice to infection with Trichomonas vaginalis was determined. Striking strain differences in susceptibility to T. vaginalis inoculum were observed in different mouse strains suggesting that susceptibility is under control of genes mapping mainly outside the major histocompatibility complex.