Raw and processed data used in the simultaneous analysis of electrical characteristics and microstructure of crystallised PEDOT:PSS based OECTs under strain

Here is presented raw and analysed data collected during study of the evolution, with uniaxial stretching, of the electrical and microcrystalline characteristics of polystyrene sulfonate doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) organic electrochemical transistors (OECTs). X-ray diffraction data from GIWAXS measurements of the PEDOT:PSS material, performed at the SOLEIL light source are presented in raw and partially analysed forms. Current-voltage data, collected concurrently with the GIWAXS data, are also presented, and the evolution of the transconductance of the OECT devices with stretching is shown. GIWAXS data are only examined along the qz specular reflection ridge, and scans along this ridge are extracted and presented. However, the off-specular data may also be of interest to readers and is therefore made available here in its entirety.

Monitoring of cell layer coverage and differentiation with the organic electrochemical transistor

High resolution monitoring of cell layer integrity with the OECT was up until now, limited to high resistance, barrier tissue type cells. In this work, the sensitivity and versatility of the device is expanded to monitor all adherent cell types.

[Strategies for bacterial virulence genes identification]

One of the recent preoccupations of medical microbiology has been to characterise the mechanisms of virulence of bacterial pathogens at the molecular level. One hundred years after Koch, Stanley Falkow proposed a new, molecular version of Koch's postulates to define avirulence gene: (a) the gene confers a certain phenotype to the studied bacteria, (b) inactivation of the gene abolishes the phenotype, (c)reintroduction of the gene restores the wild type to the mutant. Although this strategy, based upon mutagenesis and the use of experimental models, allows the identification of many genes, it is not comprehensive. Other methods can be used to complete the identification of virulence factors such as differential expression, either at the level of transcription (transcriptome) or at the level of protein expression (proteome). All these techniques are now supported by the data from complete genome sequencing projects. The pool of information obtained from these approaches allows the definition of the 'virulome', which is the assembly of factors a pathogen requires for virulence. Understanding the virulome will open the way to the development of new strategies for vaccination or the development of new generation of antimicrobials.

Chemo-enzymatic synthesis of the Galili epitope Gal(alpha)(1-->3)Galbeta(1-->4)GlcNAc on a homogeneously soluble PEG polymer by a multi-enzyme system

The alpha-Gal trisaccharide Gal(alpha)(1-->3)Galbeta(1-->4)GlcNAc 11 was synthesized on a homogeneously soluble polymeric support (polyethylene glycol, PEG) by use of a multi-enzyme system consisting of beta-1,4-galactosyltransferase (EC 2.4.1.38), alpha-1,3-galactosyltransferase (EC 2.4.1.151), sucrose synthase (EC 2.4.1.13) and UDP-glucose-4-epimerase (EC 5.1.3.2). In addition workup was simplified by use of dia-ultrafiltration. Thus the advantages of classic chemistry/enzymology and solid-phase synthesis could be united in one. Subsequent hydrogenolytic cleavage afforded the free alpha-Gal trisaccharide.

Aromatic compound-dependent Brucella suis is attenuated in both cultured cells and mouse models

The aroC gene of the facultative intracellular pathogen Brucella suis was cloned and sequenced. The cloned aroC gene complements Escherichia coli and Salmonella enterica serovar Typhimurium aroC mutants. A B. suis aroC mutant was found to be unable to grow in a defined medium without aromatic compounds. The mutant was highly attenuated in tissue culture (THP1 macrophages and HeLa cells) and murine virulence models.

Reduction of selenite and detoxification of elemental selenium by the phototrophic bacterium Rhodospirillum rubrum

The effect of selenite on growth kinetics, the ability of cultures to reduce selenite, and the mechanism of detoxification of selenium were investigated by using Rhodospirillum rubrum. Anoxic photosynthetic cultures were able to completely reduce as much as 1. 5 mM selenite, whereas in aerobic cultures a 0.5 mM selenite concentration was only reduced to about 0.375 mM. The presence of selenite in the culture medium strongly affected cell division. In the presence of a selenite concentration of 1.5 mM cultures reached final cell densities that were only about 15% of the control final cell density. The cell density remained nearly constant during the stationary phase for all of the selenite concentrations tested, showing that the cells were not severely damaged by the presence of selenite or elemental selenium. Particles containing elemental selenium were observed in the cytoplasm, which led to an increase in the buoyant density of the cells. Interestingly, the change in the buoyant density was reversed after selenite reduction was complete; the buoyant density of the cells returned to the buoyant density of the control cells. This demonstrated that R. rubrum expels elemental selenium across the plasma membrane and the cell wall. Accordingly, electron-dense particles were more numerous in the cells during the reduction phase than after the reduction phase.

A homologue of the Agrobacterium tumefaciens VirB and Bordetella pertussis Ptl type IV secretion systems is essential for intracellular survival of Brucella suis

Analysis of a TnblaM mutant of Brucella suis 1330, identified as being unable to multiply in Hela cells, allowed us to identify a 11 860 bp region of the B. suis genome encoding a type IV secretion system, homologous to the VirB system of Agrobacterium tumefaciens and the Ptl system of Bordetella pertussis. DNA sequence revealed 12 open reading frames (ORFs) encoding homologues of the 11 VirB proteins present in the pTi plasmid of Agrobacterium with a similar genetic organization, and a twelfth ORF encoding a putative lipoprotein, homologous to a protein involved in mating pair formation during bacterial conjugation and to adhesins used by Pseudomonas species to bind to plant roots. Phylogenetic trees based on the sequences of VirB4 and VirB9 protein homologues suggest that evolution of the systems from DNA transfer towards protein secretion did not stem from a single event but that the protein secretion systems have evolved independently. Four independent mutants in virB5, virB9 or virB10 were highly attenuated in an in vitro infection model with human macrophages. The virulence was restored by complementation with a plasmid containing the full virB region. The virB region appears to be essential for the intracellular survival and multiplication of B. suis.

[Perspectives and hopes in infectious pathology]

Over the last few decades, changes in socio-economic conditions and social practices as well as aggressive therapy of many diseases have led to the emergence of new infectious pathologies. These new pathologies are either associated with newly identified microbial species or the emergence of known microbes which have encountered new environments in which they are able to cause disease. Recent progress has allowed us to understand the mechanisms by which these pathogens express their virulence and will certainly allow us to diagnose and treat these infections more efficiently in the future.

Unconventional genomic organization in the alpha subgroup of the Proteobacteria

Pulsed-field gel electrophoresis was used to analyze the genomic organization of 16 bacteria belonging or related to the family Rhizobiaceae of the alpha subgroup of the class Proteobacteria. The number and sizes of replicons were determined by separating nondigested DNA. Hybridization of an rrn gene probe was used to distinguish between chromosomes and plasmids. Members of the genus Agrobacterium all possess two chromosomes, and each biovar has a specific genome size. As previously demonstrated for Agrobacterium tumefaciens C58, the smaller chromosomes of Agrobacterium biovar 1 and Agrobacterium rubi strains appear to be linear. The genomes of Rhizobium strains were all of similar sizes but were seen to contain either one, two, or three megareplicons. Only one chromosome was present in the member of the related genus Phyllobacterium. We found one or two chromosomes in Rhodobacter and Brucella species, two chromosomes in Ochrobactrum anthropi, and one chromosome in Mycoplana dimorpha and Bartonella quintana; all of these genera are related to the Rhizobiaceae. The presence of multiple chromosomes is discussed from a phylogenetic and taxonomic point of view.

Differences in chromosome number and genome rearrangements in the genus Brucella

We have studied the genomic structure and constructed the SpeI, PacI and I-CeuI restriction maps of the four biovars of the pathogenic bacterium Brucella suis. B. suis biovar 1 has two chromosomes of 2.1 Mb and 1.15 Mb, similar to those of the other Brucella species: B. melitensis, B. abortus, B. ovis and B. neotomae. Two chromosomes were also observed in the genome of B. suis biovars 2 and 4, but with sizes of 1.85 Mb and 1.35 Mb, whereas only one chromosome with a size of 3.1 Mb was found in B. suis biovar 3. We show that the differences in chromosome size and number can be explained by rearrangements at chromosomal regions containing the three rrn genes. The location and orientation of these genes confirmed that these rearrangements are due to homologous recombination at the rrn loci. This observation allows us to propose a scheme for the evolution of the genus Brucella in which the two chromosome-containing strains can emerge from an hypothetical ancestor with a single chromosome, which is probably similar to that of B. suis biovar 3. As the genus Brucella is certainly monospecific, this is the first time that differences in chromosome number have been observed in strains of the same bacterial species.

Genome structure and phylogeny in the genus Brucella

PacI and SpeI restriction maps were obtained for the two chromosomes of each of the six species of the genus Brucella: B. melitensis, B. abortus, B. suis, B. canis, B. ovis, and B. neotomae. Three complementary techniques were used: hybridization with the two replicons as probes, cross-hybridization of restriction fragments, and a new mapping method. For each type strain, a unique I-SceI site was introduced in each of the two replicons, and the location of SpeI sites was determined by linearization at the unique site, partial digestion, and end labeling of the fragments. The restriction and genetic maps of the six species were highly conserved. However, numerous small insertions or deletions, ranging from 1 to 34 kb, were observed by comparison with the map of the reference strain of the genus, B. melitensis 16M. A 21-kb Spel fragment specific to B. ovis was found in the small chromosome of this species. A 640-kb inversion was demonstrated in the B. abortus small chromosome. All of these data allowed the construction of a phylogenetic tree, which reflects the traditional phenetic classification of the genus.

Investigation of the Actinobacillus actinomycetemcomitans genome by pulsed field gel electrophoresis

Pulsed field gel electrophoresis was used to investigate nineteen strains of Actinobacillus actinomycetemcomitans. The genome was found to contain a single chromosome whose size we estimate to be 2300 kb from the sum of restriction fragments generated with rare cutting endonucleases. We detected the presence of large plasmids with sizes ranging from 35 to 300 kb. In some strains, extrachromosomal elements constitute over 20% of the total genome. Comparison of the profiles of ApaI digests of the 19 strains showed a high degree of polymorphism with 13 different profiles, providing a new tool for epidemiological studies.

[Enzyme determination in vitro of inhibitor activity of beta-lactamase from tazobactam. Comparison with high performance liquid chromatography]

We developed an enzymatic method using nitrocefin to assay tazobactam in vitro. Tazobactam was incubated with TEM-1 beta-lactamase. Then, residual beta-lactamase activity was assayed by adding nitrocefin. This activity corresponded indirectly to the initial concentration of tazobactam. Within-assay, between-assay and accuracy coefficients of variation were below 15%. The correlation coefficients between enzymatic method and high performance liquid chromatography (the reference method)was 0.98. The enzymatic method is rapid, easy to perform and should be applied to daily clinical practice.

[A genetic and molecular biological study of the pathogenicity factors in Brucella]

The use of gene engineering techniques made it possible to obtain strain GSE830, capable of a higher level of expression of the gene of 38-kD protein in immunoblotting with sheep and rabbit antibrucellar sera in comparison with the expression of this gene of other Escherichia coli strains, containing recombinant plasmids with this gene. Due to the presence of the gene of 38-kD protein, recombinant E.coli strains were capable of survival in macrophage-like cell line U937 3.6-6.3 times more effectively. The model of interaction of Brucella pathogenic and nonpathogenic species with HeLa cells was studied. The bank of insertion mutants of B.suis virulent strain 1330 was studied with the use of transposon TnblaM. Out of 380 insertion mutants, 7 clones expressing beta-lactamase and having decreased capacity for multiplication in HeLa cells 48 hours after inoculation were selected. Detailed analysis revealed that 3 of them had lower adhesive capacity, 1 of them had lower invasive capacity and 3 other mutants were less capable of intracellular multiplication in HeLa cells than the initial B.suis strain 1330. All these 7 mutants had different sites of TnblaM insertion into the chromosome of B.suis strain 1330.

Polymorphism in Brucella strains detected by studying distribution of two short repetitive DNA elements

Thirty-four Brucella reference or field strains representing all the species and biovars were studied by repetitive element sequence-based PCR, a PCR using primers complementary to two enterobacterial short repetitive sequences: repetitive extragenic palindromic and enterobacterial repetitive intergenic consensus sequences. All the stains showed a positive amplification, suggesting that the Brucella genome contains such sequences. Repetitive extragenic palindromic PCR was less discriminating than enterobacterial repetitive intergenic consensus PCR in terms of distinguishing strains, but a combination of the two methods was able to distinguish all the isolates, except for some strains belonging to biovars 3 and 9 of Brucella abortus. Repetitive element sequence-based PCR appears to be a simple and useful method for the study of brucellosis epidemiology.

In-vitro evaluation of beta-lactamase inhibition by latamoxef and imipenem

The in-vitro 50% inhibitory concentrations (IC50s) of latamoxef and imipenem against a set of plasmid-mediated beta-lactamases including TEM-1, TEM-3, TEM-5 and TEM-10 were determined by an enzymatic method using nitrocefin as substrate. The IC50s of both antibiotics against extended-spectrum beta-lactamases were below 0.2 mg/L. The conventional spectrum beta-lactamase TEM-1 was not inhibited by either antibiotic at the highest concentration tested. Except for TEM-10 for which the IC50s of the two antibiotics were the same, imipenem showed significantly greater activity than latamoxef against TEM-3 and TEM-5. Clavulanic acid taken as a control demonstrated greater and wider inhibitory activity, but on the other hand it has no significant antibiotic activity.

Study of the organization of the genomes of Escherichia coli, Brucella melitensis and Agrobacterium tumefaciens by insertion of a unique restriction site

Tn5Map, a Tn5 derivative containing the 18 bp I-SceI site, was delivered from a RP4-mobilizable, RK6-derived suicide vector to Escherichia coli HB101, Brucella melitensis and Agrobacterium tumefaciens C58, which all lack natural I-SceI sites in their genomes. Digestion of the DNA from Tn5Map-containing strains and analysis by pulsed-field gel electrophoresis (PFGE) revealed that these derivatives contained a single transposon insertion. These digests also gave direct and independent proof for the single circular chromosome of E. coli, and for the presence of two circular chromosomes in B. melitensis and of a circular and a linear chromosome in A. tumefaciens C58 (which also contains two large circular plasmids). This rapid and versatile technique is potentially applicable to the study of the genomic organization in all Gram-negative bacteria which support Tn5 transposition. Moreover, linearization of circular replicons could be the first step for a rapid method of physical mapping.

An enzymatic method for assaying sulbactam in human serum: comparison with high performance liquid chromatography

An enzymatic method using nitrocefin as substrate was developed to assay sulbactam in human serum. Serum containing sulbactam was incubated with purified titrated TEM-1 beta-lactamase and nitrocefin was then added to the mixture to determine the remaining beta-lactamase activity and consequently the concentration of sulbactam. Assays were carried out on five patients with pulmonary infections receiving sulbactam plus amoxycillin iv. The values for serum sulbactam concentrations determined by the enzymatic method were compared with those determined by high performance liquid chromatography (HPLC). The correlation coefficient was 0.990 for serum sulbactam concentrations below 15 mg/L.

Genetic variability among Chlamydia trachomatis reference and clinical strains analyzed by pulsed-field gel electrophoresis

Pulsed-field gel electrophoresis (PFGE) was applied to Chlamydia trachomatis reference strains representing each of the 18 serovars and to 29 clinical isolates from genital specimens collected in Bordeaux, France, or Malmö, Sweden. Comparison of the fingerprint patterns of the reference strains revealed a high level of polymorphism of the total DNA when SmaI was used (14 profiles), whereas the other enzymes, Sse8387I and ApaI, showed fewer differences. Some serovars, considered to be closely related on the basis of their antigenic determinants located on the major outer membrane protein (MOMP), such as D and Da or I and Ia, were shown to be different after PFGE of their genomic DNAs. However, serovars B and Ba and serovars L2 and L2a had identical patterns after analysis with the three endonucleases. When applied to clinical isolates, which were typed by restriction fragment length polymorphism analysis of the MOMP gene, PFGE allowed the detection of intragenotype polymorphisms and showed the identity of two strains successively isolated from the same patient. This technique seems to be an efficient tool for epidemiological studies when used in addition to serotyping or genotyping by restriction fragment length polymorphism analysis of the MOMP gene.

Epidemiological study by pulsed-field gel electrophoresis of an outbreak of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a geriatric hospital

Twelve cases of infections caused by extended-spectrum beta-lactamase (ESBla)-producing Klebsiella pneumoniae were reported between August 1991 and March 1993 in the Geriatric Department of the Nimes University Hospital, where these bacterial had not been previously isolated. Restriction profiles of total genomic DNAs cleaved by XbaI and SpeI were compared by pulsed-field gel electrophoresis. The strains that were tested included the 12 isolates from K. pneumoniae-infected patients, strains recovered from rectal swabs of asymptomatic patients in the same ward, and strains isolated in other hospitals in Nîmes at the same time. The restriction profiles of the 12 isolates and those recovered from asymptomatic patients in the same ward were very similar. Over a period of more than 1 year, extended-spectrum beta-lactamases were not detected in K. pneumoniae isolates with restriction patterns different from that of the epidemic strain. It seems, therefore, that there was no transfer of a plasmid or a gene coding for ESBla to strains of K. pneumoniae that were different from the epidemic strain. At the same time, ESBla-producing K. pneumoniae isolates exhibiting restriction endonuclease profiles very different from that of the epidemic strain were isolated from other hospitals in Nîmes. None of these strains caused an outbreak. Pulsed-field gel electrophoresis, which allows precise characterization of strains beyond the species level, is a useful tool for studying the ESBla-producing K. pneumoniae strains involved in nosocomial outbreaks.

Identification and sequence analysis of IS6501, an insertion sequence in Brucella spp.: relationship between genomic structure and the number of IS6501 copies

An insertion sequence (IS) element of Brucella ovis, named IS6501, was isolated and its complete nucleotide sequence determined. IS6501 is 836 bp in length and occurs 20-35 times in the B. ovis genome and 5-15 times in other Brucella species. Analysis of the junctions at the sites of insertion revealed a small target site duplication of four bases and inverted repeats of 17 bp with one mismatch. IS6501 presents significant similarity (53.4%) with IS427 identified in Agrobacterium tumefaciens, suggesting a common ancestral sequence. A long ORF of 708 bp was identified encoding a protein with a predicted molecular mass of 26 kDa and sharing sequence identity with the hypothetical protein 1 of A. tumefaciens and with the transposase of Mycobacterium tuberculosis. IS6501 is present in all Brucella strains we have tested. Restriction fragment length polymorphism of reference and field strains of two species (B. melitensis and B. ovis) was studied using either pulsed field gel electrophoresis (PFGE) on XbaI-digested DNA or hybridization of EcoRI-digested DNA using IS6501 as a probe. The genome of B. melitensis biovar 3 contains about 10 IS copies per genome and field strains of the same species could not be distinguished either by IS hybridization or by XbaI (PFGE) restriction patterns. In contrast, the number of IS copies in the B. ovis genome is around 30 and the different field strains can be differentiated by both methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Presence of one linear and one circular chromosome in the Agrobacterium tumefaciens C58 genome

Analysis of the entire Agrobacterium tumefaciens C58 genome by pulsed-field gel electrophoresis (PFGE) reveals four replicons: two large molecules of 3,000 and 2,100 kb, the 450-kb cryptic plasmid, and the 200-kb Ti plasmid. Digestion by PacI or SwaI generated 12 or 14 fragments, respectively. The two megabase-sized replicons, used as probes, hybridize with different restriction fragments, showing that these replicons are two independent genetic entities. A 16S rRNA probe and genes encoding functions essential to the metabolism of the organism were found to hybridize with both replicons, suggesting their chromosomal nature. In PFGE, megabase-sized circular DNA does not enter the gel. The 2.1-Mb chromosome always generated an intense band, while the 3-Mb band was barely visible. After linearization of the DNA by X-irradiation, the intensity of the 3-Mb band increased while that of the 2.1-Mb remained constant. This suggests that the 3-Mb chromosome is circular and that the 2.1-Mb chromosome is linear. To confirm this hypothesis, genomic DNA, trapped in an agarose plug, was first submitted to PFGE to remove any linear DNA present. The plug was then recovered, and the remaining DNA was digested with either PacI or SwaI and then separated by PFGE. The fragments corresponding to the small chromosome were found to be absent, while those corresponding to the circular replicon remained, further proof of the linear nature of the 2.1-Mb chromosome.

Presence of two independent chromosomes in the Brucella melitensis 16M genome

Mapping the restriction fragments of the Brucella melitensis 16M genome with a new restriction endonuclease, PacI, which cut the DNA into only eight fragments, indicated that this species contains two unique and independent replicons of about 2,100 and 1,150 kb. Pulsed-field gel electrophoresis of intact DNA revealed two bands migrating the expected distances. These replicons were identified as two unique and independent chromosomes by the presence of rRNA operons and genes for heat shock proteins mapping to separate replicons.

DNA polymorphisms in methicillin-susceptible and methicillin-resistant strains of Staphylococcus aureus

Restriction fragment length polymorphisms in methicillin-susceptible and methicillin-resistant (MRSA) strains of Staphylococcus aureus isolated in the same hospital over a 4-month period were studied by using SmaI and ApaI digestion of genomic DNA and pulsed-field gel electrophoresis. Each of the 20 methicillin-susceptible strains had a unique SmaI pattern, but the 27 MRSA strains showed only seven SmaI patterns. More than half of the SmaI fragments in all of these seven patterns were identical, as were those in the patterns from two unrelated MRSA strains. Digestion with ApaI, which cuts staphylococcus DNA into at least twice as many fragments, confirmed the results obtained with SmaI. Lastly, the plasmid contents of MRSA strains showing identical SmaI and ApaI electrophoretic patterns were not identical. These results are interpreted as supporting the hypothesis that all MRSA strains arose from a single clone and emphasize the need to use several methods in epidemiological investigations of MRSA outbreaks.

Teicoplanin treatment of alkaline encrusted cystitis due to Corynebacterium group D2

Alkaline-encrusted cystitis (AEC) is a chronic inflammation of the bladder related to the gram-positive bacillus Corynebacterium Group D2. This germ is often resistant to many antibiotics and is particularly difficult to eradicate in the particular setting of AEC. The authors report two observations of AEC treated with the glycopeptid antibiotic teicoplanin, which led to permanent cure of AEC.

DNA polymorphism in strains of Listeria monocytogenes

DNA polymorphism in 35 Listeria monocytogenes strains belonging to serovars 1/2a, 1/2b, 1/2c, and 4b was studied by genomic DNA digestion. The restriction endonucleases ApaI and NotI, which cleave DNA at rare sequences, were used, and DNA fragments were analyzed by pulsed-field gel electrophoresis. Restriction fragment length polymorphism varied among different serovars and was used for epidemiological studies, but serovar 1/2c isolates could not be analyzed because their restriction patterns were indistinguishable. The genome sizes were calculated by addition of the sizes of the ApaI fragments and were found to be about 2,660 kb for serovar 1/2a strains, 2,640 kb for serovar 1/2b strains, and 2,710 kb for serovar 4b strains but only 2,340 kb for serovar 1/2c strains. This last group therefore appears to differ from the other serovar strains by the absence of restriction fragment length polymorphism and a chromosome that is 15% shorter, suggesting that strains of serovar 1/2c have quite recently emerged.

Physical map of the Brucella melitensis 16 M chromosome

We present the first restriction map of the Brucella melitensis 16 M chromosome obtained by Southern blot hybridization of SpeI, XhoI, and XbaI fragments separated by pulsed-field gel electrophoresis. All restriction fragments (a total of 113) were mapped into an open circle. The main difficulty in mapping involved the exceedingly high number of restriction fragments, as was expected considering the 59% G + C content of the Brucella genome. Several cloned genes were placed on this map, especially rRNA operons which are repeated three times. The size of the B. melitensis chromosome, estimated as 2,600 kb long in a previous study, appeared longer (3,130 kb) by restriction mapping. This restriction map is an initial approach to achieve a genetic map of the Brucella chromosome.

Use of low-frequency-cleavage restriction endonucleases for DNA analysis in epidemiological investigations of nosocomial bacterial infections

Epidemiological investigations of bacterial infections are generally based on multiple phenotypic markers that are often difficult to verify. A more general and reliable method is genomic DNA analysis by restriction endonucleases. However, the commonly used endonucleases produce too many fragments for correct separation by agarose electrophoresis. In contrast, simple electrophoretic patterns are obtained after genomic DNA digestion by low-frequency-cleavage restriction endonucleases and pulsed-field gel electrophoresis, making it easier to compare numerous strains from the same species. This technique was used to investigate an Acinetobacter calcoaceticus outbreak in a urologic department and bronchial colonization of artificially ventilated patients by Pseudomonas aeruginosa in an intensive care unit. The method allowed a clear distinction between epidemic and self-contaminating strains in these different epidemiological situations.

DNA polymorphism in strains of the genus Brucella

Preparations of DNA from 23 Brucella strains including 19 reference strains were compared by restriction endonuclease analysis. Pulsed-field gel electrophoresis resulted in optimal resolution of fragments generated by digestion with low-cleavage-frequency restriction enzymes such as XbaI. By this technique, five electrophoretypes were distinguished in five reference strains of the different species, i.e., B. abortus, B. melitensis, B. suis, B. canis, and B. ovis. Minor profile differences allowed us to discriminate between most biovars within a species. However, the differences in the DNA patterns of different field strains of biovar 2 of B. melitensis were not sufficient to serve as markers for epidemiological studies. From the XbaI fragments, we were able to estimate the size of the genomes of B. abortus 544T and B. melitensis 16 MT. This method revealed a relationship between DNA fingerprints, species, and pathovars which could shed light on problems concerning the classification and evolution of members of the genus Brucella.

Two cases of Mycobacterium haemophilum infection in a renal-dialysis unit

Two cases of Mycobacterium haemophilum infection in renal-transplant patients occurred in the same hospital department. This raised the possibility that infection may have been acquired in hospital.

Previously undescribed 6.6-kilobase R plasmid in penicillinase-producing Neisseria gonorrhoeae

A penicillin-resistant Neisseria gonorrhoeae strain was isolated. The resistance was due to the production of TEM-1 beta-lactamase encoded by a plasmid. This 6.6-kilobase plasmid was compared with the previously known 7.4- and 5.3-kilobase penicillin R plasmids of N. gonorrhoeae.

Mycobacterium haemophilum and mycobacterium xenopi associated infection in a renal transplant patient

The case is presented of a renal-transplant patient in Europe with a Mycobacterium haemophilum infection in association with M. xenopi infection. Clinical signs suggested the diagnosis of mycobacteriosis, which was confirmed by a skin biopsy. Despite antitubercular treatment which rapidly eliminated M. xenopi, the patient's condition did not improve until M. haemophilum was identified. Minimal inhibitory concentrations of various antimicrobial compounds showed a lack of efficacy of isoniazid, and rifampin had no clinical effect. The patient recovered only after careful surgical drainage of the lesions and the administration of minocycline. The pathogenesis of such mycobacterioses is discussed, with focus on the immunodepressive status which in our patient may have been partially induced by a cytomegalovirus reinfection.

In vitro immunosuppressive activity of gram-positive (Streptococcus pyogenes) peptidoglycan on mouse lymphocytes

A peptidoglycan fraction prepared from group-A streptococcus was assayed for in vitro mitogenicity on mouse lymphocytes. This fraction reduced considerably the uptake of radioactive thymidine both on unstimulated cell suspensions and on suspensions stimulated by T(PHA)- or B(LPS)-mitogens. The immunosuppression was induced by relatively moderate doses of the fraction, and was dose-dependent. Several experiments ruled out the possibility that these results could be due to a cytotoxicity of the fraction, or to a non-specific interference with the uptake or metabolism of the radioactive precursor. These results are coherent with the observations made in vivo on the mouse and previously published. It is suggested that the mechanism of the immunosuppression could be in relation with the capacity of this fraction to stimulate the reticulo-macrophagic system.

[Adherent cell and T lymphocyte cooperation for the "in vitro" production of Brucella-induced interferon by murine spleen cells (author's transl)]

Although Brucella is a good in vivo inducer of interferon, in vitro infection of murine spleen cells by Brucella suis has not, to the present time, led to in vitro synthesis. In the present work we show that normal spleen cells can however synthetize interferon in vitro when cultured together with adherent cells obtained from the spleens of syngeneic mice 45 min after in vivo inoculation. Induction and synthesis are thus shown to be distinct phenomena. Moreover soluble factors are shown to be involved in the induction phenomenon and T cells to be essential for synthesis. This in vitro brucella-induced interferon differs from in vivo brucella-induced interferon: its acid lability and its antigenic properties are characteristic of type II "immune" interferon.