Lactobacillus strains reduce the toxic effects of a subchronic exposure to arsenite through drinking water

The aim of the present study was to determine the efficacy of LAB strains in reducing the intestinal toxicity of arsenite [As(III)] and its tissue accumulation. For this purpose, Balb/c mice were randomly separated in four groups. One group received no treatment (control), one group received only As(III) (30 mg/L) via drinking water and the remaining two groups received As(III) via water and a daily dose of two LAB strains (Lactobacillus intestinalis LE1 and Lacticaseibacillus paracasei BL23) by gavage during 2 months. The results show that both strains reduce the pro-inflammatory and pro-oxidant response observed at the colonic level, partially restore the expression of the intercellular junction proteins (CLDN3 and OCLN) responsible for the maintenance of epithelial integrity, and increase the synthesis of the major mucin of the colonic mucus layer (MUC2), compared to animals treated with As(III) alone. Microbial metabolism of short-chain fatty acids also undergoes a recovery and the levels of fatty acids in the lumen reach values similar to those of untreated animals. All these positive effects imply the restoration of mucosal permeability, and a reduction of the marker of endotoxemia LPS binding protein (LBP). Treatment with the bacteria also has a direct impact on intestinal absorption, reducing the accumulation of As in the internal organs. The data suggest that the protective effect may be due to a reduced internalization of As(III) in intestinal tissues and to a possible antioxidant and anti-inflammatory activity of the bacteria through activation of pathways such as Nrf2 and IL-10. In vitro tests show that the protection may be the result of the combined action of structural and metabolic components of the LAB strains.

Intestinal homeostasis disruption in mice chronically exposed to arsenite-contaminated drinking water

Chronic exposure to inorganic arsenic [As(III) and As(V)] affects about 200 million people, and is linked to a greater incidence of certain types of cancer. Drinking water is the main route of exposure, so, in endemic areas, the intestinal mucosa is constantly exposed to the metalloid. However, studies on the intestinal toxicity of inorganic As are scarce. The objective of this study was to evaluate the toxicity of a chronic exposure to As(III) on the intestinal mucosa and its associated microbiota. For this purpose, BALB/c mice were exposed during 6 months through drinking water to As(III) (15 and 30 mg/L). Treatment with As(III) increased reactive oxygen species (43-64%) and lipid peroxidation (8-51%). A pro-inflammatory response was also observed, evidenced by an increase in fecal lactoferrin (23-29%) and mucosal neutrophil infiltration. As(III) also induced an increase in the colonic levels of pro-inflammatory cytokines (24-201%) and the activation of some pro-inflammatory signaling pathways. Reductions in the number of goblet cells and mucus production were also observed. Moreover, As(III) exposure resulted in changes in gut microbial alpha diversity but no differences in beta diversity. This suggested that the abundance of some taxa was significantly affected by As(III), although the composition of the population did not show significant alterations. Analysis of differential taxa agreed with this, 21 ASVs were affected in abundance or variability, especially ASVs from the family Muribaculaceae. Intestinal microbiota metabolism was also affected, as reductions in fecal concentration of short-chain fatty acids were observed. The effects observed on different components of the intestinal barrier may be responsible of the increased permeability in As(III) treated mice, evidenced by an increase in fecal albumin (48-66%). Moreover, serum levels of Lipopolysaccharide binding proteins and TNF-α were increased in animals treated with 30 mg/L of As(III), suggesting a low-level systemic inflammation.

Improving bitter pit prediction by the use of X-ray fluorescence (XRF): A new approach by multivariate classification

Bitter pit (BP) is one of the most relevant post-harvest disorders for apple industry worldwide, which is often related to calcium (Ca) deficiency at the calyx end of the fruit. Its occurrence takes place along with an imbalance with other minerals, such as potassium (K). Although the K/Ca ratio is considered a valuable indicator of BP, a high variability in the levels of these elements occurs within the fruit, between fruits of the same plant, and between plants and orchards. Prediction systems based on the content of elements in fruit have a high variability because they are determined in samples composed of various fruits. With X-ray fluorescence (XRF) spectrometry, it is possible to characterize non-destructively the signal intensity for several mineral elements at a given position in individual fruit and thus, the complete signal of the mineral composition can be used to perform a predictive model to determine the incidence of bitter pit. Therefore, it was hypothesized that using a multivariate modeling approach, other elements beyond the K and Ca could be found that could improve the current clutter prediction capability. Two studies were carried out: on the first one an experiment was conducted to determine the K/Ca and the whole spectrum using XRF of a balanced sample of affected and non-affected 'Granny Smith' apples. On the second study apples of three cultivars ('Granny Smith', 'Brookfield' and 'Fuji'), were harvested from two commercial orchards to evaluate the use of XRF to predict BP. With data from the first study a multivariate classification system was trained (balanced database of healthy and BP fruit, consisting in 176 from each group) and then the model was applied on the second study to fruit from two orchards with a history of BP. Results show that when dimensionality reduction was performed on the XRF spectra (1.5 - 8 KeV) of 'Granny Smith' apples, comparing fruit with and without BP, along with K and Ca, four other elements (i.e., Cl, Si, P, and S) were found to be deterministic. However, the PCA revealed that the classification between samples (BP vs. non-BP fruit) was not possible by univariate analysis (individual elements or the K/Ca ratio).Therefore, a multivariate classification approach was applied, and the classification measures (sensitivity, specificity, and balanced precision) of the PLS-DA models for all cultivars evaluated ('Granny Smith', 'Fuji' and 'Brookfield') on the full training samples and with both validation procedures (Venetian and Monte Carlo), ranged from 0.76 to 0.92. The results of this work indicate that using this technology at the individual fruit level is essential to understand the factors that determine this disorder and can improve BP prediction of intact fruit.

Lipoteichoic acid depletion in Lactobacillus impacts cell morphology and stress response but does not abolish mercury surface binding

Lipoteichoic acid (LTA) is a key component of the cell wall of most Gram-positive bacteria and plays many structural and functional roles. In probiotic lactobacilli, the function of LTA in mediating bacteria/host cross-talk has been evidenced and it has been postulated that, owing to its anionic nature, LTA may play a role in toxic metal sequestration by these bacteria. However, studies on this last aspect employing strains unable to synthesise LTA are lacking. We have inactivated the LTA polymerase encoding gene ltaS in two different Lactobacillus plantarum strains. Analysis of LTA contents in wild-type and ltaS mutant strains corroborated the role of this gene as a major contributor to LTA synthesis in L. plantarum. The mutant strains displayed strain-dependent anomalous cell morphologies that resulted in elongated or irregular cells with aberrant septum formation. They also exhibited higher sensitivity to several stresses (osmotic and heat) and to antimicrobials that target the cell wall. The toxicity of inorganic [(Hg(II)] and organic mercury (methyl-Hg) was also increased upon ltaS mutation in a strain-dependent manner. However, the mutant strains showed 0 to 50% decrease in their capacity of Hg binding compared to their corresponding parental strains. This result suggests a partial contribution of LTA to Hg binding onto the cell surface that was dependent on the strain and the Hg form.

Effects of Three Irrigation Strategies on Gas Exchange Relationships, Plant Water Status, Yield Components and Water Productivity on Grafted Carménère Grapevines

In the Chilean viticultural industry, Carménère is considered an emblematic cultivar that is cultivated mainly in arid and semi-arid zones. For this reason, it is necessary to use precise irrigation scheduling for improving water use efficiency (WUE), water productivity (WP), yield and wine quality. This study evaluated the effects of three deficit irrigation strategies on gas exchange variables, WUE, WP and yield components in a drip-irrigated Carménère vineyard growing under semi-arid climatic conditions during two consecutive seasons (2011/12 and 2012/13). The irrigation strategies were applied in completely randomized design from fruit set (S) to harvest (H). The first irrigation strategy (T1) involved continuous irrigation at 100% of actual evapotranspiration (ETa) from S to the veraison (V) period and at 80% of ETa from V to H. The second irrigation strategy (T2) involved irrigation at 50% of ETa from S to H and the third one (T3) involved no-irrigation from S to V and at 30% of ETa from V to H. The results indicated that there was a significant non-linear correlation between net CO2 assimilation (AN) and stomatal conductance (gs), which resulted in three zones of water stress (zone I = gs > 0.30 mol H2O m-2s-1; zone II = between 0.06 and 0.30 mol H2O m-2s-1; and zone III = gs < 0.06 mol H2O m-2s-1). The use of less water by T2 and T3 had a significant effect on yield components, with a reduction in the weight and diameter of grapes. A significant increase in WP (7.3 kg m-3) occurred in T3, which resulted in values of WUE that were significantly higher than those from T1 and T2. Also, a significant non-linear relationship between the integral water stress (SIΨ) and WP (R2 = 0.74) was established. The results show that grafted Carménère vines were tolerant to water stress although differences between cultivars/genotypes still need to be evaluated.

The malate sensing two-component system MaeKR is a non-canonical class of sensory complex for C4-dicarboxylates

Microbial colonization of different environments is enabled to a great extent by the plasticity of their sensory mechanisms, among them, the two-component signal transduction systems (TCS). Here, an example of TCS plasticity is presented: the regulation of L-malate catabolism via malic enzyme by MaeRK in Lactobacillales. MaeKR belongs to the citrate family of TCS as the Escherichia coli DcuSR system. We show that the Lactobacillus casei histidine-kinase MaeK is defective in autophosphorylation activity as it lacks a functional catalytic and ATP binding domain. The cognate response regulator MaeR was poorly phosphorylated at its phosphoacceptor Asp in vitro. This phosphorylation, however, enhanced MaeR binding in vitro to its target sites and it was required for induction of regulated genes in vivo. Elucidation of the MaeR structure revealed that response regulator dimerization is accomplished by the swapping of α4-β5-α5 elements between two monomers, generating a phosphoacceptor competent conformation. Sequence and phylogenetic analyses showed that the MaeKR peculiarities are not exclusive to L. casei as they are shared by the rest of orthologous systems of Lactobacillales. Our results reveal MaeKR as a non-canonical TCS displaying distinctive features: a swapped response regulator and a sensor histidine kinase lacking ATP-dependent kinase activity.

Response of Lactobacillus casei BL23 to phenolic compounds

AIMS

To determine the inhibitory effect of phenolic compounds on Lactobacillus casei BL23, the role of two component signal transduction systems (TCS) and the response of Lact. casei BL23 to p-coumaric acid.

METHODS AND RESULTS

Growth of Lact. casei BL23 and 17 derivative strains defective in each TCS harboured by this strain in the presence of p-coumaric acid, ferulic acid, caffeic acid or methyl gallate was monitored. Furthermore, changes in the protein content of Lact. casei BL23 when exposed to p-coumaric acid were evaluated by 2D-SDS-PAGE. Eleven proteins differentially expressed in the presence of p-coumaric acid were detected. Six of them could be identified: ClpP and HtrA, involved in protein turnover and folding, acetyl-CoA carboxylase, involved in lipid metabolism, and an arginyl-tRNA synthetase were more abundant, whereas PurL and PurN, involved in purine biosynthesis, were less abundant.

CONCLUSIONS

No significant differences were observed between the parental strain and the TCS-defective mutants. p-Coumaric acid elicited a response against membrane and cytoplasmic damages.

SIGNIFICANCE AND IMPACT OF THE STUDY

The inhibitory effect of phenolic compounds on Lact. casei BL23 has been determined. For the first time, cytoplasmic proteins presumably involved in the response of Lact. casei BL23 against p-coumaric acid have been identified.

Maternal diabetes affects cell proliferation in developing rat placenta

Placentation starts with the formation of a spheroidal trophoblastic shell surrounding the embryo, thus facilitating both implantation into the uterine stroma and contact with maternal blood. Although it is known that diabetes increases the placental size and weight, the mechanisms responsible for this alteration are still poorly understood. In mammals, cellular proliferation occurs in parallel to placental development and it is possible that diabetes induces abnormal uncontrolled cell proliferation in the placenta similar to that seen in other organs (e.g. retina). To test this hypothesis, the objective of this work was to determine cell proliferation in different regions of the placenta during its development in a diabetic rat model. Accordingly, diabetes was induced on day 2 of pregnancy in Wistar rats by a single injection of alloxan (40 mg/kg i.v.). Placentas were collected on days 14, 17, and 20 postcoitum. Immunoperoxidase was used to identify Ki67 nuclear antigen in placental sections. The number of proliferating cells was determined in the total placental area as well as in the labyrinth, spongiotrophoblast and giant trophoblast cell regions. During the course of pregnancy, the number of Ki67 positive cells decreased in both control and diabetic rat placentas. However, starting from day 17 of pregnancy, the number of Ki67 positive cells in the labyrinth and spongiotrophoblast regions was higher in diabetic rat placentas as compared to control. The present results demonstrate that placentas from the diabetic rat model have a significantly higher number of proliferating cells in specific regions of the placenta and at defined developmental stages. It is possible that this increased cell proliferation promotes thickness of the placental barrier consequently affecting the normal maternal-fetal exchanges.

Characterization of faecal enterococci from rabbits for the selection of probiotic strains

AIMS

To characterize the facultative anaerobic intestinal microbiota of healthy rabbits, especially enterococci, for the selection of potential probiotic strains.

METHODS AND RESULTS

Phenotypic and molecular methods were used to identify enterococcal isolates. Results obtained indicated that enterococcal microbiota widely varied among individuals both in size and in composition. Antibacterial and haemolytic activities, and resistance to acid and bile salts were determined. A small group of strains produced bacteriocins active against listeriae and indigenous clostridia and therefore they were selected as potential probiotics. One such strain, 8G, was assayed for colonization capacity. Results obtained suggested that the fate of the introduced strain depended on the composition of the enterococcal indigenous microbiota.

CONCLUSIONS

Enterococcus faecalis and Ent. faecium are the predominant enterococcal species in the gut of rabbits. Other species of lactic acid bacteria were not recovered.

SIGNIFICANCE AND IMPACT OF THE STUDY

The enterococcal intestinal microbiota of healthy rabbits has been characterized in detail. Monitoring the fate of an introduced probiotic in vivo is required in order to evaluate potential probiotic strains.

[Guides for rational use of B-lactam antibiotics:resistance mechanism and clinical interpretation]

beta-lactams are the antibiotic compounds most widely used against hospital and community acquired infections. However, resistance has emerged in both Gram-positive and Gram-negative bacteria, limiting their therapeutic efficacy. The choice of appropriate treatment depends on analysis of susceptibility data that indicates a specific mechanism of resistance. Correct interpretation of susceptibility tests permits a rational approach to the resistance problem and selection of alternatives for treatment. The laboratory must first be able to identify accurately microorganisms to the species level and then test a minimum of relevant antimicrobials. beta-lactam resistance in Enterobacteriaceae is mainly due to the production of plasmid or chromosomal encoded beta-lactamases. In Gram-negative non-fermenting bacteria, impermeability and efflux are relatively more important to the treatment selected. In Gram-positive bacteria, resistance mechanisms can involve changes in penicillin-binding proteins (PBPs), production of new PBPs or synthesis of beta-lactamases. The range of therapeutic options must be based on the current status of local resistance mechanisms.

Multicentre surveillance of antimicrobial resistance in enterococci and staphylococci from Colombian hospitals, 2001-2002

Invasive isolates of staphylococci and enterococci were collected from 15 tertiary care centres in five Colombian cities from 2001 to 2002. A total of 597 isolates were available for analysis. Identification was confirmed by both automated methods and multiplex PCR assays in a central laboratory. Staphylococcus aureus and coagulase-negative staphylococci (CoNS) corresponded to 49.6% and 29.6% of isolates, respectively, and 20.8% were identified as enterococci. MICs of ampicillin, ciprofloxacin, chloramphenicol, erythromycin, gentamicin, linezolid, oxacillin, rifampicin, teicoplanin, tetracycline, trimethoprim/sulfamethoxazole (SXT) and vancomycin were determined using an agar dilution method as appropriate. Screening for vancomycin-resistant S. aureus was also carried out on brain-heart infusion agar plates supplemented with vancomycin. The presence of mecA and van genes was investigated in methicillin-resistant staphylococci and glycopeptide-resistant enterococci (GRE), respectively. All staphylococci were susceptible to vancomycin, teicoplanin and linezolid. No VISA isolates were found. In S. aureus and CoNS, the lowest rates of resistance were found for SXT (7.4%) and chloramphenicol (10.7%), respectively. Resistance to oxacillin in S. aureus and CoNS was 52% and 73%, respectively. The mecA gene was detected in 97.5% of methicillin-resistant S. aureus isolates. In enterococci, resistance to glycopeptides was 9.7%: vanA (58.3%) and vanB (41.7%) genes were found. Pulsed-field gel electrophoresis indicated that the GRE isolates were closely related. Rates of resistance to ampicillin, ciprofloxacin, chloramphenicol, rifampicin and high levels of gentamicin and streptomycin were 9.7%, 27.4%, 8.9%, 43%, 17% and 28.2%, respectively. All enterococci were susceptible to linezolid.

Cellular biomarkers in native and transplanted populations of the mussel Perumytilus purpuratus in the intertidal zones of San Jorge Bay, Antofagasta, Chile

Cellular biomarkers were measured in the mussel Perumytilus purpuratus from intertidal zones of San Jorge Bay, Antofagasta, Chile. They were also used to measure sublethal effects on individuals exposed to Cu under laboratory conditions. Lysosomal stability in hemocytes, and the degree of vacuolization and the content of lipofuscin granules in digestive cells were the cellular responses measured. Three study sites were established in San Jorge Bay: Coloso, E.R., and Reference. Both E.R. and Coloso receive effluent discharges. Reference does not receive any sewage discharges. Before sampling, mussels from Reference were transplanted into the intertidal zone of each site. Samplings were obtained at the beginning, after 45 days, and after 90 days after transplantation. Seawater samples for total dissolved Cu analysis and adult mussels ( P. purpuratus) from native and transplanted populations were collected each time. Cellular biomarkers and Cu concentrations in gonads, gills, and remaining tissues (gut and muscle) were measured. Mussels from Reference were exposed to sublethal Cu concentrations (5, 10, 20, 30, 40, and 80 microg x L(-1)) during 45 days under laboratory conditions. Lysosomal stability was measured in mussel hemocytes by means of the neutral red retention assay. The degree of vacuolization and the extent of lipofuscin granules were determined in the digestive cells by image analysis of histological sections stained with the Schmorl's method. Seawater Cu concentrations and tissue Cu concentrations in P. purpuratus were higher in E.R. than in Reference and Coloso (p < 0.02). Native mussel populations from E.R. showed lower lysosomal stability (p < 0.05), higher vacuolization degree (p < 0.001), and lower amounts of lipofuscin granules (p < 0.001) than those from Coloso and Reference. Transplanted mussel to E.R. showed significant reduction in lysosomal stability (p < 0.05) and in extent of lipofuscin granules (p < 0.05) and significant increase in vacuolization degree (p < 0.05), whereas Reference and Coloso are not significantly dissimilar between them. Seawater Cu concentration was positively correlated with Cu content in gonads ( r2 = 0.61; p < 0.02), gills ( r2 = 0.66; p < 0.01), remaining tissues ( r2 = 0.56; p < 0.05), and the degree of vacuolization ( r2 = 0.65; p < 0.01) and negatively with lysosomal stability ( r2 = 0.79; p < 0.001) and lipofuscin granules extent ( r2 = 0.53; p < 0.05). Mussels exposed to Cu under laboratory conditions showed decreased lysosomal stability (over 30 microg Cu x L(-1)) (p < 0.02) and increased degree of vacuolization (at 80 microg Cu x L(-1)) (p < 0.05) and an increased lipofuscin granules extent (although differences among treatments were not statistically significant).

Construction of compatible wide-host-range shuttle vectors for lactic acid bacteria and Escherichia coli

A new collection of shuttle cloning vectors has been constructed that can be used in a broad host range, because they carry replication origins which are functional in Escherichia coli (p15A, pWV01, ColE1), Lactococcus lactis, lactobacilli, and Bacillus subtilis (pAMbeta1, pWV01). These plasmids contain the lacZ-T1T2 cassette from pJDC9, which allows the X-gal selection and cloning of DNA fragments that could cause plasmid instability in E. coli. In addition, they have been proved to be structurally and segregationally stable in Lactobacillus casei, in which their copy number has been determined by real-time quantitative PCR. Furthermore, the antibiotic resistance markers (beta-lactamase, chloramphenicol acetyl transferase, and erythromycin transacetylase) and the theta and rolling circle replicating origins have been combined to obtain this set of compatible plasmids (pIA family) that can be cotransformed, both in lactic acid bacteria and in E. coli.

Degradation of proteins from the ER of S. cerevisiae requires an intact unfolded protein response pathway

To dissect the requirements of membrane protein degradation from the ER, we expressed the mouse major histocompatibility complex class I heavy chain H-2K(b) in yeast. Like other proteins degraded from the ER, unassembled H-2K(b) heavy chains are not transported to the Golgi but are degraded in a proteasome-dependent manner. The overexpression of H-2K(b) heavy chains induces the unfolded protein response (UPR). In yeast mutants unable to mount the UPR, H-2K(b) heavy chains are greatly stabilized. This defect in degradation is suppressed by the expression of the active form of Hac1p, the transcription factor that upregulates UPR-induced genes. These results indicate that induction of the UPR is required for the degradation of protein substrates from the ER.

[Clinical manifestations of heterozygote familial hypercholesterolemia in Spain. Study of 301 cases from the central and northern areas]

RATIONALE

To characterize clinical manifestations of familial hypercholesterolemia (FH) in Spain.

PATIENTS AND METHODS

A group of 301 cases of FH from central and north regions of Spain.

RESULTS

With a mean (SD) cholesterol level of 346 (58) mg/dl, only 7.6% of the patients have xanthomas and 20% ischaemic heart disease. 51% have a familial history of ischaemic heart disease.

CONCLUSIONS

Different from the results of literature, xanthomas are very infrequent in FH in Spain, so diagnosis should be suspected from other data. The high prevalence of familial history of ischaemic heart disease supports the usefulness of this feature as a marker for diagnosis and prevention.

[Microbial etiology of mild and moderate pelvic inflammatory disease]

Pelvic inflammatory disease (PID) is one of the most severe complications of sexually transmitted disease (STD). It can be due to the ascending of normal endogenous microorganisms of the female genital tract or the infection by microorganisms related to STD as Chlamydia trachomatis and Neisseria gonorrhoeae. PID leads to serious gynecoobstetric consequences as infertility and ectopic pregnancy. Clinicians face the problem of knowing the ethiology of PID in order to treat appropriatly patients with this clinical diagnosis. So that, this work pretends to establish what kind of microorganisms are implicated in PID. A proper isolation and identification of microorganisms achieved by culture of lower genital tract samples from endocervix, endometrium and peritoneal fluid, leading to a betther, specific and proper treatment of this disease.

Structural and functional analysis of the gene cluster encoding the enzymes of the arginine deiminase pathway of Lactobacillus sake

Lactobacillus sake can use arginine via the arginine deiminase (ADI) pathway. We designed degenerate primers based on an alignment of known sequences of ornithine transcarbamoylase (OTC)-encoding genes in order to amplify the L. sake counterpart sequences by PCR. Screening a genomic library of L. sake in lambdaEMBL3 allowed us to isolate a clone containing a 10-kb L. sake genomic DNA insert. Sequence analysis revealed that the genes involved in arginine catabolism were clustered and encoded ADI (arcA), OTC (arcB), carbamate kinase (arcC), and a putative carrier with high similarity to the arginine/ornithine antiporter of Pseudomonas aeruginosa (arcD). Additionally, a putative transaminase-encoding gene (arcT) was located in this region. The genes followed the order arcA arcB arcC arcT arcD, which differs from that found in other microorganisms. arcA, arcB, arcC, and arcD mutants were constructed, and the ADI pathway was impaired in all of them. Transcriptional studies indicated that arcA gene is subject to catabolite repression, and under the conditions used, several transcripts could be detected, suggesting the existence of different initiation sites or processing of a larger mRNA.

Nucleotide sequence of plasmid p4028, a cryptic plasmid from Leuconostoc oenos

The Leuconostoc oenos plasmid p4028 was cloned in pBlueScript (SK+), and its complete nucleotide sequence was determined. The analysis of the nucleotide sequence revealed five open reading frames, all of them located on the same strand and grouped in two clusters separated by a short noncoding stretch. A similarity search against the other sequences deposited in the EMBL and GenBank databases showed that p4028 has no significant similarity with any of the sequences checked. Nevertheless, a putative ATP-binding motif was found in ORF2. A more detailed analysis of this ORF suggests that it could encode for a DNA-dependent ATPase.

Transposons Tn916 and Tn925 can transfer from Enterococcus faecalis to Leuconostoc oenos

The streptococcal transposons Tn916 and Tn925 were transferred to several strains of Leuconostoc (Ln.) oenos using the filter mating method. The insertion of both transposons into the chromosome occurred at different sites. Transconjugants of Ln. oenos carrying Tn916 could serve as donors in mating experiments with Lactococcus lactis LM2301. Further analysis of L. lactis LM2301 transconjugants showed that the insertion of the transposon Tn916 into the chromosome was site-specific. These studies establish a basis for the initiation of genetic studies in this Leuconostoc species since there are no efficient conjugal or transformation systems previously described for this microorganism.

An improved medium for distinguishing between homofermentative and heterofermentative lactic acid bacteria

An improved solid medium for differentiating between homofermentative and heterofermentative lactic acid bacteria is proposed. It was developed to support the growth of wine strains unable to grow in other media. However, it can be employed as a general medium for the lactic acid bacteria that utilize fructose.

Listeria monocytogenes meningitis in previously healthy adults: long-term follow-up

A few cases of Listeria meningitis in healthy individuals have been recorded in the world literature. The lack of a prolonged follow-up in most of these cases makes it difficult to exclude the existence of an underlying disease. The clinical and CSF data of four previously healthy patients with meningitis due to Listeria monocytogenes are presented. These patients were followed prospectively over 2-6 years; during this time none developed any disease associated with immunosuppression, including HIV infection, and none died. Listeria meningitis in an otherwise healthy person is, therefore, not always a sign of underlying immunosuppressive disease, and does not necessarily have a poor prognosis.

Immunoprophylactic trial with combined Mycobacterium leprae/BCG vaccine against leprosy: preliminary results

In an attempt to find a vaccine that gives greater and more consistent protection against leprosy than BCG vaccine, we compared BCG with and without killed Mycobacterium leprae in Venezuela. Close contacts of prevalent leprosy cases were selected as the trial population since they are at greatest risk of leprosy. Since 1983, 29,113 contacts have been randomly allocated vaccination with BCG alone or BCG plus 6 x 10(8) irradiated, autoclaved M leprae purified from the tissues of infected armadillos. We excluded contacts with signs of leprosy at screening and a proportion of those whose skin-test responses to M leprae soluble antigen (MLSA) were 10 mm or more (positive reactions). By July, 1991, 59 postvaccination cases of leprosy had been confirmed in 150,026 person-years of follow-up through annual clinical examinations of the trial population (31 BCG, 28 BCG/M leprae). In the subgroup for which we thought an effect of vaccination was most likely (onset more than a year after vaccination, negative MLSA skin-test response before vaccination), leprosy developed in 11 BCG recipients and 9 BCG/M leprae recipients; there were 18% fewer cases (upper 95% confidence limit [CL] 70%) in the BCG/M leprae than in the BCG alone group. For all cases with onset more than a year after vaccination irrespective of MLSA reaction the relative efficacy was 0% (upper 95% CL 54%; 15 cases in each vaccine group). Retrospective analysis of data on the number of BCG scars found on each contact screened suggested that BCG alone confers substantial protection against leprosy (vaccine efficacy 56%, 95% CL 27-74%) and there was a suggestion that several doses of BCG offered additional protection. There is no evidence in the first 5 years of follow-up of this trial that BCG plus M leprae offers substantially better protection against leprosy than does BCG alone, but the confidence interval on the relative efficacy estimate is wide.

Dynamics of Microbial Populations during Fermentation of Wines from the Utiel-Requena Region of Spain

The dynamics of fungi, yeasts, and lactic acid bacteria during fermentation of four musts were studied. Fungi disappeared quickly in the fermenting must. The lactic acid bacteria population diminished during alcoholic fermentation, then they increased and performed malolactic fermentation. Yeasts grew quickly, reaching maximum populations at different times depending on the vinification treatment.