Detection of genes encoding for enterotoxins and determination of the production of enterotoxins by HBL blood plates and immunoassays of psychrotrophic strains of Bacillus cereus isolated from pasteurised milk

The presence of genes for the production of the three components of the HBL enterotoxin complex and enterotoxin-T in Bacillus cereus was evaluated by PCR tests for strains isolated from milk. In addition enterotoxin production of B. cereus was evaluated by means of the HBL blood agar plate and two commercially available toxin tests. All three genes for the HBL enterotoxin complex were detected in 55% of the 86 strains tested, the enterotoxin-T gene was detected in 62% of the strains. A few strains showed a weak reaction in the PCR tests for the L1 or L2 components of the HBL enterotoxin complex. Many strains that were found to contain the genes for the HBL complex gave negative or doubtful results in the HBL blood agar plate test. All strains that contain the L2 part of the HBL complex showed a titer of at least 8 in the Oxoid RPLA test. Two strains that did not contain the L2 part of the HBL enterotoxin complex gave high titers (= 64) in the RPLA test.

The S-layer protein of Lactobacillus acidophilus ATCC 4356: identification and characterisation of domains responsible for S-protein assembly and cell wall binding

Lactobacillus acidophilus, like many other bacteria, harbors a surface layer consisting of a protein (S(A)-protein) of 43 kDa. S(A)-protein could be readily extracted and crystallized in vitro into large crystalline patches on lipid monolayers with a net negative charge but not on lipids with a net neutral charge. Reconstruction of the S-layer from crystals grown on dioleoylphosphatidylserine indicated an oblique lattice with unit cell dimensions (a=118 A; b=53 A, and gamma=102 degrees ) resembling those determined for the S-layer of Lactobacillus helveticus ATCC 12046. Sequence comparison of S(A)-protein with S-proteins from L. helveticus, Lactobacillus crispatus and the S-proteins encoded by the silent S-protein genes from L. acidophilus and L. crispatus suggested the presence of two domains, one comprising the N-terminal two-thirds (SAN), and another made up of the C-terminal one-third (SAC) of S(A)-protein. The sequence of the N-terminal domains is variable, while that of the C-terminal domain is highly conserved in the S-proteins of these organisms and contains a tandem repeat. Proteolytic digestion of S(A)-protein showed that SAN was protease-resistant, suggesting a compact structure. SAC was rapidly degraded by proteases and therefore probably has a more accessible structure. DNA sequences encoding SAN or Green Fluorescent Protein fused to SAC (GFP-SAC) were efficiently expressed in Escherichia coli. Purified SAN could crystallize into mono and multi-layered crystals with the same lattice parameters as those found for authentic S(A)-protein. A calculated S(A)-protein minus SAN density-difference map revealed the probable location, in projection, of the SAC domain, which is missing from the truncated SAN peptide. The GFP-SAC fusion product was shown to bind to the surface of L. acidophilus, L. helveticus and L. crispatus cells from which the S-layer had been removed, but not to non-stripped cells or to Lactobacillus casei.

Analysis of the dynamics of fungal communities in soil via fungal-specific PCR of soil DNA followed by denaturing gradient gel electrophoresis

A molecular method for profiling of fungal communities in soil was applied in experiments in soil microcosms, with two objectives, (1) to assess the persistence of two selected fungal species in soil, and (2) to analyze the response of the natural fungal community to a spill of sulphurous petrol in the same soil. To achieve the aims, two soil DNA extraction methods, one originally designed for the direct extraction of bacterial community DNA and the other one aimed to obtain fungal DNA, were tested for their efficiency in recovering DNA of fungal origin from soil. Both methods allowed for the efficient extraction of DNA from introduced Trichoderma harzianum spores as well as Arthrobotrys oligospora mycelial fragments, at comparable rates. Several PCR amplification systems based on primers specific for fungal 18S ribosomal RNA genes were tested to design strategies for the assessment of fungal communities in soil. The PCR systems produced amplicons of expected size with DNA of most fungi studied, which included members of the Ascomycetes, Basidiomycetes, Zygomycetes and Chytridiomycetes. On the other hand, the 18S rRNA genes of Oomycetes (including key plant pathogens) were poorly amplified. Plant (Solanum tuberosum), nematode (Meloidogyne sp.) and bacterial DNA was not amplified. For studies of soil fungal communities, a nested PCR approach was selected, in which the first PCR provided the required specificity for fungi, whereas the second (nested) PCR served to produce amplicons separable on denaturing gradient gels. Denaturing gradient gel electrophoresis (DGGE) allowed the resolution of mixtures of PCR products of several different fungi, as well as products resulting from mixed-template amplifications, into distinct banding patterns. The persistence of fungal species in soil was assessed using T. harzianum spores and A. oligospora hyphal fragments added to silt loam soil microcosms. Using PCR-DGGE, these fungi were detectable for about 14 days and 2 months, respectively. Both singly-inoculated soils and soils that had received mixed inoculants revealed, next to bands resulting from indigenous fungi, the expected bands in the DGGE profiles. The A. oligospora specific amplicon, by virtue of its unique migration in the denaturing gradient, was well detectable, whereas the T. harzianum specific product comigrated with products from indigenous fungi. PCR-DGGE analysis of DNA obtained from the silt loam soil treated with dibenzothiophene-containing petrol showed the progressive selection of specific fungal bands over time, whereas this selection was not observed in untreated soil microcosms. Cloning of individual molecules from the selected bands and analysis of their sequences revealed a complex of targets which clustered with the 18S rDNA sequences of the closely-related species Nectria haematococca, N. ochroleuca and Fusarium solani. Fungal isolates obtained from the treated soil on PDA plates were identified as Trichoderma sp., whereas those on Comada agar fell into the Cylindrocarpon group (anamorph of Nectria spp).

Expression of cbsA encoding the collagen-binding S-protein of Lactobacillus crispatus JCM5810 in Lactobacillus casei ATCC 393(T)

The cbsA gene encoding the collagen-binding S-layer protein of Lactobacillus crispatus JCM5810 was expressed in L. casei ATCC 393(T). The S-protein was not retained on the surface of the recombinant bacteria but was secreted into the medium. By translational fusion of CbsA to the cell wall sorting signal of the proteinase, PrtP, of L. casei, CbsA was presented at the surface, rendering the transformants able to bind to immobilized collagens.

Oxidative stress in HIV-1-infected injection drug users

Low serum antioxidant levels observed in many HIV-infected populations could be largely due to an increase in oxidative stress (defined as a disturbance in the equilibrium status of prooxidant/antioxidant systems of intact cells). In HIV infection, oxidative stress may be caused by both overproduction of reactive oxygen intermediates (ROIs) and a simultaneous deficiency of antioxidant defenses. Furthermore, injection drug use has been associated with increased levels of oxidative stress in animal models. Currently, there is widespread use of self-prescribed antioxidant supplementation among the HIV-infected population and a prevailing belief that high-dose supplementation is beneficial, or at the very least, not harmful. Data from our studies show that HIV-positive injection drug users (IDUs) who are on antiretroviral combination therapies including a protease inhibitor have significantly higher mean serum levels of several antioxidants, independent of dietary and supplemental intake, compared with both HIV-negative IDUs and HIV-positive IDUs not taking protease inhibitors. This suggests that oxidative stress may be reduced in patients taking protease inhibitors. Preliminary data suggest that the future of antioxidant supplementation therapy, if any, will be one in which different doses of supplements are recommended for HIV-infected patients on the various antiretroviral treatment regimens. More research is needed to determine the interactions among injection drug use, oxidative stress, antiretroviral therapy, and the use of antioxidant supplements in HIV infection. Until more is known, caution should be exercised when using or recommending high-dose antioxidant supplementation in HIV-infected individuals, particularly in those on protease inhibitors, since moderate levels of oxidative stress are involved in a number of useful physiologic processes.

Nutritional assessment in intravenous drug users with HIV/AIDS

Studying metabolic, endocrine, and gastrointestinal (MEG) disorders in drug abuse and HIV infection is important. Equally important, however, are the tools we use to assess these disorders. Assessment of nutritional status may include any combination of biochemical and body composition measurements, dietary intake assessment, and metabolic studies. Each method has its strengths and weaknesses and there is no perfect tool. When assessing nutritional status in injection drug users (IDU) and in HIV-infected people, the decision on which method or methods to use becomes even more complex. A review of studies reported during the XII World Conference on AIDS reveals that of 64 abstracts on the topic of nutrition in HIV-infected adults, only 11 assessed diet, 41 assessed anthropometry, and 24 assessed some form of biochemical measure. The most commonly reported methods for dietary intake included 24-hour recalls, food records, and food frequencies. The commonest methods used for measuring body composition included height, weight, bioimpedance, and dual-energy x-ray absorptiometry (DEXA). Biochemical measurements included various blood nutrients, lipids, and albumin. Methods varied greatly between studies, and caution should be taken when trying to compare results across studies, especially among those using different methods. Currently, few studies deal with the development of methods that can be used for research in HIV-infected and IDU populations. We need to work toward better tools in dietary intake assessment, body composition, and biochemical measurements, especially methods that will allow us to track changes in nutritional status over time.

Improved antioxidant status among HIV-infected injecting drug users on potent antiretroviral therapy

Low serum antioxidant levels in HIV-infected people have been attributed to altered metabolism associated with excess oxidative stress. We conducted a study to examine serum antioxidant levels in 175 HIV-positive and 210 HIV-negative injecting drug users (IDUs) in Baltimore, Maryland. At the time of data collection, 30 of the HIV-positive IDUs were receiving antiretroviral therapies (ART) including a protease inhibitor (PI), 43 ART without a PI, 22 monotherapies, and 80 not on any ART. Serum antioxidants examined included retinol, alpha-tocopherol and gamma-tocopherol, alpha-carotene and beta-carotene, lycopene, lutein/zeaxanthin, and beta-cryptoxanthin. Mean serum levels of lycopene and lutein/zeaxanthin were significantly lower in HIV-positive IDUs than HIV-negative IDUs. Contrary to the findings in other studies, however, levels of the remaining antioxidants in HIV-positive study subjects were not lower than in HIV-negative study subjects. In fact, serum alpha-tocopherol levels were significantly higher in HIV-positive IDUs than HIV-negative IDUs (medians = 744 microg/dl and 718 microg/dl, respectively; p = .04). Among HIV-positive study subjects, there were significant differences in antioxidant levels by ART regimen. In multivariate models adjusting for injecting drug use, dietary intake, supplement intake, gender, and alcohol intake, significant overall differences by ART regimen were observed for alpha-tocopherol, beta-carotene, and beta-cryptoxanthin. Serum levels of these three antioxidants were significantly higher in the PI group than in the other three ART groups combined (p = .0008, 0.02, and 0.02, respectively). These data provide indirect evidence of the effectiveness of PIs in lowering oxidative stress levels in HIV-positive IDUs.

Race/ethnicity, social class and their relation to physical inactivity during leisure time: results from the Third National Health and Nutrition Examination Survey, 1988-1994

BACKGROUND

Physical inactivity is more prevalent among racial and ethnic minorities than among Caucasians. It is not known if differences in participation in leisure time physical activity are due to differences in social class. Thus, this paper provides estimates of the prevalence of physical inactivity during leisure time and its relationship to race/ethnicity and social class.

METHODS

This was a national representative cross-sectional survey with an in-person interview and medical examination. Between 1988 and 1994, 18,885 adults aged 20 or older responded to the household adult and family questionnaires as part of the Third National Health and Nutrition Examination Survey . Mexican-Americans and African-Americans were over-sampled to produce reliable estimates for these groups. Multiple assessment of social class included education, family income, occupation, poverty status, employment status, and marital status.

RESULTS

The age-adjusted prevalence (per 100) of adults reporting leisure time inactivity is lower among Caucasians (18%) than among African-Americans (35%) and Mexican-Americans (40%). African-American and Mexican-American men and women reported higher prevalence of leisure time inactivity than their Caucasian counterparts across almost every variable, including education, family income, occupation, employment, poverty and marital status.

CONCLUSIONS

Current indicators of social class do not seem to explain the higher prevalence of physical inactivity during leisure time among African-American and Mexican-American. More research is needed to examine the effect of other constructs of social class such as acculturation, safety, social support and environmental barriers in promoting successful interventions to increase physical activity in these populations.

Virologic, immunologic, and immune activation markers as predictors of HIV-associated weight loss prior to AIDS. Multicenter AIDS Cohort Study

OBJECTIVES

To study weight patterns among HIV-positive men and associations of baseline HIV RNA, CD4+ lymphocyte count, and serum levels of neopterin and beta2-microglobulin with subsequent weight loss prior to AIDS.

METHODS

A cohort of 1558 homosexual men from the Multicenter AIDS Cohort Study comprised the main study population. Marker values obtained using samples from a baseline visit in 1984 to 1985 were associated with weight patterns and risk of weight loss events over 10 years of follow-up. To investigate the impact of protease inhibitor (PI) therapy on weight patterns, a separate analysis was conducted for men who initiated such therapy in 1995 to 1996.

RESULTS

In general, HIV-positive men demonstrated a striking tendency toward weight loss, with a rate of decline that increased over time. Distinct variations in this pattern were observed according to baseline HIV RNA levels. Each marker considered was independently predictive of weight loss events. Following use of PIs, 68 men showed a tendency toward increased weight, compared with men who did not use PIs.

CONCLUSIONS

Although baseline virologic, immunologic, and immune activation markers all predicted weight loss events in AIDS-free HIV-positive men, HIV RNA displayed the best discrimination. Shifts in weight patterns observed in this cohort after PI therapy call for further attention to nutritional and body changes as the duration of therapy increases.

Prevalence of physical inactivity and its relation to social class in U.S. adults: results from the Third National Health and Nutrition Examination Survey, 1988-1994

PURPOSE

This study examines the prevalence of physical inactivity during leisure time in a national representative sample of U.S. adults.

METHODS

Data were obtained from the Third National Health and Nutrition Examination Survey, conducted between 1988 and 1994. A total of 18,825 adults aged 20 yr and older participated in a home interview where information about physical activity, education, income, occupation, employment, and labor force participation was obtained.

RESULTS

The prevalence of physical inactivity among U.S. adults was 23%, with more women (28%) than men (17%) reporting being inactive during their leisure time. Additionally, inactivity is more common among in social class such as persons who are less educated, living below the poverty line, living in households with income below 20,000 dollars, and who are retired. In every category of social class, women experienced a higher prevalence of physical inactivity than men.

CONCLUSIONS

We conclude that social class is associated with physical inactivity and that more research is needed to better understand the effect that other social and environmental factors have on sedentary behaviors in our society.

Blood cholesterol and apolipoprotein B levels in relation to intakes of animal and plant proteins in US adults

Few studies have examined the association between specific sources of protein and blood lipids in a national sample of adults. We examined this relationship in a sample of adults 20 years and older who participated in phase 1 (1988-91) of the Third National Health and Nutrition Examination Survey, a representative sample of the United States non-institutionalized population. After excluding those participants who reported having been told they had high blood cholesterol concentrations, the final sample size was 6228. Mean intakes of different sources of proteins, as a percentage of total protein, were compared in quartiles of blood lipids. Intakes were adjusted for age, sex and race. Additional adjustments were made for other dietary variables, recall day, BMI, smoking, and income. We observed a lower percentage meat, fish and poultry (MFP) protein intake, including a lower percentage of beef and pork protein, among persons in the lowest quartile of serum total cholesterol and apolipoprotein B (ApoB) concentrations than among persons in the higher quartiles. The percentage of plant protein intake was higher in the lowest quartile than in the highest quartile of serum cholesterol. We also observed a higher percentage of fruit protein intake with lower serum cholesterol and ApoB concentrations. We conclude that in this cross-sectional sample, consumption of MFP proteins was consistently higher among persons with higher cholesterol concentrations while consumption of plant proteins was consistently higher among persons with lower cholesterol concentrations. Our findings support the importance of assessing intake of specific protein sources, especially in studies that address dietary intake in relation to blood lipids.

Estimates of animal and plant protein intake in US adults: results from the Third National Health and Nutrition Examination Survey, 1988-1991

OBJECTIVE

To describe the sources of protein intake in a sample of the US adult population and among subgroups defined by race-ethnicity, age, and gender.

DESIGN

The Third National Health and Nutrition Examination Survey, 1988-1991, is a stratified random sample of the total civilian noninstitutionalized population, drawn from the 50 United States and the District of Columbia. For all foods consumed by the participants, based on a 24-hour dietary recall, protein sources and the contribution of each protein type to the total protein intake were determined.

SUBJECTS

Adult participants in the third National Health and Nutrition Examination Survey (n = 7,924).

STATISTICAL ANALYSES

Weighted total, age-specific, and age-adjusted mean protein intakes were calculated using SAS and WesVarPC. Statistical differences were determined by 2-tailed t tests.

RESULTS

The main protein source in the American diet is animal protein (69%). Meat, fish, and poultry protein combined contributed the most to animal protein (42%), followed by dairy protein (20%). Grains (18%) contributed the most to plant protein consumption. Women consumed a lower percentage of beef (14%) and pork (7%) protein than did men (18% and 9%, respectively). Women also consumed a higher percentage of poultry (13%), dairy (22%), and fruit and vegetable (11%) protein than did men (11%, 19%, and 9%, respectively). Blacks reported eating a higher percentage of poultry (18%) and pork (11%) protein and a lower percent of dairy protein (14%) than did whites (12%, 7%, and 22%, respectively) and Mexican-Americans (11%, 8%, and 17%, respectively). Mexican-Americans consumed a higher percentage of legume (7%) and egg (7%) protein than did whites (4% and 4%, respectively) and blacks (4% and 5%, respectively). Whites consumed a higher percentage of grain protein (19%) than did blacks (16%) and Mexican-Americans (15%).

CONCLUSIONS

These results show that, although the percentage of total energy from protein may be similar among race-ethnicities and between men and women, their sources of protein are different. These differences should be taken into account when providing nutrition education for specific populations.

Analysis of fungal diversity in the wheat rhizosphere by sequencing of cloned PCR-amplified genes encoding 18S rRNA and temperature gradient gel electrophoresis

Like bacteria, fungi play an important role in the soil ecosystem. As only a small fraction of the fungi present in soil can be cultured, conventional microbiological techniques yield only limited information on the composition and dynamics of fungal communities in soil. DNA-based methods do not depend on the culturability of microorganisms, and therefore they offer an attractive alternative for the study of complex fungal community structures. For this purpose, we designed various PCR primers that allow the specific amplification of fungal 18S-ribosomal-DNA (rDNA) sequences, even in the presence of nonfungal 18S rDNA. DNA was extracted from the wheat rhizosphere, and 18S rDNA gene banks were constructed in Escherichia coli by cloning PCR products generated with primer pairs EF4-EF3 (1. 4 kb) and EF4-fung5 (0.5 kb). Fragments of 0.5 kb from the cloned inserts were sequenced and compared to known rDNA sequences. Sequences from all major fungal taxa were amplified by using both primer pairs. As predicted by computer analysis, primer pair EF4-EF3 appeared slightly biased to amplify Basidiomycota and Zygomycota, whereas EF4-fung5 amplified mainly Ascomycota. The 61 clones that were sequenced matched the sequences of 24 different species in the Ribosomal Database Project (RDP) database. Similarity values ranged from 0.676 to 1. Temperature gradient gel electrophoresis (TGGE) analysis of the fungal community in the wheat rhizosphere of a microcosm experiment was carried out after amplification of total DNA with both primer pairs. This resulted in reproducible, distinctive fingerprints, confirming the difference in amplification specificity. Clear banding patterns were obtained with soil and rhizosphere samples by using both primer sets in combination. By comparing the electrophoretic mobility of community fingerprint bands to that of the bands obtained with separate clones, some could be tentatively identified. While 18S-rDNA sequences do not always provide the taxonomic resolution to identify fungal species and strains, they do provide information on the diversity and dynamics of groups of related species in environmental samples with sufficient resolution to produce discrete bands which can be separated by TGGE. This combination of 18S-rDNA PCR amplification and TGGE community analysis should allow study of the diversity, composition, and dynamics of the fungal community in bulk soil and in the rhizosphere.

Reverse chromosome painting for the identification of marker chromosomes and complex translocations in leukemia

BACKGROUND

Chromosome banding techniques and in situ hybridization reveal the majority of chromosomal aberrations. However, difficulties remain in cases of highly contracted chromosomes, poor quality of the metaphases or the presence of markers with the involvement of several chromosomes. Here, it is demonstrated that reverse painting can be applied successfully starting with bone marrow cells from primary acute myelocytic leukemias (AML).

METHODS

This was accomplished by culturing the leukemic cells with a cocktail of various growth factors, which yielded sufficient numbers of cells in cycle to harvest chromosomes for sorting. Aberrant chromosomes were flow-sorted and amplified by degenerate oligonucleotide-primed PCR. The resulting products were labeled by nick-translation and hybridized on normal metaphase spreads.

RESULTS

Two patients with marker chromosomes in their leukemia cells were analyzed in detail. The hybridization pattern displayed the composition of the aberrant sorted chromosome. Results were compared with conventional cytogenetic analyses that were performed on material obtained from the same aspirate. The reverse-painting technique enabled identification of aberrations that were not detected by conventional cytogenetic analysis.

CONCLUSIONS

Primary AML cells can be cultured in vitro, using optimal culture conditions, facilitating the production of high quality flow karyotypes, suitable for sorting of marker chromosomes to produce DOP-PCR derived chromosome painting probes for reverse painting. Valuable additional cytogenetic information can thus be obtained about complex chromosomal rearrangements or structural aberrations that could not be completely resolved by conventional cytogenetic analysis.

Fluorescence in situ hybridization for the detection and monitoring of the Ph-positive clone in chronic myelogenous leukemia: comparison with metaphase banding analysis

In order to analyze the efficiency of interphase FISH for the detection and monitoring of Ph+ cells in chronic myelogenous leukemia (CML) under interferon (IFN) treatment, the following experiments were performed: (1) 98 specimens derived from 32 patients were analyzed in parallel by dual-color FISH and by conventional chromosome analysis (CCA). A 300/200 kb BCR/ABL probe was used in all tests and a smaller 35.5/39 kb probe was tested in parallel in 22 BM samples; (2) 30 BM samples were prepared by direct harvest and by 24-h culture and were analyzed in parallel; (3) PB and BM samples obtained simultaneously from 11 patients were analyzed. The cut-off point for the recognition of BCR/ABL fusion was set at 2.4%, calculated as the mean percent of false positivity in 11 controls plus 3 s.d. A very close correlation was observed (r=0.994, r2=0.988, P < 0.0001) between the percentages of Ph+ cells as assessed by CCA and by interphase FISH in 98 samples (26 at diagnosis). There was a moderate overestimation of the frequency of Ph+ cells by FISH with respect to CCA, that was more evident at low-to-medium values of Ph positivity. Seven specimens without Ph+ metaphases (17-50 cells analyzed) were shown to carry 2.5-8% interphase cells with BCR/ABL fusion. Similar percentages of BCR/ABL+ nuclei were recorded in 22 samples hybridized using the 300/200 kb and the 35.5/39 kb probe-sets (variation range: 0-5%, mean 2.3%). A very good correlation between the frequency of Ph+ interphase cells was observed when analyzing in parallel BM preparations after direct harvest and after 24-h culture. Underestimation of the percentage of BCR/ABL+ cells was noted to occur in 2/11 PB samples, compared to BM samples, the remaining nine cases showing superimposable results at either sites. We arrived at the following conclusions: (1) dual-color FISH enables an accurate detection and monitoring of the size of the Ph-positive clone in CML at diagnosis and after IFN-therapy; (2) FISH is more accurate than CCA, especially at low levels of Ph-positive cells; (3) testing of directly harvested BM samples is feasible and accurate, giving the opportunity to perform centralized FISH analysis in the context of multicentre trials; (4) the percentage of BCR/ABL+ PB cells usually, though not invariably, reflects the frequency of mutated cells in the BM.

Leadership development in a nursing service. A South African ethnographic perspective

Leadership development at operational level in a nursing service is important to cope with all the transformation required. The purpose with this study is to explore and describe the views of black professional nurses on leadership behaviour, within the context of an operating theatre department, and to determine the influence of their occupational history on these views. An exploratory and descriptive research design, with an ethnographic perspective, was employed by means of semi-structured interviews (views on leadership) and questionnaires (occupational history). The results compare positively with the theoretical description of leadership behaviour. Guidelines for leadership development of these nurses were formulated, and should be followed by the necessary capacity building regarding leadership practice by professional nurses.

Lactic acid bacteria as antigen delivery vehicles for oral immunization purposes

In vaccination programmes in which large numbers of subjects are involved, the oral route of administration is more convenient as compared to the more frequently used parenteral route. This is particularly relevant when vaccines are to be applied in less industrialized countries. Lactic acid bacteria in general and strains of Lactobacillus in particular have a variety of properties which make them attractive candidates for oral vaccination purposes, e.g. GRAS status, adjuvant properties, mucosal adhesive properties and low intrinsic immunogenicity. An overview is given of current research aimed at unravelling the relationship between structure and properties of surface proteins of lactobacilli and in vivo colonization, in particular of species capable of adhering to epithelial cells in vitro. Secondly, the state of the art will be discussed with respect to antigen presentation by lactic acid bacteria. Finally, some preliminary immunological data of recombinant lactic acid bacterial strains expressing antigens from pathogens will be presented.

Self-transmissible mercury resistance plasmids with gene-mobilizing capacity in soil bacterial populations: influence of wheat roots and mercury addition

A set of mercury resistance plasmids was obtained from wheat rhizosphere soil amended or not amended with mercuric chloride via exogenous plasmid isolation by using Pseudomonas fluorescens R2f, Pseudomonas putida UWC1, and Enterobacter cloacae BE1 as recipient strains. The isolation frequencies were highest from soil amended with high levels of mercury, and the isolation frequencies from unamended soil were low. With P. putida UWC1 as the recipient, the isolation frequency was significantly enhanced in wheat rhizosphere compared to bulk soil. Twenty transconjugants were analyzed per recipient strain. All of the transconjugants contained plasmids which were between 40 and 50 kb long. Eight selected plasmids were distributed among five groups, as shown by restriction digestion coupled with a similarity matrix analysis. However, all of the plasmids formed a tight group, as judged by hybridization with two whole-plasmid probes and comparisons with other plasmids in dot blot hybridization analyses. The results of replicon typing and broad-host-range incompatibility (Inc) group-specific PCR suggested tht the plasmid isolates were not related to any previously described Inc group. Although resistance to copper, resistance to streptomycin, and/or resistance to chloramphenicol was found in several plasmids, catabolic sequences were generally not identified. One plasmid, pEC10, transferred into a variety of bacteria belonging to the beta and gamma subdivisions of the class Proteobacteria and mobilized as well as retromobilized the IncQ plasmid pSUP104. A PCR method for detection of pEC10-like replicons was used, in conjunction with other methods, to monitor pEC10-homologous sequences in mercury-polluted and unpolluted soils. The presence of mercury enhanced the prevalence of pEC10-like replicons in soil and rhizosphere bacterial populations.

Selected vitamins in HIV infection: a review

In this article we review published studies on the role of serum micronutrient levels in the natural history of HIV infection. Specifically, we have focused on vitamins B12, E, A, and beta-carotene. Deficiencies of one or several of these vitamins have been associated with an accelerated progression of HIV infection to AIDS. Most investigators have used serum micronutrient levels as an indicator of vitamin nutriture. However, serum levels are not always the most sensitive or specific indicators of vitamin status. Nonetheless, serum vitamin levels are relatively easy to obtain and have been studied in various HIV-infected populations in individuals at different stages of disease. Low serum B12 levels have been associated with increased neurologic abnormalities, more rapid HIV disease progression, and increased AZT-related bone marrow toxicity. Low serum vitamin E levels have been associated with an increase in oxidative stress in HIV-infected individuals. However, early studies of vitamin E supplementation suggest that vitamin E may have important immunostimulatory properties. Studies of vitamin A deficiency in HIV-infected populations have shown that low serum vitamin A levels are associated with increased mortality, more rapid disease progression, and increased maternal-fetal transmission. However, there is little evidence that vitamin A supplementation, beyond the correction of deficiency, is beneficial in HIV infection. Finally, several clinical trials of beta-carotene supplementation have failed to show significant or sustained improvements in the immune response of patients with HIV infection or AIDS.

Isolation, characterization, and transfer of cryptic gene-mobilizing plasmids in the wheat rhizosphere

A set of self-transmissible plasmids with IncQ plasmid-mobilizing capacity was isolated by triparental exogenous isolation from the wheat rhizosphere with an Escherichia coli IncQ plasmid host and a Ralstonia eutropha recipient. Three plasmids of 38 to 45 kb, denoted pIPO1, pIPO2, and pIPO3, were selected for further study. No selectable traits (antibiotic or heavy-metal resistance) were identified in these plasmids. The plasmids were characterized by replicon typing via PCR and hybridization with replicon-specific probes and other hybridizations. pIPO1 and pIPO3 were similar to each other, whereas pIPO2 was different. None of these plasmids belonged to any known incompatibility group. pIPO2 was selected for further work, and a mini-Tn5-tet transposon was inserted to confer selectability. Plasmid pIPO2 had a broad IncQ plasmid mobilization and self-transfer range among the alpha, beta, and gamma subclasses of the Proteobacteria but did not show productive transfer to gram-positive bacteria. Plasmid pIPO2 mobilized IncQ plasmid pIE723 from Pseudomonas fluorescence to diverse indigenous proteobacteria in the rhizosphere of field-grown wheat. Transfer of pIE723 to indigenous bacteria was not observed in the absence of added pIPO2. A specific PCR primer system and a probe were developed for the detection of pIPO2-type plasmids in soil and rhizosphere. Analysis of soil DNA provided evidence for the presence of pIPO2 in inoculated wheat rhizosphere soil in the field study, as well as in the rhizosphere of uninoculated wheat plants growing in soil microcosms. The system failed to identify major reservoirs of pIPO2 in a variety of other soils.

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Dietary intake of community-based HIV-1 seropositive and seronegative injecting drug users

Dietary intake was assessed in a subsample of a cohort of inner-city injecting drug users (IDUs). In this population of predominantly African-American IDUs, including both HIV -1-infected and noninfected men and women, a food frequency questionnaire (FFQ) and a 24-h recall were administered. One hundred seven volunteers participated. Although total caloric intake was consistently higher with the food frequency method, percent of total calories from fat, protein, and carbohydrates were similar between the FFQ and 24-h recall. Spearman's correlations for agreement between the 24-h recall and the FFQ ranged from 0.22 for vitamin E to 0.52 for carbohydrates. HIV-1 seropositives reported higher protein (p = 0.05) and fat (p = 0.02) consumption than seronegatives according to the 24-h recall. The difference in total fat consumption was due to higher intakes of saturated and monounsaturated fats (p = 0.01). Median intakes of vitamins B2 and B12, pantothenic acid (p < or = 0.05), phosphorous (p < or = 0.01), and selenium (p < or = 0.005) were also greater in HIV-1 seropositives. Reported intake of vitamins A and E, calcium, and zinc were below the recommended daily allowances for both HIV-1 seropositives and seronegatives. Although intakes of most nutrients appeared adequate for the group as a whole, extreme ranges were observed and may be the result of imbalanced food selections and day to day variation. Food group analysis indicated low intakes of fruits, vegetables, milk, and milk products. More research is needed to fully understand the implication of dietary habits and nutritional status in the free-living HIV-1-infected and noninfected IDUs.

Detection and characterization of broad-host-range plasmids in environmental bacteria by PCR

Primer systems for PCR amplification of different replicon-specific DNA regions were designed on the basis of published sequences for plasmids belonging to the incompatibility (Inc) groups IncP, IncN, IncW, and IncQ. The specificities of these primer systems for the respective Inc groups were tested with a collection of reference plasmids belonging to 21 different Inc groups. Almost all primer systems were found to be highly specific for the reference plasmid for which they were designed. In addition, the primers were tested with plasmids which had previously been grouped by traditional incompatibility testing to the IncN, IncW, IncP, or IncQ group. All IncQ plasmids gave PCR products with the IncQ primer systems tested. However, PCR products were obtained for only some of the IncN, IncP, and IncW group plasmids. Dot blot and Southern blot analyses of the plasmids revealed that PCR-negative plasmids also failed to hybridize with probes derived from the reference plasmids. The results indicated that plasmids assigned to the same Inc group by traditional methods might be partially or completely different from their respective reference plasmids at the DNA level. With a few exceptions, all plasmids related to the reference plasmid at the DNA level also reacted with the primer systems tested. PCR amplification of total DNA extracted directly from different soil and manure slurry samples revealed the prevalence of IncQ- and IncP-specific sequences in several of these samples. In contrast, IncN- and IncW-specific sequences were detected mainly in DNA obtained from manure slurries.