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PubMedDate not supplied

[Epidemiology of Salmonella typhimurium biotype 6 strains, isolated in Belgium from 1969 to 1982].

Strains of S. typhimurium biotype 6 possess neither tetrathionate reductase nor arginine dihydrolase; they use trehalose, but not inositol and glycerol. Most are multi-resistant to antibiotics and are responsible for numerous outbreaks of salmonellosis. They have been divided into four groups. Groups I includes strains of phage type 207, and was predominant in Belgium from 1969 to 1976. Group II includes strains of a classical variety belonging to phage types 49, 193 and 204. Group III includes strains of the copenhagen variety belonging to the same phage types. Strains of groups II and III are generally resistant to trimethoprim. They have predominated in Belgium since 1978 (mainly phage type 193). Group IV contains a few strains of various phage types, generally non-resistant, which have caused no epidemics.

Bacteriophage Typing↗
PubMed1984

Problems and progress in immunization.

Advances in immunology, microbial genetics, molecular biology and biochemistry are opening prospects for new purified and synthetic antigens against infectious diseases, cancers of viral origin and some immunodeficiencies. Immunization programmes against major childhood diseases with commonly used vaccines gave excellent results and are leading to their virtual eradication in developed countries. However some vaccines like the one against pertussis proved to be of considerably lower effectiveness. Results achieved in developing countries are in general lagging behind due to lower immunization coverage. While in some countries immunization strategies for eradication of measles are discussed, in others it is questionable whether immunization should continue due to failures of immunization programmes. Evaluation of the effectiveness of national immunization programmes by surveillance and various other methods including the use of epidemiological models point ot the deficiencies of vaccine potency and/or stability and the inadequacy of vaccination schemes and coverages. There is a need to determine optimal immunization programmes for control and possible eradication with currently available antigens and new ones. For newly developed vaccines, ever increasing in number, but with the uncertainty of their appropriate public health use, it is essential to study their optimal and most cost-effective uses e.g., pertussis vaccination is an old unsolved problem and that against hepatitis B a new one. Better results can be obtained with current vaccines by appropriate modification of immunization programmes. Some of the proposed strategies for using recently developed vaccines are questionable and need critical examination.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Vaccines↗
PubMed1993

[Pathogenic properties of coagulase-negative staphylococci in experimental infections].

The frequency of persistence of three Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus saprophyticus strains, respectively, was studied in BALB/c mice at the 10th day of intraperitoneal (ip) challenge. 245 out of 416 mice survived after infections with four bacterial suspensions of different colony forming units (CFU) of each strain. Staphylococci persisted in 61 mice (24,9%). The main sites of persistence were the kidneys, while cocci were rarely isolated from the spleen and the liver. S. epidermidis persisted with a significantly higher rate than the other two species, because S. epidermidis in 28,8%, S. haemolyticus in 4,9%, and S. saprophyticus in 3,6% were reisolated from the organs of the respective infected and surviving animals. The organ persistence was proportional to the amount of bacteria injected. The persistence resulted in subacute microabscesses in the organs. Reisolates of persisting bacteria remained stable in phenotype and genotype concerning antibiotic resistance patterns and biochemical activities for the taxonomic implication, whereas cell surface properties characterizable with phage types altered considerably during persistence. It is concluded that cocci of all three Staphylococcus species are invasive and can persist to a certain extent in the organs of animals with normal immune system, too, after artificial inoculation into the peritoneum i. e. to the serosal surfaces.

Animals↗
PubMedDate not supplied

[The resistance to antibiotics and chemotherapeutics in bacteria (author's transl)].

Many people today, in agricolture, zootechny and animal feeding, operate with antibiotics and chemotherapeutics. Not all perhaps, know the inconveniences that the large and uncontrolled use of these substances may cause first of all the emergency of bacteria strains resistant to these drugs. We have devoted our attention particularly to the modalities of establishment of the phenomenon: to its incidence and variability in nature, to its transferability and, at least, to its biochemical aspects.

Anti-Bacterial Agents↗
PubMed2006

Ranking the magnitude of crop and farming system effects on soil microbial biomass and genetic structure of bacterial communities.

Biological soil characteristics such as microbial biomass, community structures, activities, and functions may provide important information on environmental and anthropogenic influences on agricultural soils. Diagnostic tools and detailed statistical approaches need to be developed for a reliable evaluation of these parameters, in order to allow classification and quantification of the magnitude of such effects. The DOK long-term agricultural field experiment was initiated in 1978 in Switzerland for the evaluation of organic and conventional farming practices. It includes three representative Swiss farming systems with biodynamic, bio-organic and conventional fertilization and plant protection schemes along with minerally fertilized and unfertilized controls. Effects on microbial soil characteristics induced by the long-term management at two different stages in the crop rotation, i.e. winter wheat after potato or corn, were investigated by analyzing soil bacterial community structures using analysis of PCR-amplified rRNA genes by terminal restriction fragment length polymorphism and ribosomal intergenic spacer analysis. Application of farmyard manure consistently revealed the strongest influence on bacterial community structures and biomass contents. Effects of management and plant protection regimes occurred on an intermediate level, while the two stages in the crop rotation had a marginal influence that was not significant.

Agriculture↗
PubMedDate not supplied

Genetic determinants of microbial resistance to antibiotics.

Emergence of antibiotic resistance is related to the ease of mutation, to the extent of exchange of genetic information in bacteria by conjugation, transformation, and transduction, and to the large-scale use of antimicrobial agents in the biosphere. In addition to the development of resistance through chromosomal mutation and exchange of chromosomal genes among organisms, there is a more profound enlargement of the gene pool by the dissemination and amplification of plasmids. Two examples of the exchange of antibiotic resistance are analyzed: the transfer of plasmids from Bacteroides fragilis to Escherichia coli and the emergence of antibiotic-resistant strains of STreptococcus pneumoniae. Plasmids encoding antibiotic resistance in B. fragilis were transferred to E. coli by DNA-mediated transformation and conjugation. The beta-lactamase in the transformants and transconjugants displayed the same substrate specificity and electrophoretic mobility as the donor strain. The plasmid apparently was integrated rapidly into the chromosome of the recipient strain. Multiple antibiotic-resistant strains of S. pneumoniae were analyzed for plasmids, and none were detected. Furthermore, no evidence of linkage between the traits of multiple antibiotic resistance was observed. beta-Lactamase was not detected in the penicillin-resistant strains; therefore, it is likely that the resistance in these strains was chromosomal rather than plasmid-mediated. The range of genetic exchange and the use of Koch's postulates in determining the genetic mechanism of antibiotic resistance are illustrated and discussed.

Bacteria↗
PubMed2000

Oral microbial communities: biofilms, interactions, and genetic systems.

Oral microbial-plaque communities are biofilms composed of numerous genetically distinct types of bacteria that live in close juxtaposition on host surfaces. These bacteria communicate through physical interactions called coaggregation and coadhesion, as well as other physiological and metabolic interactions. Streptococci and actinomyces are the major initial colonizers of the tooth surface, and the interactions between them and their substrata help establish the early biofilm community. Fusobacteria play a central role as physical bridges that mediate coaggregation of cells and as physiological bridges that promote anaerobic microenvironments which protect coaggregating strict anaerobes in an aerobic atmosphere. New technologies for investigating bacterial populations with 16S rDNA probes have uncovered previously uncultured bacteria and have offered an approach to in situ examination of the spatial arrangement of the participant cells in oral-plaque biofilms. Flow cells with saliva-coated surfaces are particularly useful for studies of biofilm formation and observation. The predicted sequential nature of colonization of the tooth surface by members of different genera can be investigated by using these new technologies and imaging the cells in situ with confocal scanning laser microscopy. Members of at least seven genera now can be subjected to genetic studies owing to the discovery of gene-transfer systems in these genera. Identification of contact-inducible genes in streptococci offers an avenue to explore bacterial responses to their environment and leads the way toward understanding communication among inhabitants of a multispecies biofilm.

Bacteria↗
PubMed2001

Effect of primers hybridizing to different evolutionarily conserved regions of the small-subunit rRNA gene in PCR-based microbial community analyses and genetic profiling.

Genetic profiling techniques of microbial communities based on PCR-amplified signature genes, such as denaturing gradient gel electrophoresis or single-strand-conformation polymorphism (SSCP) analysis, are normally done with PCR products of less than 500-bp. The most common target for diversity analysis, the small-subunit rRNA genes, however, are larger, and thus, only partial sequences can be analyzed. Here, we compared the results obtained by PCR targeting different variable (V) regions (V2 and V3, V4 and V5, and V6 to V8) of the bacterial 16S rRNA gene with primers hybridizing to evolutionarily conserved flanking regions. SSCP analysis of single-stranded PCR products generated from 13 different bacterial species showed fewer bands with products containing V4-V5 (average, 1.7 bands per organism) than with V2-V3 (2.2 bands) and V6-V8 (2.3 bands). We found that the additional bands (>1 per organism) were caused by intraspecies operon heterogeneities or by more than one conformation of the same sequence. Community profiles, generated by PCR-SSCP from bacterial-cell consortia extracted from rhizospheres of field-grown maize (Zea mays), were analyzed by cloning and sequencing of the dominant bands. A total of 48 sequences could be attributed to 34 different strains from 10 taxonomical groups. Independent of the primer pairs, we found proteobacteria (alpha, beta, and gamma subgroups) and members of the genus Paenibacillus (low G+C gram-positive) to be the dominant organisms. Other groups, however, were only detected with single primer pairs. This study gives an example of how much the selection of different variable regions combined with different specificities of the flanking "universal" primers can affect a PCR-based microbial community analysis.

Bacteria↗
PubMed2005

Genetic diversity of microbial eukaryotes in anoxic sediment around fumaroles on a submarine caldera floor based on the small-subunit rDNA phylogeny.

Recent culture-independent molecular analyses have shown the diversity and ecological importance of microbial eukaryotes (protists) in various marine environments. In the present study we directly extracted DNA from anoxic sediment near active fumaroles on a submarine caldera floor at a depth of 200 m and constructed genetic libraries of PCR-amplified eukaryotic small-subunit (SSU) rDNA. By sequencing cloned SSU rDNA of the libraries and their phylogenetic analyses, it was shown that most sequences have affiliations with known major lineages of eukaryotes (Cercozoa, Alveolata, stramenopiles and Opisthokonta). In particular, some sequences were closely related to those of representatives of eukaryotic parasites, such as Phagomyxa and Cryothecomonas of Cercozoa, Pirsonia of stramenopiles and Ichthyosporea of Opisthokonta, although it is not clear whether the organisms occur in free-living or parasitic forms. In addition, other sequences did not seem to be related to any described eukaryotic lineages suggesting the existence of novel eukaryotes at a high-taxonomic level in the sediment. The community composition of microbial eukaryotes in the sediment we surveyed was different overall from those of other anoxic marine environments previously investigated.

Animals↗
PubMed2006

Genetic Diversity of Microbial Eukaryotes in Anoxic Sediment of the Saline Meromictic Lake Namako-ike (Japan): On the Detection of Anaerobic or Anoxic-tolerant Lineages of Eukaryotes.

Available sequence data on eukaryotic small-subunit ribosomal DNA (SSU rDNA) directly retrieved from various environments have increased recently, and the diversity of microbial eukaryotes (protists) has been shown to be much greater than previously expected. However, the molecular information accumulated to date does still not thoroughly reveal ecological distribution patterns of microbial eukaryotes. In the ongoing challenge to detect anaerobic or anoxic-tolerant lineages of eukaryotes, we directly extracted DNA from the anoxic sediment of a saline meromictic lake, constructed genetic libraries of PCR-amplified SSU rDNA, and performed phylogenetic analyses with the cloned SSU rDNA sequences. Although a few sequences could not be confidently assigned to any major eukaryotic groups in the analyses and are debatable regarding their taxonomic positions, most sequences obtained have affiliations with known major lineages of eukaryotes (Cercozoa, Alveolata, Stramenopiles, and Opisthokonta). Among these sequences, some branched with lineages predominantly composed of uncultured environmental clones retrieved from other anoxic environments, while others were closely related to those of eukaryotic parasites (e.g. Phytomyxea of Cercozoa, Gregarinea of Alveolata, and Ichthyosporea of Opisthokonta).

Anaerobiosis↗
PubMed1995

The genetic engineering of microbial solvent production.

Although the production of acetone and butanol by Clostridium strains was a thriving industrial fermentation process, it is no longer competitive with the chemical synthesis of solvents and has been discontinued. However, studies on the molecular biology of Clostridium strains suggest that genetic engineering for improved solvent production is feasible, and could result in the revival of the industrial fermentation process.

1-Butanol↗