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Evaluation of ribotyping techniques as applied to Arcobacter, Campylobacter and Helicobacter.

Restriction fragment length polymorphisms of ribosomal DNA (ribotyping) of many bacterial species has been useful for both epidemiologic subtyping and species identification. However, the use of ribotyping has been confined to major research and reference laboratories due to two factors: (a) the procedure must be carefully optimized for each organism one wishes to investigate and (b) most currently available protocols use hazardous chemicals or radioisotopes. The purpose of this study is to suggest an overall scheme that a clinical or research microbiologist could apply to ribotyping of any organism. In general, we recommend using a guanidium extraction method for DNA extraction, careful optimization of restriction conditions, and hybridization with non-radioactive digoxigenin-labelled probes; these procedures do not use hazardous chemicals or radioisotopes.

Blotting, Southern↗

Novel uncultured Epsilonproteobacteria dominate a filamentous sulphur mat from the 13 degrees N hydrothermal vent field, East Pacific Rise.

Rapid growth of microbial sulphur mats have repeatedly been observed during oceanographic cruises to various deep-sea hydrothermal vent sites. The microorganisms involved in the mat formation have not been phylogenetically characterized, although the production of morphologically similar sulphur filaments by a Arcobacter strain coastal marine has been documented. An in situ collector deployed for 5 days at the 13 degrees N deep-sea hydrothermal vent site on the East Pacific Rise (EPR) was rapidly colonized by a filamentous microbial mat. Microscopic and chemical analyses revealed that the mat consisted of a network of microorganisms embedded in a mucous sulphur-rich matrix. Molecular surveys based on 16S rRNA gene and aclB genes placed all the environmental clone sequences within the Epsilonproteobacteria. Although few 16S rRNA gene sequences were affiliated with that of cultured organisms, the majority was related to uncultured representatives of the Arcobacter group (< or = 95% sequence similarity). A probe designed to target all of the identified lineages hybridized with more than 95% of the mat community. Simultaneous hybridizations with the latter probe and a probe specific to Arcobacter spp. confirmed the numerical dominance of Arcobacter-like bacteria. This study provides the first example of the prevalence and ecological significance of free-living Arcobacter at deep-sea hydrothermal vents.

Bacterial Adhesion↗

PCR-mediated DNA fingerprinting of atypical campylobacter strains isolated from surface and drinking water.

This study shows that typing through polymerase chain reaction (PCR) can be used to differentiate between strains of Campylobacter and Arcobacter, whereas by means of conventional biotyping Arcobacter might be identified as atypical Campylobacter. Microaerophilic "campylobacter-like" organisms were isolated from several drinking water treatment plants as well as environmental sources. The strains were characterized by biotyping and PCR amplification of Campylobacter flaA/flaB and 16s-rRNA Arcobacter butzleri-specific genes.

Animals↗

The occurrence of campylobacters in water sources in South Africa.

Campylobacter spp., mainly C. jejuni and C. coli, are recognized as significant human bacterial pathogens, being responsible for increasing numbers of gastroenteritis cases worldwide. Several reports have indicated that environmental waters are potential reservoirs and transmitting vehicles for these bacteria. The purpose of this study was thus to examine the occurrence of campylobacters in drinking and environmental water sources of South Africa, a country with a warmer climate and higher microbial pollution levels than those previously addressed in the Northern Hemisphere where similar investigations have been undertaken. Various types of water samples (five drinking water, four ground water, 11 surface water and four raw sewage) were collected from different parts of South Africa. Detection was by enrichment in Bolton broth prior to plating on both selective mCCDA or through a 0.6microm membrane filter on non-selective blood agar isolation media. Out of 100 initially selected Campylobacter-like isolates, only 22 did not grow aerobically and were subsequently identified as Campylobacter spp. by biochemical tests. However, the results obtained by 16S rRNA sequence analysis indicated that only three of these strains (13.6%) were Campylobacter jejuni and the remaining 19 strains were identified as Arcobacter butzleri. The spread of Arcobacter via water warrants further investigation, especially in view of the higher levels of detection and pathogenic nature of these bacteria.

Campylobacter↗

Rapid identification by PCR of the genus Campylobacter and of five Campylobacter species enteropathogenic for man and animals.

The nucleotide sequences for the 16S ribosomal RNA gene were compared for 33 species comprising the epsilon subdivision of the Proteobacteria (genera: Campylobacter, Helicobacter, Arcobacter and Wolinella). Regions specific for the genus Campylobacter and for five Campylobacter species important in human and/or veterinary medicine were identified. From these regions, PCR primer pairs were designed for use in species-specific identification. Primer pairs were validated against strains representing all taxa of campylobacter-like organisms. They did not amplify products other than from their five target species (C. upsaliensis, C. helveticus, C. fetus, C. hyointestinalis and C. lari), and they generated amplicons of defined size from large numbers of strains of those species. A primer pair suitable for identification of the genus Campylobacter was also identified and validated. This generated amplicons from all species of Campylobacter as well as from unnamed groups known to be within the genus, but not from any species or unnamed strains of Helicobacter, Arcobacter or Wolinella.

Animals↗

Three supplementary diagnostic tests for Campylobacter species and related organisms.

We analyzed 307 recent clinical isolates and reference strains of Campylobacter spp., Helicobacter spp., and Arcobacter spp. for arylsulfatase and pyrazinamidase activities and susceptibility to polymyxin B. All isolates studied were identified by DNA dot hybridization prior to testing. Campylobacter concisus, C. sputorum, and Helicobacter fennelliae were positive for arylsulfatase. C. jejuni, C. coli, C. lari, C. upsaliensis, and C. concisus were positive for pyrazinamidase. Only Helicobacter spp. were resistant to polymyxin B. C. fetus subsp. fetus, C. hyointestinalis, C. mucosalis, and Arcobacter spp. were negative in all three tests. The tests were simple to perform and read, and with the exception of C. sputorum biovars, all isolates within a species gave consistently positive or negative results in all the assays. These three phenotypic tests may help refine current methods for phenotypic identification of Campylobacter spp. and related organisms in a reference laboratory setting.

Amidohydrolases↗

Usefulness of the MicroSeq 500 16S ribosomal DNA-based bacterial identification system for identification of clinically significant bacterial isolates with ambiguous biochemical profiles.

Due to the inadequate automation in the amplification and sequencing procedures, the use of 16S rRNA gene sequence-based methods in clinical microbiology laboratories is largely limited to identification of strains that are difficult to identify by phenotypic methods. In this study, using conventional full-sequence 16S rRNA gene sequencing as the "gold standard," we evaluated the usefulness of the MicroSeq 500 16S ribosomal DNA (rDNA)-based bacterial identification system, which involves amplification and sequencing of the first 527-bp fragment of the 16S rRNA genes of bacterial strains and analysis of the sequences using the database of the system, for identification of clinically significant bacterial isolates with ambiguous biochemical profiles. Among 37 clinically significant bacterial strains that showed ambiguous biochemical profiles, representing 37 nonduplicating aerobic gram-positive and gram-negative, anaerobic, and Mycobacterium species, the MicroSeq 500 16S rDNA-based bacterial identification system was successful in identifying 30 (81.1%) of them. Five (13.5%) isolates were misidentified at the genus level (Granulicatella adiacens was misidentified as Abiotrophia defectiva, Helcococcus kunzii was misidentified as Clostridium hastiforme, Olsenella uli was misidentified as Atopobium rimae, Leptotrichia buccalis was misidentified as Fusobacterium mortiferum, and Bergeyella zoohelcum was misidentified as Rimerella anatipestifer), and two (5.4%) were misidentified at the species level (Actinomyces odontolyticus was misidentified as Actinomyces meyeri and Arcobacter cryaerophilus was misidentified as Arcobacter butzleri). When the same 527-bp DNA sequences of these seven isolates were compared to the known 16S rRNA gene sequences in the GenBank, five yielded the correct identity, with good discrimination between the best and second best match sequences, meaning that the reason for misidentification in these five isolates was due to a lack of the 16S rRNA gene sequences of these bacteria in the database of the MicroSeq 500 16S rDNA-based bacterial identification system. In conclusion, the MicroSeq 500 16S rDNA-based bacterial identification system is useful for identification of most clinically important bacterial strains with ambiguous biochemical profiles, but the database of the MicroSeq 500 16S rDNA-based bacterial identification system has to be expanded in order to encompass the rarely encountered bacterial species and achieve better accuracy in bacterial identification.

Bacteria↗

Detection of campylobacter species: a comparison of culture and polymerase chain reaction based methods.

AIMS: To investigate the optimal method for the detection of campylobacters from stool samples by comparing selective culture with membrane filtration and the polymerase chain reaction (PCR). METHODS: Three hundred and forty three stool samples were investigated by each of the three methods mentioned above. Selective culture was performed with charcoal cefoperazone desoxycholate agar plates. Membrane filtration was performed using cellulose triacetate membranes with 0.45 micro m pores placed on blood agar plates. Enteropathogenic campylobacters were detected using a PCR identification algorithm, consisting of screening PCRs and species identification using a PCR enzyme linked immunosorbent assay (PCR-ELISA), both based on the 16S rRNA gene. RESULTS: Of the 343 samples tested, 23 were positive by one or more method. Of these, 17 were positive by selective culture, 12 by membrane filtration, and 20 by the PCR identification algorithm. A total of 18 of 23 positives were identified as C jejuni and/or C coli by the PCR identification algorithm, compared with 14 identified to the genus level by selective culture, and 10 by membrane filtration. Among the remaining five positive samples, one C hyointestinalis was detected only by the PCR identification algorithm; one C upsaliensis was detected only by the PCR identification algorithm; one Campylobacter sp was detected by membrane filtration and selective culture and later identified as C concisus; one Campylobacter sp was detected by membrane filtration alone and later identified as Arcobacter sp; and one Campylobacter sp detected only by selective culture was lost to study and therefore not speciated. There was no significant difference between detection by selective culture and the other two methods. However, detection by PCR was significantly better than by membrane filtration (0.05 > p > 0.02). CONCLUSION: The PCR identification algorithm can detect and identify Campylobacter spp to the species level and the result is obtained on the same day. However, PCR is expensive, labour intensive, and does not provide an isolate for further identification or typing. Selective culture is as good as the PCR identification algorithm for the detection of the two most common species, C jejuni and C coli, and it is cheap and practical. However, it does miss the less common species, results take 48 hours, and identification is only to the genus level. Membrane filtration showed a low sensitivity compared with the other methods and is not appropriate for the diagnostic laboratory, although it was the only method to detect the Arcobacter sp. The optimum method for the detection of campylobacters from stool samples in the diagnostic laboratory remains selective culture.

Agar↗

Comparative disinfection of secondary-treated sewage with chlorine dioxide and bromine chloride.

A comparison was made of the inactivation rates of Arcobacter butzleri, coliphages, total coliforms, fecal coliforms, fecal streptococci and heterotrophic plate count in secondary sewage effluent using chlorine dioxide (2 and 4 ppm) and bromine chloride (4 or 8 and 12 ppm) as disinfecting agents. Using these doses the ClO2 gave higher reduction percentages (on average more than 99% at 4 ppm) than those obtained with BrCl. The average values of the fecal indicators are well within the legal limits. Arcobacter butzleri was more sensitive to the disinfectants than other bacteria while fecal streptococci were seen to be more resistant. From the chemical point of view no differences were seen between the two disinfectants except that the action of ClO2 was stronger regarding BOD5 than that of BrCl. With the exception of dichloromethane, the concentration of volatile halogenated compounds showed little variation and values were often lower than detection limits.

Bromides↗

Clogging of a limestone fracture by stimulating groundwater microbes.

Biological clogging is promoted in aquifers either to contain or to remediate groundwater. In this study, an apparatus able to detect small changes in hydraulic conductivity (K) was developed to measure the clogging of a single fracture in limestone, following microbial stimulation. The fracture had a 2.5 mm2 section and was 50 cm long. Prior to the inoculation of the limestone, the sequencing of representative clones from 16S rRNA genes isolated from groundwater, showed significant affiliation with Cytophaga spp., Arcobacter spp. and Rhizobium spp. These bacteria are known to secrete extracellular polymeric substances and form biofilms. When nutrients were added to the inoculated limestone, a decrease in K occurred after 8 days, reaching 0.8% of its initial value after 22 days (Kfi = 340 cm min-1). This study showed that a stimulation of indigenous microbes from groundwater effectively clogged a macrofracture in limestone, suggesting the potential application of biobarriers in fractured rock aquifers.

Arcobacter↗

Distribution of potentially pathogenic bacteria as free living and plankton associated in a marine coastal zone.

AIMS: To determine the abundance of faecal and nonfaecal bacteria related to human and animal health, as free living or associated with small (>64 microm) and large (>200 microm) plankton, samples were collected monthly from the coastal zone at Messina (Italy). METHODS AND RESULTS: Different enrichment and selective cultural methods were used to determine the abundance of bacteria in sea water and plankton. The bacteria were more frequently isolated from water and large plankton than from small plankton. Vibrio and Aeromonas spp. showed different distribution patterns in water and plankton. Faecal indicators were always present in water and the large size class plankton samples. Enterococci associated with large plankton were more abundant than E. coli in the winter. Vibrio species distributions were different in water and plankton samples. Among arcobacters only A. butzleri was isolated from water and plankton samples. Campylobacter spp. was always absent in small plankton and more frequent in large plankton than in water. CONCLUSIONS: The colonization of zooplankton by potentially pathogenic bacteria is a widespread phenomenon. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of potentially pathogenic bacteria in sea water and associated with plankton can have ecological and epidemiological implications.

Aeromonas↗

Partitioning of bacterial communities between seawater and healthy, black band diseased, and dead coral surfaces.

Distinct partitioning has been observed in the composition and diversity of bacterial communities inhabiting the surface and overlying seawater of three coral species infected with black band disease (BBD) on the southern Caribbean island of Curaçao, Netherlands Antilles. PCR amplification and sequencing of bacterial 16S rRNA genes (rDNA) with universally conserved primers have identified over 524 unique bacterial sequences affiliated with 12 bacterial divisions. The molecular sequences exhibited less than 5% similarity in bacterial community composition between seawater and the healthy, black band diseased, and dead coral surfaces. The BBD bacterial mat rapidly migrates across and kills the coral tissue. Clone libraries constructed from the BBD mat were comprised of eight bacterial divisions and 13% unknowns. Several sequences representing bacteria previously found in other marine and terrestrial organisms (including humans) were isolated from the infected coral surfaces, including Clostridium spp., Arcobacter spp., Campylobacter spp., Cytophaga fermentans, Cytophaga columnaris, and Trichodesmium tenue.

Animals↗

Evidence for autotrophic CO2 fixation via the reductive tricarboxylic acid cycle by members of the epsilon subdivision of proteobacteria.

Based on 16S rRNA gene surveys, bacteria of the epsilon subdivision of proteobacteria have been identified to be important members of microbial communities in a variety of environments, and quite a few have been demonstrated to grow autotrophically. However, no information exists on what pathway of autotrophic carbon fixation these bacteria might use. In this study, Thiomicrospira denitrificans and Candidatus Arcobacter sulfidicus, two chemolithoautotrophic sulfur oxidizers of the epsilon subdivision of proteobacteria, were examined for activities of the key enzymes of the known autotrophic CO(2) fixation pathways. Both organisms contained activities of the key enzymes of the reductive tricarboxylic acid cycle, ATP citrate lyase, 2-oxoglutarate:ferredoxin oxidoreductase, and pyruvate:ferredoxin oxidoreductase. Furthermore, no activities of key enzymes of other CO(2) fixation pathways, such as the Calvin cycle, the reductive acetyl coenzyme A pathway, and the 3-hydroxypropionate cycle, could be detected. In addition to the key enzymes, the activities of the other enzymes involved in the reductive tricarboxylic acid cycle could be measured. Sections of the genes encoding the alpha- and beta-subunits of ATP citrate lyase could be amplified from both organisms. These findings represent the first direct evidence for the operation of the reductive tricarboxylic acid cycle for autotrophic CO(2) fixation in epsilon-proteobacteria. Since epsilon-proteobacteria closely related to these two organisms are important in many habitats, such as hydrothermal vents, oxic-sulfidic interfaces, or oilfields, these results suggest that autotrophic CO(2) fixation via the reductive tricarboxylic acid cycle might be more important than previously considered.

Arcobacter↗

Development of a PCR ELISA assay for the identification of Campylobacter jejuni and Campylobacter coli.

A polymerase chain reaction (PCR) assay was developed based on a solution-hybridization colorimetric end-point detection format (PCR ELISA) for the identification of Campylobacter jejuni and Campylobacter coli. PCR primers were designed to target a gene sequence with species-specific motifs. Five biotin-labelled probes targeted to the species-specific motifs were investigated for the detection of digoxygenin-labelled PCR products from C. jejuni and C. coli using the PCR ELISA format. Two probes were identified, one which reacts with both the C. jejuni and C. coli target sequences (probe CC2) and one probe which reacts with the C. jejuni target sequence only (probe CJ2). The specificity of the assay with the CJ2 and CC2 probes was investigated with a range of Campylobacter spp., Arcobacter spp., Helicobacter spp. and a range of unrelated organisms. The PCR ELISA assay and probes were demonstrated to be specific for C. jejuni and C. coli. The sensitivity of the PCR ELISA assay was demonstrated to be 10-100-fold more sensitive than a gel-based PCR method using the same primers. This PCR ELISA assay is sensitive, specific and significantly reduces the time needed for the identification of C. jejuni and C. coli and has the potential to facilitate early detection of these important gastro-intestinal pathogens.

Campylobacter Infections↗

Molecular, biochemical and ecological characterisation of a bio-catalytic calcification reactor.

Bio-catalytic calcification (BCC) reactors utilise microbial urea hydrolysis by autochthonous bacteria for the precipitation-removal of calcium, as calcite, from industrial wastewater. Due to the limited knowledge available concerning natural ureolytic microbial calcium carbonate (CaCO(3)) precipitation, the microbial ecology of BCC reactors has remained a black box to date. This paper characterises BCC reactor evolution from initialisation to optimisation over a 6-week period. Three key parameters were studied: (1) microbial evolution, (2) the (bio)chemical CaCO(3) precipitation pathway, and (3) crystal nucleation site development. Six weeks were required to establish optimal reactor performance, which coincided with an increase in urease activity from an initial 7 mg urea l(-1) reactor h(-1) to about 100 mg urea l(-1) reactor h(-1). Urease activity in the optimal period was directly proportional to Ca(2+) removal, but urease gene diversity was seemingly limited to a single gene. Denaturing gradient gel electrophoresis of 16S rRNA genes revealed the dynamic evolution of the microbial community structure of the calcareous sludge, which was eventually dominated by a few species including Porphyromonas sp., Arcobacter sp. and Bacteroides sp. Epi-fluorescence and scanning electron microscopy showed that the calcareous sludge was colonised with living bacteria, as well as the calcified remains of organisms. It appears that the precipitation event is localised in a micro-environment, due to colonisation of crystal nucleation sites (calcareous sludge) by the precipitating organisms.

Base Sequence↗

Analysis of the composition of bacterial communities in oil reservoirs from a southern offshore Brazilian basin.

The aim of this study was to characterize and compare the bacterial community structure of two distinct oil samples from a petroleum field in Brazil by using both molecular, based on the construction of 16S rRNA gene libraries, and cultivation methods. Statistical comparisons of libraries based on Amplified Ribosomal DNA Restriction Analysis (ARDRA) data revealed no significant differences between the communities recovered in the non-biodegraded (NBD) and highly biodegraded oils (HBD). BlastN analysis of the 16S rRNA gene sequences representative of distinct ribotypes from both oils showed the presence of nine different bacterial genera in these samples, encompassing members of the genera Arcobacter, Halanaerobium, Marinobacter, Propionibacterium, Streptomyces, Leuconostoc, Acinetobacter, Bacillus and Streptococcus. Enrichments obtained using oil as inoculum and sole carbon source yielded bacterial isolates showing high 16S rRNA gene sequence similarity with Achromobacter xylosoxidans, Bacillus subtilis, Brevibacillus sp., Dietzia sp. and Methylobacterium sp. Comparison between the data obtained using cultivation-independent and enrichment cultures suggests that different selection of community members may occur when using distinct approaches. All the organisms found, except for Leuconostoc sp. and Streptococus sp., have been previously reported in the literature as hydrocarbon degraders and/or associated to oil field environments.

Bacteria↗