32 research outputs found
Does virulence assessment of Vibrio anguillarum using sea bass (Dicentrarchus labrax) larvae correspond with genotypic and phenotypic characterization?
Background: Vibriosis is one of the most ubiquitous fish diseases caused by bacteria belonging to the genus Vibrio such as Vibrio (Listonella) anguillarum. Despite a lot of research efforts, the virulence factors and mechanism of V. anguillarum are still insufficiently known, in part because of the lack of standardized virulence assays.
Methodology/Principal Findings: We investigated and compared the virulence of 15 V. anguillarum strains obtained from different hosts or non-host niches using a standardized gnotobiotic bioassay with European sea bass (Dicentrarchus labrax L.) larvae as model hosts. In addition, to assess potential relationships between virulence and genotypic and phenotypic characteristics, the strains were characterized by random amplified polymorphic DNA (RAPD) and repetitive extragenic palindromic PCR (rep-PCR) analyses, as well as by phenotypic analyses using Biolog's Phenotype MicroArray (TM) technology and some virulence factor assays.
Conclusions/Significance: Virulence testing revealed ten virulent and five avirulent strains. While some relation could be established between serotype, genotype and phenotype, no relation was found between virulence and genotypic or phenotypic characteristics, illustrating the complexity of V. anguillarum virulence. Moreover, the standardized gnotobiotic system used in this study has proven its strength as a model to assess and compare the virulence of different V. anguillarum strains in vivo. In this way, the bioassay contributes to the study of mechanisms underlying virulence in V. anguillarum
MALDI-TOF/MS identification of species from the Acinetobacter baumannii (Ab) group revisited: inclusion of the novel A. seifertii and A. dijkshoorniae species
OBJECTIVES: Rapid identification of Acinetobacter species is
critical since members of the A. baumannii (Ab) group differ in
antibiotic susceptibility and clinical outcomes. A. baumannii,
A. pittii and A. nosocomialis can be identified by MALDI-TOF/MS,
while the novel species A. seifertii and A. dijkshoorniae
cannot. Low identification rates for A. nosocomialis have also
been reported. We evaluated the use of MALDI-TOF/MS to identify
isolates of A. seifertii and A. dijkshoorniae and revisited the
identification of A. nosocomialis to update the Bruker taxonomy
database. METHODS: Species characterisation was performed by
rpoB-clustering and MLSA. MALDI-TOF/MS spectra were recovered
from formic acid/acetonitrile bacterial extracts overlaid with
alpha-cyano-4-hydroxy-cinnamic acid matrix on a MicroflexLT in
linear positive mode and 2,000-20,000 m/z range mass. Spectra
were examined with the ClinProTools v2.2 software. Mean spectra
(MSP) were created with the BioTyper software. RESULTS:
Seventy-eight Acinetobacter isolates representative of the Ab
group were used to calculate the average spectra/species and
generate pattern recognition models. Species-specific peaks were
identified for all species, and MSPs derived from 3 A.
seifertii, 2 A. dijkshoorniae and 2 A. nosocomialis strains were
added to the Bruker taxonomy database, allowing successful
identification of all isolates using spectra from either
bacterial extracts or direct colonies, resulting in a positive
predictive value (PPV) of 99.6% (777/780) and 96.8% (302/312),
respectively. CONCLUSIONS: The use of post-processing data
software identified statistically significant species-specific
peaks to generate reference signatures for rapid accurate
identification of species within the Ab group, providing
relevant information for the clinical management of
Acinetobacter infections
Acinetobacter dijkshoorniae sp. nov., a new member of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex mainly recovered from clinical samples in different countries
The recent advances in bacterial species identification methods
have led to the rapid taxonomic diversification of the genus
Acinetobacter. In the present study, phenotypic and molecular
methods have been used to determine the taxonomic position of a
group of 12 genotypically distinct strains belonging to the
Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB)
complex, initially described by Gerner-Smidt and Tjernberg in
1993, that are closely related to A. pittii. Strains
characterized in this study originated mostly from human samples
obtained in different countries over a period of 15 years. rpoB
and MLST sequences were compared against those of 94 strains
representing all species included in the ACB complex. Cluster
analysis based on such sequences showed that all 12 strains
grouped together in a distinct clade closest to A. pittii that
was supported by bootstrap values of 99%. Values of average
nucleotide identity based on BLAST between the genome sequence
of strain JVAP01 (NCBI accession n masculine. LJPG00000000) and
those of other species from the ACB were always < 91.2%,
supporting the species status of the group. In addition, the
metabolic characteristics of the group matched those of the ACB
complex and the analysis of their protein signatures by
matrix-assisted laser desorption ionization-time-of-flight mass
spectrometry identified some specific peaks. Our results support
the designation of these strains as a novel species and we
propose the name A. dijkshoorniae sp. nov. The type strain is
JVAP01T (CECT 9134T, LMG 29605T)
PhD Ado Van Assche
Characterization of the bacterial community composition in drinking water production and distribution systems, emphasizing Acinetobacter species
Synergy between UV and NaOCl for disinfection and biofilm treatment in closed water circuits
epub onlystatus: publishe
Phenotypic characterization of Brettanomyces bruxellensis strains for the tolerance to stresses encountered during second generation bioethanol production
Brettanomyces (teleomorph Dekkera) bruxellensis has been generally considered a spoilage yeast in fuel ethanol production plants. However, due to its peculiar carbon- and nitrogen metabolism, the yeast is also believed to hold great potential for bioethanol production in continuous reactors. Nevertheless, before actually being useful in the production of second generation bioethanol there are still some challenges to overcome. For example, the use of lignocellulosic biomass results in the need for an extensive pretreatment process during which often several inhibiting compounds are released, leading to less efficient or stuck fermentations. The objective of this study was to phenotypically characterize B. bruxellensis strains for tolerance to stresses typically encountered during second generation bioethanol fermentation and to develop a screening plate for the evaluation of yeast strains against stresses relevant for the second generation bioethanol production. To this end, a plate was developed containing a dose range of different inhibitors (i.e. vanillin, catechol, levulinic acid, formic acid, furfural, ethanol, low pH, and high osmotic pressure). Further the plate included a negative and positive control well. Subsequently, several B. bruxellensis strains from different ecological niches were screened using the developed plate. Plates were incubated for eight days at 25 °C and analyzed by the OmniLog incubator/reader (Biolog, Hayward, CA, USA). All analysis were performed in duplicate. The different B. bruxellensis strains were ranked by calculating the average well colour development (AWCD). Additionally, each strain was scored for its tolerance to the tested inhibitory conditions. This resulted in a huge variation among strains, demonstrating the need for screening a large collection of strains to identify superior yeast strains. Highly ranked B. bruxellensis strains can then be further tested for tolerance against a mixture of inhibitors and real hydrolyzed biomass fermentation broths. Additionally, features such as ethanol yield and performance in pilot plants should be evaluated to truly see its potential for industrial second generation bioethanol production.status: publishe
Peracetic acid oxidation as an alternative pre-treatment for the anaerobic digestion of waste activated sludge
Anaerobic digestion is generally considered to be an economic and environmentally friendly technology
for treating waste activated sludge, but has some limitations, such as the time it takes for the sludge to be
digested and also the ineffectiveness of degrading the solids. Various pre-treatment technologies have
been suggested to overcome these limitations and to improve the biogas production rate by enhancing
the hydrolysis of organic matter. This paper studies the use of peracetic acid for disintegrating sludge
as a pre-treatment of anaerobic digestion. It has been proved that this treatment effectively leads to a
solubilisation of organic material. A maximum increase in biogas production by 21% is achieved. High
dosages of PAA lead to a decrease in biogas production. This is due to the inhibition of the anaerobic
micro-organisms by the high VFA-concentrations. The evolution of the various VFAs during digestion
is studied and the observed trends support this hypothesis.status: publishe
Evaluation of disinfection techniques for the treatment of biofilms in reused process water
status: publishe
Optimization and evaluation of a DNA array for simultaneous detection of multiple Legionella species in environmental samples
status: publishe
Characterization of the bacterial community composition in water of drinking water production and distribution systems in Flanders, Belgium
The quality of drinking water is influenced by its chemical and microbial composition which in turn may be affected by the source water and the different processes applied in drinking water purification systems. In this study, we investigated the bacterial diversity in different water samples from the production and distribution chain of thirteen drinking water production and distribution systems from Flanders (Belgium) that use surface water or groundwater as source water. Water samples were collected over two seasons from the source water, the processed drinking water within the production facility and out of the tap in houses along its distribution network. 454-pyrosequencing of 16S ribosomal RNA gene sequences revealed a total of 1,570 species-level bacterial operational taxonomic units. Strong differences in community composition were found between processed drinking water samples originating from companies that use surface water and other that use groundwater as source water. Proteobacteria was the most abundant phylum in all samples. Yet, several phyla including Actinobacteria were significantly more abundant in surface water while Cyanobacteria were more abundant in surface water and processed water originating from surface water. Gallionella, Acinetobacter, and Pseudomonas were the three most abundant genera detected. Members of the Acinetobacter genus were even found at a relative read abundance of up to 47.5% in processed water samples, indicating a general occurrence of Acinetobacter in drinking water (systems).status: publishe