bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification and Characterization of Integron-Mediated Antibiotic Resistance among Shiga Toxin-Producing
Escherichia coli
Isolates
Authors: Zhao Shaohua , White David G. , Ge Beilei , Ayers Sherry , Friedman Sharon , English Linda , Wagner David , Gaines Stuart , Meng Jianghong 
Published: July 2002

ABSTRACT

A total of 50 isolates of Shiga toxin-producing
Escherichia coli
(STEC), including 29 O157:H7 and 21 non-O157 STEC strains, were analyzed for antimicrobial susceptibilities and the presence of class 1 integrons. Seventy-eight (
n
= 39) percent of the isolates exhibited resistance to two or more antimicrobial classes. Multiple resistance to streptomycin, sulfamethoxazole, and tetracycline was most often observed. Class 1 integrons were identified among nine STEC isolates, including serotypes O157:H7, O111:H11, O111:H8, O111:NM, O103:H2, O45:H2, O26:H11, and O5:NM. The majority of the amplified integron fragments were 1 kb in size with the exception of one
E. coli
O111:H8 isolate which possessed a 2-kb amplicon. DNA sequence analysis revealed that the integrons identified within the O111:H11, O111:NM, O45:H2, and O26:H11 isolates contained the
aadA
gene encoding resistance to streptomycin and spectinomycin. Integrons identified among the O157:H7 and O103:H2 isolates also possessed a similar
aadA
gene. However, DNA sequencing revealed only 86 and 88% homology, respectively. The 2-kb integron of the
E. coli
O111:H8 isolate contained three genes,
dfr
XII,
aadA
2, and a gene of unknown function,
orfF
, which were 86, 100, and 100% homologous, respectively, to previously reported gene cassettes identified in integrons found in
Citrobacter freundii
and
Klebsiella pneumoniae
. Furthermore, integrons identified among the O157:H7 and O111:NM strains were transferable via conjugation to another strain of
E. coli
O157:H7 and to several strains of
Hafnia alvei
. To our knowledge, this is the first report of integrons and antibiotic resistance gene cassettes in STEC, in particular
E. coli
O157:H7.
Phylogenetic Diversity of Bacterial and Archaeal Communities in the Anoxic Zone of the Cariaco Basin
Authors: Madrid Vanessa M. , Taylor Gordon T. , Scranton Mary I. , Chistoserdov Andrei Y. 
Published: July 2002

ABSTRACT

Microbial community samples were collected from the anoxic zone of the Cariaco Basin at depths of 320, 500, and 1,310 m on a November 1996 cruise and were used to construct 16S ribosomal DNA libraries. Of 60 nonchimeric sequences in the 320-m library, 56 belonged to the ɛ subdivision of the
Proteobacteria
(ɛ-
Proteobacteria
) and 53 were closely related to ectosymbionts of
Rimicaris exoculata
and
Alvinella pompejana
, which are referred to here as epsilon symbiont relatives (ESR). The 500-m library contained sequences affiliated with the fibrobacteria, the
Flexibacter-Cytophaga-Bacteroides
division, the division
Verrucomicrobia
, the division
Proteobacteria
, and the OP3 candidate division. The Proteobacteria included members of the γ, δ, ɛ and new candidate subdivisions, and γ-proteobacterial sequences were dominant (25.6%) among the proteobacterial sequences. As in the 320-m library, the majority of the ɛ-proteobacteria belonged to the ESR group. The genus
Fibrobacter
and its relatives were the second largest group in the library (23.6%), followed by the δ-proteobacteria and the ɛ-proteobacteria. The 1,310-m library had the greatest diversity; 59 nonchimeric clones in the library contained 30 unique sequences belonging to the planctomycetes, the fibrobacteria, the
Flexibacter-Cytophaga-Bacteroides
division, the
Proteobacteria
, and the OP3 and OP8 candidate divisions. The proteobacteria included members of new candidate subdivisions and the β, γ, δ, and ɛ-subdivisions. ESR sequences were still present in the 1,310-m library but in a much lower proportion (8.5%). One archaeal sequence was present in the 500-m library (2% of all microorganisms in the library), and eight archaeal sequences were present in the 1,310-m library (13.6%). All archaeal sequences fell into two groups; two clones in the 1,310-m library belonged to the kingdom
Crenarchaeota
and the remaining sequences in both libraries belonged to the kingdom
Euryarchaeota
. The latter group appears to be related to the Eel-TA1f2 sequence, which belongs to an archaeon suggested to be able to oxidize methane anaerobically. Based on phylogenetic inferences and measurements of dark CO
2
fixation, we hypothesized that (i) the ESR are autotrophic anaerobic sulfide oxidizers, (ii) sulfate reduction and fermentative metabolism may be carried out by a large number of bacteria in the 500- and 1,310-m libraries, and (iii) members of the
Euryarchaeota
found in relatively large numbers in the 1,310-m library may be involved in anaerobic methane oxidation. Overall, the composition of microbial communities from the Cariaco Basin resembles the compositions of communities from several anaerobic sediments, supporting the hypothesis that the Cariaco Basin water column is similar to anaerobic sediments.
Hydrolysis of 4-Hydroxybenzoic Acid Esters (Parabens) and Their Aerobic Transformation into Phenol by the Resistant
Enterobacter cloacae
Strain EM
Authors: Valkova Nelly , Lépine François , Valeanu Loredana , Dupont Maryse , Labrie Louisette , Bisaillon Jean-Guy , Beaudet Réjean , Shareck François , Villemur Richard 
Published: July 2002

ABSTRACT

Enterobacter cloacae
strain EM was isolated from a commercial dietary mineral supplement stabilized by a mixture of methylparaben and propylparaben. It harbored a high-molecular-weight plasmid and was resistant to high concentrations of parabens. Strain EM was able to grow in liquid media containing similar amounts of parabens as found in the mineral supplement (1,700 and 180 mg of methyl and propylparaben, respectively, per liter or 11.2 and 1.0 mM) and in very high concentrations of methylparaben (3,000 mg liter
−1
, or 19.7 mM). This strain was able to hydrolyze approximately 500 mg of methyl-, ethyl-, or propylparaben liter
−1
(3 mM) in less than 2 h in liquid culture, and the supernatant of a sonicated culture, after a 30-fold dilution, was able to hydrolyze 1,000 mg of methylparaben liter
−1
(6.6 mM) in 15 min. The first step of paraben degradation was the hydrolysis of the ester bond to produce 4-hydroxybenzoic acid, followed by a decarboxylation step to produce phenol under aerobic conditions. The transformation of 4-hydroxybenzoic acid into phenol was stoichiometric. The conversion of approximately 500 mg of parabens liter
−1
(3 mM) to phenol in liquid culture was completed within 5 h without significant hindrance to the growth of strain EM, while higher concentrations of parabens partially inhibited its growth.
Requirement for Phosphoglucomutase in Exopolysaccharide Biosynthesis in Glucose- and Lactose-Utilizing
Streptococcus thermophilus
Authors: Levander Fredrik , Rådström Peter 
Published: July 2002

ABSTRACT

To study the influence of phosphoglucomutase (PGM) activity on exopolysaccharide (EPS) synthesis in glucose- and lactose-growing
Streptococcus thermophilus
, a knockout PGM mutant and a strain with elevated PGM activity were constructed. The
pgmA
gene, encoding PGM in
S. thermophilus
LY03, was identified and cloned. The gene was functional in
Escherichia coli
and was shown to be expressed from its own promoter. The
pgmA
-deficient mutant was unable to grow on glucose, while the mutation did not affect growth on lactose. Overexpression of
pgmA
had no significant effect on EPS production in glucose-growing cells. Neither deletion nor overexpression of
pgmA
changed the growth or EPS production on lactose. Thus, the EPS precursors in lactose-utilizing
S. thermophilus
are most probably formed from the galactose moiety of lactose via the Leloir pathway, which circumvents the need for a functional PGM.
Assessing the Risk of Primary Amoebic Meningoencephalitis from Swimming in the Presence of EnvironmentalNaegleria fowleri
Authors: Cabanes Pierre-André , Wallet France , Pringuez Emmanuelle , Pernin Pierre 
Published: July 2002

ABSTRACTFree-livingNaegleria fowleriamoebae cause primary amoebic meningoencephalitis (PAM). Because of the apparent conflict between their ubiquity and the rarity of cases observed, we sought to develop a model characterizing the risk of PAM after swimming as a function of the concentration ofN. fowleri. The probability of death from PAM as a function of the number of amoebae inhaled is modeled according to results obtained from animals infected with amoeba strains. The calculation of the probability of inhaling one or more amoebae while swimming is based on a double hypothesis: that the distribution of amoebae in the water follows a Poisson distribution and that the mean quantity of water inhaled while swimming is 10 ml. The risk of PAM for a given concentration of amoebae is then obtained by summing the following products: the probability of inhalingnamoebae × the probability of PAM associated with inhaling thesenamoebae. We chose the lognormal model to assess the risk of PAM because it yielded the best analysis of the studentized residuals. Nonetheless, the levels of risk thereby obtained cannot be applied to humans without correction, because they are substantially greater than those indicated by available epidemiologic data. The curve was thus adjusted by a factor calculated with the least-squares method. This provides the PAM risk in humans as a function of theN. fowlericoncentration in the river. For example, the risk is 8.5 × 10−8at a concentration of 10N. fowleriamoebae per liter.
Generation of a Novel
Saccharomyces cerevisiae
Strain That Exhibits Strong Maltose Utilization and Hyperosmotic Resistance Using Nonrecombinant Techniques
Authors: Higgins Vincent J. , Bell Philip J. L. , Dawes Ian W. , Attfield Paul V. 
Published: July 2002

ABSTRACT

A yeast strain capable of leavening both unsugared and sweet bread dough efficiently would reduce the necessity of carrying out the expensive procedure of producing multiple baker's yeast strains. But issues involving the use of genetically modified foods have rendered the use of recombinant techniques for developing yeast strains controversial. Therefore, we used strong selection and screening systems in conjunction with traditional mass mating techniques to develop a strain of
Saccharomyces cerevisiae
that efficiently leavens both types of dough.
Intraspecies Genomic Groups in
Enterococcus faecium
and Their Correlation with Origin and Pathogenicity
Authors: Vancanneyt Marc , Lombardi Angiolella , Andrighetto Christian , Knijff Edo , Torriani Sandra , Björkroth K. Johanna , Franz Charles M. A. P. , Foulquié Moreno María R. , Revets Hilde , De Vuyst Luc , Swings Jean , Kersters Karel , Dellaglio Franco , Holzapfel Wilhelm H. 
Published: July 2002

ABSTRACT

Seventy-eight
Enterococcus faecium
strains from various sources were characterized by random amplified polymorphic DNA (RAPD)-PCR, amplified fragment length polymorphism (AFLP), and pulsed-field gel electrophoresis (PFGE) analysis of
Sma
I restriction patterns. Two main genomic groups (I and II) were obtained in both RAPD-PCR and AFLP analyses. DNA-DNA hybridization values between representative strains of both groups demonstrated a mean DNA-DNA reassociation level of 71%. PFGE analysis revealed high genetic strain diversity within the two genomic groups. Only group I contained strains originating from human clinical samples or strains that were vancomycin-resistant or beta-hemolytic. No differentiating phenotypic features between groups I and II were found using the rapid ID 32 STREP system. The two groups could be further subdivided into, respectively, four and three subclusters in both RAPD-PCR and AFLP analyses, and a high correlation was seen between the subclusters generated by these two methods. Subclusters of group I were to some extent correlated with origin, pathogenicity, and bacteriocinogeny of the strains. Host specificity of
E. faecium
strains was not confirmed.
Spatially Oscillating Activity and Microbial Succession of Mercury-Reducing Biofilms in a Technical-Scale Bioremediation System
Authors: von Canstein Harald , Li Ying , Leonhäuser Johannes , Haase Elke , Felske Andreas , Deckwer Wolf-Dieter , Wagner-Döbler Irene 
Published: July 2002

ABSTRACT
Mercury-contaminated chemical wastewater of a mercury cell chloralkali plant was cleaned on site by a technical-scale bioremediation system. Microbial mercury reduction of soluble Hg(II) to precipitating Hg(0) decreased the mercury load of the wastewater during its flow through the bioremediation system by up to 99%. The system consisted of a packed-bed bioreactor, where most of the wastewater's mercury load was retained, and an activated carbon filter, where residual mercury was removed from the bioreactor effluent by both physical adsorption and biological reduction. In response to the oscillation of the mercury concentration in the bioreactor inflow, the zone of maximum mercury reduction oscillated regularly between the lower and the upper bioreactor horizons or the carbon filter. At low mercury concentrations, maximum mercury reduction occurred near the inflow at the bottom of the bioreactor. At high concentrations, the zone of maximum activity moved to the upper horizons. The composition of the bioreactor and carbon filter biofilms was investigated by 16S-23S ribosomal DNA intergenic spacer polymorphism analysis. Analysis of spatial biofilm variation showed an increasing microbial diversity along a gradient of decreasing mercury concentrations. Temporal analysis of the bioreactor community revealed a stable abundance of two prevalent strains and a succession of several invading mercury-resistant strains which was driven by the selection pressure of high mercury concentrations. In the activated carbon filter, a lower selection pressure permitted a steady increase in diversity during 240 days of operation and the establishment of one mercury-sensitive invader.
Inactivation of the Regulatory Gene
algU
or
gacA
Can Affect the Ability of Biocontrol
Pseudomonas fluorescens
CHA0 To Persist as Culturable Cells in Nonsterile Soil
Authors: Mascher Fabio , Moënne-Loccoz Yvan , Schnider-Keel Ursula , Keel Christoph , Haas Dieter , Défago Geneviève 
Published: July 2002

ABSTRACT

Rifampin-resistant
Pseudomonas fluorescens
CHA0-Rif and mutants in which the regulatory gene
algU
(encoding sigma factor σ
E
) or
gacA
(encoding a global regulator of secondary metabolism) was inactivated were compared for persistence in three nonsterile soils. Functional
algU
and (particularly)
gacA
were needed for CHA0-Rif to maintain cell culturability in soil.
Assessment of the Genetic Diversity among Arcobacters Isolated from Poultry Products by Using Two PCR-Based Typing Methods
Authors: Houf Kurt , De Zutter Lieven , Van Hoof Jan , Vandamme Peter 
Published: July 2002

ABSTRACT

In this study, enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and randomly amplified polymorphic DNA PCR (RAPD-PCR) were optimized for characterization of
Arcobacter butzleri
,
Arcobacter cryaerophilus
, and
Arcobacter skirrowii
. In addition, a simple and rapid DNA extraction method was tested for use in both typing procedures. Both methods had satisfactory typeability and discriminatory power, but the fingerprints generated with ERIC-PCR were more reproducible and complex than those obtained with RAPD-PCR. The use of nondiluted boiled cell suspensions as DNA templates was found to be very useful in ERIC-PCR. Characterization of large numbers of
Arcobacter
isolates is therefore preferably performed by the ERIC-PCR procedure. Isolates for which almost identical ERIC fingerprints are generated may subsequently be characterized by RAPD-PCR, although adjustment and standardization of the amount of the DNA template are necessary. In the second part of this study, the genotypic diversity of arcobacters present on broiler carcasses was assessed by using both typing methods. A total of 228 cultures from 24 samples were examined after direct isolation and enrichment. The isolates were identified by using a multiplex PCR as
A. butzleri
(
n
= 182) and
A. cryaerophilus
(
n
= 46). A total of 131 types (91
A. butzleri
types and 40
A. cryaerophilus
types) were discerned without discordance between the two typing techniques. The analysis of the poultry isolates showed that poultry products may harbor not only more than one species but also multiple genotypes. All genotypes were confined to one poultry sample, and only three genotypes were found after simultaneous enrichment and direct isolation. These results demonstrate that different outcomes can be obtained in epidemiological studies depending on the isolation procedure used and the number of isolates characterized.
Microbial Load of Drinking Water Reservoir Tributaries during Extreme Rainfall and Runoff
Authors: Kistemann T. , Claßen T. , Koch C. , Dangendorf F. , Fischeder R. , Gebel J. , Vacata V. , Exner M. 
Published: July 2002

ABSTRACT

Hygienic and microbiological examinations of watercourses are usually not carried out during heavy rainfall and runoff events. After rainfall or snowmelt, there are often massive increases in turbidity in flooding creeks in mountain ranges, which are frequently interpreted as an indication of microbial contamination. The aim of this study was to quantify the microbial loads of watercourses during such runoff events and to compare these loads with loads occurring during regular conditions. In a 14-month monitoring period we investigated the microbial loads of three tributaries of different drinking water reservoirs. A total of 99 water samples were taken under different runoff conditions and analyzed to determine physical, chemical, bacterial, and parasitic parameters. Thirty-two water samples were considered event samples during nine measuring series. The criteria for events, based on duration and intensity of precipitation, water depth gauge measurements, and dynamics, had been fixed before the investigation for each creek individually. Of the physical and chemical parameters examined, only the turbidity, pH, and nitrate values differed clearly from the values obtained for regular samples. Most of the bacteriological parameters investigated (colony,
Escherichia coli
, coliform, fecal streptococcal, and
Clostridium perfringens
counts) increased considerably during extreme runoff events. If relevant sources of parasitic contamination occurred in catchment areas, the concentrations of
Giardia
and
Cryptosporidium
rose significantly during events. The results show that substantial shares of the total microbial loads in watercourses and in drinking water reservoirs result from rainfall and extreme runoff events. Consequently, regular samples are considered inadequate for representing the microbial contamination of watercourse systems. The procedures for raw water surveillance in the context of multiple-barrier protection and risk assessment ought to include sampling during extreme runoff situations.
Differences in Growth of
Salmonella enterica
and
Escherichia coli
O157:H7 on Alfalfa Sprouts
Authors: Charkowski A. O. , Barak J. D. , Sarreal C. Z. , Mandrell R. E. 
Published: July 2002

ABSTRACT

Sprout producers have recently been faced with several
Salmonella enterica
and
Escherichia coli
O157:H7 outbreaks. Many of the outbreaks have been traced to sprout seeds contaminated with low levels of human pathogens. Alfalfa seeds were inoculated with
S. enterica
and
E. coli
O157:H7 strains isolated from alfalfa seeds or other environmental sources and sprouted to examine growth of these human pathogens in association with sprouting seeds.
S. enterica
strains grew an average of 3.7 log
10
on sprouting seeds over 2 days, while
E. coli
O157:H7 strains grew significantly less, an average of 2.3 log
10
. The initial
S. enterica
or
E. coli
O157:H7 inoculum dose and seed-sprouting temperature significantly affected the levels of both
S. enterica
and
E. coli
O157:H7 on the sprouts and in the irrigation water, while the frequency of irrigation water replacement affected only the levels of
E. coli
O157:H7. Colonization of sprouting alfalfa seeds by
S. enterica
serovar Newport and
E. coli
O157:H7 strains transformed with a plasmid encoding the green fluorescent protein was examined with fluorescence microscopy.
Salmonella
serovar Newport colonized both seed coats and sprout roots as aggregates, while
E. coli
O157:H7 colonized only sprout roots.
Uranium Reduction by
Desulfovibrio desulfuricans
Strain G20 and a Cytochrome
c
3
Mutant
Authors: Payne Rayford B. , Gentry Darren M. , Rapp-Giles Barbara J. , Casalot Laurence , Wall Judy D. 
Published: July 2002

ABSTRACT

Previous in vitro experiments with
Desulfovibrio vulgaris
strain Hildenborough demonstrated that extracts containing hydrogenase and cytochrome
c
3
could reduce uranium(VI) to uranium(IV) with hydrogen as the electron donor. To test the involvement of these proteins in vivo, a cytochrome
c
3
mutant of
D. desulfuricans
strain G20 was assayed and found to be able to reduce U(VI) with lactate or pyruvate as the electron donor at rates about one-half of those of the wild type. With electrons from hydrogen, the rate was more severely impaired. Cytochrome
c
3
appears to be a part of the in vivo electron pathway to U(VI), but additional pathways from organic donors can apparently bypass this protein.
Characterization of a Predominant Immunogenic Outer Membrane Protein of
Riemerella anatipestifer
Authors: Subramaniam Sumathi , Huang Bin , Loh Hilda , Kwang Jimmy , Tan Hai-Meng , Chua Kim-Lee , Frey Joachim 
Published: July 2002

ABSTRACT

The
ompA
gene, encoding the 42-kDa major antigenic outer membrane protein OmpA of
Riemerella anatipestifer
, the etiololgical agent of septicemia anserum exsudativa, was cloned and expressed in
Escherichia coli
. Recombinant OmpA displayed a molecular mass similar to that predicted from the nucleotide sequence of the
ompA
gene but lower than that observed in total cell lysates of
R. anatipestifer
. The
ompA
gene showed a conserved C-terminal region comprising the OmpA-like domain and a variable N-terminal region. This structure is similar to those of the analogous outer membrane proteins of several gram-negative bacteria. However, OmpA of
R. anatipestifer
contains six EF-hand calcium-binding domains and two PEST regions, which distinguish it from other outer membrane proteins. The occurrence of these motifs in OmpA suggests a possible role in virulence for this protein. The
ompA
gene is present in the
R. anatipestifer
type strain and in all serotype reference strains. However, it exhibits some minor genetic heterogeneity among different serotypes, which seems not to affect the strong antigenic characteristics of the protein. OmpA is a conserved and strong antigenic determinant of
R. anatipestifer
and hence is suggested to be a valuable protein for the serodetection of
R. anatipestifer
infections, independent of their serotype.
Description of a Nonlethal Herpes Simplex Virus Type 1 Glycoprotein D Deletion Mutant Affecting a Site Frequently Used for PCR
Authors: Coyle P. V. , Jain S. , Wyatt D. , McCaughey C. , O'Neill H. J. 
Published: July 2002

ABSTRACTWe report a herpes simplex virus type 1 mutant which failed to amplify with a commonly used glycoprotein D primer set. The virus contained a nine-base deletion in the gene's 5′ nontranslated region. The altered amplicon was clearly distinguishable on a 4% high-resolution agarose gel.