Comparative analysis of ESBL-positive Escherichia coli isolates from animals and humans from the UK, The Netherlands and Germany

The putative virulence and antimicrobial resistance gene contents of extended spectrum β-lactamase (ESBL)-positive E. coli (n=629) isolated between 2005 and 2009 from humans, animals and animal food products in Germany, The Netherlands and the UK were compared using a microarray approach to test the suitability of this approach with regard to determining their similarities. A selection of isolates (n=313) were also analysed by multilocus sequence typing (MLST). Isolates harbouring bla_{CTX-M-group-1} dominated (66%, n=418) and originated from both animals and cases of human infections in all three countries; 23% (n=144) of all isolates contained both bla_{CTX-M-group-1} and bla_OXA-1-like genes, predominantly from humans (n=127) and UK cattle (n=15). The antimicrobial resistance and virulence gene profiles of this collection of isolates were highly diverse. A substantial number of human isolates (32%, n=87) did not share more than 40% similarity (based on the Jaccard coefficient) with animal isolates. A further 43% of human isolates from the three countries (n=117) were at least 40% similar to each other and to five isolates from UK cattle and one each from Dutch chicken meat and a German dog; the members of this group usually harboured genes such as mph(A), mrx, aac(6’)-Ib, catB3, bla_OXA-1-like and bla_{CTX-M-group-1.} forty-four per cent of the MLST-typed isolates in this group belonged to ST131 (n=18) and 22% to ST405 (n=9), all from humans. Among animal isolates subjected to MLST (n=258), only 1.2% (n=3) were more than 70% similar to human isolates in gene profiles and shared the same MLST clonal complex with the corresponding human isolates. The results suggest that minimising human-to-human transmission is essential to control the spread of ESBL-positive E. coli in humans.

Reversion to susceptibility of a carbapenem-resistant clinical isolate of Klebsiella pneumoniae producing KPC-3

OBJECTIVES

We report the case of a kidney-transplant patient, suffering an intra-abdominal abscess at the surgical site caused by a carbapenem-resistant ST258 Klebsiella pneumoniae clone, producing the KPC-3 carbapenemase. Under tigecycline treatment, the patient developed a sepsis caused by a carbapenem-susceptible ST258 K. pneumoniae strain. Complete DNA sequences of the plasmids carried by the resistant and susceptible strains from this patient were determined.

METHODS

The complete DNA sequences of plasmids were obtained by applying the 454 Genome Sequencer FLX-PLUS procedure on a library constructed of total plasmid DNA purified from the carbapenem-resistant and -susceptible strains.

RESULTS

In the carbapenem-resistant strain, four plasmids encoding 24 resistance genes, including blaKPC-3, and two putative virulence clusters were detected. In the susceptible strain, large rearrangements occurred in the KPC-carrying plasmid, causing the deletion of the entire Tn4401::blaKPC-3 transposon, with the consequent reversion of the strain to carbapenem susceptibility. The patient was successfully treated with carbapenems and fully recovered.

CONCLUSIONS

The description of the plasmid content in these two strains gives interesting insights into the plasticity of KPC-carrying plasmids in K. pneumoniae.

Polyethersulfone solid-phase microextraction followed by liquid chromatography quadrupole time-of-flight mass spectrometry for benzotriazoles determination in water samples

A microextraction method for the determination of 1H-benzotriazole (BTri), and four polar derivatives (4 and 5-methyl-1H-benzotriazole, 4-TTri and 5-TTri; 5,6-dimethyl-1H-benzotriazole, XTri; and 5-chloro-1H-benzotriazole, 5-ClBTri), in surface and wastewater samples is presented. Analytes were pre-concentrated using a disposable, low cost polyethersulfone (PES) sorbent and further analysed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Parameters affecting the efficiency of sample preparation (extraction conditions and desorption solvent) and those controlling the performance of LC-MS determination were investigated. Analytes were extracted from 15mL water samples, containing a 30% (w/v) of sodium chloride (4.5g) and adjusted at pH 4.5, using a tubular PES sorbent (5cm length×0.7mm o.d., sorbent volume 42μL). After methanol desorption and solvent exchange, benzotriazoles were determined by LC-MS, with chromatograms extracted using a mass window of 20ppm, centred in their [M+H](+) ions. The identity of chromatographic peaks was confirmed with accurate ion product scan (MS/MS) spectra. The method provided limits of quantification (LOQs) between 0.005 and 0.100μgL(-1), and relative recoveries from 81% to 124% (except for XTri in sewage samples, ca. 60%) with associated standard deviations between 2% and 9%. When compared with polydimethylsiloxane covered stir-bars (coating volume 24μL), the PES polymer achieved significant higher responses (5-20-fold) for these polar pollutants. BTri and tolyltriazoles (4-TTri and 5-TTri) were found in urban sewage and river water samples, affected by wastewater discharges, with the maximum concentration (5.9μgL(-1)) corresponding to BTri in raw wastewater.

Characterisation of plasmids implicated in the mobilisation of extended-spectrum and AmpC β-lactamase genes in clinical Salmonella enterica isolates and temporal stability of the resistance genotype

Plasmids implicated in the mobilisation of β-lactamase genes in extended-spectrum β-lactamase (ESBL)- and AmpC-producing Salmonella enterica isolates recovered from three Spanish hospitals were characterised. The temporal stability of these plasmids and of the resistance phenotype without antimicrobial pressure was also assessed in the laboratory setting. The resistance determinants and their genetic environments were characterised by PCR sequencing, and their genomic location was analysed by S1 nuclease pulsed-field gel electrophoresis (PFGE) and I-CeuI PFGE, followed by Southern blot hybridisation. The 11 S. enterica studied strains carried blaCTX-M-9 (serovar Virchow, 2 isolates), blaCTX-M-10 (Virchow, 2), blaCTX-M-14 (Enteritidis, 1), blaCTX-M-15 (Gnesta and S. enterica group C, 2), blaSHV-2 (Livingstone, 1), blaSHV-12 (Enteritidis, 1) and blaCMY-2 (Bredeney, 2). The ISEcp1-blaCTX-M-14-IS903 and ISEcp1-blaCTX-M-15-orf477 genetic structures were detected. IncI1 and IncA/C plasmids carried blaCTX-M-14, blaCTX-M-15, blaSHV-2, blaSHV-12 and blaCMY-2 genes. blaCTX-M-9 included in an In60 complex integron and blaCTX-M-10 linked to a phage-related element were found in non-typeable plasmids. Conjugation and temporal stability experiments were performed in vitro through daily passages (100 days) in the absence of antimicrobial pressure. In the stability experiments, 5 of the 11 tested isolates lost the ESBL or AmpC plasmidic genes and this was associated with concomitant loss of the whole or partial plasmid. In conclusion, successful plasmids belonging to different Inc groups mobilise ESBL- and AmpC-encoding genes in S. enterica. Loss of ESBL/AmpC genes in the absence of antimicrobial pressure might explain the low prevalence of these β-lactamases among Salmonella isolates.

First result from the Alpha Magnetic Spectrometer on the International Space Station: precision measurement of the positron fraction in primary cosmic rays of 0.5-350 GeV

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250  GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

Liquid chromatography time-of-flight mass spectrometry evaluation of fungicides reactivity in free chlorine containing water samples

Liquid chromatography (LC) combined with tandem mass spectrometry (MS/MS), based on the use of a hybrid quadrupole-time-of-flight mass analyzer, was used to investigate the reactivity of nine fungicides in free chlorine-containing water samples. Three of the selected compounds (fenhexamid, FEN; pyrimethanil, PYR; and cyprodinil, CYP) displayed a poor stability in presence of moderate chlorine levels; thus, the effects of different parameters on their half-lives (t(1/2)) were evaluated. Sample pH, bromide traces, and the water matrix affected their relative stabilities. Despite such variations, the three fungicides are degraded at significant rates not only in ultrapure, but also in surface water spiked with chlorine levels up to 2 µg ml(-1), and when mixed with chlorinated tap water, generating several transformation products (TPs). The time-course of precursor species and their TPs was followed in the LC-MS mode, using the information contained in accurate, full scan mass spectra (MS) to propose the empirical formulae of TPs. Thereafter, their ion product scan (MS/MS) spectra were considered to set their chemical structures; allowing, in some cases, to distinguish between isomeric TPs. The reaction pathway of FEN, the less stable fungicide, involved just an electrophilic substitution of hydrogen per chlorine, or bromine, and cleavage of the molecule to render an amide. PYR and CYP shared common reaction routes consisting of halogenation, hydroxylation, and condensation processes leading to complex mixtures of TPs, which were relatively stable to further transformations.

pMdT1, a small ColE1-like plasmid mobilizing a new variant of the aac(6')-Ib-cr gene in Salmonella enterica serovar Typhimurium

OBJECTIVES

To characterize a 5.9 kb aac(6')-Ib-cr-harbouring plasmid that was detected in a clinical Salmonella Typhimurium DT104B strain.

METHODS

Extraction and purification of plasmid DNA and electrotransformation assays were carried out in order to obtain kanamycin-resistant transformants. MICs of several fluoroquinolones and aminoglycosides were determined. DNA sequencing was performed by primer walking on purified plasmid preparations. The new plasmid nucleotide sequence was analysed and compared with available sequences using bioinformatic tools.

RESULTS

pMdT1 is a 5.9 kb mobilizable ColE1-like plasmid that harbours aac(6')-Ib-cr4, a gene encoding a new variant of the AAC(6')-Ib-cr protein (225 amino acids). This active protein conferred resistance to tobramycin and kanamycin, and also decreased susceptibility to ciprofloxacin and norfloxacin in the transformant strain, as MICs demonstrated. The mobilization region, necessary for horizontal transfer and composed of the mobA, mobB, mobC and mobD genes, displayed a high degree of identity with those from representative ColE1-like plasmids. The basis of mobility (bom), oriT and origin of replication regions were also detected. Apart from the acetylase-encoding gene, three other open reading frames (ORFs) were determined. No similarities were found when the ORF1 sequence was compared with the sequences included in GenBank. The deduced ORF2 protein predicted a CopG-like structure characteristic of transcriptional regulators, and the deduced ORF3 protein was identical to macrophage stimulating factors.

CONCLUSIONS

The pMdT1 is the smallest mobilizable ColE1-like plasmid containing an aac(6')-Ib-cr gene that has been described so far.

The essential role of the 3' terminal template base in the first steps of protein-primed DNA replication

Bacteriophages φ29 and Nf from Bacillus subtilis start replication of their linear genomes at both ends using a protein-primed mechanism by means of which the DNA polymerase initiates replication by adding dAMP to the terminal protein, this insertion being directed by the second and third 3′ terminal thymine of the template strand, respectively. In this work, we have obtained evidences about the role of the 3′ terminal base during the initiation steps of φ29 and Nf genome replication. The results indicate that the absence of the 3′ terminal base modifies the initiation position carried out by φ29 DNA polymerase in such a way that now the third position of the template, instead of the second one, guides the incorporation of the initiating nucleotide. In the case of Nf, although the lack of the 3′ terminal base has no effect on the initiation position, its absence impairs further elongation of the TP-dAMP initiation product. The results show the essential role of the 3′ terminal base in guaranteeing the correct positioning of replication origins at the polymerization active site to allow accurate initiation of replication and further elongation.

Potential international spread of multidrug-resistant invasive Salmonella enterica serovar enteritidis

In developing countries, Salmonella enterica serovar Enteritidis causes substantial illness and death, and drug resistance is increasing. Isolates from the United Kingdom containing virulence-resistance plasmids were characterized. They mainly caused invasive infections in adults linked to Africa. The common features in isolates from these continents indicate the role of human travel in their spread.

Apparent diffusion coefficient of hyperpolarized (3)He with minimal influence of the residual gas in small animals

The apparent diffusion coefficient (ADC) of hyperpolarized (HP) gases is a parameter that reflects changes in lung microstructure. However, ADC is dependent on many physiological and experimental variables that need to be controlled or specified in order to ensure the reliability and reproducibility of this parameter. A single breath-hold experiment is desirable in order to reduce the amount of consumed HP gas. The application of a positive end-expiratory pressure (PEEP) causes an increase in the residual gas volume. Depending on the applied PEEP, the ratio between the incoming and residual gas volumes will change and the ADC will vary, as long as both gases do not have the same diffusion coefficient. The most standard method for human applications uses air for breathing and a bolus of pure HP (3)He for MRI data acquisition. By applying this method in rats, we have demonstrated that ADC values are strongly dependent on the applied PEEP, and therefore on the residual gas volume in the lung. This outcome will play an important role in studies concerning certain diseases, such as emphysema, which is characterized by an increase in the residual volume. Ventilation with an oxygen-helium mixture (VOHeM) is a proposed single breath-hold method that uses two different gas mixtures (O(2)-(4)He for ventilation and HP (3)He-N(2) for imaging). The concentration of each gas in its respective mixture was calculated in order to obtain the same diffusion coefficient in both mixtures. ADCs obtained from VOHeM are independent of PEEP, thus minimizing the effect of the different residual volumes.

Postmarketing study for assessment of tolerability of a grass allergen immunotherapy tablet (GRAZAX) in patients with rhinitis or rhinoconjunctivitis

BACKGROUND AND OBJECTIVE

Many patients with grass pollen allergy in Spain have concomitant sensitization to other allergens such as profilin. Since this type of sensitization is more common in Mediterranean countries than in countries where most patients were enrolled in clinical trials on GRAZAX (Phleum pratense 75,000 SQ-T/2, 800 BAU, ALK), the aim of this study was to analyze tolerability to GRAZAX under clinical practice conditions in patients with grass pollen allergy.

METHODS

A total of 155 patients were enrolled consecutively in a prospective, open-label, observational study. Adverse reactions were recorded during the first month of treatment at 3 different timepoints: after the first dose, when patients were kept under observation for 30 minutes, and on days 15 and 30 after starting treatment

RESULTS

With the first dose, 117 adverse reactions were recorded in 63 patients (40.7%). The commonest reactions (>10% patients) were oral pruritus (25.2%) and throat irritation (24.5%). Ear pruritus was recorded in 7.7%. All reactions but 1 occurred within 30 minutes of administration and all were mild-to-moderate. At the end of treatment, the percentage of patients with adverse reactions had decreased significantly (21.3%). Most adverse reactions (95.2%) were mild-to-moderate and only 3 (1.4%) were severe. No serious adverse reactions were recorded.

CONCLUSION

GRAZAX seems to be well tolerated, and most reactions were mild-to-moderate. Many of these reactions occur with the first dose. Therefore, according to the Summary of Product Characteristics, the first dose has to be administered under medical supervision.

Analysis of quality of nuchal translucency measurements: its role in prenatal diagnosis

Objective. Quantitative analysis of the quality of nuchal translucency (NT) measurements. Methods. First-trimester combined screening for Down syndrome was performed to all pregnant women attended in our Department from October 2003 to November 2009. NT was measured according to the Fetal Medicine Foundation (FMF) criteria by 20 trained obstetricians. The performance of NT measurements was retrospectively analyzed with regard to several quality control standards. Accuracy according to experience, professional profile, crown rump length (CRL) values, and FMF certification was statistically tested. Results. A total of 14978 NT measurements were assessed. (1) The mean operator-specific median NT-MoM values was 0,98. (2) Mean percentage of cases >95th and <5th centiles were 5,0% and 4,2%, respectively. (3) Logarithmic mean and SD of the NT MoM values were 0,00 and 0,13, respectively. (4) The DR for trisomy 21 at screening time was 90,7% for a FPR of 6,7% for standard screening strategy. (5) According to Cumulative SUM (CUSUM) figures, the performance was more acceptable in FMF-certified operators. Conclusion. Overall, quality standards show optimal NT measurements in our unit. Operator experience, a dedicated profile to fetal medicine, CRL over 60 mm, and FMF certification have a significant positive impact on the quality standards.

Telomerase-driven expression of the sodium iodide symporter (NIS) for in vivo radioiodide treatment of cancer: a new broad-spectrum NIS-mediated antitumor approach

CONTEXT

Telomerase promoters (hTERT and hTR) are useful for transcriptional targeting in gene therapy models of cancer. Telomerase-driven expression of the sodium iodide symporter (NIS) in tumor cells has been successfully used as a reporter gene in vivo using positron emission tomography (PET) imaging.

OBJECTIVE

The aim of this study was to investigate the NIS-mediated therapeutic effect of telomerase promoters in a wide variety of human cancer cell lines.

DESIGN AND METHODS

Promoter fragments from either hTERT or hTR were used to drive the expression of NIS in cell lines derived from melanoma (M14), breast (MDA-MB-231), colon (HT-29), lung (H460), ovarian (OVCAR-3), and thyroid (TPC-1) carcinomas. Iodide uptake assays, protein immunodetection, and clonigenic assays were used to confirm NIS functional expression and the (131)I-mediated cytopathic effect. Tumor xenografts in mice were infected with hTERT and hTR and then treated using radioiodide.

RESULTS

Both promoters were selectively active in cancer cells that were effectively killed by exposure to (131)I. One single dose of 1 mCi (131)I markedly suppressed tumor growth of melanoma-derived tumor xenografts compared with controls. This effect was more modest in colon cancer-derived xenografts in part due to the reduced infectivity and the tumor cystic nature. The therapeutic effect of hTR promoter was found to be stronger than that of hTERT promoter.

CONCLUSIONS

These results demonstrate that telomerase-driven expression of NIS could potentially have applications for (131)I therapy of a wide variety of cancers. Additionally, this is the first study to report NIS-mediated (131)I therapy of melanoma tumors in vivo.