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Biomedical subjects

K L Hopkins

Publications and source records attributed to K L Hopkins.

At least 19 recordsLinked to original sources
PubMed2006

Characterisation of CTX-M and AmpC genes in human isolates of Escherichia coli identified between 1995 and 2003 in England and Wales.

CTX-M and AmpC genes in human isolates of Escherichia coli, their genetic environment and their host plasmids were examined. Isolates (n=103) were selected based on resistance (minimum inhibitory concentration (MIC)> or =1 microg/mL) to ceftriaxone and cefotaxime. Polymerase chain reaction (PCR) and sequencing identified 29 isolates containing bla(CTX-M-15), 1 each of bla(CTX-M-2) (a strain originating from Israel) and bla(CTX-M-40), 20 isolates containing bla(CMY-7), 4 bla(CMY-2) and 1 bla(CMY-21). This is the first study of plasmid-mediated AmpC genes in E. coli in the UK. Eleven cefoxitin-resistant, AmpC PCR-negative isolates had ampC promoter region mutations. All bla(CTX-M-15) and 24 of 25 bla(CMY) genes were associated with an ISEcp1-like element. The bla(CTX-M-2) was located in an orf513-bearing class 1 integron. Plasmid restriction digests suggest transfer of genes between different plasmid backbones.

Anti-Bacterial Agents↗
PubMed2006

Longitudinal farm study of extended-spectrum beta-lactamase-mediated resistance.

Extended-spectrum beta-lactamase (ESBL)-mediated resistance is of considerable importance in human medicine. Recently, such enzymes have been reported in bacteria from animals. We describe a longitudinal study of a dairy farm suffering calf scour with high mortality rates. In November 2004, two Escherichia coli isolates with resistance to a wide range of beta-lactams (including amoxicillin-clavulanate and cefotaxime) were isolated from scouring calves. Testing by PCR and sequence analysis confirmed the isolates as being both bla(CTX-M14/17) and bla(TEM-35) ((IRT-4)) positive. They had indistinguishable plasmid and pulsed-field gel electrophoresis (PFGE) profiles. Transferability studies demonstrated that bla(CTX-M) was located on a conjugative 65-MDa IncK plasmid. Following a farm visit in December 2004, 31/48 calves and 2/60 cows were positive for E. coli with bla(CTX-M). Also, 5/48 calf and 28/60 cow samples yielded bla(CTX)- and bla(TEM)-negative E. coli isolates that were resistant to cefotaxime, and sequence analysis confirmed that these presented mutations in the promoter region of the chromosomal ampC gene. Fingerprinting showed 11 different PFGE types (seven in bla(CTX-M)-positive isolates). Six different PFGE clones conjugated the same bla(CTX-M)-positive IncK plasmid. One clone carried a different-sized, bla(CTX-M)-positive, transformable plasmid. This is the first report of bla(CTX-M) from livestock in the United Kingdom, and this report demonstrates the complexity of ESBL epidemiology. Results indicate that horizontal plasmid transfer between strains as well as horizontal gene transfer between plasmids have contributed to the spread of resistance. We have also shown that some clones can persist for months, suggesting that clonal spread also contributes to the perpetuation of resistance.

Animals↗
PubMed2005

Multiple antimicrobial resistant Salmonella enterica serovar Paratyphi B variant Java in cattle: a case report.

An epidemiological investigation of a calf rearing premises and a closely associated dairy herd was carried out after the isolation of Salmonella enterica serovar Paratyphi B variant Java phage type 3b variant 2 from clinically diseased calves on the premises. The isolate was resistant to ampicillin, chloramphenicol, streptomycin, sulphonamides, tetracyclines, trimethoprim and cefoperazone. The organism was widespread on the calf unit and was also recovered from the dairy premises, mainly from groups of weaned calves. The investigation was extended to 10 epidemiologically linked farms but no S Java was isolated from any of the 40 to 60 samples collected from each premises. Molecular studies showed that the S Java isolates were genetically most similar to isolates from cases of human disease associated with ornamental fish tanks or feed. Long PCR and resistance gene profiling identified a resistance island which was indistinguishable from the human 'fish tank' strain of S Java and animal and human epidemic strains of S Typhimurium DT104. The isolates were clearly distinguished from multi-resistant S Java strains commonly associated with continental poultry. This is the first report of S Java with this resistance pattern in Great Britain.

Animals↗
PubMed2005

Resistance to oxyiminocephalosporins mediated by blaTEM-52 genes in Salmonella typhimurium from humans in England and Wales.

The emergence of antimicrobial resistance among Salmonella is a matter of great public health concern, more so in the case of extended-spectrum cephalosporins, since these antimicrobials are normally regarded as the drugs of choice for complicated cases of infection. This study was designed to determine the occurrence of resistance mediated by the presence of extended-spectrum beta-lactamases (ESBL) enzymes belonging to the TEM family. Only two isolates were detected after analysis of the 278,308 Salmonella isolates from the last 10 years. In both cases, the gene involved was a bla (TEM-52)-like, and infections were linked with foreign travel. ESBL-TEM enzymes remain very rare in Salmonella in England and Wales, and no domestic cases have been detected to date.

Cephalosporin Resistance↗
PubMed2005

Characterization of AmpC-mediated resistance in clinical Salmonella isolates recovered from humans during the period 1992 to 2003 in England and Wales.

The increase in AmpC-mediated resistance in salmonellae constitutes a serious public health concern, since these enzymes confer resistance to a wide range of beta-lactams. One hundred six isolates were selected from 278,308 Salmonella isolates based on resistance to ampicillin and cephalosporins and were subjected to further characterization. Nine isolates had a cefoxitin inhibition diameter < or = 17 mm and were proven to be AmpC positive by multiplex PCR. Sequence analysis revealed the presence of bla(DHA-1), bla(CMY-2), and bla(CMY-4) genes. All nine isolates presented different pulsed-field gel electrophoresis restriction profiles. The AmpC genetic determinants were present in transferable plasmids of around 11, 42, 70, 98, and 99 MDa. A combination of size and restriction fragment length polymorphism (RFLP) analysis showed that all the bla(CMY) plasmids investigated in our study were different, which suggests that bla(CMY) may be located in different plasmid environments. Some United Kingdom isolates linked to foreign travel showed RFLP plasmid patterns consistent with plasmids previously seen in the United States, which suggests that bla(CMY-2) has also been disseminated through plasmid transfer. The fact that two of the domestically acquired United Kingdom isolates presented previously unseen RFLP plasmid patterns could indicate that these strains have followed routes different from those prevalent in North America or other parts of the world. This study represents the first report of bla(CMY) genes in Salmonella isolates in the United Kingdom and the first report of CMY-4 in Salmonella enterica serotype Senftenberg worldwide.

Bacterial Proteins↗
PubMed2001

YPD, PombePD and WormPD: model organism volumes of the BioKnowledge library, an integrated resource for protein information.

The BioKnowledge Library is a relational database and web site (http://www.proteome.com) composed of protein-specific information collected from the scientific literature. Each Protein Report on the web site summarizes and displays published information about a single protein, including its biochemical function, role in the cell and in the whole organism, localization, mutant phenotype and genetic interactions, regulation, domains and motifs, interactions with other proteins and other relevant data. This report describes four species-specific volumes of the BioKnowledge Library, concerned with the model organisms Saccharomyces cerevisiae (YPD), Schizosaccharomyces pombe (PombePD) and Caenorhabditis elegans (WormPD), and with the fungal pathogen Candida albicans (CalPD). Protein Reports of each species are unified in format, easily searchable and extensively cross-referenced between species. The relevance of these comprehensively curated resources to analysis of proteins in other species is discussed, and is illustrated by a survey of model organism proteins that have similarity to human proteins involved in disease.

Animals↗
PubMed2001

Imaging findings of perforative appendicitis: a pictorial review.

Appendicitis is common in children. Early diagnosis depends on recognition of characteristic signs and symptoms: right lower quadrant or periumbilical pain, localized tenderness, fever, and leukocytosis. Because these classic features may be difficult to elicit or masked by other complaints, the incidence of perforative appendicitis in children is high. This paper reviews the imaging sequelae with emphasis on CT and sonography findings. Areas of focus include abdominopelvic abscess, peritonitis, pyelephlebitis, pyelethrombosis, and hepatic abscess. Secondary involvement of the urinary and gastrointestinal tracts is also discussed.

Adolescent↗
PubMed2001

Magnetic resonance phase-shift velocity mapping in pediatric patients with pulmonary venous obstruction.

OBJECTIVES: This study evaluated the accuracy, advantages and clinical efficacy of magnetic resonance (MR) phase-shift velocity mapping, in delineating the site and the hemodynamic severity of pulmonary venous (PV) obstruction in patients with congenital heart disease (CHD). BACKGROUND: Magnetic resonance phase-shift velocity mapping of normal pulmonary veins and of obstructed PV pathways have been previously reported in a mainly adult population. METHODS: The study population (33 pts) underwent MR phase-shift velocity mapping of their PV pathways. These results were compared with cardiac catheterization and Doppler echocardiography data. RESULTS: The study population (0.4 to 19.5 years) consisted of a study group (PV pathway obstruction, n = 7) and a control group (no PV obstruction, n = 26). No patients had any left-to-right shunt lesions. The MR imaging displayed precise anatomical detail of the pulmonary veins. Phase velocities in the control group ranged from 20 to 71 cm/s, whereas velocities in the study group ranged from 100 to 250 cm/s (p = 0.002). The MR phase velocities (154 +/- 0.53 cm/s) compared favorably with Doppler echocardiography (147 +/- 0.54 cm/s), (r = 0.76; p = 0.05). The MR velocity mapping was 100% specific and 100% sensitive in detecting PV obstruction, although the absolute gradient measurements among MR phase mapping, echocardiographic Doppler and catheterization did not show statistically significant correlation. CONCLUSIONS: In the absence of any associated left-to-right shunt lesions, PV velocities of 100 cm/s and greater indicated significant obstruction. The MR phase-shift velocity mapping, together with MR spin echocardiography and MR angiography, provides comprehensive anatomic and physiologic data that may obviate the need for further invasive studies.

Adolescent↗
PubMed2001

Imaging of head trauma in infancy and childhood.

Neurologic trauma is one of the most common and challenging problems encountered in the pediatric emergency setting. Early and accurate diagnosis is essential to minimize morbidity and mortality. The primary goal of the neuroimager in the acute setting is to provide rapid diagnosis, to monitor the development of complications, and to aid in the determination of prognosis. Unique features of the immature brain and skull influence the patterns and types of injuries observed. It is incumbent on the radiologist to understand these features as an aid to diagnosis. Further, the radiologist must be aware of the pathophysiology and appearance of nonaccidental trauma to ensure recognition of this devastating problem. Lastly, the radiologic tools available, their appropriate use, and their limitations should be understood by the entire trauma team to provide cost-effective and timely care. This article summarizes the pathophysiology and current imaging of neurotrauma in the pediatric population, including trauma, nonaccidental trauma, accidental anoxic injury, and birth injury.

Adolescent↗
PubMed2001

Optimization of random amplification of polymorphic DNA analysis for molecular subtyping of Escherichia coli O157.

Random amplification of polymorphic DNA (RAPD) analysis using the polymerase chain reaction has proved to be a useful technique in the epidemiological investigation of micro-organisms but may suffer from a lack of reproducibility in poorly optimized protocols. In this study a method of obtaining reproducible genomic fingerprints using RAPD analysis of Escherichia coli O157 is described. By systematic optimization of reaction conditions and selection of suitable primers, reproducible and discriminatory profiles could be obtained from all E. coli O157 strains tested. In addition, two other methods of obtaining reproducible profiles from E. coli O157 strains without the need to purify genomic DNA are described.

Buffers↗
PubMed2001

Nonaccidental pediatric head injury: diffusion-weighted imaging findings.

OBJECTIVE: Diffusion-weighted imaging (DWI) reveals nonhemorrhagic posttraumatic infarction hours to days before conventional computed tomographic scanning or magnetic resonance imaging (MRI). We evaluated the diagnostic utility of DWI in children with nonaccidental head trauma. METHODS: The medical records and imaging examinations obtained between January 1998 and May 2000 for all children less than 2 years of age with presumed or suspected nonaccidental head injury were reviewed retrospectively. Twenty children who had undergone DWI within 5 days of presentation were included in the study. Computed tomographic scans, conventional MRI sequences, and DWI combined with apparent diffusion coefficient (ADC) maps were evaluated. RESULTS: Eleven girls and nine boys (median age, 5 mo) were studied. Eighteen children had presumed nonaccidental head trauma, and two children had suspected nonaccidental head trauma. Of the 18 children with presumed nonaccidental trauma, 16 (89%) demonstrated abnormalities on DWI/ADC, as compared with neither of the two children with suspected nonaccidental trauma. In 13 (81%) of 16 positive cases, DWI revealed more extensive brain injury than was demonstrated on conventional MRI sequences or showed injuries not observed on conventional MRI. DWI combined with ADC maps allowed better delineation of the extent of white matter injury. DWI/ADC abnormalities in the nonaccidental head-injured children were likely to involve posterior aspects of the cerebral hemispheres, with relative sparing of the frontal and temporal poles. Severity on DWI correlated significantly with poor outcome (P < 0.005). CONCLUSION: DWI has broad applications in the early detection of infarction in children with nonaccidental head injury and enhances the sensitivity of conventional MRI. In the patients in this study, early DWI provided an indicator of severity that was more complete than any other imaging modality. The use of DWI may help to identify children at high risk for poor outcome and to guide management decisions.

Accidents, Traffic↗
PubMed2001

Use of multiple primers in RAPD analysis of clonal organisms provides limited improvement in discrimination.

Randomly amplified polymorphic DNA (RAPD) analysis using two or more primers has been reported to provide additional discriminatory ability over one primer used individually. This may be of particular application in epidemiological typing of clonal organisms, such as Shiga toxin-producing E. coli O157, where strain differentiation can be difficult. Using four arbitrary primers individually, and in all possible permutations, E. coli O157 isolates and other arbitrarily chosen E. coli strains were typed using RAPD analysis. For most nonclonal strains, the use of two primers resulted in increased differentiation between isolates; however, more than two primers did not increase further the discriminatory capacity. E. coli O157 isolates that produced virtually identical profiles using one primer did not show increased differentiation when using two or more primers, demonstrating that in some cases, where strains of an organism are highly related, there is limited advantage to using more than one primer in RAPD analysis.

Bacterial Typing Techniques↗
PubMed2000

Simultaneous molecular subtyping and shiga toxin gene detection in Escherichia coli using multiplex polymerase chain reaction.

A robust random amplification of polymorphic DNA (RAPD)-polymerase chain reaction (PCR) protocol was developed for the combined epidemiological typing and shiga toxin detection of clinical shiga toxin-producing O157 and non-O157 Escherichia coli isolates. Using shiga toxin gene-specific primers, combined with two short 10-mer primers, in a multiplex shiga toxin/RAPD-PCR the fingerprints generated allowed differentiation between epidemiologically unrelated strains and allowed identification of a band amplified from the shiga toxin gene(s). Hybridization with a digoxigenin-labelled probe specific for stx1 and stx2 confirmed its identity. The combination of primers in this way allows valuable additional information to be gained from discriminatory RAPD profiles, with further benefits of time and cost savings over tests performed individually.

Bacterial Toxins↗
PubMed1999

Electrocardiographic predictors of right ventricular volume measured by magnetic resonance imaging late after total repair of tetralogy of Fallot.

BACKGROUND: Right ventricular dysfunction occurs in many patients with significant pulmonary valve regurgitation late after initial total repair of tetralogy of Fallot. Methods to predict which of these patients are at increased risk of late morbidity and mortality are not yet known. HYPOTHESIS: This study evaluated electrocardiographic (ECG) predictors of severe right ventricular dilatation determined by magnetic resonance imaging (MRI) volumes in patients with tetralogy of Fallot late after initial corrective repair. METHODS: We retrospectively reviewed the ECGs and MRI right ventricular volume measurements of 20 patients (age 4.4 to 19.3 years, mean 10.0 years) with significant pulmonary valve regurgitation late after repair of tetralogy of Fallot. All patients had enlarged, hypokinetic right ventricles by echocardiography. The patients were grouped based on an indexed right ventricular end-diastolic volume (RVEDV/BSA) of < 102 ml/m2 (Group 1) or > or = 102 ml/m2 (Group 2). We determined the sensitivity, specificity, positive and negative predictive values of QRS duration, and mean frontal plane QRS axis for predicting right ventricular volumes. RESULTS: A maximal QRS duration of > or = 150 ms or a northwest quadrant frontal plane QRS axis had 85% sensitivity, 86% specificity, 92% positive predictive value, and 75% negative predictive value for predicting an RVEDV/BSA of > or = 102 ml/m2. The mean QRS duration was significantly longer in Group 2 than in Group 1 patients (156 ms vs. 125 ms, p = 0.005). CONCLUSIONS: In patients late after repair of tetralogy of Fallot with significant pulmonary valve regurgitation a maximal manually measured QRS duration of > or = 150 ms and/or a frontal plane QRS northwest quadrant axis can predict patients with marked right ventricular enlargement. The presence of either of these findings on the ECG signifies patients who require further evaluation and consideration for pulmonary valve replacement.

Adolescent↗
PubMed1999

Sedation for pediatric imaging studies.

This article discusses safe sedation for pediatric imaging. Emphasis is placed upon implementation of an institutional sedation program according to guidelines of the American Academy of Pediatrics. Standards for patient assessment and preparation, sedative administration, monitoring, and discharge are reviewed. A comparison of available sedative agents is also provided.

Anesthesia Recovery Period↗
PubMed1999

Imaging of the pediatric orbit and visual pathways: computed tomography and magnetic resonance imaging.

Techniques for pediatric MR imaging and computed tomography and anatomy of the orbit and intracranial visual pathways are presented and reviewed in this article. Imaging findings are presented for the following categories of abnormality: a) orbital anomalies related to congenital disorders of the brain, b) disorders of the orbit (ocular, nonocular, or multicompartmental), c) disorders of the intracranial visual pathways (suprasellar cistern, optic radiations, or occipital cortex), and d) disorders of gaze (extraocular muscles, cranial nerves, and brainstem). Careful assessment of the clinical findings, anatomic location of the visual impairment, and familiarity with disorders that often affect pediatric patients are helpful in guiding neuroimaging evaluation of the child with ocular, orbital, or central patterns of visual disturbance.

Brain Diseases↗