Therapeutic developments for neurodegenerative GM1 gangliosidosis

GM1 gangliosidosis (GM1) is a rare but fatal neurodegenerative disease caused by dysfunction or lack of production of lysosomal enzyme, β-galactosidase, leading to accumulation of substrates. The most promising treatments for GM1, include enzyme replacement therapy (ERT), substrate reduction therapy (SRT), stem cell therapy and gene editing. However, effectiveness is limited for neuropathic GM1 due to the restrictive nature of the blood-brain barrier (BBB). ERT and SRT alleviate substrate accumulation through exogenous supplementation over the patient's lifetime, while gene editing could be curative, fixing the causative gene, GLB1, to enable endogenous enzyme activity. Stem cell therapy can be a combination of both, with ex vivo gene editing of cells to cause the production of enzymes. These approaches require special considerations for brain delivery, which has led to novel formulations. A few therapeutic interventions have progressed to early-phase clinical trials, presenting a bright outlook for improved clinical management for GM1.

Optimizing enzyme-responsive polymersomes for protein-based therapies

Aims: Stimuli-responsive polymersomes are promising tools for protein-based therapies, but require deeper understanding and optimization of their pathology-responsive behavior. Materials & methods: Hyaluronic acid (HA)-poly(b-lactic acid) (PLA) polymersomes self-assembled from block copolymers of varying molecular weights of HA were compared for their physical properties, degradation and intracellular behavior. Results: Major results showed increasing enzyme-responsivity associated with decreasing molecular weight. The major formulation differences were as follows: the HA(5 kDa)-PLA formulation exhibited the most pronounced release of encapsulated proteins, while the HA(7 kDa)-PLA formulation showed the most different release behavior from neutral. Conclusion: We have discovered design rules for HA-PLA polymersomes for protein delivery, with lower molecular weight leading to higher encapsulation efficiency, greater release and greater intracellular uptake.

Development of BNBSL: A β-ν spectra library for spectrometry applications

While modern nuclear decay data can provide many details of a given nuclides β-decay modes (branching ratios, decay heating etc.), knowledge of the emitted β-energy spectrum is often not included. This limitation hampers the use of decay data in some analysis, such as β-spectrometry of irradiated material, prediction of β-decay Bremsstrahlung or antineutrino, ν̄, detection. To address this deficiency, and for increased ease of β-spectrometry studies of complex samples, a library of β, ν and Bremsstrahlung-spectra, called BNBSL (Beta-Neutrino-Bremsstrahlung spectra library), has been produced. It has been found that the content compares favourably with experimental data and methodologies for its application to complex nuclear inventories have been developed. BNBSL contains spectra for over 1500 nuclides, which is hoped will benefit applied nuclear, radiation and materials science studies.

Polymeric Metal Contrast Agents for T1-Weighted Magnetic Resonance Imaging of the Brain

Imaging plays an integral role in diagnostics and treatment monitoring for conditions affecting the brain; enhanced brain imaging capabilities will improve upon both while increasing the general understanding of how the brain works. T₁-weighted magnetic resonance imaging is the preferred modality for brain imaging. Commercially available contrast agents, which are often required to render readable brain images, have considerable toxicity concerns. In recent years, much progress has been made in developing new contrast agents based on the magnetic features of gadolinium, iron, or magnesium. Nanotechnological approaches for these systems allow for the protected integration of potentially harmful metals with added benefits like reduced dosage and improved transport. Polymeric enhancement of each design further improves biocompatibility while allowing for specific brain targeting. This review outlines research on polymeric nanomedicine designs for T₁-weighted contrast agents that have been evaluated for performance in the brain.

Acupuncture, Nutritional Augmentation, and Physical Rehabilitation: Improving Recovery Following Spinal Fusion

Spinal fusion is one of the most common procedures performed in spinal surgery. The increasing complexity and frequency with which this operation is performed has led to a rise in postoperative complications and delayed recovery. Perioperative care of patients with spinal conditions aims to adequately manage pain and accelerate the return to function following surgery. Traditional pharmaceutical interventions, especially opioid utilization, are associated with delayed recovery and significant adverse effects. As such, many studies are now evaluating the benefits and efficacy of non-pharmacological therapies for enhancing recovery after spinal fusion surgery. In this review, the mechanism of acupuncture relative to postoperative pain control and symptom reduction will be discussed. Additionally, this review examines the implications of malnutrition, current preclinical and clinical approaches for improving nutritional status, and various forms of physical rehabilitation that aim to combat postoperative complications and support recovery after spinal fusion surgery.

Supporting safe and gradual reduction of long‐term benzodiazepine receptor agonist use: Development of the SAFEGUARDING‐BZRAs toolkit using a codesign approach

Introduction

Long‐term benzodiazepine receptor agonist (BZRA) use persists in healthcare settings worldwide and poses risks of patient harm.

Objective

This study aimed to develop an intervention to support discontinuation of long‐term BZRA use among willing individuals.

Methods

The intervention development process aligned with the UK Medical Research Council's complex intervention framework. This involved a previous systematic review of brief interventions targeting long‐term BZRA use in primary care and qualitative interviews based on the Theoretical Domains Framework that explored barriers and facilitators to discontinuing long‐term BZRA use. A codesign approach was used involving an active partnership between experts by experience, researchers and clinicians. Intervention content was specified in terms of behaviour change techniques (BCTs).

Results

The SAFEGUARDING‐BZRAs (Supporting sAFE and GradUAl ReDuctIon of loNG‐term BenZodiazepine Receptor Agonist uSe) toolkit comprises 24 BCTs and includes recommendations targeted at primary care‐based clinicians for operationalizing each BCT to support individuals with BZRA discontinuation.

Conclusion

The SAFEGUARDING‐BZRAs toolkit has been developed using a systematic and theory‐based approach that addresses identified limitations of previous research. Further research is needed to assess its usability and acceptability by service users and clinicians, as well as its potential to effectively support safe and gradual reduction of long‐term BZRA use.

Patient or Public Contribution

The qualitative interview phase included patients as participants. The codesign process included ‘experts by experience’ with either current or previous experience of long‐term BZRA use as collaborators.

Supporting sAFE and GradUAl ReDuctIon of loNG-term BenzodiaZepine Receptor Agonist uSe: development of the SAFEGUARDING-BZRAs toolkit using a co-design approach

Introduction

Long-term benzodiazepine receptor agonist (BZRA) use (>3 months) persists worldwide and poses risks of harm. Effective interventions are needed to address this issue.

Aim

To develop an intervention to support discontinuation of long-term benzodiazepine receptor agonist (BZRA) use.

Methods

The intervention development process built on previous qualitative work that used the Theoretical Domains Framework (TDF) to explore perceived barriers and facilitators to discontinuing long-term BZRA use (1). A co-design approach was used whereby lay individuals and professionals worked as equals during the research process based on principles of authentic participation and collaboration (2). The co-design team included five ‘experts by lived experience’ with experience of long-term BZRA use who previously provided input on other related work as patient and public involvement representatives or responded to an expression of interest call on social media. Two online co-design team meetings were held. During the first meeting, a summary of previous findings was presented together with a long-list of behaviour change techniques (BCTs) generated using established mapping matrices in which BCTs were reliably allocated to the TDF. Each team member independently documented their decision as to whether each BCT should be included in a short-list for potential inclusion in the final intervention using online polling software. The a priori decision rule was that 70% of team members had to agree regarding the inclusion/exclusion of a BCT. All other BCTs were then discussed at a follow-up meeting. A finalised list of BCTs for inclusion in the intervention was agreed at the second meeting using a consensus-based approach involving the same decision rule. Potential ways in which BCTs could be operationalised were then discussed.

Results

Thirty BCTs were discussed and six BCTs were excluded. For example, team members recommended avoiding ‘Social comparison’ as individual circumstances and experiences of discontinuation and associated withdrawal symptoms are unique and not directly comparable. Given the number of included BCTs, the co-design team recommended presenting them as a toolkit. The SAFEGUARDING-BZRAs (Supporting sAFE and GradUAl ReDuctIon of loNG-term BenzodiaZepine Receptor Agonist uSe) toolkit comprises 24 BCTs: ‘Goal setting (behaviour)’, ‘Review behaviour goal(s)’, ‘Review outcome goal(s)’, ‘Feedback on behaviour’, ‘Self-monitoring of behaviour’, ‘Social support (practical)’, ‘Social support (emotional)’, ‘Information about health consequences’, ‘Monitoring of emotional consequences’, ‘Information about emotional consequences’, ‘Prompts/cues’, ‘Habit reversal’, ‘Graded tasks’, ‘Pros and cons’, ‘Comparative imagining of future outcomes’, ‘Social reward’, ‘Self-reward’, ‘Reduce negative emotions’, ‘Distraction’, ‘Adding objects to the environment’, ‘Body changes’, ‘Verbal persuasion about capability’, ‘Focus on past success’ and ‘Credible source’. The toolkit includes recommendations targeted at primary care-based clinicians for operationalising each BCT to support BZRA discontinuation.

Conclusion

The SAFEGUARDING-BZRAs toolkit has been developed using a systematic, theory-based approach that addresses identified limitations of previous research (e.g. lack of detailed intervention description). In terms of limitations, it is possible that a different group of individuals may have developed a different type of intervention. To overcome this, a priori decision rules were used for decision making. Further research is needed to assess the toolkit’s usability and acceptability by service users and clinicians.

References

(1) Lynch et al. Health Expect. [in press] DOI: 10.1111/hex.13392.

(2) O’Donnell et al. BMC Health Serv Res. 2019;19(1):797

Evidence of sheep and abattoir environment as important reservoirs of multidrug resistant Salmonella and extended-spectrum beta-lactamase Escherichia coli

The increase in antimicrobial-resistant (AMR) foodborne pathogens, including E. coli and Salmonella in animals, humans, and the environment, is a growing public health concern. Among animals, cattle, pigs, and chicken are reservoirs of these pathogens worldwide. There is a knowledge gap on the prevalence and AMR of foodborne pathogens in small ruminants (i.e., sheep and goats). This study investigates the prevalence and antimicrobial resistance of extended-spectrum beta-lactamase (ESBL) E. coli and Salmonella from sheep and their abattoir environment in North Carolina. We conducted a year-round serial cross-sectional study and collected a total of 1128 samples from sheep (n = 780) and their abattoir environment (n = 348). Sheep samples consisted of feces, cecal contents, carcass swabs, and abattoir resting area feces. Environmental samples consisted of soil samples, lairage swab, animal feed, and drinking water for animals. We used CHROMAgar EEC with 4 μg/ml of Cefotaxime for isolating ESBL E. coli, and ESBL production was confirmed by double-disk diffusion test. Salmonella was isolated and confirmed using standard methods. All of the confirmed isolates were tested against a panel of 14 antimicrobials to elucidate susceptibility profiles. The prevalence of ESBL E. coli and Salmonella was significantly higher in environmental samples (47.7% and 65.5%) compared to the sheep samples (19.5% and 17.9%), respectively (P < 0.0001). We recovered 318 ESBL E. coli and 368 Salmonella isolates from sheep and environmental samples. More than 97% (310/318) of ESBL E. coli were multidrug-resistant (MDR; resistant to ≥3 classes of antimicrobials). Most Salmonella isolates (77.2%, 284/368) were pansusceptible, and 10.1% (37/368) were MDR. We identified a total of 24 different Salmonella serotypes by whole genome sequencing (WGS). The most common serotypes were Agona (19.8%), Typhimurium (16.2%), Cannstatt (13.2%), Reading (13.2%), and Anatum (9.6%). Prevalence and percent resistance of ESBL E. coli and Salmonella isolates varied significantly by season and sample type (P < 0.0001). The co-existence of ESBL E. coli in the same sample was associated with increased percent resistance of Salmonella to Ampicillin, Chloramphenicol, Sulfisoxazole, Streptomycin, and Tetracycline. We presumed that the abattoir environment might have played a great role in the persistence and dissemination of resistant bacteria to sheep as they arrive at the abattoir. In conclusion, our study reaffirms that sheep and their abattoir environment act as important reservoirs of AMR ESBL E. coli and MDR Salmonella in the U.S. Further studies are required to determine associated public health risks.

Modelling the potential impact of mask use in schools and society on COVID-19 control in the UK

As the UK reopened after the first wave of the COVID-19 epidemic, crucial questions emerged around the role for ongoing interventions, including test-trace-isolate (TTI) strategies and mandatory masks. Here we assess the importance of masks in secondary schools by evaluating their impact over September 1-October 23, 2020. We show that, assuming TTI levels from August 2020 and no fundamental changes in the virus's transmissibility, adoption of masks in secondary schools would have reduced the predicted size of a second wave, but preventing it would have required 68% or 46% of those with symptoms to seek testing (assuming masks' effective coverage 15% or 30% respectively). With masks in community settings but not secondary schools, the required testing rates increase to 76% and 57%.

Acidity, fluoride and silver ion concentrations in silver diamine fluoride solutions: a pilot study

BACKGROUND

There has been renewed interest in the use of silver diamine fluoride (SDF) for the management of carious lesions in high-risk groups. Previous studies have found a difference in clinical efficacy among different concentrations of SDF and discrepancies between ionic concentrations of fluoride (F) and silver (Ag) in SDF preparations. The aim of this study was to measure the free F, Ag ion concentrations and pH of a variety of commercially available SDF preparations.

METHODS

Seven SDF products used globally were evaluated for F and Ag ion concentrations using a calibrated ion-selective electrode and optical emission spectrometry respectively. Acidity was determined with a pH electrode.

RESULTS

The 30% SDF solution contained almost half the F concentration and a much higher Ag concentration than expected (16 343 ppmF and 246 000 ppmAg). Comparatively, the mean F concentration of the remaining six 38% solutions was 74 802 ppm (expected mean 44 800 ppm) ranging from 36 457 ppm to 120 760 ppm. The mean Ag concentration was 326 000 ppm (expected mean 253 870 ppm) and ranged from 246 000 ppm to 425 451 ppm. All solutions were found to be neutral or mildly alkaline in nature (pH 7-10.3).

CONCLUSIONS

Wide variations between claimed and measured F and Ag ion concentrations exist among the different brands of commercially available SDF products.

Equine cheek tooth extraction: Comparison of outcomes for five extraction methods

BACKGROUND

Post-operative complications are reported for all methods of equine cheek tooth extraction but not all methods carry the same risks. An outcome comparison for commonly used methods is needed so that clinicians can make informed treatment decisions.

OBJECTIVES

We conducted a side-by-side comparison of five cheek tooth extraction methods, comparing types and incidence of complications among oral extraction, tooth repulsion (three surgical approaches) and lateral buccotomy techniques.

STUDY DESIGN

Retrospective clinical study using hospital medical records.

METHODS

Medical records of all horses undergoing cheek tooth extraction between 1997 and 2013 were reviewed. Logistic regression was used to determine the likelihood of various post-operative complications, comparing oral extraction, tooth repulsion by maxillary and mandibular trephination or maxillary sinus bone flap, and lateral buccotomy.

RESULTS

The study included 137 horses and 162 cheek teeth extractions. Oral extraction was successful in 71% of patients in which it was attempted. Oral extraction (n = 55) had the lowest incidence of complications (20%) and repulsion by sinus bone flap (n = 20) the highest (80%). Complication rates for repulsion by maxillary (n = 19) and mandibular trephination (n = 28), and extraction by lateral buccotomy (n = 15) were 42, 54 and 53%, respectively. Cheek tooth repulsion by sinus bone flap significantly increased the odds of damage to adjacent teeth, post-operative sinusitis, damage to alveolar bone, delayed alveolar granulation and orosinus fistulation. Repulsion by maxillary trephination significantly increased the odds of superficial incisional surgical site infection; and extraction by lateral buccotomy significantly increased the odds of facial nerve neuropraxia. Post-operative pyrexia was more common in all repulsion methods.

MAIN LIMITATIONS

Some clinically relevant differences may have been missed due to small group numbers in several categories.

CONCLUSIONS

Oral extraction was associated with fewer post-operative complications than any other methods. Standing oral extraction remains the preferred choice, and recent surgical advances promise to further improve its success rate.

Polymyxin B hemoperfusion in endotoxemic septic shock patients without extreme endotoxemia: a post hoc analysis of the EUPHRATES trial

PURPOSE

The EUPHRATES trial examined the impact of polymyxin B hemoperfusion (PMX) on mortality in patients with septic shock and endotoxemia, defined as EAA ≥ 0.60. No difference was found in 28-day all-cause mortality. However, the trial showed that in some patients with septic shock the burden of endotoxin activity was extreme (EAA ≥ 0.9). In a post hoc analysis, we evaluated the impact of PMX use in patients with septic shock and endotoxin activity measured between 0.6-0.89.

METHODS

Post-hoc analysis of the EUPHRATES trial for the 194 patients with EAA ≥ 0.6-0.89 who completed two treatments (PMX or sham). The primary end point was mortality at 28 days adjusted for APACHE II score and baseline mean arterial pressure (MAP). Additional end points included changes in MAP, cumulative vasopressor index (CVI), median EAA reduction, ventilator-free days (VFD), dialysis-free days (DFD) and hospital length of stay. Subpopulations analyzed were site and type of infection and those with norepinephrine dose > 0.1 mcg/kg/min at baseline.

RESULTS

At 28 days, 23 patients of 88 (26.1%) in the PMX group died versus 39 of 106 (36.8%) in the sham group [risk difference 10.7%, OR 0.52, 95% CI (0.27, 0.99), P = 0.047]. When unadjusted for baseline variables, P = 0.11. The 28-day survival time in the PMX group was longer than for the sham group [HR 0.56 (95% CI 0.33, 0.95) P = 0.03]. PMX treatment compared with sham showed greater change in MAP [median (IQR) 8 mmHg (- 0.5, 19.5) vs. 4 mmHg (- 4.0, 11) P = 0.04] and VFD [median (IQR) 20 days (0.5, 23.5) vs. 6 days (0, 20), P = 0.004]. There were no significant differences in other end points. There was a significant difference in mortality in PMX-treated patients with no bacterial growth on culture [PMX, 6/30 (20%) vs. sham, 13/31 (41.9%), P = 0.005]. The median EAA change in the population was - 12.9% (range: increase 49.2%-reduction 86.3%). The mortality in the above median EAA change group was PMX: 6/38 (15.7%) vs. sham 15/49 (30.6%), P = 0.08.

CONCLUSIONS

These hypothesis-generating results, based on an exploratory post hoc analysis of the EUPHRATES trial, suggest measurable responses in patients with septic shock and an EAA ≥ 0.6 to 0.89 on changes in mean arterial pressure, ventilator-free days and mortality.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT01046669. Funding Spectral Medical Incorporated.

Crossover between liquidlike and gaslike behavior in CH_{4} at 400 K

We report experimental evidence for a crossover between a liquidlike state and a gaslike state in fluid methane (CH_{4}). This crossover is observed in all of our experiments, up to a temperature of 397 K, 2.1 times the critical temperature of methane. The crossover has been characterized with both Raman spectroscopy and x-ray diffraction in a number of separate experiments, and confirmed to be reversible. We associate this crossover with the Frenkel line-a recently hypothesized crossover in dynamic properties of fluids extending to arbitrarily high pressure and temperature, dividing the phase diagram into separate regions where the fluid possesses liquidlike and gaslike properties. On the liquidlike side the Raman-active vibration increases in frequency linearly as pressure is increased, as expected due to the repulsive interaction between adjacent molecules. On the gaslike side this competes with the attractive van der Waals potential leading the vibration frequency to decrease as pressure is increased.

Knotted fields and explicit fibrations for lemniscate knots

We give an explicit construction of complex maps whose nodal lines have the form of lemniscate knots. We review the properties of lemniscate knots, defined as closures of braids where all strands follow the same transverse (1, ℓ) Lissajous figure, and are therefore a subfamily of spiral knots generalizing the torus knots. We then prove that such maps exist and are in fact fibrations with appropriate choices of parameters. We describe how this may be useful in physics for creating knotted fields, in quantum mechanics, optics and generalizing to rational maps with application to the Skyrme-Faddeev model. We also prove how this construction extends to maps with weakly isolated singularities.

Readmissions - can they be predicted on admission?

This paper looks at the development of logistic regression models to predict readmissions for medical patients on their initial admission to hospital. The design of our study was a retrospective analysis of a large dataset drawn from a range of secondary sources - medical, nursing, therapy and social care records. Three northern hospitals and related community health districts and social care organizations in the UK participated. Records of 1,192 patients discharged from medical wards during the period April 1992-March 1995 were analysed. Readmission within six weeks of discharge was the main outcome measure.Four logistic regression equations were produced. Three individual site equations were calculated and classification levels for readmission of 17-22 per cent were achieved. Component factors that differed in importance were age, GP contact, social services contact, marital status and living status. The weakest equation was the equation that encompassed patients from all three sites, which classified 7 per cent of readmissions. It is possible to develop equations that will explain readmission for a fifth of medical patients on admission to individual hospitals. Further exploratory work needs to be undertaken to explore reasons for differences between districts and develop more generalizable predictive equations.

Laryngeal manifestations of haemochromatosis

We present a case with sudden onset of throat pain, dysphagia and hoarseness. On endoscopic examination, supraglottic swelling and a brown covering of the mucous membranes were seen. The diagnosis of haemochromatosis was made on laryngeal biopsy. The patient admitted to long-term iron treatment for anaemia. Haemochromatosis can affect many different organs. If the larynx is involved, the airway may be endangered.

Comparison of cerebral pharmacokinetics of buprenorphine and norbuprenorphine in anin vivosheep model

The pharmacokinetics and time course of blood-brain equilibration of buprenorphine (BUP) and norbuprenorphine (norBUP) in sheep were characterized. Sheep were administered 0.04 mg kg(-1) BUP or 0.6 mg kg(-1) norBUP as 4-min i.v. infusions. The cerebral kinetics were inferred from arterio-sagittal sinus concentration gradients and changes in cerebral blood flow. These data were fitted to physiologically based pharmacokinetic models. BUP cerebral kinetics were best described by a membrane-limited model with a large equilibration delay (half-life of 20 min) between brain and blood due to intermediate permeability (47 ml min(-1)) and a large cerebral distribution volume (595 ml). Significant limitation in permeability (6 ml min(-1)) characterized the cerebral kinetics of norBUP with a cerebral distribution volume (157 ml) giving a blood-brain equilibration half-life (21 min) similar to that for BUP. The logD of BUP and norBUP were 3.93 +/- 0.08 and 1.18 +/- 0.04 (mean +/- SD), respectively. Both compounds revealed slow cerebral equilibration with variations in degree of permeability and distribution volume reflecting the difference in lipophilicity. It is possible that norBUP contributes to the central effects seen after chronic BUP administration as this study demonstrated its entry into the brain.

Molecular subtyping of mastitis-associated Klebsiella pneumoniae isolates shows high levels of diversity within and between dairy herds

Despite advances in controlling mastitis (inflammation of the mammary gland), udder infections caused by Klebsiella pneumoniae continue to affect dairy cattle. Mastitis caused by K. pneumoniae responds poorly to antibiotic treatment, and as a consequence, infections tend to be severe and long lasting. We sought to determine whether a nonrandom distribution of specific genotypes of K. pneumoniae was associated with mastitis from 6 dairy herds located in 4 different states. A total of 635 isolates were obtained and fingerprinted by repetitive DNA sequence PCR. Significant genetic diversity was observed in 4 of the 6 dairy herds analyzed, and a total of 49 genotypic variants were identified. Within a herd, Simpson's diversity indices were 91.0, 94.1, 91.7, 88.6, 53.3, and 64.3% for dairies A, B, C, D, E, and F, respectively. The association between matrices of genetic similarity and matrices of temporal distance was negative in all the dairies analyzed. Four dairies had a high incidence of K. pneumoniae mastitis during the winter. The majority of genotypes were unique to herds of origin, and only 5 genotypes were detected in more than 2 dairies. Genotype 1 (arbitrary designation) occurred most frequently across dairies and was found in 25.2% of all mastitis cases and among 22.8% of reinfected and culled cows in dairy A. Specific genotypes also tended to be associated with a specific bedding type and dairy location. Analysis of molecular variance showed that 18% of the genetic diversity was due to variation among herds within states, and 82% of the genetic diversity was accounted for by variation of genotypes within herds. The data support the idea that mastitis is caused by a diverse group of K. pneumoniae genotypes and thus has major implications for the diagnosis, prevention, and treatment of udder infections in dairy cows.

Genetic diversity of mastitis-associated Klebsiella pneumoniae in dairy cows

The objectives of this study were to determine the level of genetic diversity of Klebsiella pneumoniae isolated from clinical mastitis cases and to define genotypes most commonly associated with the disease. Individual quarter milk samples were collected from a single privately owned dairy herd over a 2-yr period and submitted to the Laboratory for Udder Health, Minnesota Veterinary Diagnostic Laboratory, University of Minnesota, for bacteriological culture. Eighty-four K. pneumoniae isolates were obtained and fingerprinted by repetitive DNA sequence PCR, 43 by pulsed-field gel electrophoresis (PFGE), and 29 by multilocus sequence typing (MLST). Significant genetic diversity was observed among the isolates regardless of the fingerprinting method used. Simpson's diversity index was 93.5, 96.1, and 97.0% when analyzed by repetitive DNA sequence PCR (n = 84), pulse field gel electrophoresis (n = 43), and MLST (n = 29), respectively. In some cases more than 1 genotype was obtained from a single milk sample originating from an individual quarter. The majority of infections were observed during the winter and accounted for 69.0% of K. pneumoniae mastitis cases. There was a negative correlation between a matrix of fingerprints similarity and a matrix of temporal distances. The MLST results revealed 5 new and novel allelic types, which have not been previously reported in the MLST database. Three isolates shared MLST types with human clinical isolates, raising the possibility that some K. pneumoniae isolates, of bovine origin, may be capable of causing disease in humans. There were 21 genotypes present within the herd, and there was no evidence for nonrandom distribution of genotypes uniquely associated with mastitis. We have shown, using 3 distinct genotyping methods, that K. pneumoniae isolated from clinical mastitis within a single dairy herd is caused by a genetically diverse population and that multiple genotypes can be isolated from a mastitic quarter. The data suggest that mastitis can be caused by a variety of K. pneumoniae genotypes. Diverse genotypes may have different levels of invasiveness and virulence and may originate from various sources within the dairy.

Nocardia infections in cats: a retrospective multi-institutional study of 17 cases

OBJECTIVE

To record 17 cases of nocardiosis in cats from eastern Australia and to compare this series with cases previously reported.

DESIGN

Retrospective/prospective study.

RESULTS

Nocardia spp infections were diagnosed in 17 cats over 14 years from the three eastern states of Australia. There were no isolates from dogs during this period, but one isolate from a koala and two from dairy cows. The majority of cats presented with spreading lesions of the subcutis and skin associated with draining sinus tract(s). Early cutaneous lesions consisted of circumscribed abscesses. Infections spread at a variable rate, generally by extension to adjacent tissues. Lesions were generally located in regions subjected to cat bite or scratch injuries, including limbs, body wall, inguinal panniculus and nasal bridge. In some other cases, lesions were situated on distal extremities. The clinical course was variable, from chronic, indolent, initially localised infections to acute fulminating disease. Of the 17 cats, 14 were domestic crossbreds and three were purebreds. There was a preponderance of male cats (12 castrated, 1 entire young adult, 1 entire kitten). Nine of 17 cats were 10 years or older. Interestingly, the majority of infections were attributable to N nova. Immediate and/or predisposing causes could be identified in all cases, and included: renal transplantation [one cat]; chronic corticosteroid administration [three cats]; catabolic state following chylothorax surgery [one cat]; fight injuries [seven cats]; FIV infections [three of seven cats tested]. Of the 17 cats, three were apparently cured. Four were thought to be cured, but infection recurred after several months. Three cats responded partially but were euthanased, while another was improving when it died of unrelated complications. Two died despite treatment and two were euthanased without an attempt at therapy. For two cats there were either insufficient records or the patient was lost to follow up.

CONCLUSION

Nocardiosis is a rare, serious disease. Currently it is more common in cats than dogs. Nocardial panniculitis may be clinically indistinguishable from the syndrome caused by rapidly growing mycobacteria. Although the prognosis is guarded, patients with localised infections caused by N nova often respond to appropriate therapy. If definitive treatment is delayed because of misdiagnosis, the disease tends to become chronic, extensive and refractory. Insufficient duration of therapy leads to disease recurrence.

Downregulation of N1 gene expression inhibits the initial heartbeating and heart development in axolotls

Recessive mutant gene c in the axolotl results in a failure of affected embryos to develop contracting hearts. This abnormality can be corrected by treating the mutant heart with RNA isolated from normal anterior endoderm or from endoderm conditioned medium. A cDNA library was constructed from the total conditioned medium RNA using a random priming technique in a pcDNAII vector. We have previously identified a clone (designated as N1) from the constructed axolotl cDNA library, which has a unique nucleotide sequence. We have also discovered that the N1 gene product is related to heart development in the Mexican axolotl [Cell Mol. Biol. Res. 41 (1995) 117]. In the present studies, we further investigate the role of N1 on heartbeating and heart development in axolotls. N1 mRNA expression has been determined by using semi-quantitative RT-PCR with specifically designed primers. Normal embryonic hearts (at stages 30-31) have been transfected with anti-sense oligonucleotides against N1 to determine if downregulation of N1 gene expression has any effect on normal heart development. Our results show that cardiac N1 mRNA expression is partially blocked in the hearts transfected with anti-sense nucleotides and the downregulation of N1 gene expression results in a decrease of heartbeating in normal embryos, although the hearts remain alive as indicated by calcium spike movement throughout the hearts. Confocal microscopy data indicate some myofibril disorganization in the hearts transfected with the anti-sense N1 oligonucleotides. Interestingly, we also find that N1 gene expression is significantly decreased in the mutant axolotl hearts. Our results suggest that N1 is a novel gene in Mexican axolotls and it probably plays an important role in myofibrillogenesis and in the initiation of heartbeating during heart development.