Mouse models of dominant ACTA1 disease recapitulate human disease and provide insight into therapies

Mutations in the skeletal muscle α-actin gene (ACTA1) cause a range of pathologically defined congenital myopathies. Most patients have dominant mutations and experience severe skeletal muscle weakness, dying within one year of birth. To determine mutant ACTA1 pathobiology, transgenic mice expressing ACTA1(D286G) were created. These Tg(ACTA1)(D286G) mice were less active than wild-type individuals. Their skeletal muscles were significantly weaker by in vitro analyses and showed various pathological lesions reminiscent of human patients, however they had a normal lifespan. Mass spectrometry revealed skeletal muscles from Tg(ACTA1)(D286G) mice contained ∼25% ACTA1(D286G) protein. Tg(ACTA1)(D286G) mice were crossed with hemizygous Acta1(+/-) knock-out mice to generate Tg(ACTA1)(D286G)(+/+).Acta1(+/-) offspring that were homozygous for the transgene and hemizygous for the endogenous skeletal muscle α-actin gene. Akin to most human patients, skeletal muscles from these offspring contained approximately equal proportions of ACTA1(D286G) and wild-type actin. Strikingly, the majority of these mice presented with severe immobility between postnatal Days 8 and 17, requiring euthanasia. Their skeletal muscles contained extensive structural abnormalities as identified in severely affected human patients, including nemaline bodies, actin accumulations and widespread sarcomeric disarray. Therefore we have created valuable mouse models, one of mild dominant ACTA1 disease [Tg(ACTA1)(D286G)], and the other of severe disease, with a dramatically shortened lifespan [Tg(ACTA1)(D286G)(+/+).Acta1(+/-)]. The correlation between mutant ACTA1 protein load and disease severity parallels effects in ACTA1 families and suggests altering this ratio in patient muscle may be a therapy for patients with dominant ACTA1 disease. Furthermore, ringbinden fibres were observed in these mouse models. The presence of such features suggests that perhaps patients with ringbinden of unknown genetic origin should be considered for ACTA1 mutation screening. This is the first experimental, as opposed to observational, evidence that mutant protein load determines the severity of ACTA1 disease.

A mutation in an alternative untranslated exon of hexokinase 1 associated with hereditary motor and sensory neuropathy -- Russe (HMSNR)

Hereditary Motor and Sensory Neuropathy -- Russe (HMSNR) is a severe autosomal recessive disorder, identified in the Gypsy population. Our previous studies mapped the gene to 10q22-q23 and refined the gene region to approximately 70 kb. Here we report the comprehensive sequencing analysis and fine mapping of this region, reducing it to approximately 26 kb of fully characterised sequence spanning the upstream exons of Hexokinase 1 (HK1). We identified two sequence variants in complete linkage disequilibrium, a G>C in a novel alternative untranslated exon (AltT2) and a G>A in the adjacent intron, segregating with the disease in affected families and present in the heterozygote state in only 5/790 population controls. Sequence conservation of the AltT2 exon in 16 species with invariable preservation of the G allele at the mutated site, strongly favour the exonic change as the pathogenic mutation. Analysis of the Hk1 upstream region in mouse mRNA from testis and neural tissues showed an abundance of AltT2-containing transcripts generated by extensive, developmentally regulated alternative splicing. Expression is very low compared with ubiquitous Hk1 and all transcripts skip exon1, which encodes the protein domain responsible for binding to the outer mitochondrial membrane, and regulation of energy production and apoptosis. Hexokinase activity measurement and immunohistochemistry of the peripheral nerve showed no difference between patients and controls. The mutational mechanism and functional effects remain unknown and could involve disrupted translational regulation leading to increased anti-apoptotic activity (suggested by the profuse regenerative activity in affected nerves), or impairment of an unknown HK1 function in the peripheral nervous system (PNS).

Increase in VTEC cases in the south of Ireland: link to private wells?

High levels of verotoxigenic Escherichia coli (VTEC) have been recorded to date in 2008 in the Republic of Ireland. One hundred and forty-eight VTEC cases were notified up to the end of August 2008 (Figure 1), compared to 70-90 confirmed cases reported in the equivalent time period in 2006 and 2007. Thirty three percent of cases notified in Ireland in 2008 indicated that their usual drinking water supply was a private well.

Large outbreak of E. coli O157 in 2005, Ireland

In October/November 2005, the largest outbreak of verotoxin-producing Escherichia coli (VTEC) ever recorded in Ireland occurred. Eighteen E. coli O157 culture-positive cases, phage type 32, verotoxin 2 positive, were identified in a small rural area of mid-west Ireland. Half of these patients were asymptomatic. Two children were admitted to hospital with haemolytic uraemic syndrome, one of whom required peritoneal dialysis, and both recovered. All 18 culture-positive patients had indistinguishable or closely related pulsed field gel electrophoresis (PFGE) patterns. Nine of the VTEC O157 culture-positive individuals were in preschool children attending two local crèches. Several culture-positive individuals apparently had exposure to a vulnerable private group water scheme (GWS) in an agricultural area. No microbiological evidence of VTEC was found in food or water. One veterinary sample (an animal rectal swab) was positive for E. coli O157 and the PFGE strain was indistinguishable from the outbreak strain. A case control study showed analytical epidemiological evidence of risk related to potential exposure to the GWS but not related to reported consumption of that water. Selection of cases and controls proved challenging. Transmission occurred primarily in childcare and family settings, with significant person-to-person spread. Control measures included voluntary closure of the crèches, exclusion of culture-positive individuals in risk groups until microbiological clearance was achieved and the issuing of a ‘boil water’ advisory for drinking water pending upgrading of disinfection facilities.

Haemolytic uraemic syndrome associated with interfamilial spread of E. coli O26:H11

In September 2000, haemolytic uraemic syndrome (HUS) was diagnosed in a 10-month-old child with a prodromal history of vomiting and diarrhoea (non-bloody). Investigation revealed that a self-limiting gastrointestinal illness (mean duration 48 h) had occurred among immediate and extended family in the 2 weeks prior to the child's admission. The epidemiology of the illness suggested person-to-person spread. Five children (close family contacts) had E. coli O26 verocytotoxin (VT1 and VT2) isolated from stools. Stool culture and serology from the index case were negative for shiga toxin-producing E. coli (STEC) organisms. Control measures in accordance with the Public Health Laboratory Service (PHLS), verocytotoxogenic organisms (VTEC) guidelines were applied to prevent further spread among the extended family and contacts. Despite detailed food and environmental exposure histories, the source of the illness was not identified. This incident highlights the importance of investigation of cases of post-diarrhoeal HUS, for potential shiga toxin E. coli aetiology.

Antibiotic resistance of retail food and human Campylobacter isolates on the island of Ireland from 2001-2002

The antimicrobial resistance profiles of Campylobacter isolates recovered from a range of retail food samples (n=374) and humans (n=314) to eight antimicrobial compounds were investigated. High levels of resistance in food C. jejuni isolates were observed for ceftiofur (58%), ampicillin (25%) and nalidixic acid (17%) with lower levels observed for streptomycin (7.9%) and chloramphenicol (8.3%). A total of 80% of human C. jejuni isolates were resistant to ceftiofur, while 17% showed resistance to ampicillin and nalidixic acid, 8.6% to streptomycin and 4.1% to chloramphenicol. Resistance to clinically relevant antimicrobials such as erythromycin, ciprofloxacin and tetracycline was 6.7, 12, and 15% respectively for all food isolates and was similar to corresponding resistance prevalences observed for human isolates, where 6.4, 12 and 13% respectively were found to be resistant. Comparisons of C. jejuni isolates in each location showed a high degree of similarity although some regional variations did exist. Comparison of total C. jejuni and C. coli populations showed minor differences, with C. jejuni isolates more resistant to ampicillin and ceftiofur. Multidrug resistance patterns showed some profiles common to human and clinical isolates.

Occurrence of Campylobacter in retail foods in Ireland

A surveillance study was carried out to determine the prevalence of Campylobacter in a range of retail foods purchased in three Irish cities over a 20-month period between March 2001 and October 2002. In total 2391 food samples were analysed during this period. Campylobacter was isolated from 444 raw chicken (49.9%), 33 turkey (37.5%) and 11 duck samples (45.8%). Lower isolation rates of 7/221 (3.2%), 10/197 (5.1%) and 31/262 (11.8%) were observed for raw beef, pork and lamb, respectively. One sample of pork paté from 120 samples analysed (0.8%) was Campylobacter-positive. A total of three shellfish samples (oysters) from 129 raw specimens examined (2.3%) were found to contain Campylobacter. Low prevalences of the organism (0.9%) were also isolated from fresh mushrooms. Of 62 raw bulk tank milk samples analysed, Campylobacter was recovered in a single sample (1.6%). Campylobacter was not detected in any of the comminuted pork puddings, prepared vegetables and salads, retail sandwiches or cheeses made from unpasteurised milk. In total, 543 Campylobacter were isolated from all of the food samples analysed, of which 453 (83.4%) were confirmed as Campylobacter jejuni and the remaining 90 (16.6%) as Campylobacter coli.

Nutrition in the community - an exploratory study of oral nutritional supplements in a health board area in Ireland

BACKGROUND

A review of the General Medical (Payments) Scheme data in the Midland Health Board (MHB) Ireland identified a spend of just over euro 0.5 million on enteral nutritional supplements (oral and tube feeds) in an 11-month period in 1998 [General Medical Services (Payments) Board, 1998, MHB Clinical Nutritional Products: January-December 1998, Dublin]. In 2000, a figure of euro5 million was reported as the annual spend (oral and tube feeds) [General Medical Services (Payments) Board, 2000, MHB Clinical Nutritional Products: January-December 2000, Dublin]. Research has shown that a high proportion of Oral Nutritional Supplements (ONS) are inappropriately prescribed by primary care practitioners (Gall et al., 2001). The role of General Practitioners (GPs) and Public Health Nurses (PHNs) in prescribing ONS to patients aged 65 years and older was examined, as they are directly involved in the delivery of primary health care.

AIM

(i) Assess current trends, decision-making processes and monitoring procedures in the use of ONS for older patients in the community. (ii) Identify whether nutritional assessments and appropriate nutritional criteria are standard practice in determining selection of ONS.

METHODS

A study was conducted among 99 GPs and 120 PHNs in the MHB. All GPs were selected to participate and 50% (60) of PHNs were randomly selected. A telephone questionnaire was administered to each subject over a 2-week period.

RESULTS

Both GPs (78%) and PHNs (47%) reported that their prescription of/recommendations for ONS had increased in the last 4 years. None conducted a full nutritional assessment, but 25% of PHNs used a Nutrition Screening Tool when trying to ascertain whether a patient requires an ONS. Only 19.6% of GPs and 6.8% of PHNs surveyed were aware of the calorie content of a standard 200 mL ONS (sip-feed). In addition, a very significant proportion of both GPs and PHNs do not appear to give appropriate dietary advice to patients who may be at risk of malnutrition. Only 55% of GPs stated that they would specifically review a patient's ONS prescription. All GPs said that they would not conduct a full nutritional assessment at the review appointment.

CONCLUSION

The results of this study raise concerns as to the appropriateness of current ONS prescription and monitoring in the community. They also highlight the need for further intervention in the primary care setting in order to ensure that elderly malnourished patients are detected, treated and monitored in an appropriate and cost-effective manner.

A twelve-year review of central nervous system bacterial abscesses; presentation and aetiology

OBJECTIVES

To review and document the changing patterns in diagnosis, causes and treatment of bacterial infections of the central nervous system (CNS) in a national neurosurgical unit only in patients from whom a specimen was obtained for culture.

METHODS

The case notes, radiological results and laboratory records of all 163 patients in our institution who underwent a neurosurgical procedure between 1988 and 2000 for a CNS abscess in a national center were reviewed retrospectively. Those patients from whom there were no operative specimens (i.e. neurosurgical intervention was not performed) and who were treated empirically were excluded, as were patients with mycobacterial infection.

RESULTS

The mean age of the 163 patients was 35.2 years. Headache, pyrexia and an altered mental state were the commonest presentations. The frontal lobe was the commonest anatomical site (62 patients, 38%) and the majority of abscesses occurred following community infections such as sinusitis and mastoiditis; no primary source could be identified in 32 (20%) patients. Bacteria were isolated from 73% of patients and polymicrobial infections occurred in 29 (17.7%) patients. Anaerobes accounted for only 13.6% of isolates and methicillin-resistant Staphylococcus aureus (MRSA) was isolated on five occasions, all in the last five years of this review. Sixteen (9.8%) patients died prior to discharge or transfer back to the original referring hospital and 18 (11%) patients developed epilepsy.

CONCLUSION

There was a relatively high incidence of polymicrobial infection but the number of specimens with anaerobes was small, which may be because of the use of empiric metronidazole before surgical intervention. Most infections were community-acquired and responded well to a combination of surgical drainage and antibiotic therapy. The emergence of MRSA in this group of patients is, however, worrying.

Tube feeding controversial patients: what do dietitians think?

The use of tube feeding in some patients can be controversial, however, few studies have investigated dietitians' opinions on this subject. A cross-sectional survey of 345 members the Irish Nutrition and Dietetic Institute was conducted using a self-administered, anonymous, postal questionnaire. A 44% response rate was achieved. Mean number of years qualified was 9.3 (8.4). Eighty-one per cent of responders were involved in initiating tube feeding in stroke patients, and 8.5% in discontinuing tube feeding in a patient in a persistent vegetative state (PVS). Nine per cent felt that their input had no influence on the care plan of the patient with dementia and 67% felt that the information given to families (or other decision makers) concerning tube feeding was inadequate. The majority of respondents favoured tube feeding fictitious stroke and cancer patients, but less than half favoured tube feeding a fictitious patient in a PVS or a patient with dementia. When given similar scenarios involving themselves, fewer dietitians wanted to be tube fed.

Epidemiological studies of human and animal Salmonella typhimurium DT104 and DT104b isolates in Ireland

A total of 122 human and animal Salmonella Typhimurium DT104 isolates and 6 epidemiologically related DT104b isolates from human and animal products were analysed by pulsed-field gel electrophoresis (PFGE). Genomic DNA was subjected to macrorestriction with three enzymes, SpeI, SfiI and XbaI. A total of 14 restriction fragment length polymorphism (RFLP) profiles were identified when the PFGE patterns from the three enzymes were combined. The majority of isolates (81.2%) exhibited the same RFLP profile. Six animal DT104 isolates, susceptible to enrofloxacin and resistant to naladixic acid, were identified from the antibiotic susceptibility test. Four of these isolates had a different PFGE profile from the common RFLP. In addition, 4 of the 6 isolates were geographically clustered in one region. It was concluded that there was one predominant strain of S. Typhimurium DT104 in Ireland and that the potential and selection pressures for emergence of fluoroquinolone-resistant isolates were present.

Pharmacokinetics of penicillin G procaine versus penicillin G potassium and procaine hydrochloride in horses

OBJECTIVE

To compare the pharmacokinetics of penicillin G and procaine in racehorses following i.m. administration of penicillin G procaine (PGP) with pharmacokinetics following i.m. administration of penicillin G potassium and procaine hydrochloride (PH).

ANIMALS

6 healthy adult mares.

PROCEDURE

Horses were treated with PGP (22,000 units of penicillin G/kg of body weight, i.m.) and with penicillin G potassium (22,000 U/kg, i.m.) and PH (1.55 mg/kg, i.m.). A minimum of 3 weeks was allowed to elapse between drug treatments. Plasma and urine penicillin G and procaine concentrations were measured by use of high-pressure liquid chromatography.

RESULTS

Median elimination phase half-lives of penicillin G were 24.7 and 12.9 hours, respectively, after administration of PGP and penicillin G potassium. Plasma penicillin G concentration 24 hours after administration of penicillin G potassium and PH was not significantly different from concentration 24 hours after administration of PGP. Median elimination phase half-life of procaine following administration of PGP (15.6 hours) was significantly longer than value obtained after administration of penicillin G potassium and PH (1 hour).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that i.m. administration of penicillin G potassium will result in plasma penicillin G concentrations for 24 hours after drug administration comparable to those obtained with administration of PGP Clearance of procaine from plasma following administration of penicillin G potassium and PH was rapid, compared with clearance following administration of PGP.

Interpretative reporting and selective antimicrobial susceptibility release in non-critical microbiology results

The action taken in response to 169 positive sputum, urine and wound culture reports was examined. All reports included interpretative comments. Antimicrobial susceptibilities were released in 29 (17%). Therapy was significantly more likely to be started or altered in response to reports where susceptibilities were released (13 of 29, 45%) versus those without susceptibility release (31 of 140, 22%). Susceptibility release did not influence the appropriateness of antibiotic therapy. The clinical microbiology team was contacted for therapeutic advice in response to 32 (19%) reports. Of the remaining 137 reports, therapy was started or altered in response to 30 (22%) reports, but was considered appropriate in only seven (22%) of these.

Clostridium difficile colitis associated with chronic renal failure

BACKGROUND

Clostridium difficile-associated diarrhoea (CDAD) is a potentially life-threatening illness which has been shown to be more common and more severe in patients with chronic renal failure (CRF) than in other groups. A review of CDAD in our nephrology unit was carried out.

METHODS

A review of microbiology and histology records identified 32 cases of CDAD in the nephrology unit over a 24-month period. Patient notes were reviewed to identify risk factors, clinical features and outcome. Available isolates of C. difficile underwent 16S ribosomal RNA typing.

RESULTS

The incidence of CDAD in the nephrology unit was 10.7 per 1000 admissions, compared to 2.7 per 1000 in other areas of the hospital (P<0.0001). CDAD was considered the sole or principal cause of death in six (19%) and was considered a contributing factor in a further seven (22%). Mortality was significantly higher among patients with established CRF (P=0.04). Seven cases occurred as a cluster, over a 1-month period. Isolates from this cluster, along with comparative strains from other areas of the hospital, were found to be PCR type 1. Diarrhoea occurred in 28 (89%) of cases, pyrexia in 17 (53%) and ileus or abdominal pain in 14 (44%). Six patients responded to discontinuation of antibiotics alone and 22 required metronidazole and/or vancomycin. Three patients had colectomy and one caecostomy because of toxic megacolon. Four patients died before specific therapy could be given and in two of these cases the diagnosis was made at autopsy. Twenty-six patients had a record of recent antibiotic therapy. Of these, 15 had at least one agent considered to be inappropriate (excessively broad spectrum agent in 11, excessive duration of therapy in four). Nine patients had only received antibiotics prior to admission.

CONCLUSIONS

CDAD carries a high mortality in nephrology patients, especially those with established CRF. The diagnosis may be missed if a careful antibiotic history is not taken, including agents received prior to admission. Rational antibiotic prescribing and adherence to infection control measures are vital to reduce the incidence of this serious condition.

Is this the right time to come out? Case study

In this fictional case study, Adam Lawson is a promising young associate at Kirkham McDowell Securities, a St. Louis underwriting and financial advisory firm. Recently, Adam helped to bring in an extremely lucrative deal, and soon he and a few other associates will be honored for their efforts at the firm's silver anniversary dinner. George Campbell, vice president in mergers and acquisitions, is caught unprepared when Adam tells him that, after serious reflection, he has decided to bring his partner, Robert Collins, to the banquet. George is one of Adam's biggest supporters at the firm, and he personally has no problem with Adam being gay. But it is one thing for Adam to come out of the closet at the office. It is quite another to do so at a public company-client event. After all, Kirkham McDowell's client roster includes some very conservative companies--one of the country's largest defense contractors, for example. George is concerned with how Adam's openness about his sexual orientation will play with their clients and, as a result, how senior management will react. Adam has not come to George for permission to bring Robert to the dinner. But clearly Adam wants some sort of response. George has never faced sexual diversity issues in the workplace before, and there is no company policy to guide him. Just how negative an effect could Robert have on Adam's career with the firm and the firm's relationship with its clients? Isn't it possible that even the firm's most conservative clients will simply decide that Adam's choice of guest is a personal matter--not a business one?(ABSTRACT TRUNCATED AT 250 WORDS)