Capture of a novel, antibiotic resistance encoding, mobile genetic element from Escherichia coli using a new entrapment vector

AIMS

Antimicrobial resistance genes (ARGs) are often associated with mobile genetic elements (MGEs), which facilitate their movement within and between bacterial populations. Detection of mobility is therefore important to understand the dynamics of MGE dissemination and their associated genes, especially in resistant clinical isolates that often have multiple ARGs associated with MGEs. Therefore, this study aimed to develop an entrapment vector to capture active MGEs and ARGs in clinical isolates of Escherichia coli.

METHODS AND RESULTS

We engineered an entrapment vector, called pBACpAK, to capture MGEs in clinical E. coli isolates. It contains a cI-tetA positive selection cartridge in which the cI gene encodes a repressor that inhibits the expression of tetA. Therefore, any disruption of cI, for example, by insertion of a MGE, will allow tetA to be expressed and result in a selectable tetracycline-resistant phenotype. The pBACpAK was introduced into clinical E. coli isolates and grown on tetracycline-containing agar to select for clones with the insertion of MGEs into the entrapment vector. Several insertion sequences were detected within pBACpAK, including IS26, IS903B and ISSbo1. A novel translocatable unit (TU), containing IS26 and dfrA8 was also captured, and dfrA8 was shown to confer trimethoprim resistance when it was cloned into E. coli DH5α.

CONCLUSIONS

The entrapment vector, pBACpAK was developed and shown to be able to capture MGEs and their associated ARGs from clinical E. coli isolates. We have captured, for the first time, a TU encoding antibiotic resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first time that a TU and associated resistance gene has been captured from clinical E. coli isolates using an entrapment vector. The pBACpAK has the potential to be used not only as a tool to capture MGEs in clinical E. coli isolates, but also to study dynamics, frequency and potentiators of mobility for MGEs.

Fingerprints of partial oxidation of biogenic magnetite from cultivated and natural marine magnetotactic bacteria using synchrotron radiation

Magnetotactic bacteria are a multi-phyletic group of bacteria that synthesize membrane-bound magnetic minerals. Understanding the preservation of these minerals in various environments (e.g., with varying oxygen concentrations and iron supply) is important for understanding their role as carriers of primary magnetizations in sediments and sedimentary rocks. Here we present X-ray near edge structure (XANES) spectra for Fe in magnetotactic bacteria samples from recent sediments to assess surface oxidation and crystal structure changes in bacterial magnetite during early burial. Our results are compared with a XANES spectrum of cultivated Magnetofaba australis samples, and with magnetic properties, and indicate that oxidation of magnetite to maghemite increases with depth in the sediment due to longer exposure to molecular oxygen. These results are relevant to understanding magnetic signatures carried by magnetofossils in oxic sediments and sedimentary rocks of different ages.

Abnormal loading and functional deficits are present in both limbs before and after unilateral knee arthroplasty

Unilateral knee replacement is often followed by a contralateral replacement in time and the biomechanics of the other knee before and after knee replacement remains poorly understood. The aim of this paper is to distinguish the features of arthritic gait in the affected and unaffected legs relative to a normal population and to assess the objective recovery of gait function post-operatively, with the aim of defining patients at risk of poor post-operative function. Twenty patients with severe knee OA but no pain or deformity in any other lower limb joint were compared to twenty healthy subjects of the same age. Gait analysis was performed and quadriceps and hamstrings co-contraction was measured. Fifteen subjects returned 1year following knee arthroplasty. Moments and impulses were calculated, principal component analysis was used to analyse the waveforms and a classification technique (the Cardiff Classifier) was used to select the most discriminant data and define functional performance. Comparing pre-operative function to healthy function, classification accuracies for the affected and unaffected knees were 95% and 92.5% respectively. Post-operatively, the affected limb returned to the normal half of the classifier in 8 patients, and 7 of those patients returned to normal function in the unaffected limb. Recovery of normal gait could be correctly predicted 13 out of 15 times at the affected knee, and 12 out of 15 times at the unaffected knee based on pre-operative gait function. Focused rehabilitation prior to surgery may be beneficial to optimise outcomes and protect the other joints following knee arthroplasty.

Bipolar seesaw control on last interglacial sea level

Our current understanding of ocean-atmosphere-cryosphere interactions at ice-age terminations relies largely on assessments of the most recent (last) glacial-interglacial transition, Termination I (T-I). But the extent to which T-I is representative of previous terminations remains unclear. Testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control. However, such age control has been lacking for even the penultimate glacial termination (T-II), which culminated in a sea-level highstand during the last interglacial period that was several metres above present. Here we show that Heinrich Stadial 11 (HS11), a prominent North Atlantic cold episode, occurred between 135 ± 1 and 130 ± 2 thousand years ago and was linked with rapid sea-level rise during T-II. Our conclusions are based on new and existing data for T-II and the last interglacial that we collate onto a single, radiometrically constrained chronology. The HS11 cold episode punctuated T-II and coincided directly with a major deglacial meltwater pulse, which predominantly entered the North Atlantic Ocean and accounted for about 70 per cent of the glacial-interglacial sea-level rise. We conclude that, possibly in response to stronger insolation and CO2 forcing earlier in T-II, the relationship between climate and ice-volume changes differed fundamentally from that of T-I. In T-I, the major sea-level rise clearly post-dates Heinrich Stadial 1. We also find that HS11 coincided with sustained Antarctic warming, probably through a bipolar seesaw temperature response, and propose that this heat gain at high southern latitudes promoted Antarctic ice-sheet melting that fuelled the last interglacial sea-level peak.

Toxicity of noradrenaline, a novel anti-biofouling component, to two non-target zooplankton species, Daphnia magna and Ceriodaphnia dubia

Noradrenaline (NA) is the active component of novel antifouling agents and acts by preventing attachment of fouling organisms. The goal of this study was to examine the toxicity of NA to the non-target zooplankton D. magna and C. dubia. Neonates were exposed to one of five concentrations of NA and effects on survival, reproduction and molting were determined. Calculated LC50 values were determined to be 46 and 38 μM in C. dubia and D. magna, respectively. A 10-day C. dubia study found that reproduction metrics were significantly impacted at non-lethal concentrations. In D. magna, concentrations greater than 40 μM significantly impacted molting. A toxicity test was conducted with D. magna using oxidized NA, which yielded similar results. These data indicate that both NA and oxidized NA are toxic to non-target zooplankton. Results obtained from this study can be used to guide future ecological risk assessments of catecholamine-based antifouling agents.

Photo-induced toxicity of titanium dioxide nanoparticles to Daphnia magna under natural sunlight

Titanium dioxide nanoparticles (TiO2 NP) are one of the most abundantly utilized nanoparticles in the world. Studies have demonstrated the ability of the anatase crystal of TiO2 NP to produce reactive oxygen species (ROS) in the presence of ultraviolet radiation (UVR), a co-exposure likely to occur in aquatic ecosystems. The goal of this study was to examine the photo-induced toxicity of anatase TiO2 NP under natural sunlight to Daphnia magna. D. magna were exposed to a range of UVR intensities and anatase TiO2 concentrations in an outdoor exposure system using the sun as the source of UVR. Different UVR intensities were achieved using UVR opaque and transparent plastics. AnataseTiO2-NP demonstrated the reciprocal relationship seen in other phototoxic compounds such as polycyclic aromatic hydrocarbons (PAHs) at higher UVR treatments. The calculated 8h LC50 of anatase TiO2 NP was 139 ppb under full intensity ambient natural sunlight, 778 ppb under 50% natural sunlight, and >500 ppm under 10% natural sunlight. Mortality was also compared between animals allowed to accumulate a body burden of anatase TiO2 for 1h and organisms whose first exposure to anatase TiO2 aqueous suspensions occurred under UVR. A significantly greater toxic effect was observed in aqueous, low body burden suspensions than that of TiO2 1h body burdens, which is dissimilar from the model presented in PAHs. Anatase TiO2 presents a unique photo-induced toxic model that is different than that of established phototoxic compounds.

Sea-level and deep-sea-temperature variability over the past 5.3 million years

Ice volume (and hence sea level) and deep-sea temperature are key measures of global climate change. Sea level has been documented using several independent methods over the past 0.5 million years (Myr). Older periods, however, lack such independent validation; all existing records are related to deep-sea oxygen isotope (δ(18)O) data that are influenced by processes unrelated to sea level. For deep-sea temperature, only one continuous high-resolution (Mg/Ca-based) record exists, with related sea-level estimates, spanning the past 1.5 Myr. Here we present a novel sea-level reconstruction, with associated estimates of deep-sea temperature, which independently validates the previous 0-1.5 Myr reconstruction and extends it back to 5.3 Myr ago. We find that deep-sea temperature and sea level generally decreased through time, but distinctly out of synchrony, which is remarkable given the importance of ice-albedo feedbacks on the radiative forcing of climate. In particular, we observe a large temporal offset during the onset of Plio-Pleistocene ice ages, between a marked cooling step at 2.73 Myr ago and the first major glaciation at 2.15 Myr ago. Last, we tentatively infer that ice sheets may have grown largest during glacials with more modest reductions in deep-sea temperature.

Effect of subinhibitory concentrations of four commonly used biocides on the conjugative transfer of Tn916 in Bacillus subtilis

Objectives

Large amounts of biocides are used to reduce and control bacterial growth in the healthcare sector, food production and agriculture. This work explores the effect of subinhibitory concentrations of four commonly used biocides (ethanol, hydrogen peroxide, chlorhexidine digluconate and sodium hypochlorite) on the conjugative transposition of the mobile genetic element Tn916.

Methods

Conjugation assays were carried out between Bacillus subtilis strains. The donor containing Tn916 was pre-exposed to subinhibitory concentrations of each biocide for a defined length of time, which was determined by an analysis of the transcriptional response of the promoter upstream of tet(M) using β-glucuronidase reporter assays.

Results

Ethanol significantly (P = 0.01) increased the transfer of Tn916 by 5-fold, whereas hydrogen peroxide, chlorhexidine digluconate and sodium hypochlorite did not significantly affect the transfer frequency.

Conclusions

These results suggest that exposure to subinhibitory concentrations of ethanol may induce the transfer of Tn916-like elements and any resistance genes they contain.

The effect of osteoarthritis of the knee on the biomechanics of other joints in the lower limbs

The aim of this study was to examine the loading of the other joints of the lower limb in patients with unilateral osteoarthritis (OA) of the knee. We recruited 20 patients with no other symptoms or deformity in the lower limbs from a consecutive cohort of patients awaiting knee replacement. Gait analysis and electromyographic recordings were performed to determine moments at both knees and hips, and contraction patterns in the medial and lateral quadriceps and hamstrings bilaterally. The speed of gait was reduced in the group with OA compared with the controls, but there were only minor differences in stance times between the limbs. Patients with OA of the knee had significant increases in adduction moment impulse at both knees and the contralateral hip (adjusted p-values: affected knee: p < 0.01, unaffected knee p = 0.048, contralateral hip p = 0.03), and significantly increased muscular co-contraction bilaterally compared with controls (all comparisons for co-contraction, p < 0.01).

The other major weight-bearing joints are at risk from abnormal biomechanics in patients with unilateral OA of the knee.

Cite this article: Bone Joint J 2013;95-B:348–53.

Improved health status with insulin degludec compared with insulin glargine in people with type 1 diabetes

AIMS

The efficacy and safety of insulin degludec (degludec), a new-generation ultra-long-acting basal insulin, was compared with insulin glargine (glargine) in people with Type 1 diabetes mellitus in a 16-week, open-label, randomized trial. Health status, an important aspect of effective diabetes management, was also assessed.

METHODS

Degludec (n = 59) or glargine (n = 59) were injected once daily, with insulin aspart at mealtimes. Health status assessment utilized the validated Short Form 36 Health Survey, version 2, which has two summary component scores for mental and physical well-being, each comprising four domains.

RESULTS

At study end, HbA(1c) reductions were comparable between groups, but confirmed nocturnal hypoglycaemia was significantly less frequent with degludec [relative rate 0.42 (95% CI 0.25-0.69)], and overall hypoglycaemia numerically less frequent [relative rate 0.72 (95% CI 0.52-1.00)]. After 16 weeks, a significant improvement in Short Form 36 Health Survey mental component score of +3.01 (95% CI 0.32-5.70) was obtained for degludec against glargine, attributable to significant differences in the social functioning [+8.04 (95% CI 1.89-14.18)] and mental health domains [+2.46 (95% CI 0.10-4.82)]. For mental component score, Cohen's effect size was 0.42, indicating a small-to-medium clinically meaningful difference. The physical component score [+0.66 (95% CI -2.30 to 3.62)] and remaining domains were not significantly different between degludec and glargine.

CONCLUSIONS

In the context of comparable overall glycaemic control with glargine, degludec improved mental well-being as measured using the mental component score of the Short Form 36 Health Survey. The improvements in overall mental component score and the underlying social functioning and mental health domains with degludec compared with glargine may relate to the observed reduction in hypoglycaemic events.

Risedronate prevents bone loss in early postmenopausal women: a prospective randomized, placebo-controlled trial

OBJECTIVES

To assess the efficacy and tolerability of risedronate, a pyridinyl bisphosphonate, in preventing loss of bone mineral density (BMD) of the lumbar spine and proximal femur in early postmenopausal women.

METHODS

A total of 383 patients were randomly assigned to receive risedronate 2.5 or 5 mg or placebo once daily for 24 months. All patients received 1 g elemental calcium daily. BMD was measured by dual X-ray absorptiometry at baseline and at 3, 6, 12, 18, and 24 months.

RESULTS

Risedronate 5 mg significantly increased BMD at the lumbar spine and femoral neck and trochanter in early postmenopausal women. Significant results were observed as early as 3 months. In the control calcium-supplemented group, BMD decreased steadily at each site throughout the study. The mean percentage change from baseline in BMD in the risedronate 5 mg group was significantly different from that in the control group at each determination at each site. At 24 months, the differences were 4.5 +/- 0.45% at the lumbar spine, 3.3 +/- 0.49% at the femoral neck, and 4.3 +/- 0.67% at the femoral trochanter. Risedronate 2.5 mg maintained BMD at each site, although the effect was less pronounced than that of risedronate 5 mg. Risedronate was well tolerated and was not associated with an increased incidence of overall or upper gastrointestinal adverse events.

CONCLUSIONS

Risedronate 5 mg prevents bone loss in early postmenopausal women, is well tolerated, and represents an effective choice to maintain bone mass and prevent osteoporosis.

Continuum diffusion on networks: trees with hyperbranched trunks and fractal branches

The probability that a random walker returns to its origin for large times scales as t;{-d[over ]2} , where d[over ] is the spectral dimension. We calculate d[over ] for a class of tree structures using a renormalization technique on an infinite continued fraction. We consider a wide range of homogeneous networks based on replacing the branches of a self-similar tree with arbitrary fractals and composite fractals. We also consider a new class of inhomogeneous hyperbranched trees.

Diversity of putative Tn5253-like elements in Streptococcus pneumoniae

Pneumococcal resistance to tetracycline, chloramphenicol, erythromycin and clindamycin is often attributed to carriage of conjugative transposons of the Tn916 family. The less well studied conjugative transposon Tn5253 is a composite transposon consisting of a Tn916-like element inserted within the unrelated Tn5252 element, which has also been associated with chloramphenicol and tetracycline resistance. Here, carriage of the Tn5252 integrase (int(5252)), Tn5252-encoded umuC and umuD homologues and Tn916 integrase (int(916)) was examined among 55 clinical isolates of Streptococcus pneumoniae resistant to one or more of the above mentioned antibiotics. Tn5253-associated genes were common among the antibiotic-resistant S. pneumoniae examined, including members of international clones, although the spectrum of genes and resistances carried was diverse. Analysis of five isolates demonstrated insertion of a Tn5253-related element at the same chromosomal locus but sequence and restriction site diversity. This study shows for the first time a high degree of variability of Tn5253-related elements within clinical isolates of pneumococci. The fact that these elements are prevalent among internationally recognised pandemic clones warrants a more intensive investigation.

Global first-passage times of fractal lattices

The global first passage time density of a network is the probability that a random walker released at a random site arrives at an absorbing trap at time T . We find simple expressions for the mean global first passage time <T> for five fractals: the d-dimensional Sierpinski gasket, T fractal, hierarchical percolation model, Mandelbrot-Given curve, and a deterministic tree. We also find an exact expression for the second moment <T(2)> and show that the variance of the first passage time, Var(T) , scales with the number of nodes within the fractal N such that Var(T) approximately N(4/d[over]), where d[over] is the spectral dimension.

An investigation of the action of the hamstring muscles during standing in crouch using functional electrical stimulation (FES)

The hamstring muscle moment arms indicate that they act as hip extensors and knee flexors. Previous work using induced acceleration (IA) analysis and functional electrical stimulation (FES) has, however, revealed counter-intuitive muscle actions, particularly for biarticular muscles during the stance phase of normal gait. In conditions such as cerebral palsy the hamstrings have been associated with the development of pathological gait patterns, particularly crouch gait. This study examines the role of these muscles in the control of crouched standing postures. Five unimpaired adult subjects had their muscles stimulated during quiet standing in different degrees of crouch. Kinematic and kinetic changes were observed and measured using a 3D motion analysis system. The hamstring muscles were shown to act strongly to retrovert the pelvis and extend the hip. The action at the knee changes as crouch increases, moving from flexing to extending.

External validation of established risk adjustment models for procedural complications after percutaneous coronary intervention

BACKGROUND

Workable risk models for patients undergoing percutaneous coronary intervention (PCI) are needed urgently.

OBJECTIVE

To validate two proposed risk adjustment models (Mayo Clinic Risk Score (MC), USA and North West Quality Improvement Programme (NWQIP), UK models) for in-hospital PCI complications on an independent dataset of relatively high risk patients undergoing PCI.

SETTING

Tertiary centre in northern England.

METHODS

Between September 2002 and August 2006, 5034 consecutive PCI procedures (validation set) were performed on a patient group characterised by a high incidence of acute myocardial infarction (MI; 16.1%) and cardiogenic shock (1.7%). Two external models-the NWQIP model and the MC model-were externally validated.

MAIN OUTCOME MEASURE

Major adverse cardiovascular and cerebrovascular events: in-hospital mortality, Q-wave MI, emergency coronary artery bypass grafting and cerebrovascular accidents.

RESULTS

An overall in-hospital complication rate of 2% was observed. Multivariate regression analysis identified risk factors for in-hospital complications that were similar to the risk factors identified by the two external models. When fitted to the dataset, both external models had an area under the receiver operating characteristic curve >or=0.85 (c index (95% CI), NWQIP 0.86 (0.82 to 0.9); MC 0.87(0.84 to 0.9)), indicating overall excellent model discrimination and calibration (Hosmer-Lemeshow test, p>0.05). The NWQIP model was accurate in predicting in-hospital complications in different patient subgroups.

CONCLUSIONS

Both models were externally validated. Both predictive models yield comparable results that provide excellent model discrimination and calibration when applied to patient groups in a different geographic population other than that in which the original model was developed.

NT-proBNP and the diagnosis of left ventricular systolic dysfunction within two acute NHS trust catchment areas: the initial Teesside experience

PURPOSE

To evaluate the predictive value of N-terminal pro B-type natiuretic peptide (NT-proBNP) reference cut-off values as diagnostic markers for left ventricular systolic dysfunction (LVSD).

STUDY DESIGN

A retrospective study assessing the use of NT-proBNP in the diagnostic algorithm for the investigation of patients with suspected signs and symptoms of LVSD presenting to primary care.

RESULTS

A generic NT-proBNP cut-off (150 ng/l) value has similar negative and positive predictive valves, specificity and sensitivity compared to age and sex specific cut-off values.

CONCLUSION

When using NT-proBNP as a triage tool for screening patients with signs and symptoms suggestive of LVSD, a simple generic cut-off level is as effective as more complex age sex specific cut-off values.

A preliminary study investigating the survival of tetracycline resistant Enterococcus faecalis after root canal irrigation with high concentrations of tetracycline

AIM

To compare the ability of two Enterococcus faecalis strains to survive exposure to an irrigation solution containing a high concentration of tetracycline in the root canals of bovine teeth.

METHODOLOGY

The root canals of twelve bovine incisor root sections were chemo-mechanically prepared using commercially available drills, sodium hypochlorite and ethylenediamine tetra-acetic acid. The root sections were divided into two groups and inoculated with either a tetracycline sensitive or resistant strain of E. faecalis. The strains are isogenic, however one contains a conjugative transposon related to Tn916 which confers resistance to tetracycline, and the other strain is sensitive to the antibiotic. After 26 days of incubation the root canals were irrigated using one of three solutions (sterile distilled water, 50% ethanol or tetracycline at a concentration of 30 mg mL(-1)). The roots were sampled by grinding dentine and canal contents and the debris collected were incubated in broth to assess growth.

RESULTS

Irrigation with sterile distilled water or 50% ethanol did not remove all of the cells present. The tetracycline containing solution was efficient in preventing any growth of sensitive E. faecalis, however the resistant strain was able to survive a 5 min exposure at 30 mg mL(-1).

CONCLUSIONS

The presence of the Tn916-like conjugative transposon containing the tetracycline resistance gene tet(M) allowed an E. faecalis strain to survive irrigation using a solution containing an extremely high concentration of tetracycline in a root canal model.

Determination of the genetic support for tet(W) in oral bacteria

The DNA sequence flanking a tet(W) gene in an oral Rothia sp. was determined. The gene was linked to two different transposases, and these were flanked by two almost identical mef (macrolide efflux) genes. This structure was found in 4 out of 20 tet(W)-containing oral bacteria investigated.

Gene expression in caged juvenile Coho Salmon (Oncorhynchys kisutch) exposed to the waters of Prince William Sound, Alaska

The 1989 Exxon Valdez oil spill (EVOS) resulted in the release of 258,000 barrels of crude oil into the waters of Prince William Sound (PWS), Alaska. The current study, conducted in 2004, sought to use juvenile Coho salmon (Oncorhynchus kisutch) caged in situ to determine whether biomarker induction differed at sites where the adjacent shoreline contained buried residues from the 1989 oil spill compared to sites that were never oiled. Juvenile Coho salmon were caged at five sites; three oiled during the 1989 EVOS and two that were not oiled. Tissue samples were collected from organisms caged at each site as well as a control group housed onboard the research vessel. Analysis of CYP1A, superoxide dismutase (SOD), and glutathione peroxidase (GPO) gene expression was conducted using real time reverse transcriptase polymerase chain reaction (rtRT-PCR). Statistically significant levels of CYP1A expression were observed at some sites indicating increased hydrocarbon exposure. No patterns were observed regarding sites that were originally oiled or not oiled by the 1989 EVOS, indicating that sources of PAHs other than EVOS oil occur in PWS.

Potential role of Veillonella spp. as a reservoir of transferable tetracycline resistance in the oral cavity

Twelve out of 96 Veillonella spp. isolated from oral samples harbored tetracycline resistance genes. The most common resistance gene was tet(M). A tet(M)-positive Veillonella dispar strain was shown to transfer a Tn916-like element to four Streptococcus spp. by conjugation at a frequency of 5.2 x 10(-6) to 4.5 x 10(-5) per recipient.

Incidence and behaviour of Tn916-like elements within tetracycline-resistant bacteria isolated from root canals

INTRODUCTION

Tetracycline resistance is commonly found in endodontic bacteria. One of the most common tetracycline-resistance genes is tet(M), which is often encoded on the broad-host-range conjugative transposon Tn916. This study aimed to determine whether tet(M) was present in bacteria isolated from endodontic patients at the Eastman Dental Institute and whether this gene was carried on the transferable conjugative transposon Tn916.

METHODS

The cultivable microflora isolated from 15 endodontic patients was screened for resistance to tetracycline. Polymerase chain reactions for tet(M) and for unique regions of Tn916 were carried out on the DNA of all tetracycline-resistant bacteria. Filter-mating experiments were used to see if transfer of any Tn916-like elements could occur.

RESULTS

Eight out of 15 tetracycline-resistant bacteria isolated were shown to possess tet(M). Furthermore, four of these eight were shown to possess the Tn916-unique regions linked to the tet(M) gene. Transfer experiments demonstrated that a Neisseria sp. donor could transfer an extremely unstable Tn916-like element to Enterococcus faecalis.

CONCLUSIONS

The tet(M) gene is present in the majority of tetracycline-resistant bacteria isolated in this study and the conjugative transposon Tn916 has been shown to be responsible for the support and transfer of this gene in some of the bacteria isolated.

The Effect of the Lipid Layer on Tear Film Behaviour

This paper investigates the effect of surfactants during tear film deposition and subsequent thinning. The surfactants occur naturally on the surface of the tear film in the form of a lipid layer. A lubrication model is developed that describes lipid spreading and film height evolution. It is shown that lipids may play an important role in drawing the tear film up the cornea during the opening phase of the blink. Further, nonuniform distributions of lipids may lead to a rapid thinning of the tear film behind the advancing lipid front (shock). Experiments using a fluorescein dye technique and using a tearscope were undertaken in order to visualise the motion of the lipid layer and any associated shocks immediately after a blink. It is found that the lipid layer continues to spread upwards on the cornea after the opening phase of the blink, in agreement with the model. Using the experimental data, lipid particles were tracked in order to determine the surface velocity and these results are compared to the model predictions.

Lifetime suicide rates in treated schizophrenia: 1875-1924 and 1994-1998 cohorts compared

BACKGROUND

Recent interest in suicide rates in schizophrenia has been considerable.

AIMS

To establish the lifetime suicide rate from the pre-chlorpromazine era and to compare this with recent lifetime suicide rates for schizophrenia.

METHOD

We have compared suicide and suicide attempt rates for 741 admissions for schizophrenia and 1303 admissions for psychoses to the North Wales Asylum between 1875 and 1924, with first admissions for psychosis in NorthWest Wales between 1994 and 1998.

RESULTS

The suicide rate in schizophrenia between 1875 and 1924 was 20 per 100 000 hospital years, a lifetime rate of less than 0.5%. The suicide rate for all psychoses was 16 per 100 000 hospital years. Current rates of suicide for schizophrenia and other psychoses appear 20-fold higher.

CONCLUSIONS

These findings point to an increase in suicide rates for patients with schizophrenia.

Dynamics of tear film deposition and draining

This paper investigates the deposition of the tear film on the cornea of the human eye. The tear film is laid down by the motion of the upper eyelid and then subsequently flows and thins. Of particular interest is the stability of the tear layer and the development of dry patches on the cornea. While there has been significant research on the behaviour of tear films between blinks, this paper focuses on understanding the mechanisms which control the shape and thickness of the deposited film and how this affects the subsequent film behaviour. Numerical and analytical methods are applied to a lubrication model which includes the effects of surface tension, viscosity, gravity and evaporation. The model reveals the importance of the eyelid velocity, motion of the surface lipid layer and the storage of tear film between blinks.

The role of routine follow-up after gynecological malignancy

The objective of this article was to determine the evidence base for routine follow-up after gynecological malignancy. Only articles with a survival analysis were included. Relevant articles were identified by a comprehensive literature search of the main biomedical databases, hand searching of references of selected articles, and expert spotting of relevant journals and proceedings of international meetings. A two-stage extraction of data was undertaken. No prospective trials were identified. Twenty-nine retrospective case series analyses and one poster presentation met the inclusion criteria. Eight articles and one letter on endometrial cancer, six articles and one poster presentation on cervical cancer, and two articles in vulval cancer were reviewed. Only one article in endometrial cancer showed any survival benefit from routine follow-up, but it was of very poor methodologic quality. Two articles found a survival benefit from routine follow-up after cervical cancer. The two articles on vulval cancer did not find any survival benefit from routine review. There is no prospective research on the benefits of routine follow-up after gynecological cancer. Retrospective evidence calls in to question the benefit of universal follow-up. Prospective research is urgently needed.

The role of routine follow-up after gynecological malignancy

The objective of this article was to determine the evidence base for routine follow-up after gynecological malignancy. Only articles with a survival analysis were included. Relevant articles were identified by a comprehensive literature search of the main biomedical databases, hand searching of references of selected articles, and expert spotting of relevant journals and proceedings of international meetings. A two-stage extraction of data was undertaken. No prospective trials were identified. Twenty-nine retrospective case series analyses and one poster presentation met the inclusion criteria. Eight articles and one letter on endometrial cancer, six articles and one poster presentation on cervical cancer, and two articles in vulval cancer were reviewed. Only one article in endometrial cancer showed any survival benefit from routine follow-up, but it was of very poor methodologic quality. Two articles found a survival benefit from routine follow-up after cervical cancer. The two articles on vulval cancer did not find any survival benefit from routine review. There is no prospective research on the benefits of routine follow-up after gynecological cancer. Retrospective evidence calls in to question the benefit of universal follow-up. Prospective research is urgently needed.

Genetic basis of erythromycin resistance in oral bacteria

We determined the prevalence of erythromycin-resistant bacteria in the oral cavity and identified mef and erm(B) as the most common resistance determinants. In addition, we demonstrate the genetic linkage, on various Tn1545-like conjugative transposons, between erythromycin and tetracycline resistance in a number of isolates.

Central core disease: clinical, pathological, and genetic features

Central core disease (CCD) is a dominantly inherited congenital myopathy allelic to malignant hyperthermia (MH) caused by mutations in the RYR1 gene on chromosome 19q13.1. Eleven individuals with RYR1 mutations are described. Four index cases showed features consistent with a congenital myopathy (hypotonia, delayed motor milestones, and skeletal abnormalities including congenital hip dislocation and scoliosis). All four cases and subsequently seven other family members were found to possess novel mutations in the RYR1 gene. The degree of disability varied from one clinically normal individual, to another who had never achieved independent ambulation (the only patient with a de novo mutation). Four cases showed a mild reduction in vital capacity, repeated nocturnal polysomnography showed hypoxaemia in one case. A variety of muscle biopsy features were found; central cores were absent in the youngest case, and the biopsy specimens from two others were more suggestive of mini-core myopathy. In all cases missense mutations in exons 101, 102, and 103 of the RYR1 gene on were found. Future laboratory diagnosis of suspected cases and family members will be less invasive and more accurate with DNA analysis. Clinicians, especially paediatricians and orthopaedic surgeons, should be aware of this disorder because of the potential risk of MH.

Mechanism of integration and excision in conjugative transposons

Translocation of conjugative transposons proceeds via excision of the element to generate a circular molecule that can then integrate into a new site, which can be in the same or a different cell. This review summarises some of the different mechanisms used for excision and integration of conjugative transposons.

Composition and antibiotic resistance profile of microcosm dental plaques before and after exposure to tetracycline

The aim of this study was to investigate the effects of tetracycline administration on the viability and antibiotic resistance profiles of microcosm dental plaques. A constant depth film fermenter was used to generate multi-species biofilms, which were grown for 216 h before tetracycline was added. The composition of the microcosm plaques was determined by viable counting on selective and non-selective media. The prevalence of antibiotic-resistant organisms was determined on antibiotic-containing media. Before administration of tetracycline, the biofilms had a total viable anaerobic count of 7 x 10(7) cfu per biofilm. They contained 7% lactobacilli, 19% streptococci and 2% Actinomyces spp. Immediately after pulsing with tetracycline, the composition of the biofilms changed and they consisted of 30% lactobacilli, 1.5% streptococci and 3% Actinomyces spp., with a total anaerobic count of 1 x 10(7) cfu per biofilm. The pre-valence and composition of the antibiotic-resistant microflora changed dramatically after the addition of tetracycline, with the proportion of the microflora displaying resistance to tetracycline increasing from 6% to 45%. Corresponding changes in the proportions of the microflora displaying resistance to other antibiotics were as follows: 5-28% for erythromycin, 1-5% for vancomycin and 0.4-3% for ampicillin. The results of this study have shown that the addition of tetracycline to microcosm dental plaques alters their composition and enriches for bacteria resistant to tetracycline and other unrelated agents.