Attributable Mortality and Excess Length of Stay associated with Third-Generation Cephalosporin Resistant Enterobacterales Bloodstream Infections - a prospective cohort study in Suva, Fiji

OBJECTIVES

There are scant primary clinical data on antimicrobial resistance (AMR) burden from low- and middle-income countries (LMICs). We adapted recent World Health Organization methodology to measure the impact of third-generation cephalosporin resistance (3GC-R) on mortality and excess length of hospital stay in Fiji.

METHODS

We conducted a prospective cohort study of inpatients with Enterobacterales bloodstream infections (BSIs) at Colonial War Memorial Hospital, Suva. We used cause-specific Cox proportional hazards models to estimate the effect of 3GC-R on the daily risk (hazard) of in-hospital mortality and being discharged alive (competing risks), and multistate modelling to estimate the excess length of hospital stay.

RESULTS

From July 2020 to February 2021 we identified 162 consecutive Enterobacterales BSIs, 3GC-R was present in 66 (40.7%). Crude mortality for patients with 3GC-susceptible and 3GC-R BSIs was 16.7% (16/96) and 30.3% (20/66), respectively. 3GC-R was not associated with the in-hospital mortality hazard rate (adjusted hazard ratio (aHR) 1.13, 95% CI 0.51-2.53) or being discharged alive (aHR 0.99, 95% CI 0.65-1.50), whereas Charlson comorbidity index score (aHR 1.62, 95% CI 1.36-1.93) and Pitt bacteraemia score (aHR 3.57, 95% CI 1.31-9.71) were both associated with an increased hazard rate of in-hospital mortality. 3GC-R was associated with an increased length of stay of 2.6 days (95% CI 2.5-2.8). 3GC-R was more common among hospital-associated infections, but genomics did not identify clonal transmission.

CONCLUSION

Patients with Enterobacterales BSIs in Fiji had high mortality. There were high rates of 3GC-R, which was associated with increased hospital length of stay but not with in-hospital mortality.

Isotope Shifts of Radium Monofluoride Molecules

Isotope shifts of ^{223-226,228}Ra^{19}F were measured for different vibrational levels in the electronic transition A^{2}Π_{1/2}←X^{2}Σ^{+}. The observed isotope shifts demonstrate the particularly high sensitivity of radium monofluoride to nuclear size effects, offering a stringent test of models describing the electronic density within the radium nucleus. Ab initio quantum chemical calculations are in excellent agreement with experimental observations. These results highlight some of the unique opportunities that short-lived molecules could offer in nuclear structure and in fundamental symmetry studies.

eCertification (eCert)

Veterinary certificates have been an integral component of animal and animal product trade for many years. These certificates are agreed to by trading partners during bilateral or multilateral negotiations on the trade of animals and animal products, and provide assurance that goods are free from specific diseases. Many countries seek to implement or adopt a more streamlined and secure method of information exchange, with some implementing the electronic exchange of certificates for cross-border trade. Such an exchange of data has many advantages over its paper counterpart, including a streamlined business process, better accessibility to information (particularly in advance of shipment arrival) and the reduction of fraudulent certificates. Although there are some challenges related to this initiative and important considerations to be taken into account for its implementation, many countries are becoming aware of its efficiencies, leading to more productive and mutually beneficial trading-partner relationships.

Laser spectroscopy of indium Rydberg atom bunches by electric field ionization

This work reports on the application of a novel electric field-ionization setup for high-resolution laser spectroscopy measurements on bunched fast atomic beams in a collinear geometry. In combination with multi-step resonant excitation to Rydberg states using pulsed lasers, the field ionization technique demonstrates increased sensitivity for isotope separation and measurement of atomic parameters over previous non-resonant laser ionization methods. The setup was tested at the Collinear Resonance Ionization Spectroscopy experiment at ISOLDE-CERN to perform high-resolution measurements of transitions in the indium atom from the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {5s}^2\text {5d}\,^2\text {D}_{5/2}$$\end{document}5s25d2D5/2 and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {5s}^2\text {5d}\,^2\text {D}_{3/2}$$\end{document}5s25d2D3/2 states to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {5s}^2n$$\end{document}5s2np \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^2$$\end{document}2P and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {5s}^2n\text {f}\,^2$$\end{document}5s2nf2F Rydberg states, up to a principal quantum number of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n=72$$\end{document}n=72. The extracted Rydberg level energies were used to re-evaluate the ionization potential of the indium atom to be \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$46,670.107(4)\,\hbox {cm}^{-1}$$\end{document}46,670.107(4)cm-1. The nuclear magnetic dipole and nuclear electric quadrupole hyperfine structure constants and level isotope shifts of the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {5s}^2\text {5d}\,^2\text {D}_{5/2}$$\end{document}5s25d2D5/2 and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {5s}^2\text {5d}\,^2\text {D}_{3/2}$$\end{document}5s25d2D3/2 states were determined for \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{113,115}$$\end{document}113,115In. The results are compared to calculations using relativistic coupled-cluster theory. A good agreement is found with the ionization potential and isotope shifts, while disagreement of hyperfine structure constants indicates an increased importance of electron correlations in these excited atomic states. With the aim of further increasing the detection sensitivity for measurements on exotic isotopes, a systematic study of the field-ionization arrangement implemented in the work was performed at the same time and an improved design was simulated and is presented. The improved design offers increased background suppression independent of the distance from field ionization to ion detection.

Spectroscopy of short-lived radioactive molecules

Molecular spectroscopy offers opportunities for the exploration of the fundamental laws of nature and the search for new particle physics beyond the standard model1-4. Radioactive molecules-in which one or more of the atoms possesses a radioactive nucleus-can contain heavy and deformed nuclei, offering high sensitivity for investigating parity- and time-reversal-violation effects5,6. Radium monofluoride, RaF, is of particular interest because it is predicted to have an electronic structure appropriate for laser cooling6, thus paving the way for its use in high-precision spectroscopic studies. Furthermore, the effects of symmetry-violating nuclear moments are strongly enhanced5,7-9 in molecules containing octupole-deformed radium isotopes10,11. However, the study of RaF has been impeded by the lack of stable isotopes of radium. Here we present an experimental approach to studying short-lived radioactive molecules, which allows us to measure molecules with lifetimes of just tens of milliseconds. Energetically low-lying electronic states were measured for different isotopically pure RaF molecules using collinear resonance ionisation at the ISOLDE ion-beam facility at CERN. Our results provide evidence of the existence of a suitable laser-cooling scheme for these molecules and represent a key step towards high-precision studies in these systems. Our findings will enable further studies of short-lived radioactive molecules for fundamental physics research.

Cost-effectiveness of interventions to improve hand hygiene in healthcare workers in middle-income hospital settings: a model-based analysis

BACKGROUND

Multi-modal interventions are effective in increasing hand hygiene (HH) compliance among healthcare workers, but it is not known whether such interventions are cost-effective outside high-income countries.

AIM

To evaluate the cost-effectiveness of multi-modal hospital interventions to improve HH compliance in a middle-income country.

METHODS

Using a conservative approach, a model was developed to determine whether reductions in meticillin-resistant Staphylococcus aureus bloodstream infections (MRSA-BSIs) alone would make HH interventions cost-effective in intensive care units (ICUs). Transmission dynamic and decision analytic models were combined to determine the expected impact of HH interventions on MRSA-BSI incidence and evaluate their cost-effectiveness. A series of sensitivity analyses and hypothetical scenarios making different assumptions about transmissibility were explored to generalize the findings.

FINDINGS

Interventions increasing HH compliance from a 10% baseline to ≥20% are likely to be cost-effective solely through reduced MRSA-BSI. Increasing compliance from 10% to 40% was estimated to cost US$2515 per 10,000 bed-days with 3.8 quality-adjusted life-years (QALYs) gained in a paediatric ICU (PICU) and US$1743 per 10,000 bed-days with 3.7 QALYs gained in an adult ICU. If baseline compliance is not >20%, the intervention is always cost-effective even with only a 10% compliance improvement.

CONCLUSION

Effective multi-modal HH interventions are likely to be cost-effective due to preventing MRSA-BSI alone in ICU settings in middle-income countries where baseline compliance is typically low. Where compliance is higher, the cost-effectiveness of interventions to improve it further will depend on the impact on hospital-acquired infections other than MRSA-BSI.

Point-of-care universal screening for meticillin-resistant Staphylococcus aureus: a cluster-randomized cross-over trial

BACKGROUND

Meticillin-resistant Staphylococcus aureus (MRSA) is frequently endemic in healthcare settings and may be transmitted by person-to-person spread. Asymptomatic MRSA carriers are potential, unsuspected sources for transmission and some of them may be identified by admission screening.

AIM

To assess whether rapid point-of-care screening (POCS) for MRSA at hospital admission may be associated with a reduction in MRSA acquisition rates when compared with slower laboratory-based methods.

METHODS

A cluster-randomized cross-over trial was conducted in four admission wards of an acute London tertiary care hospital. Polymerase chain reaction-based POCS screening was compared with conventional culture screening. Patients were screened on ward admission and discharge, and the MRSA acquisition rate on the admission wards was calculated as the primary outcome measure.

RESULTS

In all, 10,017 patients were included; 4978 in the control arm, 5039 in the POCS arm. The MRSA carriage rate on admission was 1.7%. POCS reduced the median reporting time from 40.4 to 3.7 h (P < 0.001). MRSA was acquired on the admission wards by 23 (0.46%) patients in the control arm and by 24 (0.48%) in the intervention arm, acquisition rates of 5.39 and 4.60 per 1000 days respectively. After taking account of predefined confounding factors, the adjusted incidence rate ratio (IRR) for change in trend for MRSA acquisition was 0.961 (95% confidence interval: 0.766-1.206). The adjusted IRR for step change for MRSA acquisition was 0.98 (0.304-3.162).

CONCLUSION

POCS produces a significantly faster result but has no effect on MRSA acquisition on admission wards compared with culture screening. Where compliance with infection prevention and control is high and MRSA carriage is low, POCS has no additional impact on MRSA acquisition rates over the first one to four days of admission compared with conventional culture screening.

Electrostatically Guided Rydberg Positronium

We report experiments in which positronium (Ps) atoms were guided using inhomogeneous electric fields. Ps atoms in Rydberg-Stark states with principal quantum number n=10 and electric dipole moments up to 610 D were prepared via two-color two-photon optical excitation in the presence of a 670  V cm^{-1} electric field. The Ps atoms were created at the entrance of a 0.4 m long electrostatic quadrupole guide, and were detected at the end of the guide via annihilation gamma radiation. When the lasers were tuned to excite low-field-seeking Stark states, a fivefold increase in the number of atoms reaching the end of the guide was observed, whereas no signal was detected when high-field-seeking states were produced. The data are consistent with the calculated geometrical guide acceptance.

Controlling Positronium Annihilation with Electric Fields

We show that the annihilation dynamics of excited positronium (Ps) atoms can be controlled using parallel electric and magnetic fields. To achieve this, Ps atoms were optically excited to n=2 sublevels in fields that were adjusted to control the amount of short-lived and long-lived character of the resulting mixed states. Inclusion of the former offers a practical approach to detection via annihilation radiation, whereas the increased lifetimes due to the latter can be exploited to optimize resonance-enhanced two-photon excitation processes (e.g., 1^{3}S→2^{3}P→nS/nD), either by minimizing losses through intermediate state decay, or by making it possible to separate the excitation laser pulses in time. In addition, photoexcitation of mixed states with a 2^{3}S_{1} component represents an efficient route to producing long-lived pure 2^{3}S_{1} atoms via single-photon excitation.

A trap-based pulsed positron beam optimised for positronium laser spectroscopy

We describe a pulsed positron beam that is optimised for positronium (Ps) laser-spectroscopy experiments. The system is based on a two-stage Surko-type buffer gas trap that produces 4 ns wide pulses containing up to 5 × 10(5) positrons at a rate of 0.5-10 Hz. By implanting positrons from the trap into a suitable target material, a dilute positronium gas with an initial density of the order of 10(7) cm(-3) is created in vacuum. This is then probed with pulsed (ns) laser systems, where various Ps-laser interactions have been observed via changes in Ps annihilation rates using a fast gamma ray detector. We demonstrate the capabilities of the apparatus and detection methodology via the observation of Rydberg positronium atoms with principal quantum numbers ranging from 11 to 22 and the Stark broadening of the n = 2 → 11 transition in electric fields.

Selective production of Rydberg-stark states of positronium

Rydberg positronium (Ps) atoms have been prepared in selected Stark states via two-step (1s→2p→nd/ns) optical excitation. Two methods have been used to achieve Stark-state selection: a field ionization filter that transmits the outermost states with positive Stark shifts, and state-selected photoexcitation in a strong electric field. The former is demonstrated for n=17 and 18 while the latter is performed for n=11 in a homogeneous electric field of 1.9  kV/cm. The observed spectral intensities and their dependence on the polarization of the laser radiation are in agreement with calculations that include the perturbations of the intermediate n=2 manifold. Our results pave the way for the generation of Rydberg Ps atoms with large electric dipole moments that are required for the realization of schemes to control their motion using inhomogeneous electric fields, an essential feature of some proposed Ps free-fall measurements requiring focused beams of long-lived atoms.

Positive selection and compensatory adaptation interact to stabilize non-transmissible plasmids

Plasmids are important drivers of bacterial evolution, but it is challenging to understand how plasmids persist over the long term because plasmid carriage is costly. Classical models predict that horizontal transfer is necessary for plasmid persistence, but recent work shows that almost half of plasmids are non-transmissible. Here we use a combination of mathematical modelling and experimental evolution to investigate how a costly, non-transmissible plasmid, pNUK73, can be maintained in populations of Pseudomonas aeruginosa. Compensatory adaptation increases plasmid stability by eliminating the cost of plasmid carriage. However, positive selection for plasmid-encoded antibiotic resistance is required to maintain the plasmid by offsetting reductions in plasmid frequency due to segregational loss. Crucially, we show that compensatory adaptation and positive selection reinforce each other’s effects. Our study provides a new understanding of how plasmids persist in bacterial populations, and it helps to explain why resistance can be maintained after antibiotic use is stopped.

Plasmids are important for bacterial evolution but the evolutionary mechanisms behind their maintenance are unclear. Here the authors show that the interplay between compensatory adaptation and positive selection for plasmid-encoded antibiotic resistance determines plasmid persistence in P. aeruginosa.

Targeted versus universal screening and decolonization to reduce healthcare-associated meticillin-resistant Staphylococcus aureus infection

BACKGROUND

The benefits of universal meticillin-resistant Staphylococcus aureus (MRSA) admission screening, compared with screening targeted patient groups and the additional impact of discharge screening, are uncertain.

AIMS

To quantify the impact of MRSA screening plus decolonization treatment on MRSA infection rates. To compare universal with targeted screening policies, and to evaluate the additional impact of screening and decolonization on discharge.

METHODS

A stochastic, individual-based model of MRSA transmission was developed that included patient movements between general medical and intensive care unit (ICU) wards, and between the hospital and community, informed by 18 months of individual patient data from a 900-bed tertiary care hospital. We simulated the impact of universal and targeted [for ICU, acute care of the elderly (ACE) or readmitted patients] MRSA screening and decolonization policies, both on admission and discharge.

FINDINGS

Universal admission screening plus decolonization resulted in 77% (95% confidence interval: 76-78) reduction in MRSA infections over 10 years. Screening only ACE specialty or ICU patients yielded 62% (61-63) and 66% (65-67) reductions, respectively. Targeted policies reduced the number of screens by up to 95% and courses of decolonization by 96%. In addition to screening on admission, screening on discharge had little impact, with a maximum 7% additional reduction in infection.

CONCLUSIONS

Compared with universal screening, targeted screening substantially reduced the amount of screening and decolonization required to achieve only 12% lower reduction in infection. Targeted screening and decolonization could lower the risk of resistance emerging as well as offer a more efficient use of resources.

Effect of systemic antibiotics and topical chlorhexidine on meticillin-resistant Staphylococcus aureus carriage in intensive care unit patients

Antibiotics and antiseptics have the potential to influence carriage and transmission of meticillin-resistant Staphylococcus aureus (MRSA), although effects are likely to be complex, particularly in a setting where multiple agents are used. Here admission and weekly MRSA screens and daily antibiotic and antiseptic prescribing data from 544 MRSA carriers on an intensive care unit (ICU) are used to determine the effect of these agents on short-term within-host MRSA carriage dynamics. Longitudinal data were analysed using Markov models allowing patients to move between two states: MRSA positive (detectable MRSA carriage) and MRSA negative (no detectable carriage). The effect of concurrent systemic antibiotic and topical chlorhexidine (CHX) on movement between these states was assessed. CHX targeted to MRSA screen carriage sites increased transition from culture positive to negative and there was also weaker evidence that it decreased subsequent transition from negative back to positive. In contrast, there was only weak and inconsistent evidence that any antibiotic influenced transition in either direction. For example, whereas univariate analysis found quinolones to be strongly associated with both increased risk of losing and then reacquiring MRSA carriage over time intervals of one day, no effect was seen with weekly models. Similar studies are required to determine the generalisability of these findings.

Procaine penicillin by subconjunctival injection in the treatment of infectious bovine keratoconjunctivitis

A profile off the penicillin concentration in bovine conjunctival sac fluid (CF) was determined after a single subconjunctival injection of procaine penicillin (6 x 10(5) iu in 2ml). When the injection was made through the skin of the upper eye lid, the duration of therapeutic concentration was significantly greater (P<0.01) than when the injection had been given by the perconjunctival route: approximately 68 hours or 40 hours respectively. These findings support the clinical use of subconjunctivally administered procaine penicillin in the treatment of infectious bovine keratoconjunctivitis. A single application of an equivalent dose of either procaine penicillin or benethamine penicillin, applied topically in a simple occulentum base, produced a therapeutic duration in CF of 37 +/- 4 hr and 56 +/- 4.5 hr respectively.

Glucose and Cortisol concentrations in cows treated with a slowly-absorbed betamethasone suspension

A slowly-absorbed aqueous suspension of betamethasone, intended for use in the induction;of parturition, was administered to 10 cows. Each cow received 2ml (mean individual dose, 44.4 +/- 0.5microg/kg) by subcutaneous injection. Plasma samples were collected on six occasions over a seven-day period before treatment and on 21 occasions over a 29 day period after treatment. The mean concentration of betamethasone in plasma, as measured by radioimmunoassay, peaked at 0.6ng/ml24 hours after injection and was detectable for four days. Depression of the endogenous cortisol levels, as recorded with other long-acting synthetic glucocorticoids, was observed with this preparation of betamethasone. Plasma glucose was significantly elevated for eight days after betamethasone administration.

Decontamination of the digestive tract and oropharynx in ICU patients

BACKGROUND

Selective digestive tract decontamination (SDD) and selective oropharyngeal decontamination (SOD) are infection-prevention measures used in the treatment of some patients in intensive care, but reported effects on patient outcome are conflicting.

METHODS

We evaluated the effectiveness of SDD and SOD in a crossover study using cluster randomization in 13 intensive care units (ICUs), all in The Netherlands. Patients with an expected duration of intubation of more than 48 hours or an expected ICU stay of more than 72 hours were eligible. In each ICU, three regimens (SDD, SOD, and standard care) were applied in random order over the course of 6 months. Mortality at day 28 was the primary end point. SDD consisted of 4 days of intravenous cefotaxime and topical application of tobramycin, colistin, and amphotericin B in the oropharynx and stomach. SOD consisted of oropharyngeal application only of the same antibiotics. Monthly point-prevalence studies were performed to analyze antibiotic resistance.

RESULTS

A total of 5939 patients were enrolled in the study, with 1990 assigned to standard care, 1904 to SOD, and 2045 to SDD; crude mortality in the groups at day 28 was 27.5%, 26.6%, and 26.9%, respectively. In a random-effects logistic-regression model with age, sex, Acute Physiology and Chronic Health Evaluation (APACHE II) score, intubation status, and medical specialty used as covariates, odds ratios for death at day 28 in the SOD and SDD groups, as compared with the standard-care group, were 0.86 (95% confidence interval [CI], 0.74 to 0.99) and 0.83 (95% CI, 0.72 to 0.97), respectively.

CONCLUSIONS

In an ICU population in which the mortality rate associated with standard care was 27.5% at day 28, the rate was reduced by an estimated 3.5 percentage points with SDD and by 2.9 percentage points with SOD. (Controlled Clinical Trials number, ISRCTN35176830.)

Characterizing an outbreak of vancomycin-resistant enterococci using hidden Markov models

BACKGROUND

Antibiotic-resistant nosocomial pathogens can arise in epidemic clusters or sporadically. Genotyping is commonly used to distinguish epidemic from sporadic vancomycin-resistant enterococci (VRE). We compare this to a statistical method to determine the transmission characteristics of VRE.

METHODS AND FINDINGS

A structured continuous-time hidden Markov model (HMM) was developed. The hidden states were the number of VRE-colonized patients (both detected and undetected). The input for this study was weekly point-prevalence data; 157 weeks of VRE prevalence. We estimated two parameters: one to quantify the cross-transmission of VRE and the other to quantify the level of VRE colonization from sporadic sources. We compared the results to those obtained by concomitant genotyping and phenotyping. We estimated that 89% of transmissions were due to ward cross-transmission while 11% were sporadic. Genotyping found that 90% had identical glycopeptide resistance genes and 84% were identical or nearly identical on pulsed-field gel electrophoresis (PFGE). There was some evidence, based on model selection criteria, that the cross-transmission parameter changed throughout the study period. The model that allowed for a change in transmission just prior to the outbreak and again at the peak of the outbreak was superior to other models. This model estimated that cross-transmission increased at week 120 and declined after week 135, coinciding with environmental decontamination.

SIGNIFICANCE

We found that HMMs can be applied to serial prevalence data to estimate the characteristics of acquisition of nosocomial pathogens and distinguish between epidemic and sporadic acquisition. This model was able to estimate transmission parameters despite imperfect detection of the organism. The results of this model were validated against PFGE and glycopeptide resistance genotype data and produced very similar results. Additionally, HMMs can provide information about unobserved events such as undetected colonization.

Successful use of feedback to improve antibiotic prescribing and reduce Clostridium difficile infection: a controlled interrupted time series

OBJECTIVES

To investigate the effect of reinforcing a narrow-spectrum antibiotic policy on antibiotic prescription and Clostridium difficile infection (CDI) rates by feedback of antibiotic use to doctors, as part of a departmental audit and feedback programme.

DESIGN

A prospective controlled interrupted time-series (ITS) study, with pre-defined pre- and post-intervention periods, each of 21 months.

SETTING

Three acute medical wards for elderly people in a teaching hospital.

PARTICIPANTS

Six thousand one hundred and twenty-nine consecutive unselected acute medical admissions aged >or=80 years.

INTERVENTIONS

A 'narrow-spectrum' antibiotic policy (reinforced by an established programme of audit and feedback of antibiotic usage and CDI rates) was introduced, following an unplanned rise in amoxicillin/clavulanate (Augmentin) use. It targeted broad-spectrum antibiotics for reduction (cephalosporins and amoxicillin/clavulanate) and narrow-spectrum antibiotics for increase (benzyl penicillin, amoxicillin and trimethoprim). Changes in the use of targeted antibiotics (intervention group) were compared with those of untargeted antibiotics (control group) using segmented regression analysis. Changes in CDI rates were examined by the Poisson regression model. Methicillin-resistant Staphylococcus aureus (MRSA) acquisition rates acted as an additional control.

RESULTS

There was a reduction in the use of all targeted broad-spectrum antibiotics and an increase in all targeted narrow-spectrum antibiotics, statistically significant for sudden change and/or linear trend. All other antibiotic use remained unchanged. CDI rates fell with incidence rate ratios of 0.35 (0.17, 0.73) (P=0.009). MRSA incidence did not change [0.79 (0.49, 1.28); P=0.32].

CONCLUSIONS

This is the first controlled prospective ITS study to use feedback to reinforce antibiotic policy and reduce CDI. Multicentre ITS or cluster randomized trials of this and other methods need to be undertaken to establish the most effective means of optimizing antibiotic use and reducing CDI.

The ORION statement: guidelines for transparent reporting of Outbreak Reports and Intervention studies Of Nosocomial infection

The quality of research in hospital epidemiology (infection control) must be improved to be robust enough to influence policy and practice. In order to raise the standards of research and publication, a CONSORT equivalent for these largely quasi-experimental studies has been prepared by the authors of two relevant systematic reviews, following consultation with learned societies, editors of journals and researchers. It consists of a 22 item checklist, and a summary table. The emphasis is on transparency to improve the quality of reporting and on the use of appropriate statistical techniques. The statement has been endorsed by a number of professional special interest groups and societies. Like CONSORT, ORION should be considered a 'work in progress', which requires ongoing dialogue for successful promotion and dissemination. The statement is therefore offered for further public discussion. Journals and research councils are strongly recommended to incorporate it into their submission and reviewing processes. Feedback to the authors is encouraged and the statement will be revised in 2 years.

Subspecies differentiation of Moraxella bovis by restriction endonuclease DNA analysis (BRENDA)

A total of 94 strains of Moraxella bovis have been examined by bacterial restriction endonuclease DNA analysis (BRENDA). These strains comprised isolates from the U.S.A., the U.K., in Australia, and from a number of widely separated areas within New Zealand. The strains were classified into a total of 26 different types on the basis of their BRENDA patterns. Fourteen types were present among 34 strains from the U.S.A., eight types from 17 strains in the U.K. three types from five strains in Australia but only one type resulted from all 38 New Zealand strains. Moraxella liquifaciens, M. nonliquifaciens and an atypical Moraxella sp. isolated from cattle eyes in Australia were tested and produced BRENDA patterns clearly different from those of the Moraxella bovis strains. BRENDA, when used with the restriction endonuclease EcoR1, did not provide a means of distinguishing between avirulent, nonhaemolytic M.bovis, and the virulent haemolytic strains.

Isolation measures in the hospital management of methicillin resistant Staphylococcus aureus (MRSA): systematic review of the literature

OBJECTIVE

To evaluate the evidence for the effectiveness of isolation measures in reducing the incidence of methicillin resistant Staphylococcus aureus (MRSA) colonisation and infection in hospital inpatients.

DESIGN

Systematic review of published articles.

DATA SOURCES

Medline, Embase, CINAHL, Cochrane Library, System for Information on Grey Literature in Europe (SIGLE), and citation lists (1966-2000).

REVIEW METHODS

Articles reporting MRSA related outcomes and describing an isolation policy were selected. No quality restrictions were imposed on studies using isolation wards or nurse cohorting. Other studies were included if they were prospective or employed planned comparisons of retrospective data.

RESULTS

46 studies were accepted; 18 used isolation wards, nine used nurse cohorting, and 19 used other isolation policies. Most were interrupted time series, with few planned formal prospective studies. All but one reported multiple interventions. Consideration of potential confounders, measures to prevent bias, and appropriate statistical analysis were mostly lacking. No conclusions could be drawn in a third of studies. Most others provided evidence consistent with a reduction of MRSA acquisition. Six long interrupted time series provided the strongest evidence. Four of these provided evidence that intensive control measures including patient isolation were effective in controlling MRSA. In two others, isolation wards failed to prevent endemic MRSA.

CONCLUSION

Major methodological weaknesses and inadequate reporting in published research mean that many plausible alternative explanations for reductions in MRSA acquisition associated with interventions cannot be excluded. No well designed studies exist that allow the role of isolation measures alone to be assessed. None the less, there is evidence that concerted efforts that include isolation can reduce MRSA even in endemic settings. Current isolation measures recommended in national guidelines should continue to be applied until further research establishes otherwise.

Methicillin-resistant Staphylococcus aureus in hospitals and the community: stealth dynamics and control catastrophes

Methicillin-resistant Staphylococcus aureus (MRSA) represents a serious threat to the health of hospitalized patients. Attempts to reduce the spread of MRSA have largely depended on hospital hygiene and patient isolation. These measures have met with mixed success: although some countries have almost eliminated MRSA or remained largely free of the organism, others have seen substantial increases despite rigorous control policies. We use a mathematical model to show how these increases can be explained by considering both hospital and community reservoirs of MRSA colonization. We show how the timing of the intervention, the level of resource provision, and chance combine to determine whether control measures succeed or fail. We find that even control measures able to repeatedly prevent sustained outbreaks in the short-term can result in long-term control failure resulting from gradual increases in the community reservoir. If resources do not scale with MRSA prevalence, isolation policies can fail "catastrophically."

Systematic review of isolation policies in the hospital management of methicillin-resistant Staphylococcus aureus: a review of the literature with epidemiological and economic modelling

OBJECTIVE

To review the evidence for the effectiveness of different isolation policies and screening practices in reducing the incidence of methicillin-resistant Staphylococcus aureus (MRSA) colonisation and infection in hospital in-patients. To develop transmission models to study the effectiveness and cost-effectiveness of isolation policies in controlling MRSA.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, The Cochrane Library and SIGLE (1966-2000). Hand-searching key journals. No language restrictions.

REVIEW METHODS

Key data were extracted from articles reporting MRSA-related outcomes and describing an isolation policy in a hospital with epidemic or endemic MRSA. No quality restrictions were imposed on studies using isolation wards (IW) or nurse cohorting (NC). Other studies were included if they were prospective or employed planned comparisons of retrospective data. Stochastic and deterministic models investigated long-term transmission dynamics, studying the effect of a fixed capacity IW, producing economic evaluations using local cost data.

RESULTS

A total of 46 studies were accepted: 18 IWs, 9 NC, 19 other isolation policies. Most were interrupted time series, with few planned formal prospective studies. All but one reported multiple interventions. Consideration of potential confounders, measures to prevent bias, and appropriate statistical analysis were mostly lacking. No conclusions could be drawn in a third of studies. Most others provided evidence consistent with reduction of MRSA acquisition. Six long interrupted time series provided the strongest evidence. Four of these provided evidence that intensive control measures which included patient isolation were effective in controlling MRSA. In two others IW use failed to prevent endemic MRSA. There was no robust economic evaluation. Models showed that improving the detection rate or ensuring adequate isolation capacity reduced endemic levels, with substantial savings achievable.

CONCLUSIONS

Major methodological weaknesses and inadequate reporting in published research mean that many plausible alternative explanations for reductions in MRSA acquisition associated with interventions cannot be excluded. No well-designed studies allow the role of isolation measures alone to be assessed. Nonetheless, there is evidence that concerted efforts that include isolation can reduce MRSA even when endemic. Little evidence was found to suggest that current isolation measures recommended in the UK are ineffective, and these should continue to be applied until further research establishes otherwise. The studies with the strongest evidence, together with the results of the modelling, provide testable hypotheses for future research. Guidelines to facilitate design of future research are produced.

Inhibition of apoptosis in cultured porcine granulosa cells by inhibitors of caspase and serine protease activity

Protease inhibitors were used to test the hypothesis that caspases and other proteases were active during apoptosis in cultured porcine granulosa cells. Cells isolated from 3 to 6 mm follicles were cultured for 24 h in Dulbecco's modified Eagles medium: Hams F12 (1:11 containing 1% fetal bovine serum. Final inhibitor concentrations, added in 10 microL of dimethylsulfoxide, were 0, 1, 5, 25 and 125 microM. Cells with compromised plasma membrane integrity, identified by uptake ethidium homodimer, increased during culture in the absence of inhibitors from 37% to 43%. Apoptotic (A0) cells, identified by DNA fluorescence flow cytometry, increased (P < 0.05) from 1.7% to 29%. The serine protease inhibitor N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) at 125 microM was lethal increasing (P < 0.05) cells with compromised membranes to 92%. In response to TPCK, A0 cells decreased from 55% to 1.2%; progesterone and estradiol production were decreased by 94% and 98%, respectively. The general caspase inhibitor, benzyloxycarbonyl-valinyl-alaninyl-aspartyl fluoro methylketone, decreased (P < 0.05) A0 cells linearly from 33% to 3 % between 0 and 125 microM without significant effect on steroidogenesis or on the percentage of cells with compromised plasma membranes. Other inhibitors only had a marginal effect on apoptosis; concentrations of > or = 1 microM decreased (P < 0.05) A0 cells from 29% to 18% to 21% and had no significant effect on membrane integrity or steroid production. We conclude that caspases are associated with apoptosis in cultured porcine granulosa cells. Death induced by TPCK was through a non-apoptotic mechanism.

Expression of resistance to tetracyclines in strains of methicillin-resistant Staphylococcus aureus

A diverse collection of methicillin-resistant Staphylococcus aureus (MRSA) isolates resistant to tetracycline was screened by PCR for the presence of the resistance determinants tetK, tetL, tetM or tetO. Twenty-four of 66 isolates had tetM alone, 21 had tetK alone and 21 had both tetK and tetM (tetKM). All isolates were tetL- and tetO-negative. MICs of tetracycline, doxycycline and minocycline were evaluated for all isolates with or without preincubation in the presence of subinhibitory concentrations of tetracycline or minocycline. All isolates with one or more tetracycline resistance determinants were resistant to tetracycline 8 mg/L without induction of resistance. Some MRSA isolates of each of these three genotypes showed an unexpected lack of resistance to tetracyclines when the disc diffusion or agar dilution method was applied to uninduced cells. Resistance to tetracycline and doxycycline was greater (two- to four-fold) in tetK cells preincubated with tetracycline (tetK MRSA isolates were susceptible to minocycline </=0.25 mg/L under all conditions tested). For isolates with tetM alone, preincubation with tetracycline or minocycline gave up to a four-fold increase in the level of resistance to doxycycline and minocycline. Induction of doxycycline and minocycline resistance was clearly observed for tetKM isolates when cells were preincubated with minocycline. This study suggests that, despite the results of susceptibility testing, all tetracycline-resistant S. aureus isolates should be treated as resistant to doxycycline, and all tetM-positive isolates should be treated as resistant to all tetracyclines. A double disc diffusion method has been developed to identify inducible resistance to minocycline and to distinguish between tetK, tetM and tetKM isolates.

Preliminary analysis of the transmission dynamics of nosocomial infections: stochastic and management effects

A simple mathematical model is developed for the spread of hand-borne nosocomial pathogens such as Staphylococcus aureus within a general medical-surgical ward. In contrast to previous models a stochastic approach is used. Computer simulations are used to explore the properties of the model, and the results are presented in terms of the pathogen's successful introduction rate, ward-level prevalence, and colonized patient-days, emphasizing the general effects of changes in management of patients and carers. Small changes in the transmissibility of the organism resulted in large changes in all three measures. Even small increases in the frequency of effective handwashes were enough to bring endemic organisms under control. Reducing the number of colonized patients admitted to the ward was also an effective control measure across a wide range of different situations. Increasing surveillance activities had little effect on the successful introduction rate but gave an almost linear reduction in colonized patient-days and ward-level prevalence. Shorter lengths of patient stay were accompanied by higher successful introduction rates, but had little effect on the other measures unless the mean time before detection of a colonized individual was large compared to the mean length of stay. We conclude that chance effects are likely to be amongst the most important factors in determining the course of an outbreak. Mathematical models can provide valuable insights into the non-linear interactions between a small number of processes, but for the very small populations found in hospital wards, a stochastic approach is essential.

Prescription drug coverage and spending for Medicare beneficiaries

Outpatient prescription drug coverage is not a Medicare covered benefit. Debate continues in Congress and elsewhere on modernizing the Medicare benefit package, including proposals that would help the Nation's seniors pay for prescription drugs. Very little is known about which persons within the Medicare population have drug coverage from other sources. Using 1995 data from the Medicare Current Beneficiary Survey (MCBS), the authors present information on who has coverage by various sociodemographic categories. The data indicate higher-than-average levels of coverage for minority persons, beneficiaries eligible for Medicare because of disability, and those with higher incomes.

Follicle-stimulating hormone and insulin-like growth factor-I attenuate apoptosis in cultured porcine granulosa cells

Thymocytes and granulosa cells (GC) were cultured up to 48 h to determine the effect of dexamethasone (DEX) on apoptosis in culture (in RPMI containing 10% fetal bovine serum [FBS] at 38 degrees C in a 5% CO2:95% air atmosphere). In experiment 2, GC were cultured for 24 h at a density of 0.5 x 10(6) cells/0.5 ml in Dulbecco's Modified Eagle's medium:Hams F-12 (1:1) containing 1% FBS to determine whether porcine FSH and insulin-like growth factor-I (IGF-I) attenuated apoptosis and to compare two methods of measuring apoptosis: 1) flow cytometry of dispersed cells for subdiploid DNA fluorescence and 2) densitometry of internucleosomal DNA fragments. The percentages of apoptotic (%A0) thymocytes and GC increased (p < 0.01) during 48 h of culture. Compared to no DEX, 0.1 or 1.0 microM DEX in thymocytes caused a 33% further increase (p < 0.01) in %A0 cells but had no effect in GC. In experiment 2, apoptosis, measured by %A0 GC and amount of internucleosomal fragments, decreased (p < 0.01) by 50% during culture in the presence of FSH (4 NIH-S1 mU/ml) or IGF-I (50 ng/ml); results from these techniques were correlated (r = 0.829, n = 44, p < or = 0.0001). We conclude that 1) porcine GC and thymocytes undergo spontaneous apoptosis in culture, 2) two methods of analyzing apoptosis were in excellent agreement, and 3) FSH and IGF-I attenuated spontaneous apoptosis in cultured porcine GC.

Development of an end-stage renal disease managed care demonstration

At present, end-stage renal disease (ESRD) beneficiaries cannot enroll in health maintenance organizations (HMOs) or social health maintenance organizations (SHMOs), but HMO members who develop ESRD may remain enrolled, and the Health Care Financing Administration (HCFA) pays the HMO a state-specific, but otherwise unadjusted, capitation rate that is 95% of fee-for-service (FFS) costs. Thus, more than 6,000 ESRD beneficiaries were enrolled in HMOs in 1993, when Congress mandated an ESRD SHMO demonstration in which not only Medicare-covered services, but extra benefits were to be provided to Medicare beneficiaries, with the SHMO receiving a capitation rate based on 100% of FFS costs. The demonstration will test (1) the feasibility of year-round open enrollment of ESRD beneficiaries in HMOs; (2) a capitation system based on treatment status--dialysis, transplant, or functioning graft--and adjusted for age and whether diabetes was the cause of renal failure; (3) the effect of the additional benefits; and (4) whether managed care can improve ESRD quality outcomes. HCFA made demonstration awards in September 1996 to Kaiser-Permanente in Southern California; Health Options in Southern Florida; and Phoenix Healthcare in Central Tennessee. The sites are expected to have 1 year of planning and development before beginning the congressionally mandated 3 years of service delivery. There will be an independent evaluation.

Follicular Atresia, follicular fluid hormones, and circulating hormones during the midluteal phase of the estrous cycle in pigs

The incidence of atresia, concentrations of follicular fluid steroids, and circulating concentrations of estradiol, FSH, and progesterone were investigated to determine whether there was any evidence for a wave of follicular activity or atresia between Days 7 and 15 of the estrous cycle in pigs, Cyclic pigs (gilts) were slaughtered on Days 7, 9, 11, 13, and 15 (4, 4, 4, 4, and 3 pigs per day), and 287 follicles > 2 mm were dissected from ovaries to recover follicular fluid and granulosa cells. Apoptotic (Ao) granulosa cells were those containing sub-diploid DNA fluorescence as determined by flow cytometry. follicles with > or = 10% Ao granulosa cells were classified as atretic, and those with < 10% Ao granulosa cells were designated nonatretic. The percentage of atretic follicles (AF) per pig was 35.5 +/- 4.7 (mean +/- SEM), and while the percentage of AF ranged from 12% to 73%, means did not differ significantly among days. Mean follicular estradiol concentration was higher (p < 0.05) in nonatretic follicles (NAF) than in AF; in NAF, the concentration decreased (p < 0.05) from 15 ng/ml on Day 7 to 2.5 ng/ml on Day 11 and then increased (p < 0.05) to 10 ng/ml on Day 15 of the cycle. Mean follicular progesterone concentration was higher (p < 0.05) in AF than in NAF, while follicular androstenedione concentration (20 +/- 1.5 ng/ml, overall mean +/- SEM) did not differ between AF and NAF. Mean plasma estradiol, FSH, and progesterone concentrations did not differ among days of the cycle or differ significantly during the last 42 h before slaughter. Plasma estradiol and FSH concentrations were not significantly correlated with percentage of AF or with follicular steroid concentrations. These results support the notion of continuous growth and atresia of ovarian follicles in pigs independent of changes in plasma FSH and follicular steroid concentration, without evidence for a dominant cohort of follicles during the luteal phase of the estrous cycle.

Follicular atresia in pigs: measurement and physiology

The physiological regulation of follicular atresia was investigated during the early luteal phase after ovulation and during altrenogest-synchronized preovulatory maturation in pigs (gilts). Apoptosis in dispersed granulosa cells was determined by flow cytometry. Apoptotic (A0) cells contain low, subdiploid amounts of DNA fluorescence. Follicles were classified biochemically as atretic or nonatretic based on the percentage of A0 (% A0) cells, atretic with > or = 10%, and nonatretic with < 10% A0 granulosa cells. The % A0 granulosa cells/follicle ranged from .02 to 89. Follicles containing debris in their isolated granulosa cells were classified as morphologically atretic. The morphological and biochemical criteria of atresia were in agreement for 224 of 248 follicles. Internucleosomal DNA cleavage, the hallmark of apoptosis, was determined by autoradiographic analysis of [32P]3'-end labeled DNA from granulosa cells. Densitometric analysis showed that optical density of [32P]3'-end labeled DNA fragments in the .18 to 20 kbp size range was correlated with the % A0 cells (R > .9, n = 22, P < .001). During altrenogest-synchronized preovulatory maturation, < 5% of large (> 6 mm in diameter) follicles were atretic. Among medium-sized follicles (3 to 6 mm) on d 1 and 3 of preovulatory maturation, only 17% were atretic, in contrast with d 5 when 87% were atretic. During the early luteal phase, atretic follicles/pig increased from 6% on d 5 to 50% on d 7 after estrus. Follicular fluid estradiol-17 beta concentration was greater (P < .001) in nonatretic than in atretic follicles on d 5 and 6 after estrus, but by d 7 estradiol-17 beta had decreased to a mean < 1 ng/mL in nonatretic and atretic follicles. The increase in apoptosis in granulosa cells and loss of estradiol-17 beta production in vivo indicated a high incidence of atresia among the first group of follicles grown after ovulation in pigs. These results indicate that apoptotic cell death was involved in degeneration of granulosa cells and atresia during two different stages of follicular development.

Atresia in follicles grown after ovulation in the pig: measurement of increased apoptosis in granulosa cells and reduced follicular fluid estradiol-17 beta

The incidence of atresia in the first group of follicles grown after ovulation was investigated in the pig. At slaughter, 113 follicles 3-6 mm in diameter were dissected from the ovaries of four pregnant pigs per day on Days 5, 6, and 7 after the onset of estrus. Granulosa cells were isolated from each follicle. The percentage of granulosa cells containing sub-diploid amounts of DNA (%Ao cells), a measure of apoptosis, was determined for each follicle by DNA fluorescence flow cytometry of propidium iodide (PI) stained nuclei of ethanol-fixed cells. Granulosa cell DNA condition was used to classify follicles. Follicles with > or = 10% Ao cells (n = 33) were designated biochemically atretic (BA), and follicles with < 10% Ao cells (n = 80) were designated biochemically healthy (BH). Internucleosomal cleavage, also indicative of apoptosis, was determined by autoradiographic analysis of [32P]-3'-end-labeled DNA from granulosa cells. Densitometric analysis showed that optical density of [32P]-3'-end-labeled DNA fragments in the 0.18-20-kb size range was correlated with the %Ao cells (R > or = 0.90, N = 22, p < 0.001). The incidence of pigs with BA follicles was 2 of 4, 3 of 4, and 4 of 4 on Days 5, 6, and 7, respectively. The %BA follicles per pig (mean +/- SEM) increased (p < or = 0.01) between Days 5 and 7; values were 6.2 +/- 3.6, 28.1 +/- 13.5, and 50.0 +/- 7.1, respectively, on Days 5, 6, and 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous hepatic venous reanastomosis in a patient with Budd-Chiari syndrome

A 33-year-old woman with Budd-Chiari syndrome for 9 years presented with worsening right upper quadrant pain and progressive liver dysfunction. Hepatic venography demonstrated hepatic vein occlusions, without significant IVC obstruction. Attempts at stenting a stenotic middle hepatic vein were unsuccessful. Transjugular access, however, allowed puncture from the stump of the right hepatic vein into the engorged right intrahepatic vein that had been demonstrated by retrograde hepatic venography. Two Palmaz stents were used to form the veno-venous reanastomosis. Initial success was documented angiographically and by pressure measurements before and after shunting. Followup at 7 and 16 months confirmed patency of the anastomosis without intimal hyperplasia. The patient noted near-complete resolution of her pain, and her liver function stabilized.

Flow cytometric determination of degraded deoxyribonucleic acid in granulosa cells to identify atretic follicles during preovulatory maturation in the pig

Granulosa cells of individual follicles were analyzed by DNA fluorescence flow cytometry to determine how the percentage of cells with degraded DNA and the distribution of cells in the phases of the cell cycle (Go/G1, S1, G2/M) related to the incidence of morphological atresia and to changes in follicular steroid concentrations. Follicles were dissected from ovaries recovered at slaughter on Days 1, 3, 5, or 7 of altrenogest-synchronized preovulatory maturation. Twenty-one follicles with debris among their isolated granulosa cells were classified as morphologically atretic (MA); 92 follicles with debris-free granulosa cells were classified as morphologically healthy (MH). Granulosa cells were prepared for flow cytometry by fixation in 80% ethanol and staining with propidium iodide (PI) containing RNase. DNA fluorescence intensity was determined by use of the 488-nm line of an argon laser. A subpopulation of granulosa cells with degraded DNA (Ao cells), containing less fluorescence than the Go/G1 peak, was found in the DNA histogram of every follicle. The percentage of Ao cells ranged from 0.02 to 83.6% per follicle. The percentage of Ao cells was inversely related to the percentage of Go/G1 cells (r = -0.9611, p = 0.0001). The percentage of Ao cells (mean +/- SEM) was greater (p = 0.0001) in MA (45.9 +/- 6.3%) than in MH follicles (5.3 +/- 1.6%). Follicular estradiol-17 beta was less in MA than in MH follicles, but androstenedione or progesterone did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of a bovine growth hormone transgene inhibits pregnant mare's serum gonadotropin-induced follicle maturation in prepuberal gilts

Prepuberal gilts were injected with PMSG to determine whether expression of a bovine growth hormone (bGH) transgene inhibited preovulatory maturation of ovarian follicles. Seven transgenic (TG) gilts of line 3706, which expresses a mouse metallothionein-bGH transgene, and eight nontransgenic, control (C) gilts (128 to 147 d old) were injected with PMSG, 12.5 IU/kg BW, 72 h before necropsy. Surface ovarian follicles > or = 1 mm in diameter were counted, measured for diameter, and aspirated for fluid. Follicles were classified morphologically as healthy or atretic and those with follicular fluid estradiol-17 beta > or = 100 ng/mL were classified as estrogenactive (EA). The number of follicles per gilt was 64.3 +/- 6.1 (mean +/- SEM) and did not differ significantly between bGH-TG and C gilts. The PMSG treatment induced growth of large (> 5 mm) follicles in both bGH-TG and C gilts. However, compared with C gilts, bGH-TG gilts had fewer (P < .05) large follicles (5.9 +/- 1.5 vs 18.3 +/- 5.4), a lower proportion of EA large follicles (35 +/- 12.5 vs 69 +/- 13.2%), and in large follicles less (P < .05) estradiol-17 beta (86 +/- 17 vs 350 +/- 69 ng/mL) and androstenedione (300 +/- 33 vs 1,283 +/- 221 ng/mL). Follicular fluid progesterone and inhibin did not differ significantly between bGH-TG and C gilts. The incidence of atresia among small and medium follicles did not differ significantly between bGH-TG and C gilts.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in follicular estradiol-17 beta, progesterone and inhibin immunoactivity in healthy and atretic follicles during preovulatory maturation in the pig

Follicular hormones, growth and granulosa cell gonadotropin sensitive adenylate cyclase activity were determined in healthy and atretic follicles during preovulatory maturation in pigs. Ovaries were recovered at slaughter which was 1, 3, 5 or 7 d after the last administration of a progesterone agonist (altrenogest). Plasma FSH decreased (P < .05) by 64% between days 1 and 3 and remained low through day 5. The number of large (> 5 mm) follicles increased from 2.7 on day 1 to 14.8 on day 3 and did not differ significantly among days 3, 5 and 7. The number of small (1-2 mm) and medium (3-5 mm) follicles decreased (P < or = .05) by 82% between days 3 and 5. Follicles first became estrogen-active (EA) (> or = 100 ng of estradiol-17 beta/ml of follicular fluid) on day 3, with 14.3% of medium and 73.8% of large follicles being EA. About 30% of small and 13% of medium follicles were morphologically atretic on days 1 and 3. However, by day 5, the proportion of atretic small and medium follicles had increased (P < or = .05) to 100 and 59%, respectively. Follicular fluid inhibin immunoactivity and estradiol-17 beta were lower (P < or = .05) and progesterone was greater (P < or = .05) in atretic than healthy follicles. Granulosa cells from large follicles produced (P < or = .05) more cAMP than cells from healthy or atretic small/medium follicles. Compared to control or pFSH treatment, pLH increased cAMP production by granulosa cells from large follicles on all days and from small/medium follicles on days 1 and 5; pLH had no effect on granulosa cells from atretic follicles. Compared to control, pFSH increased cAMP production in granulosa cells from healthy small/medium follicles only on day 1; no effect was detected in granulosa cells from large or atretic follicles on any day. We conclude that decreased secretion of FSH increased loss and atresia among non-ovulatory follicles. Atretic follicles were marked by loss of granulosa cell gonadotropin-sensitive adenylate cyclase activity and by low concentrations of estradiol-17 beta.

Changes in concentrations of follicular inhibin alpha and beta A subunit messenger ribonucleic acids and inhibin immunoactivity during preovulatory maturation in the pig

Ovarian tissues were collected from 5 pigs on each of days 1, 3, 5, and 7 after withdrawal of an orally active progestin to determine changes in follicular inhibin subunit mRNAs during preovulatory maturation. Follicles (N = 146) were aspirated for fluid and homogenized in guanidinium isothiocyanate for RNA isolation. Follicular RNA and inhibin alpha and beta A subunit mRNA standards were dot-blotted, hybridized with [32P]-cDNA probes, and quantified by densitometry. Mean concentrations of alpha mRNA (pg/micrograms of RNA) increased (p < or = 0.05) by 140% as healthy follicles grew from medium (3-5 mm) to large (> 5 mm). Inhibin immunoactivity was greater (p < or = 0.05) in large than medium follicles. In contrast, mean concentrations of inhibin beta A subunit mRNA did not differ between healthy medium and large follicles. However, both alpha mRNA and beta A mRNA increased (p < or = 0.05) linearly as follicular diameter increased from 3 to 5 mm on Day 1 and from 3 to 9 mm on Day 3. On Day 5, alpha mRNA remained elevated, but was not significantly correlated with diameter. In contrast, beta A mRNA decreased linearly (p < 0.05) as diameter increased from 6 to 11 mm on Day 5. The molar ratio alpha mRNA to beta A mRNA was 20:1 in healthy, large follicles on Days 3 and 5. Mean concentration of alpha mRNA in large follicles decreased (p < 0.05) by 72% between Days 5 and 7, while beta A mRNA decreased to non-detectable levels on Day 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of gonadotropin treatment on ovarian follicle growth and granulosal cell aromatase activity in prepuberal gilts

This experiment was conducted to compare the ability of USDA porcine FSH-B-1 (pFSH), USDA porcine LH-B-1 (pLH), and pregnant mare's serum gonadotropin (PMSG) to grow large follicles and induce granulosal cell aromatase activity in prepuberal gilts. Twenty-four gilts (164 d old) received one of four treatments by i.m. injection: 1) saline once, n = 8; 2) pFSH (8 micrograms/kg BW, nine times at 8-h intervals), n = 5; 3) pLH (2 micrograms/kg BW, nine times at 8-h intervals), n = 6; or 4) PMSG (15 IU/kg BW, once), n = 5. At slaughter, 72 h after the first injection, the ovaries to saline-treated gilts contained an average of 104 surface antral follicles 1 to 3 mm in diameter. compared to treatment with saline, pFSH increased (P less than .05) the number of follicles 46%, whereas pLH or PMSG decreased (P less than .05) the number by 70 and 84%, respectively. Compared with saline, treatment with PMSG or pLH induced growth of large follicles (7 to 9 mm) (10.8 and 4.8 follicles/gilt, respectively), increased plasma estrogen, increased granulosal cell aromatase activity, and decreased plasma FSH by 51 and 69%; treatment with pFSH had no significant effect on these traits. Results indicate that injected pFSH did not cause growth of large follicles or induce granulosal cell aromatase activity in prepuberal gilts. In contrast, LH initiated growth and increased granulosal cell aromatase activity in a small number of follicles and accelerated atresia among the remaining follicles.

A preliminary investigation of serum folate concentrations in sows during pregnancy and at weaning

The mean serum folate concentrations of Large White sows were compared between one group of 13 animals, 43-80 days pregnant and another group of 9 animals at weaning when the litters were 28-30 days old. The mean concentration was higher in sows at weaning (p<0.05) and the lowest levels were found in sows no more than 51 days pregnant (p<0.05).