An outbreak of Escherichia coli O157:H7 infections following a dairy education school field trip in Washington state, 2015.

On 27 April 2015, Washington health authorities identified Escherichia coli O157:H7 infections associated with dairy education school field trips held in a barn 20-24 April. Investigation objectives were to determine the magnitude of the outbreak, identify the source of infection, prevent secondary illness transmission and develop recommendations to prevent future outbreaks. Case-finding, hypothesis generating interviews, environmental site visits and a case-control study were conducted. Parents and children were interviewed regarding event activities. Odds ratios (OR) and 95% confidence intervals (CI) were computed. Environmental testing was conducted in the barn; isolates were compared to patient isolates using pulsed-field gel electrophoresis (PFGE). Sixty people were ill, 11 (18%) were hospitalised and six (10%) developed haemolytic uremic syndrome. Ill people ranged in age from <1 year to 47 years (median: 7), and 20 (33%) were female. Twenty-seven case-patients and 88 controls were enrolled in the case-control study. Among first-grade students, handwashing (i.e. soap and water, or hand sanitiser) before lunch was protective (adjusted OR 0.13; 95% CI 0.02-0.88, P = 0.04). Barn samples yielded E. coli O157:H7 with PFGE patterns indistinguishable from patient isolates. This investigation provided epidemiological, laboratory and environmental evidence for a large outbreak of E. coli O157:H7 infections from exposure to a contaminated barn. The investigation highlights the often overlooked risk of infection through exposure to animal environments as well as the importance of handwashing for disease prevention. Increased education and encouragement of infection prevention measures, such as handwashing, can prevent illness.

CO2 laser-based dispersion interferometer utilizing orientation-patterned gallium arsenide for plasma density measurements.

A dispersion interferometer based on the second-harmonic generation of a carbon dioxide laser in orientation-patterned gallium arsenide has been developed for measuring electron density in plasmas. The interferometer includes two nonlinear optical crystals placed on opposite sides of the plasma. This instrument has been used to measure electron line densities in a pulsed radio-frequency generated argon plasma. A simple phase-extraction technique based on combining measurements from two successive pulses of the plasma has been used. The noise-equivalent line density was measured to be 1.7 × 10(17) m(-2) in a detection bandwidth of 950 kHz. One of the orientation-patterned crystals produced 13 mW of peak power at the second-harmonic wavelength from a carbon dioxide laser with 13 W of peak power. Two crystals arranged sequentially produced 58 mW of peak power at the second-harmonic wavelength from a carbon dioxide laser with 37 W of peak power.

Spectral behavior of a terahertz quantum-cascade laser.

In this paper, the spectral behavior of two terahertz (THz) quantum cascade lasers (QCLs) operating both pulsed and cw is characterized using a heterodyne technique. Both lasers emitting around 2.5 THz are combined onto a whisker contact Schottky diode mixer mounted in a corner cube reflector. The resulting difference frequency beatnote is recorded in both the time and frequency domain. From the frequency domain data, we measure the effective laser linewidth and the tuning rates as a function of both temperature and injection current and show that the current tuning behavior cannot be explained by temperature tuning mechanisms alone. From the time domain data, we characterize the intrapulse frequency tuning behavior, which limits the effective linewidth to approximately 5 MHz.

Results from the low level mercury sorbent test at the Oak Ridge Y-12 Plant in Tennessee.

A mercury sorbent test was performed near the headwaters of the Upper East Fork Poplar Creek at the Oak Ridge Y-12 Plant in Tennessee. The sorbents SIR-200 (ResinTech), Keyle:X (SolmeteX), and GT-73 (Rohm and Haas) were the best materials tested for low level mercury removal. Each of these sorbents has a thiol-based active site. None of the tested sorbents reduced the mercury concentration to less than the existing 12 ng/l NPDES limit. For this small scale test, SIR-200, Keyle:X, and GT-73 reduced the mercury concentration to less than 51 ng/l, which is a regulatory treatment goal. The other sorbents tested, including granular activated carbon (Filtrasorb 300), did not reduce the mercury concentration below 51 ng/l at any tested flow up to 5 bed volumes per minute. Because of the cost and large volume of sorbent, a wastewater treatment plant for this stream would be prohibitively expensive to construct and maintain.

Potential rabies exposures in a Virginia county.

OBJECTIVE: Although records of animal bites and scratches are kept at most local health departments, little is known about the epidemiology and characteristics of these potential rabies exposures on a local level. Bite and scratch records for a four-and-a-half-year period from Montgomery County, Virginia, were examined in order to identify preventable trends. METHODS: The author retrospectively reviewed animal bite and scratch records from the Montgomery County Health Department dating from January 1992 through July 1996. RESULTS: Cat bites or scratches involved stray or feral animals more than eight times as often as dog bites or scratches. Cats were involved in the majority of incidents in which rabies postexposure prophylaxis (PEP) was recommended. Overall, PEP was recommended following 5.9% of reported incidents. The records also indicated that 65% of owned cats were unvaccinated at the time of the incident, while only 28% of owned dogs were unvaccinated. Children under the age of 18 were significantly more likely to be involved in a potential exposure than adults. CONCLUSIONS: Potential exposures should be analyzed periodically by local health departments. Suggestions for minimizing the number of potential rabies exposures in Montgomery County based on the results of the study reported here include: reducing the stray and feral cat population, targeting educational programs to children, and encouraging owners to vaccinate their pets.

Large-scale human exposures to rabid or presumed rabid animals in the United States: 22 cases (1990-1996).

OBJECTIVE: To identify common elements of large-scale human exposures to rabid or presumed rabid animals in the United States from 1990 to 1996. DESIGN: Retrospective study. PROCEDURE: Health departments in 50 states and the District of Columbia were contacted regarding episodes of large-scale human exposures to rabid animals occurring between 1990 and 1996. A large-scale exposure was defined as administration of postexposure prophylaxis (PEP) to 25 or more people after an exposure to a rabid or presumed rabid animal or littermates. Incident-specific information was obtained through questionnaires sent to states reporting episodes. Data are reported as medians. RESULTS: Fifteen of 51 (29.4%) health departments reported 22 episodes; 72.7% involved companion animals or livestock. Twenty-six animals were involved in these 22 episodes, including 10 (38.5%) dogs, 4 (15.4%) livestock, 4 (15.4%) raccoons, 3 (11.5%) cats, 3 (11.5%) bats, and 2 (7.7%) ferrets. Schools (36.4%) and public places (22.7%) were the most common settings for exposures. Reportedly, 1,908 people received PEP. The cost for 10 episodes was $61,547/episode (range, $14,199 to $1,500,000). An episode-specific written algorithm for recommending PEP had been developed for use in only 4 (18.2%) episodes. CLINICAL IMPLICATIONS: Large-scale exposures most commonly involved a single companion animal. Exposures attributable to improper handling of wildlife and unrestricted access of animals in schools and public areas can be potentially remedied by targeted education. Use of an episode-specific algorithm to determine need for PEP may also reduce the number of unnecessary treatments.

Myocarditis induced by targeted expression of the MCP-1 gene in murine cardiac muscle.

To explore the possible role of monocyte chemotactic protein (MCP-1) in inflammatory diseases of the heart, we expressed the murine MCP-1(JE) gene under the control of the alpha-cardiac myosin heavy chain promoter to attempt to target MCP-1 expression to the adult heart muscle. The five lines of transgenic mice thus produced showed targeted expression of MCP-1 transcripts and protein in the adult heart muscle and pulmonary vein but not in skeletal muscle. MCP-1 level in the transgenic hearts increased up to 30 to 45 days of age, and leukocyte infiltration into interstitium between cardiomyocytes increased up to 60 to 75 days. The infiltrate was mainly macrophages but not T cells. The presence of MCP-1 in the transgenic hearts did not induce cytokine production indicative of leukocyte activation. Echocardiographic analysis of 1-year-old mice that express MCP-1 in the myocardium and of age-matched controls revealed cardiac hypertrophy and dilation, increases in left ventricular (LV) mass, and systolic and diastolic left ventricular internal diameters. A significant decline in M-mode shortening fraction showed depressed contractile function. Transgenic hearts were 65% heavier, and histological analysis showed moderate myocarditis, edema, and some fibrosis. Thus, MCP-1 expression in the heart muscle may provide a model to investigate myocarditis and cardiomyopathy.

Phase variation and conservation of lipooligosaccharide epitopes in Haemophilus somnus.

The bovine-specific pathogen Haemophilus somnus is capable of undergoing structural and antigenic phase variation in its lipooligosaccharide (LOS) components after in vivo and in vitro passage. However, commensal isolates from the reproductive tract have not been observed to vary in phase (T. J. Inzana, R. P. Gogolewski, and L. B. Corbeil, Infect. Immun. 60:2943-2951, 1992). We now report that specific monoclonal antibodies (MAbs) to the LOSs of Haemophilus aegyptius, Neisseria gonorrhoeae, and Haemophilus influenzae, as well as H. somnus, reacted with some phase-variable epitopes in H. somnus LOS. All reactive MAbs bound to LOS components of about 4.3 kDa in the same H. somnus isolates, including a non-phase-varying strain. Following in vitro passage of a clonal variant of strain 738 that was nonreactive with the MAbs, 11.8% of young colonies shifted to a reactive phenotype. A digoxigenin-labelled 5'-CAATCAATCAATCAATCAATCAATCAAT-3' oligonucleotide probe hybridized to genomic DNA from strain 738 but did not react with DNA from a non-phase-varying strain. Sequence analysis of the gene containing 5'-CAAT-3' tandem sequences revealed 48% amino acid homology with the lex-2B gene-encoded protein of H. influenzae type b. Our results indicate that some LOS epitopes are conserved between H. somnus and other Haemophilus and Neisseria species, that LOS phase variation may occur at a high rate in some strains of H. somnus, and that phase variation may, in part, be due to 5'-CAAT-3' tandem sequences present in H. somnus genes.

Beta2-adrenergic receptor antagonists protect against ventricular fibrillation: in vivo and in vitro evidence for enhanced sensitivity to beta2-adrenergic stimulation in animals susceptible to sudden death.

BACKGROUND: The ventricular myocardium contains functional beta2-adrenergic receptors that when activated increase intracellular Ca2+ transients. Because elevated Ca2+ has been implicated in the induction of ventricular fibrillation (VF), it is possible that the activation of these receptors may also provoke malignant arrhythmias. METHODS AND RESULTS: To test this hypothesis, a 2-minute occlusion of the left circumflex coronary artery was made during the last minute of exercise in 28 dogs with healed anterior myocardial infarctions: 17 had VF (susceptible) and 11 did not (resistant). On a subsequent day, this test was repeated after administration of the beta2-adrenergic receptor antagonist ICI 118,551 (0.2 mg/kg). This drug did not alter the hemodynamic response to the coronary occlusion, yet it prevented VF in 10 of 11 animals tested (P<.001). However, heart rate was reduced in 6 animals. Therefore, the ICI 118,551 exercise-plus-ischemia test was repeated with heart rate held constant by ventricular pacing (n=3). ICI 118,551 still prevented VF when heart rate was maintained. Next, the effects of increasing doses of the beta2-adrenergic receptor agonist zinterol on Ca2+ transient amplitudes were examined in ventricular myocytes. Zinterol elicited significantly greater increases in Ca2+ transient amplitudes at all doses tested (10(-9) to 10(-6) mol/L) in myocytes prepared from susceptible versus resistant animals. The cardiomyocyte response to isoproterenol (10(-7) mol/L) in the presence or absence of the selective beta1- (CGP-20712A, 300 nmol/L) or beta2- (ICI 118,551, 100 nmol/L) adrenergic receptor antagonist was also examined. Isoproterenol elicited larger Ca2+ transient increases in the susceptible myocytes, which were eliminated by ICI but not by CGP. CONCLUSIONS: When considered together, these data demonstrate that canine myocytes contain functional beta2-adrenergic receptors that are activated to a greater extent in the susceptible animals. The resulting cytosolic Ca2+ transient increases may lead to afterpotentials that ultimately trigger VF in these animals.

Calcium handling by sarcoplasmic reticulum of neonatal swine cardiac myocytes.

In recent years, because of similarities to human infants, neonatal piglets have increasingly become the model of choice for studying neonatal heart function. However, the cardiac sarcoplasmic reticulum (SR) has not been thoroughly characterized in this species. Accordingly, Ca2+ pump kinetics, efflux channel characteristics, Ca2+ transients, and contractile movements were examined in isolated newborn piglet cardiac ventricular myocytes. Maximum uptake rate (Vmax) and concentration required to produce a half-maximal effect (K0.5) for oxalate-supported, ATP-dependent 45Ca2+ uptake by the SR of digitonin-lysed myocytes were 285 +/- 17 nmol 45Ca2+.min-1.mg-1 and 0.69 +/- 0.07 microM, respectively. In the absence of phospholamban phosphorylation, Vmax was reduced to 195 +/- 26 nmol 45Ca2+.min-1.mg-1 (P < 0.05 vs. control) and K0.5 increased to 1.28 +/- 0.13 microM (P < 0.05 vs. control). [3H]ryanodine binding studies yielded a maximum binding capacity of 181 +/- 12 fmol/mg and a dissociation constant of 1.7 +/- 0.2 nM. Raising extracellular Ca2+ (0.5-5 mM) increased peak amplitude and decreased the duration of electrically stimulated fura 2 Ca2+ transients and recordings of cell length changes. Both ryanodine and 2,5-di-tert-butylhydroquinone, an inhibitor of SR calcium adenosinetriphosphatase, completely abolished Ca2+ transients in piglet myocytes. These studies indicate that the SR has a significant role in excitation-contraction coupling in neonatal piglet myocytes.

Verapamil accelerates the transition to heart failure in obese, hypertensive, female SHHF/Mcc-fa(cp) rats.

We sought to characterize the effects of the nonselective Ca2+ channel antagonist, verapamil, and the vascular-selective Ca2+ channel antagonist, felodipine, on obese, hypertensive, heart failure-prone, female SHHF/Mcc-fa(cp) rats. Rats were treated for < or = 2 months with verapamil (57 mg/kg/day) or felodipine (24 mg/kg/day). Blood pressures were determined at monthly intervals by the tail-cuff method. Heart weights and myosin isoforms were measured at the end of treatment. Direct cardiac effects of verapamil and felodipine were examined in electrically field stimulated, fura-2/AM-loaded cardiomyocytes. Both Ca2+ channel antagonists reduced systolic blood pressures. Verapamil, but not felodipine, increased heart weights and decreased expression of the myosin V1 isoform. In older animals, 75% of those treated with verapamil developed end-stage congestive heart failure. Age-matched control and felodipine-treated rats remained healthy. In isolated cardiomyocytes, 10(-9) M verapamil significantly reduced Ca2+ transient amplitudes but 10(-9) M felodipine did not. Both Ca2+ channel antagonists reduced blood pressures in obese, hypertensive, female SHHF rats. Verapamil, but not felodipine, produced heart failure in a large number of these animals. Differences between the in vivo effects of the two Ca2+ channel antagonists may be related to the differing effects on sarcolemmal Ca2+ influx.

Anabolic implant effects on steer performance, carcass traits, subprimal yields, and longissimus muscle properties.

Crossbred steers (n = 140; 353 kg) were implanted as follows: (C) control, no implant; (S) Synovex-S (20 mg estradiol benzoate + 200 mg progesterone); (R) Revalor (20 mg estradiol + 140 mg trenbolone acetate [TBA]; international dosage); (ST) S + finaplix-S (140 mg TBA); (STT) S + finaplix-S with finaplix-S reimplanted on d 58. Steers were harvested after 119 to 126 d on feed. Left sides of 40 carcasses were fabricated into boneless subprimals for two s.c. fat levels: 2.5 and .64 cm. Steers administered an estrogen (estradiol benzoate or estradiol) plus TBA gained more rapidly (P < .05) than C or S steers. Feed efficiency was improved (P < .05) with an estrogen plus TBA. No differences (P > .05) were noted among treatments for carcass s.c. fat thickness, percentage internal fat, or lean color. Carcasses from steers receiving TBA had larger (P < .05) longissimus areas and tended to have lower (P < .10) marbling scores and yield grades than C or S steers. Steers implanted with R had a lower (P < .05) percentage of U. S. Choice carcasses (51.8%) than C, S, and ST steers (82 to 86%). Shear force values for implanted steers tended to be higher (P < .10) than for controls. Implants increased (P < .05) subprimal and total side lean yields (.64 cm) compared to controls; the largest increases of 2.3 and 2.8%, respectively, occurred in steers receiving TBA plus an estrogen. Estrogen plus TBA exhibited favorable effects on gain, efficiency, and composition; however, the single estradiol plus TBA implant (R) decreased quality grade.

Effects of calcium channel antagonists on Ca2+ transients in rat and canine cardiomyocytes.

First-generation Ca2+ channel antagonists depress myocardial contractility, but many of the newer Ca2+ channel blockers have a high degree of "vascular selectivity". This study compares the effects of the Ca2+ antagonists felodipine, amlodipine, mibefradil, verapamil and nifedipine, and the Ca2+ channel agonist. (S)(-)-Bay K-8644 on Ca2+ transient amplitudes in fura-2/AM-loaded rat and canine ventricular cardiomyocytes. At 10(-11) and 10(-10) M, felodipine increased [Ca2+]i transient amplitudes by 10-25% in field-stimulated fura-2-loaded cells from both species while at 10(-6) M it depressed [Ca2+]i transients by 80%. Mibefradil increased [Ca2+]i transient amplitudes by 16% at 10(-11) and 10(-10) M and decreased the transients by 25% at 10(-6) M. The calcium channel agonist, (S)(-)-Bay K-8644 increased [Ca2+]i transient amplitudes at 10(-10)-10(-6) M (maximally 37% at 10(-7) M) but depressed [Ca2+]i transients by 10% at 10(-5) M. Nifedipine was inhibitory at all concentrations tested (10(-11)-10(-6) M) in canine myocytes, but in rat cells. 10(-10) M nifedipine increased [Ca2+]i transient amplitudes by 37%. All concentrations of verapamil and amlodipine (10(-11)-10(-6) M) depressed [Ca2+]i transients in both rat and canine myocytes. We conclude that: (1) felodipine and mibefradil may be positive rather than negative inotropes at low concentrations, which are therapeutically relevant: and (2) low concentrations of nifedipine may have a positive inotropic effect in the rat but not the dog heart.

Response of failing canine and human heart cells to beta 2-adrenergic stimulation.

BACKGROUND: Failing human hearts lose beta 1- but not beta 2-adrenergic receptors. In canine hearts with tachypacing failure, the ratio of beta 2- to beta 1-adrenergic receptors is increased. The present study was designed to determine whether heart failure increases sensitivity to beta 2-adrenergic stimulation in isolated canine ventricular cardiomyocytes and to verify that myocytes from failing human ventricles contain functional beta 2-adrenergic receptors. METHODS AND RESULTS: Myocytes from healthy dogs, dogs with tachypacing failure, and human transplant recipients were loaded with fura 2-AM and subjected to electric field stimulation in the presence of zinterol, a highly selective beta 2-adrenergic agonist. Zinterol significantly increased [Ca2+]i transient amplitudes in all three groups. The failing canine myocytes were significantly more responsive than normal to beta 2-adrenergic stimulation. We also measured isotonic twitches, indo-1 fluorescence transients, and L-type Ca2+ currents in healthy canine myocytes. Zinterol (10(-5) mol/L) elicited large increases in the amplitudes of simultaneously recorded twitches and [Ca2+]i transients. Zinterol also increased L-type Ca2+ currents in the normal canine myocytes; this augmentation was abolished by 10(-7) mol/L ICI 118,551. cAMP production by suspensions of healthy and failing canine myocytes was not increased by zinterol (10(-9) to 10(-5) mol/L), nor did 10(-5) mol/L zinterol elicit phospholamban phosphorylation. CONCLUSIONS: Failing human ventricular cardiomyocytes contain functional beta 2-adrenergic receptors. Canine myocytes also contain functional beta 2-adrenergic receptors. The canine ventricular response to beta 2-agonists is increased in tachypacing failure. Positive inotropic responses to beta 2-stimulation are not mediated by increases in cAMP or cAMP-dependent phosphorylation of phospholamban.

Evidence against norepinephrine-stimulated efflux of mitochondrial Mg2+ from intact cardiac myocytes.

We investigated the hypotheses that norepinephrine stimulates Mg2+ efflux from intact isolated adult rat ventricular cardiomyocytes and that adenosine 3',5'-cyclic monophosphate stimulates Mg2+ efflux from permeabilized myocytes and isolated mitochondria. Norepinephrine stimulation of Mg2+ release from cardiac myocytes was observed only when cells at approximately 20 mg protein/ml in Mg(2+)-containing buffer were diluted 50- to 60-fold into an Mg(2+)-free medium. Under these conditions, > 30% of total cellular lactic acid dehydrogenase activity was also released, indicating that a significant portion of the cells had died. In other protocols, where Mg2+ efflux from myocytes was not observed, extracellular Mg2+ removal and administration of 10 microM norepinephrine increased 45Ca2+ accumulation by cells in suspension. In single myocytes, Mg2+ removal and norepinephrine administration increased intracellular free [Ca2+] as measured by fura-2 fluorescence microscopy, and this was accompanied by vigorous spontaneous contractile activity followed by Ca2+ overload hypercontracture. With permeabilized myocytes and isolated mitochondria from a variety of sources, adenosine 3',5'-cyclic monophosphate did not stimulate Mg2+ efflux. These results suggest that recent evidence for direct hormonal regulation of myocardial Mg2+ homeostasis may need to be reevaluated.

Anterior ankle arthroplasty.

Osteophytic proliferation at the anterior ankle joint level occurs secondary to repeated direct trauma to the talus and tibia during extreme dorsiflexion of the ankle. This syndrome occurs frequently, especially in athletes. As the exostosis increases in size, ankle joint motion decreases. With increased activity, patients will complain of pain at the anterior aspect of the ankle joint, secondary to the osseous impingement occurring at the tibiotalar joint. If surgical resection is planned, the following should be considered: (1) Proper planning of the incision should give optimal exposure to the tibiotalar joint. (2) Meticulous dissection should be used to identify and carefully retract the superficial and deep neurovascular structures. (3) Adequate repair of the inferior and superior bands of the extensor retinaculum is critical in order to prevent postoperative bowstringing of the anterior tendons. (4) A postoperative course of 3 weeks nonweight bearing is required to help avoid hypertrophic scar formation and allow adequate healing of the extensor retinaculum. (5) Passive range of motion may be started after suture removal at 10 to 14 days. (6) Active range of motion should begin with the initiation of weight bearing at the start of the fourth week. Rewarding results from anterior ankle arthroplasty resection have been seen in those patients presenting with the classical symptoms, as discussed previously, and radiographic evidence of exostosis formation and impingement of the anterior tibiotalar joint.