Phase Space Dynamics of a Plasma Wakefield Dechirper for Energy Spread Reduction

Plasma-based accelerators have made impressive progress in recent years. However, the beam energy spread obtained in these accelerators is still at the ∼1% level, nearly one order of magnitude larger than what is needed for challenging applications like coherent light sources or colliders. In plasma accelerators, the beam energy spread is mainly dominated by its energy chirp (longitudinally correlated energy spread). Here we demonstrate that when an initially chirped electron beam from a linac with a proper current profile is sent through a low-density plasma structure, the self-wake of the beam can significantly reduce its energy chirp and the overall energy spread. The resolution-limited energy spectrum measurements show at least a threefold reduction of the beam energy spread from 1.28% to 0.41% FWHM with a dechirping strength of ∼1  (MV/m)/(mm pC). Refined time-resolved phase space measurements, combined with high-fidelity three-dimensional particle-in-cell simulations, further indicate the real energy spread after the dechirper is only about 0.13% (FWHM), a factor of 10 reduction of the initial energy spread.

Physical mechanism of the electron-ion coupled transverse instability in laser pressure ion acceleration for different regimes

In radiation pressure ion acceleration (RPA) research, the transverse stability within laser plasma interaction has been a long-standing, crucial problem over the past decades. In this paper, we present a one-dimensional two-fluid theory extended from a recent work Wan et al. Phys. Rev. Lett. 117, 234801 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.234801 to clearly clarify the origin of the intrinsic transverse instability in the RPA process. It is demonstrated that the purely growing density fluctuations are more likely induced due to the strong coupling between the fast oscillating electrons and quasistatic ions via the ponderomotive force with spatial variations. The theory contains a full analysis of both electrostatic (ES) and electromagnetic modes and confirms that the ES mode actually dominates the whole RPA process at the early linear stage. By using this theory one can predict the mode structure and growth rate of the transverse instability in terms of a wide range of laser plasma parameters. Two-dimensional particle-in-cell simulations are systematically carried out to verify the theory and formulas in different regimes, and good agreements have been obtained, indicating that the electron-ion coupled instability is the major factor that contributes the transverse breakup of the target in RPA process.

Femtosecond Probing of Plasma Wakefields and Observation of the Plasma Wake Reversal Using a Relativistic Electron Bunch

We show that a high-energy electron bunch can be used to capture the instantaneous longitudinal and transverse field structures of the highly transient, microscopic, laser-excited relativistic wake with femtosecond resolution. The spatiotemporal evolution of wakefields in a plasma density up ramp is measured and the reversal of the plasma wake, where the wake wavelength at a particular point in space increases until the wake disappears completely only to reappear at a later time but propagating in the opposite direction, is observed for the first time by using this new technique.

Physical Mechanism of the Transverse Instability in Radiation Pressure Ion Acceleration

The transverse stability of the target is crucial for obtaining high quality ion beams using the laser radiation pressure acceleration (RPA) mechanism. In this Letter, a theoretical model and supporting two-dimensional (2D) particle-in-cell (PIC) simulations are presented to clarify the physical mechanism of the transverse instability observed in the RPA process. It is shown that the density ripples of the target foil are mainly induced by the coupling between the transverse oscillating electrons and the quasistatic ions, a mechanism similar to the oscillating two stream instability in the inertial confinement fusion research. The predictions of the mode structure and the growth rates from the theory agree well with the results obtained from the PIC simulations in various regimes, indicating the model contains the essence of the underlying physics of the transverse breakup of the target.

Nanoscale Electron Bunching in Laser-Triggered Ionization Injection in Plasma Accelerators

Ionization injection is attractive as a controllable injection scheme for generating high quality electron beams using plasma-based wakefield acceleration. Because of the phase-dependent tunneling ionization rate and the trapping dynamics within a nonlinear wake, the discrete injection of electrons within the wake is nonlinearly mapped to a discrete final phase space structure of the beam at the location where the electrons are trapped. This phenomenon is theoretically analyzed and examined by three-dimensional particle-in-cell simulations which show that three-dimensional effects limit the wave number of the modulation to between >2k_{0} and about 5k_{0}, where k_{0} is the wave number of the injection laser. Such a nanoscale bunched beam can be diagnosed by and used to generate coherent transition radiation and may find use in generating high-power ultraviolet radiation upon passage through a resonant undulator.

Capturing relativistic wakefield structures in plasmas using ultrashort high-energy electrons as a probe

A new method capable of capturing coherent electric field structures propagating at nearly the speed of light in plasma with a time resolution as small as a few femtoseconds is proposed. This method uses a few femtoseconds long relativistic electron bunch to probe the wake produced in a plasma by an intense laser pulse or an ultra-short relativistic charged particle beam. As the probe bunch traverses the wake, its momentum is modulated by the electric field of the wake, leading to a density variation of the probe after free-space propagation. This variation of probe density produces a snapshot of the wake that can directly give many useful information of the wake structure and its evolution. Furthermore, this snapshot allows detailed mapping of the longitudinal and transverse components of the wakefield. We develop a theoretical model for field reconstruction and verify it using 3-dimensional particle-in-cell (PIC) simulations. This model can accurately reconstruct the wakefield structure in the linear regime, and it can also qualitatively map the major features of nonlinear wakes. The capturing of the injection in a nonlinear wake is demonstrated through 3D PIC simulations as an example of the application of this new method.

Physics of Phase Space Matching for Staging Plasma and Traditional Accelerator Components Using Longitudinally Tailored Plasma Profiles

Phase space matching between two plasma-based accelerator (PBA) stages and between a PBA and a traditional accelerator component is a critical issue for emittance preservation. The drastic differences of the transverse focusing strengths as the beam propagates between stages and components may lead to a catastrophic emittance growth even when there is a small energy spread. We propose using the linear focusing forces from nonlinear wakes in longitudinally tailored plasma density profiles to control phase space matching between sections with negligible emittance growth. Several profiles are considered and theoretical analysis and particle-in-cell simulations show how these structures may work in four different scenarios. Good agreement between theory and simulation is obtained, and it is found that the adiabatic approximation misses important physics even for long profiles.

Quasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV

Laser-plasma accelerators of only a centimetre’s length have produced nearly monoenergetic electron bunches with energy as high as 1 GeV. Scaling these compact accelerators to multi-gigaelectronvolt energy would open the prospect of building X-ray free-electron lasers and linear colliders hundreds of times smaller than conventional facilities, but the 1 GeV barrier has so far proven insurmountable. Here, by applying new petawatt laser technology, we produce electron bunches with a spectrum prominently peaked at 2 GeV with only a few per cent energy spread and unprecedented sub-milliradian divergence. Petawatt pulses inject ambient plasma electrons into the laser-driven accelerator at much lower density than was previously possible, thereby overcoming the principal physical barriers to multi-gigaelectronvolt acceleration: dephasing between laser-driven wake and accelerating electrons and laser pulse erosion. Simulations indicate that with improvements in the laser-pulse focus quality, acceleration to nearly 10 GeV should be possible with the available pulse energy.

Laser-plasma accelerators can produce high-energy electron bunches over just a few centimetres of distance, offering possible table-top accelerator capabilities. Wang et al. break the current 1 GeV barrier by applying a petawatt laser to accelerate electrons nearly monoenergetically up to 2 GeV.

Backward Raman amplification in a plasma waveguide

Backward Raman amplification of a short laser pulse in a plasma waveguide is demonstrated. With a guided seed pulse of 0.8-microJ energy and a pump pulse of 345-mJ energy in a 9-mm-long optically preformed plasma waveguide, 910-fold energy amplification is achieved. Heating of the plasma by the long pump pulse is identified to be a key issue for plasma-waveguide-based backward Raman amplifiers.

Degenerate four-wave mixing mediated by ponderomotive-force-driven plasma gratings

Degenerate four-wave mixing mediated by ponderomotive-force-driven plasma gratings is demonstrated in the near-infrared regime. The quadratic dependence of the reflectivity of the probe pulse on plasma density indicates that the mixing is caused by the quasineutral plasma grating driven by the laser ponderomotive force. The experiment verifies that ponderomotive force is an effective means to produce a large-amplitude short-period plasma grating, which has many important applications in ultrahigh-intensity optics. In particular, such a grating is a crucial element for the development of plasma phase-conjugate mirrors that can be used to restore the wave-front distortion that is ubiquitous in nonlinear propagation.

Enhancement of relativistic harmonic generation by an optically preformed periodic plasma waveguide

Enhancement of relativistic third-harmonic generation by using an optically preformed periodic plasma waveguide was achieved. Resonant dependence of harmonic intensity on plasma density and density modulation parameters was observed, which is a distinct characteristic of quasi-phase-matching. The results demonstrate the potential of a modulated plasma waveguide in high-field applications.

Rhodococcus equi pneumonia in a heart transplant recipient in Korea, with emphasis on microbial diagnosis

Rhodococcus equi is an opportunistic pathogen that usually causes infection in immunocompromised hosts. A heart transplant recipient who had been treated with amphotericin B for pulmonary aspergillosis showed newly developed multiple nodules with a central necrotic area in the right lower lobes. Cultures of several blood samples and an aspirate of the lung nodule yielded a Gram-positive coccobacillary bacterium, which was initially reported as a Corynebacterium species, but was later identified as R. equi by API CORYNE (bioMerieux SA, Marcy l'Etoile, France) and by demonstrating the production of 'equi factor'. The identification was subsequently confirmed by an R. equi-specific polymerase chain reaction (PCR). The patient was successfully treated with ciprofloxacin and azithromycin for 14 weeks. This is the first documented case of R. equi infection in Korea. There is a possibility of underestimation of R. equi infections due to the misidentification of the organism as a contaminating diphtheroid. Because R. equi will not respond to the conventional empirical therapy, the microbiology laboratory should identify R. equi in a timely manner. R. equi-specific PCR will be a useful confirmatory test in human infection.

Effect of shock wave therapy on acute fractures of the tibia: a study in a dog model

The effect of shock wave therapy on acute fractures of the tibia was studied in eight adult dogs. A fracture with a 3-mm gap was created in both tibias and the fractures were fixed internally with a small metallic plate and screws. Each of the right limbs received 2,000 impulses of shock waves at 14 kV whereas the left limbs were used as controls. The evaluations included the callus formations based on serial radiographic examinations at 1, 4, 8, and 12 weeks and histologic examinations at 12 weeks for tissue distribution including bone tissues. Based on radiographic findings, there was no statistically significant difference in the amount of callus formation between the treated and the control groups at 8 weeks or less. However, the radiographic findings at 12 weeks statistically showed more callus formations in the treated group. In histologic examinations, there was significantly more cortical bone formation in the treated group at 12 weeks and the bone tissues were thicker, denser, and heavier. Shock wave therapy enhanced callus formation and induced cortical bone formation in acute fractures in dogs at 12 weeks. The effect of shock wave therapy seemed to be time-dependent at 3 months.

Extensor digitorum brevis rotational muscle flap for lower leg and ankle coverage

BACKGROUND

Soft tissue reconstruction around the ankle has been a challenging problem. This article reports our experience using the extensor digitorum brevis muscle flap; some technical variations are discussed.

METHODS

The extensor digitorum brevis muscle flap is vascularized by the well-defined lateral tarsal artery, a branch of the dorsalis pedis artery originating at the level of the inferior extensor retinaculum. This flap was used for coverage of soft tissue defects in the lower leg and the ankle in 10 patients with various injuries.

RESULTS

All flaps survived completely. Complications included delayed healing of donor skin in two cases. Flap elevation was possible even in the traumatized donor foot.

CONCLUSION

The advantages of this flap include constant and reliable blood supply, easy and rapid flap dissection, adequate bulk, and one-stage procedure. However, disadvantages include the small size of the flap and the sacrifice of the dorsalis pedis artery.

Multicenter surveillance study for nosocomial infections in major hospitals in Korea. Nosocomial Infection Surveillance Committee of the Korean Society for Nosocomial Infection Control

BACKGROUND

The goals of a surveillance for nosocomial infections (NIs) are to observe the magnitude and characteristics of NIs and to plan and evaluate policies and guidelines of infection control. This study was designed to determine the rate and distribution of NIs and their causative pathogens in Korean hospitals.

METHODS

Prospective surveillance was performed at 15 acute care hospitals with more than 500 beds during a 3-month period from June to August 1996. The case-finding methods were laboratory-based surveillance for patients in the general wards and a direct review of medical charts done regularly for all the patients in the intensive care units.

RESULTS

A total of 3162 NIs were found among 85,547 discharged patients, with an overall nosocomial infection rate of 3.70 per 100 patients discharged. Urinary tract infections constituted 30.3% of all NIs. Other infections were pneumonias, 17.2%, surgical site infections, 15.5%, and primary bloodstream infections, 14.5%. The infection rate was the highest in neurosurgery (14.21), followed by neurology (8. 62) and ontology services (6.70). The infection rate in intensive care units was higher than it was in the general wards (10.74 vs 2. 57, P =.001). The commonly isolated organisms were Staphylococcus aureus (17.2%), Pseudomonas aeruginosa (13.8%), and Escherichia coli (12.3%).

CONCLUSIONS

This first multicenter surveillance study provided extensive information on the current status and trends of NIs in major hospitals in Korea. The results may contribute to the evaluation of infection control programs and the development of effective strategies in these hospitals.

Vancomycin-intermediate Staphylococcus aureus in Korea

Recent reports on some methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin have been a major concern in Korea because of the widespread use of vancomycin due to a high prevalence of MRSA in the country. We describe a 45-year-old man with long-standing pelvic abscess due to MRSA. In spite of vancomycin and teicoplanin treatment for a long period of time, the patient died from MRSA sepsis. The blood culture isolate of MRSA exhibited reduced susceptibility to vancomycin (MIC, 8 microg/ml). This is the first report of a vancomycin-intermediate S. aureus case from Korea.

In vitro activities of quinupristin/dalfopristin and eight other antimicrobial agents against 360 clinical isolates from Korea

The emergence of multi-drug resistant gram-positive cocci such as methicillin-resistant (MR) staphylococci, vancomycin-resistant (VR) enterococci, and vancomycin-intermediate resistant S. aureus (VISA) has given new urgency to the development of new antimicrobial agents. One of these is quinupristin/dalfopristin (Q/D). We decided to determine the susceptibility of gram-positive cocci isolated at two university hospitals in Seoul to Q/D and compare the results with eight other antimicrobial agents. We investigated 120 isolates of S. aureus including 49 MRSAs and one VISA, 120 isolates of coagulase negative staphylococci (CNS), 64 E. faecalis and 56 E. faecium, including seven strains of VR E. faecium. Minimum inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) for several antimicrobials, including vancomycin and Q/D, were determined by broth microdilution. All S. aureus including VISA were susceptible to Q/D. Q/D MIC90 for both methicillin-susceptible S. aureus (MSSA) and MRSA was 0.25 g/mL. 49 (87.5%) of 56 E. faecium including six of seven VR E. faecium were susceptible to Q/D. E. faecalis were not susceptible to Q/D (only 1.5% susceptible), but were inhibited by ampicillin (94% susceptible) or vancomycin (95%). CNS was susceptible to Q/D (96% susceptible) and vancomycin (100% susceptible). One of 38 staphylococci and two of 17 E. faecium were tolerant to Q/D. In conclusion, Q/D showed excellent activity against all species of gram-positive cocci including MRSA, VISA, and VR E. faecium except E. faecalis, and may provide a valuable option for the treatment of infections caused by these emerging nosocomial pathogens of gram-positive cocci.

Time-kill studies of antimicrobial combinations including cefotaxime, ceftriaxone, vancomycin and meropenem against cephalosporin-resistant Streptococcus pneumoniae

BACKGROUND

Resistance of Streptococcus pneumoniae to penicillin is now widespread and rapidly increasing all over the world. This has led to the critical need for alternative antimicrobial therapy.

METHODS

To assess the activities of antimicrobial combinations, including cefotaxime, ceftriaxone, vancomycin and meropenem, time-kill studies were conducted against five strains of penicillin- and cephalosporin-resistant S. pneumoniae at clinically achievable antimicrobial concentrations in cerebrospinal fluid.

RESULTS

Combinations of an extended-spectrum cephalosporin with vancomycin were not synergistic. Meropenem had a comparable bactericidal activity to those combinations, and its killing activity was not affected by the addition of cefotaxime, ceftriaxone or vancomycin.

CONCLUSIONS

It is suggested that meropenem could be an effective alternative for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis. However, more clinical data are required before it can be recommended as an effective antimicrobial agent for such cases.

Spread of drug-resistant Streptococcus pneumoniae in Asian countries: Asian Network for Surveillance of Resistant Pathogens (ANSORP) Study

Antimicrobial susceptibility of 996 isolates of Streptococcus pneumoniae from clinical specimens was investigated in 11 Asian countries from September 1996 to June 1997. Korea had the greatest frequency of nonsusceptible strains to penicillin with 79.7%, followed by Japan (65.3%), Vietnam (60.8%), Thailand (57.9%), Sri Lanka (41.2%), Taiwan (38.7%), Singapore (23.1%), Indonesia (21.0%), China (9.8%), Malaysia (9.0%), and India (3.8%). Serotypes 23F and 19F were the most common. Pulsed-field gel electrophoresis (PFGE) of 154 isolates from Asian countries showed several major PFGE patterns. The serotype 23F Spanish clone shared the same PFGE pattern with strains from Korea, Japan, Singapore, Taiwan, Thailand, and Malaysia. Fingerprinting analysis of pbp1a, pbp2x, and pbp2b genes of 12 strains from six countries also showed identical fingerprints of penicillin-binding protein genes in most strains. These data suggest the possible introduction and spread of international epidemic clones into Asian countries and the increasing problems of pneumococcal drug resistance in Asian countries for the first time.

Antimicrobial resistance in enterococci

Enterococci have emerged as a major nosocomial pathogen and as an ever-increasing problem in antimicrobial resistance. They are ubiquitous in the intestinal flora of humans and animals and inherently resistant to a wide array of antimicrobial agents, and, more alarmingly, they seem to have a potential facility for acquiring new resistance determinants, including beta-lactamase production, high-level resistance to aminoglycosides, and recently, glycopeptide resistance. Collectively, all of these properties make enterococci one of most difficult nosocomial pathogens to treat and control today. The purpose of this review was to examine the epidemiology, the mechanisms, and laboratory detection of resistance of enterococci to the two major groups of antibiotics: aminoglycosides and glycopeptides.

Dynamic condylar screw for subtrochanteric femur fractures with greater trochanteric extension

Sixteen cases of subtrochanteric femur fractures with greater trochanteric extension were treated using the AO dynamic condylar screw (DCS). All cases were treated using the principles of strict indirect reduction to achieve anatomic alignment rather than anatomic reduction, with no bone grafting, and delayed weight bearing. The overall union rate was 93.7% (15 of 16). One unique case of implant failure with varus nonunion was encountered following repeat trauma. The advantages of the implant and technique are a simplified procedure, shorter operative time, and rapid union. Using the DCS with the indirect reduction method and delayed weight bearing is an acceptable choice in subtrochanteric femur fractures with greater trochanteric involvement when other adequate implants are not available for stable fixation.

Serum levels of interleukin-8 in alcoholic liver disease: relationship with disease stage, biochemical parameters and survival

BACKGROUND/AIMS

Interleukin-8 (IL-8), a cytokine produced by a host of cells, including monocytes, macrophages, Kupffer cells and hepatocytes, can activate neutrophils. Peripheral neutrophilia and liver neutrophil infiltration are frequently noted in patients with alcoholic liver disease. However, the relationship between IL-8 and different stages of alcoholic liver disease is uncertain. The aim of this study is to determine if a correlation exists between circulating IL-8 levels and biochemical and histological parameters and survival in alcoholic liver disease.

METHODS

Serum levels of IL-8 were determined with an enzyme-linked immunosorbent assay in 166 subjects, consisting of 30 healthy controls, 26 patients with non-alcoholic fatty liver, 15 with alcoholic fatty liver, 32 with alcoholic hepatitis, 30 with alcoholic cirrhosis, 28 with chronic hepatitis B and 5 with chronic hepatitis C.

RESULTS

Serum IL-8 levels were markedly elevated in patients with alcoholic hepatitis (437 +/- 51 pg/ml) when compared with all other groups (p < 0.05). Levels of IL-8 in patients with alcoholic fatty liver, alcoholic cirrhosis and viral hepatitis were higher than those in controls and in patients with non-alcoholic fatty liver. In addition, IL-8 levels were higher in patients who died (p = 0.007), and correlated with biochemical and histological parameters, and severity of liver injury: serum aspartate aminotransferase, alanine aminotransferase, total bilirubin, prothrombin time, indocyanine green retention ratio, tumor necrosis factor-alpha and peripheral neutrophil count in patients with alcoholic hepatitis. After a 2-year follow up, patients with IL-8 above 479 pg/ml had a higher mortality rate in the alcoholic hepatitis group (p = 0.033).

CONCLUSIONS

These findings suggest that IL-8 is activated in alcoholic liver disease, especially in alcoholic hepatitis, and is closely correlated with liver injury. IL-8 levels can reflect the stage and severity of alcoholic liver disease, and may serve as a predictor of survival in patients with alcoholic hepatitis.

Measurements of heart rate variability in patients with unexplained syncope

BACKGROUND

Syncope is a common clinical issue with complex and heterogenous etiologies. Research has shown a large proportion of syncope remained unexplained, even after serial investigations. Head-up tilt test with or without isoproterenol infusion could elicit a recurrence in most patients with unexplained syncope. Therefore, autonomically neural-mediated bradycardia and hypotension have been cited as the mainstays of the mechanism. Since the autonomic function can be reflected by heart rate rariability, this study proposed to determine 24-hour heart rate variability in patients with unexplained syncope.

METHODS

Fifteen patients, 14 males and 1 female, who were defined as showing symptoms of unexplained syncope, were the subjects of this study. Their ages ranged from 38 years to 79 years. Seventeen healthy volunteers matching in age and sex served as the control group. For each patient and volunteer, 24-hour ambulatory electrocardiographic monitoring was done. Heart rate variability was defined as SDNN index, SDNN, SDANN, rMSSD, and pNN50 in time domain measures; and low, high, and total frequency in frequency domain measures.

RESULTS

There was a significantly lower value at low frequency, high frequency, total frequency, rMSSD, and pNN50 in the syncope group than in the control group (p < 0.05). There was no significant difference in SDNN, SDNN index, SDANN and LF/HF ratio between these two groups.

CONCLUSIONS

Patients with unexplained syncope had autonomic withdrawal; this was the case either in both sympathetic and parasympathetic components without changing the sympatho-vagal balance, or in purely parasympathetic component.

Short-course doxycycline treatment versus conventional tetracycline therapy for scrub typhus: a multicenter randomized trial

To assess the clinical efficacy of short-course doxycycline in the treatment of scrub typhus, we compared conventional 7-day tetracycline therapy with 3-day doxycycline therapy in 116 patients. Patients were randomized to receive either tetracycline (500 mg four times daily; n = 50) or doxycycline (100 mg twice daily; n = 66) and were followed for 4 weeks after the completion of treatment. The cure rate was 100% in the tetracycline group and 93.9% in the doxycycline group (P > .05). The two groups did not differ significantly in terms of the interval required for defervescence or for the alleviation of symptoms. There were no relapses in either group. These data suggest that 3-day doxycycline therapy is as effective as conventional 7-day tetracycline therapy for the cure of scrub typhus and the prevention of relapses.

Does coronary artery disease with stressed myocardial ischemia alter heart rate variability?

BACKGROUND

Research has shown that decreased heart rate variability (HRV) is independently associated with increased mortality after acute myocardial infarction. However, the relationship between HRV and myocardial ischemia still remains controversial. The purposes of this study were (1) to determine the relationship between HRV and atherosclerosis of the coronary artery; and (2) to determine the relationship between HRV and the extent of coronary stenosis in patients with stressed myocardial ischemia.

METHODS

Forty-six patients, 41 males and 5 females, were included in this study. Ages ranged from 50 years to 79 years. Seventeen volunteers served as the control group, which was comprised of 15 males and 2 females of ages ranging from 40 years to 74 years. For each patient a left ventriculogram and a coronary angiogram were performed. According to their coronary angiograms, patients were divided into normal coronary artery group, atherosclerotic coronary artery group and significant coronary artery disease group. An ambulatory EKG was performed on each patient and volunteer. Heart rate variability was defined as SDNN, SDANN, rMSSD, and pNN50 in time domain measures; and low and high frequency in frequency domain measures.

RESULTS

There were no significant differences in all variables of heart rate variability between the atherosclerotic coronary artery group and normal coronary artery group. In addition, there were no significant differences in all variables between the significant coronary artery disease group and the control group or between the significant coronary artery disease group and the normal coronary artery group.

CONCLUSIONS

These studies have shown that atherosclerotic or significant coronary artery disease with stressed myocardial ischemia does not impair 24-hour heart rate variability.

Treatment of porto-systemic encephalopathy with lactitol verus lactulose: a randomized controlled study

BACKGROUND

Lactitol (beta-galactosido-sorbitol), a novel disaccharide analogue of lactulose, has been suggested as an alternative to lactulose in the treatment of portosystemic encephalopathy (PSE) in Western country. In order to assess its therapeutic effect and adverse reaction in PSE in the Chinese, we conducted this study.

METHODS

Forty-one patients with PSE were enrolled in this study. Patients were randomly divided into 2 groups to receive lactitol (n = 21) or lactulose (n = 20) for 5 days. The doses of both drugs were adjusted to keep daily bowel movement of 2 to 3 times. The PSE index (mental state, EEG, asterixis, number connection test [NCT], and ammonia) was evaluated in each patient before and after treatment. Daily doses of lactitol and lactulose, stool frequency, and side effect were recorded.

RESULTS

The mean dose of lactitol used was 66.3 +/- 36.4 gm and that of lactulose was 56.9 +/- 32.1 ml of lactulose. The majority of patients (37/41) gained clear consciousness after 5 days' treatment. In the lactitol group, blood ammonia, EEG, NCT, asterixis, mental status and PSE index before treatment were 208 +/- 62 micrograms/ml, 2.9 +/- 0.8, 4.0 +/- 0.0, 2.7 +/- 1.5, 2.9 +/- 0.7 and 77.1 +/- 10.5, respectively. All parameters decreased significantly after 5 days' treatment (119 +/- 50 micrograms/ml, 1.1 +/- 1.0, 2.9 +/- 1.2, 1.7 +/- 1.1, 0.7 +/- 0.7, and 34.4 +/- 16.0, p < 0.05). The lactulose group had the similar results. However, the improvement of PSE index after therapy in the lactitol group was significantly higher than that in the lactulose group (42.7 +/- 19.3 vs 31.1 +/- 13.7, p < 0.05). In addition, more patients in the lactitol group than in the lactulose group (67% vs 20%, p = 0.003) favored the taste of their assigned drugs. No patient who received lactitol experienced any side effects; however, six patients treated with lactulose complained of meteorism and flatulence, and four complained of nausea.

CONCLUSIONS

Both lactitol and lactulose are effective in the treatment of PSE, though the effect of lactitol seems slightly superior to that of lactulose in our study. Lactitol is more acceptable to our patients due to better palatability and less side effects. Lactitol is another good alternative in the treatment of PSE.

Traumatic dislocations of the distal carpal row

13 patients who sustained high-energy crush or blast injury of the carpal bones were reviewed after a mean follow-up period of 30 months. These complex injuries resulted in unusual disruptions of the distal carpal row and adjacent metacarpals. Frequent involvement of the carpometacarpal (CM) joints and violation of the proximal carpal row were also demonstrated. Nine were open injuries, with the majority accompanied by significant soft tissue damage. Treatment included either closed reduction or open reduction and Kirschner wire fixation, and soft tissue procedures as indicated. In this series, the majority of the open injuries gave unfavourable functional results despite adequate carpal alignment. Several cases had disastrous outcomes related to associated vascular injuries. Closed injuries, on the contrary, followed a relatively benign course. Nevertheless, decreased grip strength persisted in both groups for a long time. Patients with such a complex carpal injury should expect a less favourable prognosis due to the severe nature of the trauma.

Dupuytren's contracture: report of a Taiwanese case

This case of Dupuytren's contracture was seen in a 65-year-old Taiwanese male farmer patient. The patient complained of a progressive inability to fully extend the ring and middle fingers of his dominant hand over the last three years. Clinically, a longitudinal cord-like mass surrounded the distal palmar crease of the hand and digital flexion contraction of the ring finger was more affected than the middle finger. Histopathologically, the excised tissue was of a mixed, moderate and scantily cellular type. After surgical treatment by limited fasciectomy, the patient's hand recovered fully. No recurrent contracture was noted after three years of follow-up.

Detection of the H1-j strain of Salmonella typhi among Korean isolates by the polymerase chain reaction

Salmonella typhi, the etiologic agent of typhoid fever, typically has only a phase-1 flagellar antigen, H1-d (fliC). While most strains of S. typhi have H1-d antigen, 10-20% of Indonesian isolates have been reported to possess H1-j antigen instead. To investigate the presence H1-j strains of S. typhi isolates in Korea, where typhoid fever is still a common infectious problem, we used the polymerase chain reaction (PCR) with a pair of oligonucleotides primers that specifically amplified the flagellin gene of S. typhi. Of 375 isolates of S. typhi tested, only one was shown to possess the H1-j antigen, which was shown by the presence of a 1,269-basepair fragment on agarose gel electrophoresis after the PCR. The isolate with the H1-j antigen was cultured from a Korean-Indonesian man who was already symptomatic in Indonesia and was thought to be an Indonesian strain. Because 375 strains tested in this study were collected from cases with typhoid fever in different regions of Korea during the period from 1986 to 1991, it could be concluded that the mutation rate to j antigen is negligible among S. typhi endemic in Korea.

Carpal bone dislocations: an analysis of twenty cases with relative emphasis on the role of crushing mechanisms

Twenty cases of carpal bone dislocation were encountered during a 7-year period, with an average of 27 months of follow-up. There were ten types of dislocation in this series; the most common type was transscaphoid perilunate dislocation which was seen in nine cases. In addition, there were two scaphoid subluxations; one volar lunate dislocation; one dorsal perilunate dislocation; one scaphoid perilunate dislocation; one hamate and pisiform dislocation; one transhamate pisiform dislocation; one trapezoid dislocation with dislocation of carpometacarpal joints two to five; one dislocation of the trapezium, trapezoid, and carpometacarpal joints two to four; and two trapezium periscapholunate dislocations. Methods of treatment included open reduction, closed reduction, proximal row carpectomy, total wrist arthrodesis, and excision of the lunate. In this series, the patterns of dislocation were different for crushing injuries and dorsiflexion injuries. The clinical results associated with the soft-tissue injuries of the ipsilateral hand were mostly caused by crushing forces. Although carpal instabilities were noted, there was no significant correlation between the clinical and roentgenographic results in some of our cases. Best results invariably relied on a stable anatomic reduction and an adequate period of immobilization. Poor results were demonstrated in the cases with incomplete initial reduction, secondary degenerative arthrosis, or nonunion.

Detection of Salmonella typhi in the blood of patients with typhoid fever by polymerase chain reaction

A polymerase chain reaction (PCR)-based test was developed for the detection of Salmonella typhi in the blood specimens from patients with typhoid fever. Two pairs of oligonucleotide primers were designed to amplify a 343-bp fragment of the flagellin gene of S. typhi. Amplified products were analyzed by agarose gel electrophoresis and Southern blot hybridization by using a 32P-labeled 40-base probe internal to the amplified DNA. The nested PCR with two pairs of primers could detect 10 organisms of S. typhi as determined by serial dilutions of DNA from S. typhi. The peripheral mononuclear cells from 11 of 12 patients with typhoid fever confirmed by blood culture were positive for DNA fragment of the flagellin gene of S. typhi, whereas 10 blood specimens of patients with other febrile diseases were negative. With the nested PCR, S. typhi DNAs were detected from blood specimens of four patients with suspected typhoid fever on the basis of clinical features but with negative cultures. We suggest that the PCR technique could be used as a novel diagnostic method of typhoid fever, particularly in culture-negative cases.

Prevalence of hepatitis C virus antibody among Korean adults

To estimate the prevalence of hepatitis C virus (HCV) infection among Korean adults and to present the putative route of HCV transmission among them, serum samples from 4917 adults older than 20 years of age were tested for antibody to HCV (anti-HCV), and histories of blood transfusion and other pertinent information were obtained by self-administered questionnaires. The overall prevalence of anti-HCV was 1.7%; prevalence was 1.4% in subjects with normal levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), 3.3% in those with slightly elevated and 5.9% in those with markedly elevated levels of the enzymes. The prevalence of anti-HCV increased with increasing age (P < 0.01), but was not associated with blood transfusion. The present study suggests that the prevalence of HCV infection was 1.4% and that the major routes of HCV transmission may be other than blood transfusion in healthy Korean adults.

Carpal bone dislocations: review of 20 cases

Twenty cases of carpal bone dislocation were encountered during a 7-year period, with an average of 27 months of follow-up. There were 10 types of dislocation in this series, the most common type was transscaphoid perilunate dislocation seen in 9 cases. In addition, there were 2 scaphoid subluxations, 1 volar lunate dislocation, 1 dorsal perilunate dislocation, 1 scaphoid perilunate dislocation, 1 hamate and pisiform dislocation, 1 transhamate pisiform dislocation, 1 trapezoid and 2-5 carpometacarpal joint dislocation, 1 trapezium, trapezoid and 2-4 carpometacarpal joint dislocation, and 2 trapezium periscapholunate dislocations. Methods of treatment included open reduction, closed reduction, proximal row carpectomy, total wrist arthrodesis, and excision of the lunate. In this series, the patterns of dislocation were different for crushing injuries and dorsiflexion injuries. The clinical results associated with the soft tissue injuries of the ipsilateral hand were mostly caused by crushing forces. Although carpal instabilities were noted, there was no significant correlation between the clinical and radiographic results in some of our cases. Best results invariably relied on a stable anatomic reduction and an adequate period of immobilization. Poor results were demonstrated in those cases with incomplete initial reduction, secondary degenerative arthrosis, or nonunion.

Risk factors for Escherichia coli O157:H7 infection in an urban community

Outbreaks of Escherichia coli O157:H7 have been attributed to meat or meat products, particularly ground meat, and to unpasteurized dairy products. However, the risk factors for sporadic cases have not been clearly delineated. Study data were collected by using a self-administered dietary and historical questionnaire on all patients whose history included bloody diarrhea and who attended one of the participating emergency departments. Designation as "case" or "control" occurred after stool culture results were known, eliminating the possibility for recall bias common to this type of study. Cases (E. coli O157:H7-positive) were further matched with one diarrheal and one healthy community control, and more detailed information on food preparation practices and other data were then taken. Of 266 presentations of bloody diarrhea, 103 (38.7%) were due to E. coli O157:H7. Unmatched analyses with bloody diarrheal controls revealed a seemingly lower risk for E. coli O157:H7 infection in fast food restaurant patrons. No increased risk could be detected for ground meat consumption despite adequate study power, although an association between ingestion of undercooked meat and infection (odds ratio = 3.5, P less than .05) was found when community controls were used. Proper food cooking (and handling) rather than the avoidance of particular food products is the preventive measure of choice.

In situ enzyme immunoassay for antiviral susceptibility testing of respiratory syncytial virus

An enzyme immunoassay (EIA), performed directly on fixed infected monolayers of HEp-2 cells in microtiter plates, was compared with the conventional plaque reduction assay (PRA) method for the determination of antiviral activity of ribavirin against respiratory syncytial virus. A 50% reduction in virus replication was observed at 3.4 and 5.9 mg/L of the drug by EIA and PRA, respectively. EIA is simple to perform and reproducible and has objective end points. Moreover, EIA has advantages over PRA in that results are available sooner and a much wider range of inoculum size can be used without affecting susceptibility data. EIA is suitable for the rapid susceptibility and accurate testing of a large number of clinical isolates.

Colonic function in acute Yersinia enterocolitica infection in rabbits

The impact of acute Yersinia enterocolitica infection on colonic fluid and electrolyte absorption was studied. New Zealand White rabbits (500-600 g), were infected with Yersinia enterocolitica and compared to unmanipulated controls and pair-fed controls. Water and electrolyte transport were measured in proximal and distal colon by an in vivo single pass perfusion technique and in proximal colon in vitro under short-circuited conditions in Ussing chambers. Infection resulted in severe histologic damage in proximal colon but only mild alterations in distal colon. Pair-fed controls demonstrated decreased absorption in vivo in both proximal and distal colon and Na+ and Cl- secretion in vitro in proximal colon compared to unmanipulated controls. In contrast infection did not alter water and electrolyte absorption in vivo compared to unmanipulated controls despite evidence of net secretion of Na+ and Cl- in vitro. These results indicate that Yersinia enterocolitica infection of the colon does not contribute to fluid and electrolyte losses despite mucosal damage, but rather there appears to be a degree of compensatory colonic salvage.

Rotavirus gastroenteritis

Rotavirus gastroenteritis is a leading cause of morbidity and mortality, especially in developing countries. Dehydration, which is often isotonic, occurs in 40 to 80% of patients. Rehydration and maintenance of proper fluid and electrolyte balance remains the mainstay of treatment. In recent years, development of efficient diagnostic methods has led to better understanding of the morphology of the virus, the epidemiology and natural history, as well as the importance of rotavirus disease. Rapid progress in the development and improvement of rotavirus vaccines has also been made. Among the vaccine candidates currently available, both the bovine rotavirus strain RIT 4237 and the rhesus rotavirus strain MMU 18006 have undergone extensive clinical trials and both have shown promising results.

Effect of acute Yersinia enterocolitica infection on in vivo and in vitro small intestinal solute and fluid absorption in the rabbit

The impact of acute Yersinia enterocolitica infection on jejunal and ileal solute and water transport was examined. New Zealand White rabbits (500-600 g) were infected with Y. enterocolitica and compared with unmanipulated controls and pair-fed controls. Transport studies were performed 6 days after infection on jejunum and ileum by an in vivo single-pass perfusion technique and in vitro under short-circuited conditions in Ussing chambers. When studied in vivo, Y. enterocolitica infection resulted in decreased water and electrolyte absorption in the jejunum under basal conditions and in both jejunum and ileum in the presence of glucose. Glucose absorption was also decreased in jejunum and ileum. When studied in vitro, net basal Na+ and Cl- transport was not altered in jejunal or ileal epithelium from infected animals. Glucose-stimulated Na+ absorption was decreased in ileal epithelium, and absorption of 3-O-methyl-D-glucose was decreased in both jejunum and ileum. Secretory capacity of Cl-, as assessed by isobutylmethyl xanthine stimulation, was unimpaired in both jejunum and ileum. Decreased food intake alone, in the pair-fed animals, had little effect on intestinal transport. The results indicate that malabsorption, rather than active intestinal secretion, is the major small intestinal transport defect in acute Y. enterocolitica infection. Furthermore, the abnormalities can be directly attributed to injury induced by the organism itself, rather than malnutrition.

Invasiveness of Yersinia enterocolitica lacking the virulence plasmid: an in-vivo study

Rabbits were given, by the intra-gastric route, two isogenic strains of Yersinia enterocolitica that differed only in the presence or absence of the virulence plasmid. Clinical illness and characteristic morphological lesions of Y. enterocolitica infection were seen only in rabbits infected with the plasmid-bearing strain (MCH700S). Although rabbits infected with a strain lacking the plasmid (MCH700L) remained healthy, mild histological changes in the small intestine, consisting of epithelial-cell damage, dilatation of lymphatics and a slight increase in neutrophil polymorphonuclear leukocytes in lamina propria, were seen in the first 12 h after inoculation. Bacteria, which were identified as Y. enterocolitica by indirect fluorescent antibody staining, were seen in dilated lymphatics. These early lesions tended to abate quickly and were no longer detectable at 24 h. Strain MCH700L was recovered from the mesenteric lymph nodes in increasing numbers until 24 h after inoculation; the number then began to decrease rapidly. In contrast, the early lesions in rabbits given strain MCH700S progressed to micro-abscesses, focal destruction of villi, and ulcerations beginning 24 h after inoculation; the number of bacteria recovered from the lymph nodes continued to increase beyond 24 h after inoculation. Bacteria were also recovered from the liver and spleen. These results suggest that both plasmid-bearing and non-bearing strains of Y. enterocolitica are capable of penetrating the intestinal mucosa. However, the virulence plasmid is required for invading bacteria to proliferate in the host tissue and to establish infection.

Selective and differential medium for recovery of Pseudomonas cepacia from the respiratory tracts of patients with cystic fibrosis

A selective and differential medium, OFPBL (oxidation-fermentation base supplemented with agar, lactose, and two antimicrobial agents), for the isolation of Pseudomonas cepacia from respiratory specimens of patients with cystic fibrosis was developed and tested. Among 725 specimens submitted from seven centers over a 4- to 6-month period, 58 (8%) yielded P. cepacia on OFPBL; only 19 of these were recovered on MacConkey or sheep blood agar (P less than 0.001). No isolate was recovered on MacConkey or sheep blood agar alone. Ranges of recovery rates among centers were 0 to 15% on OFPBL and 0 to 10% on MacConkey or sheep blood agar. Ninety percent of P. cepacia isolates were detected on OFPBL in less than or equal to 3 days. Other nonfermenters and yeasts isolated on OFPBL were distinguished from P. cepacia by failure to acidify the medium. The new medium was clearly superior to MacConkey and sheep blood agars for the isolation of P. cepacia from the respiratory secretions of patients with cystic fibrosis.

The histopathology of rectosigmoid biopsies from adults with bloody diarrhea due to verotoxin-producing Escherichia coli

The histopathology of rectosigmoid biopsies from 20 patients with bloody diarrhea resulting from verotoxin-producing Escherichia coli infection is reported. The biopsies displayed a range of appearances, from normal to mild, nonspecific inflammation to acute infectious-type colitis. Surface-adherent or invasive bacteria were not identified. The morphologic features of infectious colitis and the absence of bacteria suggest that verotoxin may be responsible for the pathologic changes.

Plasmid-mediated resistance to phagocytosis in Yersinia enterocolitica

Results of our previous studies have shown that the chemiluminescence response of human neutrophils (polymorphonuclear leukocytes [PMNs]) is inhibited by plasmid-mediated cell surface components from Yersinia enterocolitica. In this study we examined the susceptibility to phagocytosis of Y. enterocolitica cells with or without plasmid-mediated surface structure and the effect of isolated outer membrane fragments on phagocytosis of Escherichia coli by PMNs in vitro. Y. enterocolitica cells with expressed plasmid-mediated surface structure were much less sensitive to ingestion by PMNs than those without it, and the resistance to phagocytosis was readily eliminated in a dose-dependent fashion by pronase treatment of whole cells, which was shown to remove plasmid-encoded outer membrane proteins. Ingestion and intracellular killing of E. coli were inhibited significantly in the presence of isolated outer membrane fragments derived from plasmid-bearing Y. enterocolitica cells. To assess the interaction of Y. enterocolitica with phagocytic cells in vivo, two isogenic strains of Y. enterocolitica, differing only in the presence or absence of the virulence plasmid, were inoculated intradermally into the backs of rabbits; and tissue sections obtained at 12 h postinoculation were examined by light and electron microscopy. The plasmidless strain was found almost entirely in PMNs or mononuclear cells. In contrast, the plasmid-bearing strain was found to be surrounded by, or interspersed with, PMNs and mononuclear cells; but most bacteria were extracellular, with little evidence of phagocytosis. These results suggest that plasmid-mediated cell surface components of Y. enterocolitica act as antiphagocytic factors, thus facilitating the survival and proliferation of the organism in the host tissue.

Sepsis and cholestasis: the in vitro effects of bacterial products on 14C-taurocholate uptake by isolated rat hepatocytes

Bacterial endotoxins are known to be an important cause of cholestasis, yet not all organisms that cause cholestasis produce endotoxins. In order to determine whether bacterial products other than endotoxins may be involved in the cholestasis process, 14C-taurocholate (TC) uptake by isolated rat hepatocytes was measured in the presence of mid-log, stationary and mid-death phase bacterial broth supernatants from eight common bacterial pathogens. The results were then correlated with a quantitative assessment of endotoxin production by each organism. Supernatants from Haemophilus influenzae, Pseudomonas aeruginosa and Klebsiella pneumonia demonstrated a striking inhibitory effect on bile salt uptake (77.2 +/- 6.7, 46.9 +/- 6.5 and 32.9 +/- 7.1% maximum inhibition of 14C-TC uptake, respectively) when compared to sterile broth controls. Streptococcus faecalis (Enterococcus), Escherichia coli, Staphylococcus aureus and Bacteroides fragilis products, on the other hand, had relatively minor effects (12.3 +/- 5.2, 12.0 +/- 7.5, 8.4 +/- 6.7 and less than 5.0% inhibition respectively), while those from Proteus mirabilis had an intermediate effect (18.5 +/- 8.3% inhibition). Bile salt efflux rates (16.0 +/- 2.7 and 25.1 +/- 4.2 nmol/min/10(6) hepatocytes, mean +/- SEM) were similar in bacteria demonstrating marked uptake inhibition (Haemophilus influenzae, Pseudomonas aeruginosa) when compared to those with only minor inhibitory effects (Staphylococcus aureus, Bacteroides fragilis) (14.3 +/- 1.1 and 18.4 +/- 2.6 nmol/min/10(6) hepatocytes, respectively, p greater than 0.05). 14C-TC uptake inhibition did not correlate with the amount of endotoxin produced by each organism (r = 0.251). The results of this study indicate that bacteria produce a factor other than endotoxin that significantly inhibits bile salt uptake by isolated rat hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental infection of infant rabbits with verotoxin-producing Escherichia coli

To study the pathogenesis of diarrheal disease due to verotoxin (VT)-producing Escherichia coli, 3-day-old rabbits were inoculated intragastrically with live E. coli O157:H7 (high VT producer), E. coli O113:K75:H21 (low VT producer), or O157:H45 (VT negative) and were examined for clinical symptoms, bacterial colonization, presence of detectable free VT in the intestines, and histological changes. Diarrhea developed consistently with 10(8) bacteria of E. coli O157:H7 but was observed only infrequently with even a higher dose of E. coli O113:K75:H21. VT-negative strains failed to cause diarrhea under the same experimental conditions. E. coli O157:H7 was recovered from the colon of infected animals in a significantly higher concentration than from the small intestine, and the clinical symptoms correlated with the presence of detectable free VT in the colon. Histological changes were seen mainly in the mid- and distal colon; these changes were characterized by a vast increase in apoptosis in the surface epithelium, increased mitotic activity in the crypts, mucin depletion, and a mild to moderate infiltration of neutrophils in the lamina propria and epithelium. Multiple foci of attached bacteria were seen on the surface epithelium of the gut-associated lymphoid tissue, cecum, and colon. Bacteria were never seen in epithelial cells or the lamina propria. These mucosal abnormalities as well as clinical symptoms were reproduced in infant rabbits by the intragastric administration of VT alone. These results are consistent with the hypothesis that VT plays a major role in the pathogenesis of diarrhea caused by E. coli O157:H7 and other VT-producing E. coli.

Rapid diagnosis of rotavirus gastroenteritis by a commercial latex agglutination test

The Rotalex test, a commercial latex agglutination test for rotavirus, was compared with direct electron microscopy (EM) and the Rotazyme test I, a commercial enzyme immunoassay, for detection of rotavirus in stools of children and neonates. For initial stool specimens from 265 children (less than 3 years old) with diarrhea, the Rotalex test had a sensitivity of 81.7% and specificity of 99.5% compared with EM results. Positive and negative predictive values were 98 and 94.9%, respectively. The Rotalex test was slightly more sensitive and specific than the Rotazyme test. When daily stool specimens from patients with rotavirus gastroenteritis were examined, the sensitivity of the Rotalex test varied depending on the time of stool collection relative to the onset of symptoms. Sensitivity was 100 (20/20), 96 (23/24), and 54% (7/13) during 1 to 4, 5 to 7, and 8 to 18 days, respectively, after the onset of symptoms. The sensitivity of the Rotazyme test varied similarly with days from onset. We also examined 214 EM-negative stool specimens from asymptomatic newborns. False positivity by the Rotalex test was only 3.3% (7/214) compared with 4.2% (9/215) for the Rotazyme test. The Rotalex test was as sensitive and specific as EM for detection of rotavirus during the acute stage of illness and much faster and cheaper than EM or the Rotazyme test. The test appears to be suitable for routine use in small hospitals, emergency wards, or even the physician's office for rapid diagnosis of rotavirus gastroenteritis.

Inhibition of human neutrophil chemiluminescence by plasmid-mediated outer membrane proteins of Yersinia enterocolitica

Recent studies have shown that the cell surface properties of Yersinia enterocolitica are altered by the presence of the virulence plasmid, which mediates temperature-inducible outer membrane proteins (OMP). We investigated the interaction of Y. enterocolitica with human polymorphonuclear leukocytes by monitoring luminol-enhanced chemiluminescence (CL) responses. A plasmid-bearing strain grown at 37 degrees C induced four- to sixfold less CL than did the same strain grown at 25 degrees C or a plasmidless, isogenic strain grown at either temperature. Inhibition of CL responses by whole cells was related to plasmid-mediated expression of OMP. The OMP alone could inhibit the CL response of polymorphonuclear leukocytes stimulated by either opsonized zymosan or whole cells of Y. enterocolitica. Pronase treatment of whole cells, which removed the plasmid-mediated OMP, resulted in partial but significant elimination of CL inhibition by whole cells and by OMP derived from them. Incubation with Y. enterocolitica for 60 min did not affect the viability of polymorphonuclear leukocytes. Our results suggest that the interaction of Y. enterocolitica with human polymorphonuclear leukocytes is directly affected by the plasmid-mediated OMP.