Rapid cycle deliberate practice improves resident performance during ELBW resuscitation.

BACKGROUND: Neonatal Resuscitation is a required competency for pediatric and family medicine residency programs. Simulation-based training can be used to supplement clinical experience. Rapid Cycle Deliberate Practice (RCDP) has been validated as an effective education model and is gaining favor over traditional simulation models. The aim of this study was to evaluate the effectiveness of a simulation-based rapid cycle deliberate practice (RCDP) intervention on extremely low birth weight (ELBW) infant resuscitation. METHODS: Pediatric and family practice residents were randomized to control and intervention groups and participated in pre- and post-NICU rotation simulations. The intervention group received one RCDP session. Simulations were scored by blinded video review for overall performance, positive pressure ventilation (PPV), endotracheal intubation and behavioral skills. Surveys assessed confidence in ELBW resuscitation. RESULTS: Forty-one residents participated in the study. The RCDP group performed better than the control group at post-rotation evaluation for overall resuscitation performance (65% vs 87%, p = 0.004), administering PPV (63% vs 88%, p = 0.006), and validated behavior skills (1.4 vs 2.0, p = 0.019). Residents in the RCDP group reported greater confidence with ELBW resuscitation. CONCLUSION: An educational intervention using RCDP was associated with improved resident performance and confidence in ELBW resuscitation. RCDP should be considered for NRP and ELBW resuscitation training.

Off-critical wetting layer divergence at the liquid/vapor interface of binary liquid mixtures.

Surface wetting phenomena impact chemistry, physics, biology, and engineering. The wetting behaviors of partially miscible binary liquid systems are especially complex. Here, we report evidence of universal behavior in the divergence of wetting layer growth at liquid-vapor interfaces of the cyclohexane + aniline, hexane + o-toluidine, and methanol + carbon disulfide systems. Layer growth on the micron scale was followed using visible light scattering from stirred samples. The layer thicknesses were found to diverge with decreasing temperature when coexistence was approached from the one-phase region, but only for solutions richer in the higher density/higher surface tension component. The onset of divergence was <1 K above the bulk coexistence temperature; nearer the critical composition, the onset temperature was the critical temperature itself. All three systems showed identical divergent wetting properties after variable normalization. In contrast, no divergent wetting layer formation was seen in the benzene + 1,2-propanediol or water + phenol systems. The mathematical sign of the Hamaker constant correlates with the contrasting behaviors. Collectively, these results have implications for theoretical descriptions of adsorption layer growth and crossover behavior, for measurements of complete wetting temperatures, and for practical applications.

Analgesic benefits of the quadratus lumborum block in total hip arthroplasty: a systematic review and meta-analysis.

The quadratus lumborum block (QLB) is reported to reduce pain and improve function following total hip arthroplasty; however, randomised controlled trials evaluating the benefits of adding this block to general or spinal anaesthesia in this population are conflicting. We performed a systematic review seeking randomised controlled trials investigating QLB benefits for total hip arthroplasty, stratifying comparisons regarding the addition of QLB to either general or spinal anaesthesia. The primary outcome was 24-h area under the curve (AUC) pain score. Pain scores were interpreted in the context of a population-specific minimal clinically important difference of 1.86 cm on a 10-cm visual analogue scale, or an AUC pain score of 5.58 cm.h. Secondary outcomes included analgesic consumption, functional recovery and opioid-related side-effects. In all, 18 trials (1318 patients) were included. Adding QLB to general or spinal anaesthesia improved 24-h AUC rest pain scores by a mean difference (95%CI) of -3.56 cm.h (-6.70 to -0.42; p = 0.034) and - 4.19 cm.h (-7.20 to -1.18; p = 0.014), respectively. These improvements failed to reach the pre-determined minimal clinically important difference, as did the reduction in analgesic consumption. Quadratus lumborum block improved functional recovery for general, but not spinal, anaesthesia. Opioid-related side-effects were reduced with QLB regardless of anaesthetic modality. Low-to-moderate quality evidence suggests that the extent to which adding QLB to either general or spinal anaesthesia reduces postoperative pain and opioid consumption after total hip arthroplasty is statistically significant but may be clinically unimportant for most patients. However, adding QLB to general anaesthesia might enhance functional recovery. Taken together, our findings do not support the routine use of QLB as part of multimodal analgesic regimens for total hip arthroplasty.

Strong exciton-plasmon coupling in dye-doped film on a planar hyperbolic metamaterial.

We experimentally demonstrate the direct strong coupling between the S0→S1 absorption transition of rhodamine 6G (R6G) dye molecules and the surface plasmon polaritons of a hyperbolic metamaterial (HMM) substrate. The surface plasmon mode was excited by a guided mode of the R6G-doped polymer thin film on the HMM. The coupling strengths of the interactions between the surface plasmon and two molecular exciton modes are greater than the average linewidths of the individual modes indicating a strong coupling regime. This is the first, to the best of our knowledge, experimental demonstration of the direct strong coupling between the resonance mode supported by the HMM and the dye molecules on the HMM surface, not embedded in the HMM structure. The study may provide the foundation for the development of novel planar photonic or electronic devices.

Spaced learning versus massed learning in resuscitation - A systematic review.

AIM: Skill decay is a recognised problem in resuscitation training. Spaced learning has been proposed as an intervention to optimise resuscitation skill performance compared to traditional massed learning. A systematic review was performed to answer 'In learners taking resuscitation courses, does spaced learning compared to massed learning improve educational outcomes and clinical outcomes?' METHODS: This systematic review followed the PRISMA guidelines. We searched bibliographic databases (Embase, MEDLINE and the Cochrane Library (CENTRAL)) from inception to 2 December 2019. Randomised controlled trials and non-randomised studies were eligible for inclusion. Two reviewers independently scrutinized studies for relevance, extracted data and assessed quality of studies. Risk of bias of studies and quality of evidence were assessed using RoB, ROBINS-I tool and GRADEpro respectively. Educational outcomes studied were skill retention and performance 1 year after completion of training; skill performance between completion of training and 1 year; and knowledge at course conclusion. Clinical outcomes were skill performance at actual resuscitation, patient survival to discharge with favourable neurological outcome. This systematic review was registered in PROSPERO (CRD42019150358). RESULTS: From 2,042 references, we included data from 17 studies (13 randomised studies, 4 cohort studies) in courses with manikins and simulation in the narrative synthesis. Eight studies reported results from basic life support training (with or without automatic external defibrillator); three studies reported from paediatric life support training; five were in neonatal resuscitation and one study reported results from a bespoke emergency medicine course which included resuscitation teaching. Fifteen out of seventeen studies reported improved performance with the use of spaced learning. The overall certainty of evidence was rated as very low for all outcomes primarily due to a very serious risk of bias. Heterogeneity across studies precluded any meta-analyses. There was a lack of data on the effectiveness of spaced learning on skill acquisition compared to maintaining skill performance and/or preventing skill decay. There was also insufficient data to examine the effectiveness of spaced learning on laypeople compared to healthcare providers. CONCLUSIONS: Despite the very low certainty of evidence this systematic review suggests that spaced learning can improve skill performance at 1 year post course conclusion and skill performance between course conclusion and 1 year. There is a lack of data from this educational intervention on skill performance in clinical resuscitation and patient survival at discharge with favourable neurological outcomes.

Positive pressure ventilation coaching during neonatal bag-mask ventilation: A simulation-based pilot study.

BACKGROUND: Positive pressure ventilation (PPV) is the most important procedure during neonatal resuscitation. Providing effective PPV seems easy. However, performing the procedure correctly is extremely challenging. Airway obstruction and face mask large leaks are common. It is estimated that two-thirds of continued neonatal respiratory depression after the time of birth is caused by ineffective or improperly provided PPV. Finding methods to improve PPV performance are critically needed. Performance coaching is a simple and easy method of improving performing in procedural skills, and has been used previously to optimize compression technique. We performed the simulation-based pilot study to evaluate the impact of PPV coaching during neonatal bag-mask ventilation. METHODS: Randomized cross-over study of nurses performing PPV on a SMART Newborn Resuscitation Training System with, and without, coaching. The PPV coach provided real-time feedback on chest rise, mask hold, and ventilation rate. The SMART system captured data on peak inspiratory pressure (PIP), tidal volume (Vt), mask leak, and ventilation rate. Data were analyzed by a blinded reviewer. RESULTS: PPV coaching resulted in more appropriate PIPs (34 cmH2O, IQR 32-38 vs. 36 cmH2O, IQR 28-37; P < 0.001), lower Vt (4.7 ml/kg, IQR 4-8 vs. 5.5 ml/kg, IQR 4-13; P < 0.001), and less mask leak (39% leak, IQR 21-70 vs. 45%, IQR 22-98; P = 0.005). There was no difference in respiratory rate (P = 0.93). CONCLUSIONS: Coaching improved PPV performance in this simulation-based pilot study. Further research on PPV coaching during neonatal resuscitation is warranted.

Boot camps in neonatal-perinatal medicine fellowship programs: A national survey.

BACKGROUND: Simulation is widely used in graduate medical education. A prior survey showed that 80% of Neonatal-Perinatal Medicine (NPM) fellowship programs in the U.S. use simulation. There are multiple ways to provide simulation-based education. One such method is through intensive simulation-based education sessions held at the beginning of a training program, common called 'boot camps'. The aim of this study was to describe the use of simulation-based boot camps in NPM fellowship programs. METHODS: Survey study of Accreditation Council for Graduate Medical Education (ACGME) accredited NPM fellowships in the U.S. RESULTS: Fifty-nine of 98 programs (60%) responded. Thirty six (61%) participated in 1st year fellow boot camps, which focused on procedural skills and newborn resuscitation. Nearly half of programs participated in regional boot camps. Most boot camps were one or two days long. Eleven programs (19%) held 2nd or 3rd year fellow boot camps, which focused on advanced resuscitation and communication. Barriers included lack of faculty protected time (57%), funding (39%), and lack of faculty experience (31%). CONCLUSIONS: A majority of ACGME accredited NPM fellowships participate in 1st year fellows' boot camps. Many participate in regional boot camps. A few programs have 2nd or 3rd year fellow boot camps. Lack of time, funding, and faculty experience were common barriers.

Accuracy of the nasal-tragus length measurement for correct endotracheal tube placement in a cohort of neonatal resuscitation simulators.

OBJECTIVE: Nasal-tragus length (NTL) estimates of endotracheal tube (ETT) depth are replacing weight-based estimates for endotracheal tube depth in neonates requiring endotracheal intubation. Existing neonatal simulators were designed before interest in using the NTL, and may lack fidelity in this measurement. The objective of this study is to evaluate the accuracy of the adjusted NTL formula and the Neonatal Resuscitation Program (NRP) gestational age/weight-based ETT depth chart in predicting proper endotracheal tube insertion depth in a cohort of neonatal simulators. STUDY DESIGN: The NTL and appropriate intubation depth to the mid-trachea were measured for 11 commonly used neonatal intubation simulators. RESULTS: The NTL+1 cm formula incorrectly estimates the mid-tracheal depth in 82% of simulators, and the weight-based chart incorrectly estimates depth in 75% of test simulators. Only one simulator experienced a mainstem intubation with ETT insertion to the depth predicted by the NTL+1 cm formula. CONCLUSIONS: The majority of neonatal resuscitation simulations lacked physical fidelity with regard to mid-tracheal ETT insertion depth. The NRP gestational age/weight-based chart outperformed the NTL+1 cm formula but still resulted in endotracheal tube misplacement in the majority of neonatal simulators. The majority of simulators had adequate functional fidelity using either method for ETT depth estimation.

Improving neonatal intubation safety: A journey of a thousand miles.

Neonatal intubation is one of the most common procedures performed by neonatologists, however, the procedure is difficult and high risk. Neonates who endure the procedure often experience adverse events, including bradycardia and severe oxygen desaturations. Because of low first attempt success rates, neonates are often subjected to multiple intubation attempts before the endotracheal tube is successfully placed. These factors conspire to make intubation one of the most dangerous procedures in neonatal medicine. In this commentary we review key elements in the journey to improve neonatal intubation safety. We begin with a review of intubation success rates and complications. Then, we discuss the importance of intubation training. Next, we examine quality improvement efforts and patient safety research to improve neonatal intubation safety. Finally, we evaluate new tools which may improve success rates, and decrease complications during neonatal intubation.

Real vs simulated umbilical cords for emergency umbilical catheterization training: a randomized crossover study.

OBJECTIVE: To measure performance, fidelity and preference of two emergency umbilical vessel catheter (eUVC) simulation models. STUDY DESIGN: A randomized crossover trial of senior pediatric residents randomized to place an eUVC first using a real cord (RC) or simulated cord (SC), and then place an eUVC using the other model. The eUVC placement times were recorded and analyzed. Subjects rated physical and functional fidelity and preference for each model. RESULTS: The eUVC placement time (mean±s.d. s) was slower in RC vs SC (153 s ±71 vs 88 s ±35, P<0.001), however, there was no difference in eUVC placement time in the group that worked with SC first (115 s ±36 vs 97 s ±35, P=0.161). Physical and functional fidelity of RC were rated higher than SC (P<0.001), and RC were preferred. CONCLUSION: RC has higher physical and functional fidelity, and are preferred for training by pediatric residents, despite longer placement times.

Resuscitation practices for infants in the NICU, PICU and CICU: results of a national survey.

OBJECTIVE: Infants requiring resuscitation at birth are resuscitated using neonatal resuscitation guidelines. Sometime after birth, resuscitation practice must transition to pediatric guidelines. There is no evidence on when this transition should occur. The objective of this study was to describe infant resuscitation practices in Neonatal Intensive Care Units (NICUs), Pediatric Intensive Care Units (PICUs) and Cardiac Intensive Care Units (CICUs). STUDY DESIGN: An electronic survey was sent to medical directors of NICUs, PICUs and CICUs in the U.S. The survey examined resuscitation practices, and preference for use of neonatal or pediatric guidelines, for different postnatal ages, clinical scenarios and etiologies of arrest. RESULTS: A total of 152 responses were received, including 118 NICUs, 19 PICUs and 15 CICUs. The majority of NICU responders used greater than 28 days as the time to change from neonatal to pediatric guidelines. The majority of PICU and CICU transitioned to pediatric guidelines immediately after birth. Pediatric guidelines were preferred in the PICU and CICU regardless of the arrest etiology. NICU responders favored pediatric guidelines only if the arrest was cardiac. CONCLUSIONS: Our results suggest that infants are resuscitated using neonatal guidelines in the NICU and pediatric guidelines in the PICU and CICU, even if they are the same age and have the same etiology of arrest. There is no agreement on the time to change from neonatal to pediatric guidelines. Further research comparing the outcomes of infants resuscitated in these different units could inform future guideline refinement.

Post-event debriefings during neonatal care: why are we not doing them, and how can we start?

Post-event debriefings are a foundational behavior of high performing teams. Despite the inherent value of post-event debriefings, the frequency with which they are used in neonatal care is extremely low. If post-event debriefings are so beneficial, why aren't they conducted more frequently? The reasons are many, but solutions are available. In this report, we provide practical advice on conducting post-event debriefing in neonatal care. In addition, we examine the perceived barriers to conducting post-event debriefings, and offer strategies to overcome them. Finally, we consider opportunities to foster a culture change within neonatal care which integrates debriefing as standard daily work. By establishing a safety culture in neonatal care that encourages and facilitates effective post-event debriefings, patient safety can be enhanced and clinical outcomes can be improved.

Neonatal-perinatal medicine fellow procedural experience and competency determination: results of a national survey.

OBJECTIVE: Ensuring that neonatal-perinatal medicine (NPM) fellows attain competency in performing neonatal procedures is a requirement of training-competent neonatologists. STUDY DESIGN: A survey of NPM fellows was performed to determine the procedural experience of current fellows, investigate techniques used to track procedural experience and examine the methods programs use to verify procedural competency. RESULTS: One hundred and sixty-three fellows in 57 accredited training programs responded to the survey. Reported number of procedures provide contemporary normative data on procedural experience during training. The majority of fellows reported using an online reporting system to track experience. The most common technique to verify procedural competency was supervised practice until an arbitrary number of procedures had been performed. CONCLUSIONS: NPM fellow procedural experience increases significantly for most, but not all, procedures duration training. We speculate that supplemental simulation training for rare neonatal procedures would help ensure the competency of graduating NPM fellows. Experience alone is insufficient to verify competency. Further work on the accurate tracking of experience and verification of procedural competency is needed.

Neonatal airway simulators, how good are they? A comparative study of physical and functional fidelity.

OBJECTIVE: Proficiency in airway management is critical for neonatal health-care professionals. Simulation is a proven method to improve airway management skills. Skills transfer from simulation to the real life requires simulators with appropriate physical and functional fidelity. STUDY DESIGN: A cohort of neonatal health-care professionals evaluated eight different neonatal airway simulators for physical and functional fidelity. RESULT: Twenty-seven subjects completed 151 simulator evaluations. Significant differences were found between the simulators evaluated (P<0.001). The manikins with the highest fidelity scores were the SimNewB, Newborn Anne and Premature Anne (Laerdal Medical). The task trainers with the highest fidelity scores were the Neonatal Intubation Trainer (Laerdal Medical) and the Newborn Airway Trainer (Syndaver Labs). CONCLUSION: Simulator fidelity is an important aspect of simulation training, but is rarely evaluated. The results of this study can aid in choosing the best simulators for training and research, and provide feedback to the industry to guide future simulator development.

Correlations between technical skills and behavioral skills in simulated neonatal resuscitations.

OBJECTIVE: Neonatal resuscitation requires both technical and behavioral skills. Key behavioral skills in neonatal resuscitation have been identified by the Neonatal Resuscitation Program. Correlations and interactions between technical skills and behavioral skills in neonatal resuscitation were investigated. STUDY DESIGN: Behavioral skills were evaluated via blinded video review of 45 simulated neonatal resuscitations using a validated assessment tool. These were statistically correlated with previously obtained technical skill performance data. RESULT: Technical skills and behavioral skills were strongly correlated (ρ=0.48; P=0.001). The strongest correlations were seen in distribution of workload (ρ=0.60; P=0.01), utilization of information (ρ=0.55; P=0.03) and utilization of resources (ρ=0.61; P=0.01). Teams with superior behavioral skills also demonstrated superior technical skills, and vice versa. CONCLUSION: Technical and behavioral skills were highly correlated during simulated neonatal resuscitations. Individual behavioral skill correlations are likely dependent on both intrinsic and extrinsic factors.

Term neonate with intracranial hemorrhage and hereditary hemorrhagic telangiectasia: a case report and review of the literature.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by mucocutaneous telangiectases and arteriovenous malformations (AVMs). The disease rarely presents in the neonatal period, primarily manifesting with epistaxis and gastrointestinal bleeding in adulthood. Occasionally, HHT can also present with symptoms related to AVMs in the cerebral, pulmonary or gastrointestinal vasculature. In prior reports, intracranial hemorrhage (ICH) secondary to cerebral AVM in neonates with HHT has been catastrophic and uniformly fatal. Here we report a case of a newborn with HHT and ICH from a suspected AVM who survived with aggressive medical management and surgical intervention, and provide a comprehensive review of the literature on ICH in neonates with HHT.

Immobilization of Russian VX skin depots by localized cooling: implications for decontamination and medical countermeasures.

The chemical weapon nerve agent known as Russian VX (VR) is a potent organophosphorus (OP) compound that is much less studied than its VX analogue with respect to toxicity, as well as to the effectiveness of several known countermeasures against it. An anaesthetized domestic swine model was utilized to assess several approaches in mitigating its toxicity, including the utility of cooling VR treated skin to increase the therapeutic window for treatment. The 6h LD50 for VR topically applied on the ear was 100 µg/kg. Treatment of VR exposed animals (5 × LD50) with pralidoxime (2PAM) very poorly regenerated inhibited blood cholinesterase activity, but was partially effective in preventing signs of OP poisoning and increasing survival. In contrast, treatment with the Hagedorn oxime HI-6 reactivated cholinesterase, eliminated all signs of poisoning and prevented death. Decontamination with the Reactive Skin Decontaminant Lotion (RSDL) 15 min after VR exposure was completely effective in preventing death. Cooling of the VR exposure sites for 2 or 6h prevented signs of OP poisoning and death during the cooling period. However, these animals died very quickly after the cessation of cooling, unless they were treated with oxime or decontaminated with RSDL. Blood analyses showed that cooling of agent exposure sites delayed the entry of VR into the bloodstream. Medical treatment with HI-6 and to a lesser extent 2PAM, or decontamination with RSDL are effective in protecting against the toxic effects of cutaneous exposure to VR. Immobilizing this agent (and related compounds) within the dermal reservoir by cooling the exposure sites, dramatically increases the therapeutic window in which these medical countermeasures are effective.

The therapeutic use of localized cooling in the treatment of VX poisoning.

The organophosphate (OP) nerve agent VX is a weaponized chemical warfare agent that has also been used by terrorists against civilians. This contact poison produces characteristic signs of OP poisoning, including miosis, salivation, mastication, dysrhythmias and respiratory distress prior to death. Although successful treatment of OP poisoning can be obtained through decontamination and/or oxime reactivation of agent-inhibited cholinesterase, medical countermeasures that increase the therapeutic window for these measures would be of benefit. An anaesthetized swine model was utilized to examine the effects of lethal VX exposure to the skin, followed by cooling the exposure site prior to decontamination or treatment. The cooling was simply accomplished by using crushed ice in grip-seal plastic bags applied to the exposure sites. Cooling of skin exposed to lethal doses of VX significantly increased the window of opportunity for successful decontamination using the Reactive Skin Decontaminant Lotion(®) (RSDL(®)) or treatment with the oxime antidotes HI-6 and 2PAM. Analyses of blood VX levels showed that cooling acted to slow or prevent the entry of VX into the bloodstream from the skin. If the exposure site is known, the simple and non-invasive application of cooling provides a safe means with which to dramatically increase the therapeutic window in which decontamination and/or antidote treatment against VX are life-saving.

Sonographic measurement of diaphragm movement in patients with tetraplegia.

STUDY DESIGN: This was an observational, descriptive case-series study. The magnitude and direction of diaphragm movement during tidal and maximal inspiratory breaths in tetraplegic subjects were measured using B-mode sonography on a single occasion. Data were tabulated for descriptive analysis. OBJECTIVE: There is a paucity of literature reporting dynamic movements of the paralyzed diaphragm. The aim of this pilot study was to investigate and record diaphragm movement in subjects with a cervical spinal cord injury (C1-C5), which had resulted in tetraplegia with partial or complete diaphragm paralysis. Subjects were patients of the Royal Adelaide Hospital in South Australia. RESULTS: Three subjects participated in the study. The magnitude of diaphragm movement was small in two subjects and approached normal in one subject. During tidal inspiratory and maximal inspiratory breaths, the diaphragm moved in a caudal direction in two subjects. In the other subject, the diaphragm moved in a cephalad direction during a maximal inspiratory breath. CONCLUSION: Imaging of diaphragm movement was well tolerated by three subjects with cervical spinal cord injury. The difference in magnitude of diaphragm movement was not fully explained by the level of injury and the American Spinal Injury Association classification.

Implications of pathogenesis by Erwinia amylovora on rosaceous stigmas to biological control of fire blight.

As a prerequisite to infection of flowers, Erwinia amylovora grows epiphytically on stigmas, which provide a conducive habitat for bacterial growth. Stigmas also support growth of several other bacterial genera, which allows for biological control of fire blight; although, in practice, it is very difficult to exclude E. amylovora completely from this habitat. We investigated the dynamics of growth suppression of E. amylovora by comparing the ability of virulent and avirulent strains of E. amylovora to compete with each other on stigmas of pear, apple, and blackberry, and to compete with a co-inoculated mixture of effective bacterial antagonists. When strains were inoculated individually, virulent E. amylovora strain Ea153N attained the highest population size on stigmas, with population sizes that were approximately double those of an avirulent hrpL mutant of Ea153 or the bacterial antagonists. In competition experiments, growth of the avirulent derivative was suppressed by the antagonist mixture to a greater extent than the virulent strain. Unexpectedly, the virulent strain enhanced the population size of the antagonist mixture. Similarly, a small dose of virulent Ea153N added to inoculum of an avirulent hrpL mutant of Ea153 significantly increased the population size of the avirulent strain. A pathogenesis-gene reporter strain, Ea153 dspE::gfp, was applied to flowers and a subset of the population expressed the green fluorescent protein while growing epiphytically on stigmas of apple. These results are consistent with the hypothesis that virulent E. amylovora modifies the epiphytic habitat presented by the stigma through a pathogenesis-related process, which increases host resources available to itself and, coincidentally, to nonpathogenic competitors. Over nine orchard trials, avirulent Ea153 hrpL significantly suppressed the incidence of fire blight four times compared with six for the antagonist mixture. The degree of biological control achievable with an avirulent strain of E. amylovora likely is limited by its inability to utilize the stigmatic habitat to the same degree as a virulent strain.