Waveguide-Integrated Colloidal Nanocrystal Supraparticle Lasers.

Supraparticle (SP) microlasers fabricated by the self-assembly of colloidal nanocrystals have great potential as coherent optical sources for integrated photonics. However, their deterministic placement for integration with other photonic elements remains an unsolved challenge. In this work, we demonstrate the manipulation and printing of individual SP microlasers, laying the foundation for their use in more complex photonic integrated circuits. We fabricate CdSxSe1-x/ZnS colloidal quantum dot (CQD) SPs with diameters from 4 to 20 µm and Q-factors of approximately 300 via an oil-in-water self-assembly process. Under a subnanosecond-pulse optical excitation at 532 nm, the laser threshold is reached at an average number of excitons per CQD of 2.6, with modes oscillating between 625 and 655 nm. Microtransfer printing is used to pick up individual CQD SPs from an initial substrate and move them to a different one without affecting their capability for lasing. As a proof of concept, a CQD SP is printed on the side of an SU-8 waveguide, and its modes are successfully coupled to the waveguide.

Core-Shell Nanorods as Ultraviolet Light-Emitting Diodes.

Existing barriers to efficient deep ultraviolet (UV) light-emitting diodes (LEDs) may be reduced or overcome by moving away from conventional planar growth and toward three-dimensional nanostructuring. Nanorods have the potential for enhanced doping, reduced dislocation densities, improved light extraction efficiency, and quantum wells free from the quantum-confined Stark effect. Here, we demonstrate a hybrid top-down/bottom-up approach to creating highly uniform AlGaN core-shell nanorods on sapphire repeatable on wafer scales. Our GaN-free design avoids self-absorption of the quantum well emission while preserving electrical functionality. The effective junctions formed by doping of both the n-type cores and p-type caps were studied using nanoprobing experiments, where we find low turn-on voltages, strongly rectifying behaviors and significant electron-beam-induced currents. Time-resolved cathodoluminescence measurements find short carrier liftetimes consistent with reduced polarization fields. Our results show nanostructuring to be a promising route to deep-UV-emitting LEDs, achievable using commercially compatible methods.

The association between chiropractic integration in an Ontario community health centre and continued prescription opioid use for chronic non-cancer spinal pain: a sequential explanatory mixed methods study.

BACKGROUND: Emerging evidence suggests that access to chiropractic care may reduce the likelihood of initiating an opioid prescription for spinal pain; however, the impact of chiropractic care for patients already prescribed opioids is uncertain. We undertook a sequential explanatory mixed methods study to evaluate the association between initiating chiropractic care and continued opioid use among adult patients attending an Ontario community health centre (CHC) and receiving opioid therapy for chronic non-cancer spinal pain. METHODS: We conducted a retrospective cohort study of 210 patient records between January 1, 2014 and December 31, 2020. We used generalized estimating equations, adjusted for patient demographics, co-morbidities, visit frequency, and calendar year, to evaluate the association between receipt versus non-receipt of chiropractic services and continued opioid use (e.g., unique opioid fills, number of refills, and dosages) up to one year following the index chiropractic visit. We also completed follow-up interviews with 14 patients and nine general practitioners from the CHC and integrated these data with our quantitative findings. RESULTS: Over 12-month follow-up, there were lower rates of opioid fills (incidence rate ratio [IRR] = 0.66; 95% confidence interval [CI], 0.52-0.83) and refills (IRR = 0.27; 95% CI, 0.17-0.42) among chiropractic recipients (n = 49) versus non-recipients (n = 161). Although patients who did and did not receive chiropractic care began the study with the same dose of opioids, recipients were less likely to be prescribed higher-dose opioids (i.e., ≥ 50 mg morphine equivalents daily) compared to non-recipients at three months (odds ratio [OR] = 0.14; 95% CI, 0.04-0.47), six months (OR = 0.14; 95% CI, 0.05-0.40), nine months (OR = 0.19; 95% CI, 0.07-0.57), and 12 months (OR = 0.22; 95% CI, 0.08-0.62). Interviews suggested that patient self-efficacy, limited effectiveness of opioids for chronic pain, stigma regarding use of opioids, and access to chiropractic treatment were important influencing factors. CONCLUSION: We found that continued prescription opioid use among patients with chronic non-cancer spinal pain who received chiropractic care was lower than in patients who did not receive chiropractic care. Four themes emerged in our qualitative interviews to help provide a richer understanding of this association. Randomized controlled trials are needed to establish the effect of chiropractic care on opioid use for chronic spinal pain.

Association of Chiropractic Care With Receiving an Opioid Prescription for Noncancer Spinal Pain Within a Canadian Community Health Center: A Mixed Methods Analysis.

OBJECTIVE: The purpose of this study was to examine the association between receipt of chiropractic services and initiating a prescription for opioids among adult patients with noncancer spinal pain in a Canadian community health center. METHODS: In this sequential explanatory mixed methods analysis, we conducted a retrospective study of 945 patient records (January 2014 to December 2020) and completed interviews with 14 patients and 9 general practitioners. We used Cox proportional hazards regression analyses, adjusted for patient demographics, comorbidities, visit frequency, and calendar year to evaluate the association between receipt of chiropractic care and time to first opioid prescription up to 1 year after presentation. Qualitative data were analyzed thematically and integrated with our quantitative findings. RESULTS: There were 24% of patients (227 of 945) with noncancer spinal pain who received a prescription for opioids. The risk of initiating a prescription for opioids at 1 year after presentation was 52% lower in chiropractic recipients vs nonrecipients (hazard ratio [HR], 0.48; 99% confidence interval [CI], 0.29-0.77) and 71% lower in patients who received chiropractic services within 30 days of their index visit (HR, 0.29; 99% CI, 0.13-0.68). Patients whose index visit date was in a more recent calendar year were also less likely to receive opioids (HR, 0.86; 99% CI, 0.76-0.97). Interviews suggested that self-efficacy, access to chiropractic services, opioid stigma, and treatment impact were influencing factors. CONCLUSION: Patients with noncancer spinal pain who received chiropractic care were less likely to obtain a prescription for opioids than patients who did not receive chiropractic care.

Novel custom made composite spacer for first-stage revision total hip replacement in the presence of extensive acetabular/femoral bone loss with abductor deficiency.

A two-stage revision total hip replacement (THR) remains the gold standard for treating chronic periprosthetic joint infection. The goals for the first stage are twofold: (1) remove infected tissue/implants, obtaining tissue samples for culture; (2) deliver local antibiotics and maintain hip function with a prosthesis with antibiotic-loaded acrylic cement. With extensive bone loss prefabricated spacers are not sufficient, therefore customised spacers are required. The current technique, coating cephalomedually femoral nail in cement, is complex, time consuming, functions poorly and causes wear debris from excessive friction at the femoral/acetabular articulation. We report a technique to create a custom made composite spacer using a short femoral nail, standard Exeter femoral stem (Stryker), Trident acetabular cup (Stryker) and polymethyl methacrylate (PMMA) bone cement with antibiotics. This technique restores hip biomechanics and gives a stable articulation, even in the presence of abductor deficiency, due to dual mobility bearings.

Chiropractic integration within a community health centre: a cost description and partial analysis of cost-utility from the perspective of the institution.

OBJECTIVE: To evaluate costs and consequences of a new back pain service provided by chiropractors integrated into a Community Health Centre in Cambridge, Ontario. The study sample included 95 consecutive patients presenting between January 2014 to January 2016 with a mixture of sub-acute and chronic back pain. METHODS: A secondary cost-utility analysis was performed and conducted from the perspective of the healthcare institution. Cost-utility was calculated as cost per quality-adjusted life year (QALY) gained over a time horizon of 90 days. RESULTS: According to the EuroQol 5 Domain questionnaire, nearly 70% of patients improved. The mean number of treatment sessions was 8.4, and an average of 0.21 QALYs were gained at an average cost per QALY of $1,042. Seventy-seven percent of patients did not visit their primary care provider over the 90-day period, representing potential cost savings to the institution of between $2,022.23 and $6,135.82. CONCLUSION: Adding chiropractic care to usual medical care was associated with improved outcomes at a reasonable cost in a sample of complex patients with sub-acute and chronic back pain. Future comparative cost-effectiveness studies are needed.

OBJECTIF: Évaluer les coûts et les conséquences d'un nouveau service pour soulager les maux de dos offert par des chiropraticiens intégrés à un centre de santé communautaire à Cambridge, en Ontario. L'échantillon de l'étude comprenait 95 patients qui se sont présentés consécutivement entre janvier 2014 et janvier 2016 et qui étaient atteints de diverses douleurs dorsales subaiguës et chroniques. MÉTHODES: Une analyse coût-utilité secondaire a été effectuée du point de vue de l'établissement de santé. Le coût-utilité a été calculé en tant que coût par année de vie ajustée en fonction de la qualité (AVAQ) obtenu sur une période de 90 jours. RÉSULTATS: Selon les résultats du questionnaire EuroQol 5 Domain, près de 70 % des patients ont observé une amélioration de leurs symptômes. Le nombre moyen de séances de traitement était de 8,4 et une moyenne de 0,21 AVAQ a été obtenue à un coût moyen par AVAQ de 1 042 $. Soixante-dix-sept pour cent des patients n'ont pas consulté leur fournisseur de soins primaires au cours de la période de 90 jours, ce qui représente des économies potentielles de l'ordre de 2 022,23 $ à 6 135,82 $ pour l'établissement. CONCLUSION: L'ajout de soins chiropratiques aux soins médicaux habituels a entraîné une amélioration des résultats à un coût raisonnable pour un échantillon de patients ayant des besoins complexes et présentant des douleurs dorsales subaiguës et chroniques. De futures études comparatives coût-efficacité sont nécessaires.

Hysteretic Photochromic Switching (HPS) in Doubly Doped GaN(Mg):Eu-A Summary of Recent Results.

Europium is the most-studied and least-well-understood rare earth ion (REI) dopant in GaN. While attempting to increase the efficiency of red GaN light-emitting diodes (LEDs) by implanting Eu⁺ into p-type GaN templates, the Strathclyde University group, in collaboration with IST Lisbon and Unipress Warsaw, discovered hysteretic photochromic switching (HPS) in the photoluminescence spectrum of doubly doped GaN(Mg):Eu. Our recent work, summarised in this contribution, has used time-, temperature- and light-induced changes in the Eu intra-4f shell emission spectrum to deduce the microscopic nature of the Mg-Eu defects that form in this material. As well as shedding light on the Mg acceptor in GaN, we propose a possible role for these emission centres in quantum information and computing.

Canadian Registry of Implantable Electronic Device Outcomes: Longer-term follow-up of the Riata lead under advisory.

BACKGROUND: The Riata lead advisory was announced in 2011 and has posed unique management challenges because of cable externalization and insulation abrasion, in some cases leading to sudden loss of defibrillation. OBJECTIVE: The purpose of this study was to provide further data on the rate of electrical failure in a population of patients with a Riata lead under advisory. METHODS: Using the Canadian Registry of Electronic Device Outcomes, prospective follow-up data were collected on 1352 Riata leads under advisory in 17 implantable cardioverter-defibrillator (ICD) implantation centers in Canada. Data on electrical and structural failure were collected, as well as periprocedural complications related to lead revision (abandonment or extraction). RESULTS: Of the 1352 leads included in this 12-month follow-up cohort, 110 leads were revised. Mean follow-up time was 10.4 ± 1.5 years. The 12-year rate of electrical failure for the 8Fr lead was 9.45%, whereas the 10-year failure rate for the 7Fr lead was 7.25% and was not found to be accelerating. Of the leads revised because of advisory only (patient preference, advisory related, electrical or structural failure), the majority were abandoned (n = 54 [76.0%]), whereas 17 (24.0%) were extracted using power tools. The rate of major complications in each group was 5.6% and 5.9%, respectively. CONCLUSION: This report provides further data on the risk of electrical lead failure over a long lead dwell time. The risk of failure exceeds the risk of periprocedural major complications, indicating that the risk-to-benefit ratio is favorable to revise the lead in appropriate clinical scenarios.

Management of Back Pain-related Disorders in a Community With Limited Access to Health Care Services: A Description of Integration of Chiropractors as Service Providers.

OBJECTIVE: The purpose of this study was to evaluate a chiropractic service for back pain patients integrated within a publicly funded, multidisciplinary, primary care community health center in Cambridge, Ontario, Canada. METHODS: Patients consulting for back pain of any duration were referred by their medical doctor or nurse practitioner for chiropractic treatment at the community health center. Patients completed questionnaires at baseline and at discharge from the service. Data were collected prospectively on consecutive patients between January 2014 and January 2016. RESULTS: Questionnaire data were obtained from 93 patients. The mean age of the sample was 49.0 ± 16.27 years, and 66% were unemployed. More than three-quarters (77%) had had their back pain for more than a month, and 68% described it as constant. According to the Bournemouth Questionnaire, Bothersomeness, and global improvement scales, a majority (63%, 74%, and 93%, respectively) reported improvement at discharge, and most (82%) reported a significant reduction in pain medication. More than three-quarters (77%) did not visit their primary care provider while under chiropractic care, and almost all (93%) were satisfied with the service. According to the EuroQol 5 Domain questionnaire, more than one-third of patients (39%) also reported improvement in their general health state at discharge. CONCLUSION: Implementation of an integrated chiropractic service was associated with high levels of improvement and patient satisfaction in a sample of patients of low socioeconomic status with subacute and chronic back pain.

Stercoral perforation of the colon in a heroin addict.

A 27-year-old female heroin addict presented with a peritonitic and distended abdomen. Her medical history included depression and a 3-year history of heroin abuse with attendant constipation. CT scan showed free intraperitoneal gas, massive faecal distension of the rectum and sigmoid colon and likely bowel necrosis. She underwent an emergency Hartmann's procedure for perforation of the sigmoid colon. Pathology identified two areas of stercoral ulceration, one of them being the area of perforation. Postoperatively, the patient developed a deep vein thrombosis and is now on anticoagulant therapy. She was discharged 4 weeks after admission. The patient has been reviewed at follow-up clinic by the surgical team and specialist stoma nurses. She is coping well with good stoma function. We will perform a colonoscopy to identify any further areas of stercoral ulceration but there are no plans for further surgery at present.

Canadian Registry of Implantable Electronic Device Outcomes: Surveillance of the Riata Lead Under Advisory.

BACKGROUND: The Riata lead under advisory has posed a unique clinical scenario where inside-out abrasion results in externalization of conductor cables, with a higher risk of electrical failure. We developed a comprehensive registry to assist with clinical management of this lead. METHODS AND RESULTS: This Canadian registry reports the findings of 3763 (74.2% of all Riata leads in Canada) Riata leads under advisory, with a mean follow-up time of 8.9±1.5 years. The overall electrical failure rate was 5.2% at 8 years, with no difference between 7-French and 8-French lead models. Cable externalization was found to be more common in the 8-French model (12.3% versus 5.2%, P<0.0001) and was associated with a higher risk of electrical failure. Predictors of electrical lead failure included cable externalization, higher left ventricular ejection fraction, younger age, higher body mass index, and a passive fixation lead. One patient died due to electrical failure, a further 2 patients survived an event where the device failed to deliver high-voltage therapy. Major complications because of lead extraction were higher when compared with lead abandonment, no difference among lead model observed. Two deaths occurred as a consequence of lead extraction, in the context of an underlying infection. CONCLUSIONS: The Riata lead under advisory has a steady electrical failure rate over time. There are identifiable predictors of lead failure that can assist with clinical decisions as to whether lead revision should be performed prophylactically.

Rapid Device-Detected Nonsustained Ventricular Tachycardia in the Risk Stratification of Hypertrophic Cardiomyopathy.

BACKGROUND: Nonsustained ventricular tachycardia (NSVT) detected by ambulatory Holter (Holter NSVT) is a major risk factor for sudden cardiac death in hypertrophic cardiomyopathy (HCM). We hypothesized that the prognostic utility of Holter NSVT in HCM would improve with prolonged monitoring and a higher heart rate cut-off for detection. METHODS: We enrolled 60 patients (44 ± 14 years) with HCM, who had a prophylactic implantable cardioverter defibrillator (ICD). Positive Holter NSVT (prior to implant) was defined as ≥3 beats at ≥120 beats per minute (bpm). We assessed the prevalence of rapid NSVT (RNSVT) detected by their ICD within 12 months of its implant, defined as 4-16 beats at ≥150-200 bpm. The primary outcome was appropriate ICD therapy (antitachycardia pacing and shocks) for sustained ventricular arrhythmia (VA). RESULTS: Holter NSVT was detected in 34 patients. RNSVT occurred in 21 (35%) patients of whom five did not have Holter NSVT. Over a median follow-up of 61 (interquartile range 29, 129) months after ICD implant, nine patients had VA. RNSVT, but not Holter NSVT, was significantly associated with VA (hazard ratio 6.2, 95% confidence interval [1.3-30], P = 0.01) by multivariable Cox regression analysis that included conventional risk factors. Receiver operating characteristic analysis for RNSVT (area under curve 0.80, P = 0.005) showed that the occurrence of ≥2 episodes of RNSVT discriminated patients for VA optimally (sensitivity 78%, specificity 84%, positive predictive value 47%, negative predictive value 96%). CONCLUSIONS: In this pilot study, RNSVT detected by continuous monitoring independently predicted VA in HCM and offered superior discrimination of VA risk compared to conventional risk factors, including Holter NSVT. Future studies are needed to validate these findings in a larger, unselected HCM cohort.

Insight into the mechanism of failure of the Riata lead under advisory.

BACKGROUND: Cable externalization and insulation abrasion are known to occur with the St Jude Medical Riata leads under advisory. The distribution of these abnormalities and how they relate to clinical presentation have not been well described. OBJECTIVE: In this study, we sought to determine the relationship between structural lead failure and clinical presentation by using the analysis of returned Riata products in Canada. METHODS: The analyses of returned Riata products in Canada were obtained from St Jude Medical, Sylmar, CA. These data were correlated with the clinical presentation of patients just before lead removal from service. RESULTS: As of May 1, 2013, there were 263 returned Riata leads in Canada. Of these, 43 (16.8%) were found to have insulation abrasion that was due to either lead-can or lead-other device interaction (70%) or inside-out abrasion (27.9%). The predilection of lead-to-can abrasion was seen in the Riata 7-F leads (84.2% vs 58.4%; P = .07), while inside-out abrasion was more common in the Riata 8-F leads (37.5% vs 15.8%; P = .12). Electrical abnormalities were frequent (20 of 31 [65.4%]) and most often due to electrical noise (45.2%), although inappropriate shocks were present (25.8%). Death occurred in 1 of 43 (2.3%) of those patients with an insulation defect in the lead-can abrasion group. CONCLUSION: Lead-can abrasion is the most common form of insulation defect in the Riata group of leads under advisory. Management of this group of leads under advisory should not neglect the issue of lead-can abrasion, in addition to detection of cable externalization.

Survival after implantable cardioverter-defibrillator implantation in the elderly.

BACKGROUND: The benefit of implantable cardioverter-defibrillators (ICDs) among elderly patients is controversial and may be attenuated by nonarrhythmic death. We examined the impact of age on device-delivered therapies and outcomes after primary or secondary prevention ICD. METHODS AND RESULTS: In a prospective, inclusive registry of 5399 ICD recipients in Ontario, Canada (February 2007 to September 2010), device-delivered therapies and complications were determined at routine clinic visits. Among primary prevention ICD recipients aged 18 to 49 (n=317), 50 to 59 (n=769), 60 to 69 (n=1336), 70 to 79 (n=1242), and ≥80 (n=275) years, mortality increased with age, as follows: 2.1, 3.0, 5.4, 6.9, and 10.2 deaths per 100 person-years, respectively (P<0.001). Secondary prevention ICD recipients aged 18 to 49 (n=114), 50 to 59 (n=244), 60 to 69 (n=481), 70 to 79 (n=462), and ≥80 (n=159) years also exhibited increasing mortality, as follows: 2.2, 3.8, 6.1, 8.7, and 15.5 deaths per 100 person-years, respectively (P<0.001). However, rates of appropriate shock were similar across age groups: from 6.7 (18-49 years) to 4.2 (≥80 years) per 100 person-years after primary prevention ICDs (P=0.139) and from 11.4 (18-49 years) to 11.9 (≥80 years) per 100 person-years after secondary prevention ICDs (P=0.993). Covariate-adjusted competing risk analysis demonstrated higher risk of death (Ptrend<0.001 for both primary and secondary prevention) but no significant decline in appropriate shocks with older age after primary (P=0.130) or secondary (P=0.810) prevention ICD implantation. CONCLUSIONS: Whereas elderly patients exhibited increased mortality after ICD implantation, rates of appropriate device shocks were similar across age groups. Decisions regarding ICD candidacy should not be based on age alone but should consider factors that predispose to mortality despite defibrillator implantation.

High-throughput genome scanning in constant tension fluidic funnels.

Genome Sequence Scanning (GSS) is a bacterial identification technology that detects sparse sequence-specific fluorescent tags on long DNA molecules linearized in a continuous-flow microfunnel. The efficiency and sensitivity of GSS depends on the detection throughput of well-stretched molecules. Previous studies have investigated the fundamental roles of elongational and shear flow on DNA stretching in continuous flow devices. Here, we present a novel compound funnel design that significantly improves effective molecule throughput over previously described devices. First, exploring the relationship between fluid strain rate and molecule tension allows for design of funnel geometries that accommodate high fluid velocities without compromising molecules due to overstretching under high tension. Second, a constant-strain detection channel is utilized to significantly reduce the number of molecules lost to further analysis due to shear-induced molecular tumbling and relaxation. Finally, application of the constant-strain detection channel allows for a priori prediction of spatial resolution bias due to accelerating flow. In all, the refined funnel geometries presented here yield over thirty-fold increase in effective molecule throughput due to increased fluid flow and improved retention of stretched molecules, compared to previously described devices.

Ventricular Tachycardia Precipitated by Short-long-short Sequence in a Patient with Implantable-cardioverter Defibrillator.

Abrupt changes in heart rate, particularly short-long-short sequences in the ventricular cycle length (CL), might precede initiation of ventricular tachycardia/fibrillation (VT/VF). These changes may be facilitated or caused by pacing activity in patients with pacemakers or implantable-cardioverter defibrillators (ICDs). We describe a patient with two episodes of acquired VT precipitated by short-long-short sequences and diagnosed from the ICD recordings. In such cases, the knowledge of the device parameters is extremely important for a correct diagnosis and management.

Predictors of short-term complications after implantable cardioverter-defibrillator replacement: results from the Ontario ICD Database.

BACKGROUND: Complications after implantable cardioverter-defibrillator (ICD) replacement are often clinically devastating, particularly when infection or reoperation occurs. Identifying factors contributing to complications may permit identification of high-risk individuals that warrant incremental monitoring and therapy to attenuate risk. In addition, replacement may be a discretionary decision in the context of an advisory or borderline device performance and patient, device, and implanter factors that predict adverse outcome may assist in clinical decision-making. METHODS AND RESULTS: In a prospective, multicenter, population-based registry of all ICD patients at 18 centers in Ontario, Canada, we examined 45-day complication and all-cause mortality rates from February 2007 to August 2009 in patients undergoing ICD generator replacement. Complications were determined longitudinally and were categorized as major or minor. ICD replacement was performed in 1081 of 5176 patients (20.8%) undergoing ICD implantation (age, 64.3±12.7 years; 78.5% men). In patients undergoing ICD replacement, 47 patients (4.3%) had a complication within 45 days, with 47 major complications in 28 patients (2.6%), most commonly infection (n=23), lead revision (n=35), electrical storm (n=14), and pulmonary edema (n=13). Minor complications occurred in 2.3% of patients, most commonly incisional infection (n=10) and pocket hematoma (n=10). On multivariable analysis, risk factors associated with major complications were Canadian Cardiovascular Society angina class (adjusted hazard ratio [HR], 3.70 for class 2 to 4 versus 0 to 1; P=0.027) and multiple previous procedures on the pocket (adjusted HR, 3.35 for >1 versus 1; P=0.058). Risk factors associated with any complication were the use of antiarrhythmic therapy (adjusted HR, 6.29; P=0.001), implanter volume (adjusted HR 10.4 for <60/y versus >120/y, P=0.026), and Canadian Cardiovascular Society angina class (adjusted HR, 3.00 for class 2 to 4 versus 0 to 1; P=0.031). In a Cox model with a time-dependent variable of major complication within 45 days after replacement, major complications after ICD replacement were associated with an increased risk of mortality at 45, 90, and 180 days (adjusted HR, 9.61, 12.69, and 6.41, respectively; P=0.002 to 0.039). CONCLUSIONS: Risk factors associated with complications after ICD replacement include the presence of angina, antiarrhythmic therapy, increased number of previous procedures, and low implanter volume. Major complications may be associated with increased risk of subsequent mortality.

Fast high-resolution mapping of long fragments of genomic DNA based on single-molecule detection.

Here we describe bacterial genotyping by direct linear analysis (DLA) single-molecule mapping. DLA involves preparation of restriction digest of genomic DNA labeled with a sequence-specific fluorescent probe and stained nonspecifically with intercalator. These restriction fragments are stretched one by one in a microfluidic device, and the distribution of probes on the fragments is determined by single-molecule measurement of probe fluorescence. Fluorescence of the DNA-bound intercalator provides information on the molecule length. Because the probes recognize short sequences, they encounter multiple cognate sites on 100- to 300-kb-long DNA fragments. The DLA maps are based on underlying DNA sequences of microorganisms; therefore, the maps are unique for each fragment. This allows fragments of similar lengths that cannot be resolved by standard DNA sizing techniques to be readily distinguished. DNA preparation, data collection, and analysis can be carried out in as little as 5h when working with monocultures. We demonstrate the ability to discriminate between two pathogenic Escherichia coli strains, O157:H7 Sakai and uropathogenic 536, and we use DLA mapping to identify microorganisms in mixtures. We also introduce a second color probe to double the information used to distinguish molecules and increase the length range of mapped fragments.