The impact of the Covid-19 pandemic on postnatal anxiety and posttraumatic stress: Analysis of two population-based national maternity surveys in England.

BACKGROUND: Few studies have evaluated postnatal anxiety and posttraumatic stress (PTS) before and during the Covid-19 pandemic using comparable data across time. We used data from two national maternity surveys in England to explore the impact of the pandemic on prevalence and risk factors for postnatal anxiety and PTS. METHODS: Analysis was conducted using population-based surveys carried out in 2018 (n = 4509) and 2020 (n = 4611). Weighted prevalence estimates for postnatal anxiety and PTS were compared across surveys. Adjusted risk ratios (aRR) were estimated for the association between risk factors and postnatal anxiety and PTS. FINDINGS: Prevalence of postnatal anxiety increased from 13.7 % in 2018 to 15.1 % in 2020 (+1.4 %(95%CI:-0.4-3.1)). Prevalence of postnatal PTS increased from 9.7 % in 2018 to 11.5 % in 2020 (+1.8 %(95%CI:0.3-3.4)), due to an increase in PTS related to birth trauma from 2.5 % to 4.3 % (+1.8 %(95%CI:0.9-2.6); there was no increase in PTS related to non-birth trauma. Younger age (aRR = 1.31-1.51), being born in the UK (aRR = 1.29-1.59), long-term physical or mental health problem(s) (aRR = 1.27-1.94), and antenatal anxiety (aRR = 1.97-2.22) were associated with increased risk of postnatal anxiety and PTS before and during the pandemic, whereas higher satisfaction with birth (aRR = 0.92-0.94) and social support (aRR = 0.81-0.82) were associated with decreased risk. INTERPRETATION: Prevalence of postnatal PTS was significantly higher during the pandemic, compared to before the pandemic, due to an increase in PTS related to birth trauma. Prevalence of postnatal anxiety was not significantly higher during the pandemic. Risk factors for postnatal anxiety and PTS were similar before and during the pandemic.

"It's not just the medical aspects that are important": A qualitative exploration of first-time parents' experiences of antenatal imaging and their influence on parent-fetal bonding.

INTRODUCTION: Antenatal imaging provides clinical information regarding fetal growth and development. The additional benefit afforded by imaging for expectant parents in developing an emotional connection (bond) to the unborn baby is also acknowledged. However, the relationship between imaging and bonding is not fully understood, particularly where there are differing parental and pregnancy circumstances, for example use of advanced imaging techniques or the prenatal diagnosis of a congenital fetal condition. This study aimed to explore the role of antenatal imaging in enhancing the developing parent-fetal bond in first-time parents. METHODS: A descriptive, qualitative methodology was used. Semi-structured telephone interviews were conducted with first-time expectant parents attending a London hospital for clinical ultrasound (n = 20) or research MRI (n = 8) imaging during pregnancy. The sample included parents receiving specialist antenatal care for a diagnosed fetal cardiac condition (n = 8). Thematic analysis was conducted. RESULTS: The analysis generated three themes: 1) Our baby, our scan too; 2) Destination parenthood; and 3) Being in the dark, then finding the light. These themes highlight the important, but transient role of antenatal imaging in enhancing parent-fetal bonding, as well as the differing care needs of expectant parents. The integral role of healthcare professionals in providing a personalised, supportive, imaging experience to facilitate bonding is also reflected. CONCLUSION: Adopting parent-centred care approaches which involve expectant parents in fetal imaging influences bonding by helping parents to consider the reality of their impending parenthood. Knowledge acquired during scans is used to create an identity for the unborn baby, which parents can develop an emotional connection to. IMPLICATIONS FOR PRACTICE: To optimise the potential for enhanced parent-fetal bonding, care provision in fetal imaging should be tailored to the individual needs of expectant parents.

"It has been the most difficult time in my career": A qualitative exploration of UK obstetric sonographers' experiences during the COVID-19 pandemic.

INTRODUCTION: Substantial changes were made to the provision of pregnancy ultrasound services during the COVID-19 pandemic with the intention of minimising virus transmission and maintaining service continuity. Published literature describing the impact of the pandemic on obstetric sonographers is predominantly quantitative in nature, however statistics cannot fully convey sonographers' voices. This study aimed to gain a deeper understanding of the lived experiences of UK obstetric sonographers performing pregnancy ultrasound scans during the pandemic. METHODS: A UK-wide, online, anonymous cross-sectional survey on Qualtrics XM™ was open to responses between 9th March and 6th May 2021. Whilst this survey contained some quantitative elements, open questions were included to capture additional qualitative detail from respondents about their perceptions and experiences of scanning during the pandemic. Key themes were generated from free text responses using thematic analysis. RESULTS: Written responses were received from 111/138 sonographers participating in the survey. Five themes were generated, depicting the impact of the pandemic on obstetric sonographers: 1) continuity in a crisis; 2) decisions about me, without me; 3) battle scars - the lasting damage of COVID-19; 4) what people think I do vs. what I really do; and 5) the human touch. A cross-cutting theme was sonographers' feelings of disconnection from senior figures and expectant parents which created a sense of abandonment and distrust. CONCLUSION: Survey respondents' self-reported experiences of ineffective leadership and management, and perceived lack of understanding of the complexity of the sonographer role are potential contributory factors in the high levels of moral injury and occupational burnout reported within the workforce during the pandemic.

Prevalence and factors associated with postpartum posttraumatic stress in a population-based maternity survey in England.

BACKGROUND: Studies on prevalence and factors associated with postpartum posttraumatic stress (PTS) typically do not distinguish between PTS related to childbirth (PTS-C) and PTS related to other stressors (PTS-O). This study aimed to describe the prevalence, clinical characteristics, and factors associated with PTS-C and PTS-O in postpartum women. METHODS: The study was a cross-sectional population-based survey of 16,000 postpartum women, selected at random from birth registrations in England to receive a postal questionnaire, including the Primary Care Posttraumatic Stress Disorder Screen. RESULTS: Questionnaires were returned by 4,509 women. The median age was 32 years (IQR=29-36), 64% were married, 77% were UK-born, and 76% were White-British. Prevalence of PTS-C was 2.5% (95%CI:2.0-3.0) and prevalence of PTS-O was 6.8% (95%CI:6.0-7.8). Women with PTS-C were significantly more likely to report re-experiencing symptoms (Chi-Square=7.69,p<0.01). Factors associated with PTS-C were: higher level of deprivation, not having a health professional to talk to about sensitive issues during pregnancy, and the baby being admitted for neonatal intensive care. Factors associated with PTS-O were: age ≤24 years, depression during pregnancy, and having a pregnancy affected by long-term health problems. Factors associated with both were: living without a partner, anxiety during pregnancy, pregnancy-specific health problems, and lower birth satisfaction. CONCLUSIONS: PTS during the postpartum period is relatively common and, for many women, unrelated to childbirth. Increased awareness among health professionals of prevalence, clinical characteristics and factors associated with postpartum PTS-C and PTS-O will aid the development of appropriate management protocols to identify and support women during the perinatal period. Posttraumatic stress, posttraumatic stress disorder, postpartum PTSD/PTS, birth-related PTSD/PTS, birth trauma, perinatal mental health.

Tokophobia and fear of birth: a workshop consensus statement on current issues and recommendations for future research.

Objective: To discuss and develop a statement on the current state of the evidence and opinion in Fear of Childbirth (FoC) and Tokophobia (Tocophobia), and to provide recommendations. Background: A group met in 2019 to discuss the state of clinical and academic knowledge relating to FoC/Tokophobia. Five key areas were agreed as the focus of the meeting. Methods: 12 internationally acknowledged experts, in this or a closely related area (e.g. PTSD) met to discuss their understanding of the evidence for FoC/ Tokophobia and current practice. The consensus described in this paper constitutes the expression of the general opinion of the participants and does not necessarily imply unanimity. Keys points: Work focussed on tokophobia is recent and there remains a wide range of issues, which were addressed in the workshop including complexity in defining prevalence, a theoretical lack of understanding, which creates challenge for robust assessment and the identification of risk factors. An improved aetiological and developmental understanding of the tokophobia is required to underpin appropriate, effective and evidence-based interventions. Evaluation of pathways of care and relevant interventions, should be a focus of future research. Conclusion: Significant gaps remain within the FoC/tokophobia knowledge base. Further research is necessary.

Time-Resolved Fuel Density Profiles of the Stagnation Phase of Indirect-Drive Inertial Confinement Implosions.

The implosion efficiency in inertial confinement fusion depends on the degree of stagnated fuel compression, density uniformity, sphericity, and minimum residual kinetic energy achieved. Compton scattering-mediated 50-200 keV x-ray radiographs of indirect-drive cryogenic implosions at the National Ignition Facility capture the dynamic evolution of the fuel as it goes through peak compression, revealing low-mode 3D nonuniformities and thicker fuel with lower peak density than simulated. By differencing two radiographs taken at different times during the same implosion, we also measure the residual kinetic energy not transferred to the hot spot and quantify its impact on the implosion performance.

A meta-synthesis of women's experiences of online forums for maternal mental illness and stigma.

Perinatal mental illness affects 15% of women; however, only half of these women access treatment. Some women with untreated perinatal mental illness may continue to suffer with mental illness after the perinatal period. Evidence suggests that one barrier to accessing treatment is stigma. Forums may provide an acceptable place for women to converse about the stigmatised symptoms of maternal mental illness. Reducing stigma may increase treatment uptake. This study aimed to review and synthesise the qualitative research on maternal mental illness forums and stigma so that stigma can be addressed and treatment improved. A meta-synthesis was conducted to describe and interpret qualitative studies regarding forum use and maternal mental illness stigma. A systematic search of seven electronic databases and Google Scholar was performed. Additional references were collected through screening references of the identified studies. Five studies were identified that reported women's experiences of online forums for maternal mental illness and stigma. The synthesis identified four key themes: (1) a safe place to talk; (2) virtual support; (3) stigma and identity; and (4) repair of the mother identity. Stigma maybe reduced by forum discourse that reconceptualises what is to be a "good mother" and separates stigma and maternal identity. This synthesis provides a novel and more detailed framework for the stigma of maternal mental illness and forum use. This suggests forums may enable women to explore their dual identity and repair their maternal identity, and this may reduce stigma. Healthcare providers could discuss forum use with their clients.

The Crystal Backlighter Imager: A spherically bent crystal imager for radiography on the National Ignition Facility.

The Crystal Backlighter Imager (CBI) is a quasi-monochromatic, near-normal incidence, spherically bent crystal imager developed for the National Ignition Facility (NIF), which will allow inertial confinement fusion capsule implosions to be radiographed close to stagnation. This is not possible using the standard pinhole-based area-backlighter configuration, as the self-emission from the capsule hotspot overwhelms the backlighter signal in the final stages of the implosion. The CBI mitigates the broadband self-emission from the capsule hot spot by using the extremely narrow bandwidth inherent to near-normal-incidence Bragg diffraction. Implementing a backlighter system based on near-normal reflection in the NIF chamber presents unique challenges, requiring the CBI to adopt novel engineering and operational strategies. The CBI currently operates with an 11.6 keV backlighter, making it the highest energy radiography diagnostic based on spherically bent crystals to date. For a given velocity, Doppler shift is proportional to the emitted photon energy. At 11.6 keV, the ablation velocity of the backlighter plasma results in a Doppler shift that is significant compared to the bandwidth of the instrument and the width of the atomic line, requiring that the shift be measured to high accuracy and the optics aligned accordingly to compensate. Experiments will be presented that used the CBI itself to measure the backlighter Doppler shift to an accuracy of better than 1 eV. These experiments also measured the spatial resolution of CBI radiographs at 7.0 µm, close to theoretical predictions. Finally, results will be presented from an experiment in which the CBI radiographed a capsule implosion driven by a 1 MJ NIF laser pulse, demonstrating a significant (>100) improvement in the backlighter to self-emission ratio compared to the pinhole-based area-backlighter configuration.

Calibration of proton dispersion for the NIF electron positron proton spectrometer (NEPPS) for short-pulse laser experiments on the NIF ARC.

Experiments using the Advanced Radiographic Capability (ARC) laser at the National Ignition Facility (NIF) aim to characterize short-pulse-driven proton beams for use as both probes and drivers for high-energy-density physics experiments. Measurements of ARC-driven proton beam characteristics, such as energy spectrum and conversion efficiency, rely on the NIF Electron Positron Proton Spectrometer (NEPPS). The NEPPS diagnostic is a version of an existing particle spectrometer which is used for detecting MeV electron and positron spectra via permanent magnetic field dispersion. These spectrometers have not yet been calibrated for protons and instead use an analytical calculation to estimate the dispersion. Small variations in the field uniformity can affect the proton dispersion due to the relatively small resolving power (E/dE) for this diagnostic. A broadband energy, laser-accelerated proton source was produced at the Titan laser to experimentally calibrate the proton dispersion. These experimental data were used to test the theoretical dispersion. Numerical simulations using measurements of the magnetic field variation within the diagnostic were used to obtain a realistic proton dispersion curve for the new NEPPS units. This procedure for obtaining each independent dispersion is applicable to all EPPS and NEPPS diagnostics, given the axial magnetic field profile.

The impact of childbirth-related post-traumatic stress on a couple's relationship: a systematic review and meta-synthesis.

OBJECTIVE: This review aimed to identify the impact of childbirth-related post-traumatic stress disorder (PTSD) or symptoms (PTSS) on a couple's relationship. BACKGROUND: Childbirth can be psychologically traumatic and can lead to PTSD. There is emerging evidence that experiencing a traumatic birth can affect the quality of the couple's relationship. This is an important issue because poor-quality relationships can impact on the well-being of partners, their parenting and the welfare of the infant. METHODS: A systematic search was conducted of Amed, CENTRAL, Cinahl, Embase, Maternity and Infant Care, Medline, MITCognet, POPLINE, PsycARTICLES, PsycBITE, PsycINFO, Pubmed and Science Direct. Additionally, grey literature, citation and reference searches were conducted. Papers were eligible for inclusion if they reported qualitative data about parents who had experienced childbirth and measures of PTSD or PTSS and the relationship were taken. Analysis was conducted using meta-ethnography. RESULTS: Seven studies were included in the meta-synthesis. Results showed that childbirth-related PTSD or PTSS can have a perceived impact on the couple's relationship and five themes were identified: negative emotions; lack of understanding and support; loss of intimacy; strain on the relationship; and strengthened relationships. A model of proposed interaction between these themes is presented. CONCLUSIONS: The impact of childbirth-related PTSD or PTSS on the couple's relationships is complex. As the quality of the couple relationship is important to family well-being, it is important that healthcare professionals are aware of the impact of experiencing psychologically traumatic childbirth as impetus for prevention and support.

The impact of postpartum post-traumatic stress disorder symptoms on child development: a population-based, 2-year follow-up study.

BACKGROUND: Against the background of very limited evidence, the present study aimed to prospectively examine the impact of maternal postpartum post-traumatic stress disorder (PTSD) symptoms on four important areas of child development, i.e. gross motor, fine motor, communication and social-emotional development. METHOD: This study is part of the large, population-based Akershus Birth Cohort. Data from the hospital's birth record as well as questionnaire data from 8 weeks and 2 years postpartum were used (n = 1472). The domains of child development that were significantly correlated with PTSD symptoms were entered into regression analyses. Interaction analyses were run to test whether the influence of postpartum PTSD symptoms on child development was moderated by child sex or infant temperament. RESULTS: Postpartum PTSD symptoms had a prospective relationship with poor child social-emotional development 2 years later. This relationship remained significant even when adjusting for confounders such as maternal depression and anxiety or infant temperament. Both child sex and infant temperament moderated the association between maternal PTSD symptoms and child social-emotional development, i.e. with increasing maternal PTSD symptom load, boys and children with a difficult temperament were shown to have comparatively higher levels of social-emotional problems. CONCLUSIONS: Examining four different domains of child development, we found a prospective impact of postpartum PTSD symptoms on children's social-emotional development at 2 years of age. Our findings suggest that both boys and children with an early difficult temperament may be particularly susceptible to the adverse impact of postpartum PTSD symptoms. Additional studies are needed to further investigate the mechanisms at work.

Development of a high resolution x-ray spectrometer for the National Ignition Facility (NIF).

A high resolution (E/ΔE = 1200-1800) Bragg crystal x-ray spectrometer is being developed to measure plasma parameters in National Ignition Facility experiments. The instrument will be a diagnostic instrument manipulator positioned cassette designed mainly to infer electron density in compressed capsules from Stark broadening of the helium-ß (1s2-1s3p) lines of krypton and electron temperature from the relative intensities of dielectronic satellites. Two conically shaped crystals will diffract and focus (1) the Kr Heß complex and (2) the Heα (1s2-1s2p) and Lyα (1s-2p) complexes onto a streak camera photocathode for time resolved measurement, and a third cylindrical or conical crystal will focus the full Heα to Heß spectral range onto an image plate to provide a time integrated calibration spectrum. Calculations of source x-ray intensity, spectrometer throughput, and spectral resolution are presented. Details of the conical-crystal focusing properties as well as the status of the instrumental design are also presented.

The aetiology of post-traumatic stress following childbirth: a meta-analysis and theoretical framework.

There is evidence that 3.17% of women report post-traumatic stress disorder (PTSD) after childbirth. This meta-analysis synthesizes research on vulnerability and risk factors for birth-related PTSD and refines a diathesis-stress model of its aetiology. Systematic searches were carried out on PsycINFO, PubMed, Scopus and Web of Science using PTSD terms crossed with childbirth terms. Studies were included if they reported primary research that examined factors associated with birth-related PTSD measured at least 1 month after birth. In all, 50 studies (n = 21 429) from 15 countries fulfilled inclusion criteria. Pre-birth vulnerability factors most strongly associated with PTSD were depression in pregnancy (r = 0.51), fear of childbirth (r = 0.41), poor health or complications in pregnancy (r = 0.38), and a history of PTSD (r = 0.39) and counselling for pregnancy or birth (r = 0.32). Risk factors in birth most strongly associated with PTSD were negative subjective birth experiences (r = 0.59), having an operative birth (assisted vaginal or caesarean, r = 0.48), lack of support (r = -0.38) and dissociation (r = 0.32). After birth, PTSD was associated with poor coping and stress (r = 0.30), and was highly co-morbid with depression (r = 0.60). Moderator analyses showed that the effect of poor health or complications in pregnancy was more apparent in high-risk samples. The results of this meta-analysis are used to update a diathesis-stress model of the aetiology of postpartum PTSD and can be used to inform screening, prevention and intervention in maternity care.

Commissioning of a frequency-resolved optical gating system at the OMEGA EP laser facility: SpecFROG.

We present the design and commissioning of a new single-shot, frequency-resolved optical gating system on the OMEGA EP laser facility - dubbed "SpecFROG" - for characterizing the instantaneous intensity and phase of ∼10 ps pulses used to study ultra-intense laser-plasma interactions. A polarization-gating geometry is employed to ensure tha the diagnostic is broadband and has unambiguous time directionality. SpecFROG is capable of characterizing ∼10 s of mJ pulses with durations between 0.5-25 ps with ≲285 fs geometrical temporal blurring and ∼0.1% spectral shift resolutions over an adjustable total spectral shifting window of ∼15% of the carrier wavelength λo; configurations currently exist for both the fundamental (1ω, λo = 1.054 µm) and second harmonic (2ω, λo = 0.527 µm) of the EP pulse. Initial specular reflectivity measurements of the ∼1 kJ, ∼10 ps OMEGA EP laser off solid density aluminum targets suggest drastically different scalings for specular pulse properties compared to picosecond-scale pulses of comparable intensities.

The NIF x-ray spectrometer calibration campaign at Omega.

The calibration campaign of the National Ignition Facility X-ray Spectrometer (NXS) was carried out at the Omega laser facility. Spherically symmetric, laser-driven, millimeter-scale x-ray sources of K-shell and L-shell emission from various mid-Z elements were designed for the 2-18 keV energy range of the NXS. The absolute spectral brightness was measured by two calibrated spectrometers. We compare the measured performance of the target design to radiation hydrodynamics simulations.

A magnetic particle time-of-flight (MagPTOF) diagnostic for measurements of shock- and compression-bang time at the NIF (invited).

A magnetic particle time-of-flight (MagPTOF) diagnostic has been designed to measure shock- and compression-bang time using D(3)He-fusion protons and DD-fusion neutrons, respectively, at the National Ignition Facility (NIF). This capability, in combination with shock-burn weighted areal density measurements, will significantly constrain the modeling of the implosion dynamics. This design is an upgrade to the existing particle time-of-flight (pTOF) diagnostic, which records bang times using DD or DT neutrons with an accuracy better than ±70 ps [H. G. Rinderknecht et al., Rev. Sci. Instrum. 83, 10D902 (2012)]. The inclusion of a deflecting magnet will increase D(3)He-proton signal-to-background by a factor of 1000, allowing for the first time simultaneous measurements of shock- and compression-bang times in D(3)He-filled surrogate implosions at the NIF.

Measuring parents' experiences and satisfaction with care during very preterm birth: a questionnaire development study.

OBJECTIVE: To develop a questionnaire to assess parents' experiences and satisfaction with care during very preterm birth. DESIGN: Questionnaire development. SETTING: Parents whose babies had been cared for at five tertiary neonatal units in England. POPULATION: A total of 145 women who gave birth before 32 weeks of gestation, and 85 of their partners. METHODS: A 30-item questionnaire was developed on the basis of qualitative interviews with parents of very preterm babies, a literature review and discussion with relevant experts. The questionnaire was posted to a second group of parents, and its reliability and validity were explored. MAIN OUTCOME MEASURES: The Preterm Birth Experience and Satisfaction Scale (P-BESS) was correlated with two global questions measuring satisfaction with care during the birth. Internal consistency was measured using Cronbach's α. RESULTS: Parents of 458 babies were invited to take part and 147 (32%) responded. Two women and 22 partners were excluded or ineligible, leaving 145 women and 85 partners. Factor analysis produced three clear dimensions: Staff professionalism and empathy, Information and explanations, and Confidence in staff. The total scale and three subscales showed high reliability. Strong positive correlations were found between the questionnaire scales and the two global questions, indicating convergent validity. For women whose partners were present at the birth, a fourth factor was identified 'Partner Involvement'. CONCLUSIONS: The P-BESS appears to be a valid measure of satisfaction with care during very preterm birth.

Parents' experiences and satisfaction with care during the birth of their very preterm baby: a qualitative study.

OBJECTIVE: To assess parents' experiences and satisfaction with care during very preterm birth and to identify domains associated with positive and negative experiences of care. DESIGN: Qualitative study using semi-structured interviews. SETTING: Three neonatal units in tertiary care hospitals in South-East England. POPULATION: Thirty-two mothers and seven fathers who had a baby born before 32 weeks of gestation and spoke English well. METHODS: Semi-structured interviews were conducted. Results were analysed using thematic analysis. MAIN OUTCOME MEASURES: Participants' experiences and satisfaction with care during the birth of their preterm baby. RESULTS: Overall, 80% of participants were extremely satisfied with the care during the birth of their preterm baby, seven were generally satisfied but felt some things could be improved and one was dissatisfied. Four key determinants of experiences of care were identified: staff professionalism, which included information and explanation, being calm in a crisis, appearing confident and in control, and conversely not listening to the woman; staff empathy, which included caring and emotional support, and encouragement and reassurance; involvement of the father; and birth environment. CONCLUSIONS: Although the determinants of experiences of care are generally consistent with previous research on term births, unique factors to preterm birth were identified. These were the importance of the staff appearing calm during the birth, and the staff portraying confidence and taking control during the birth. Women valued being listened to, and both they and their partners valued staff helping fathers to feel involved during the birth.

Characterization of extended-spectrum cephalosporin-resistant Salmonella enterica serovar Heidelberg isolated from food animals, retail meat, and humans in the United States 2009.

Salmonella enterica is one of the most common causes of foodborne illness in the United States. Although salmonellosis is usually self-limiting, severe infections typically require antimicrobial treatment, and ceftriaxone, an extended-spectrum cephalosporin (ESC), is commonly used in both adults and children. Surveillance conducted by the National Antimicrobial Resistance Monitoring System (NARMS) has shown a recent increase in ESC resistance among Salmonella Heidelberg isolated from food animals at slaughter, retail meat, and humans. ESC resistance among Salmonella in the United States is usually mediated by a plasmid-encoded bla(CMY) ß-lactamase. In 2009, we identified 47 ESC-resistant bla(CMY)-positive Heidelberg isolates from humans (n=18), food animals at slaughter (n=16), and retail meats (n=13) associated with a spike in the prevalence of this serovar. Almost 90% (26/29) of the animal and meat isolates were isolated from chicken carcasses or retail chicken meat. We screened NARMS isolates for the presence of bla(CMY), determined whether the gene was plasmid-encoded, examined pulsed-field gel electrophoresis patterns to assess the genetic diversities of the isolates, and categorized the bla(CMY) plasmids by plasmid incompatibility groups and plasmid multi-locus sequence typing (pMLST). All 47 bla(CMY) genes were found to be plasmid encoded. Incompatibility/replicon typing demonstrated that 41 were IncI1 plasmids, 40 of which only conferred bla(CMY)-associated resistance. Six were IncA/C plasmids that carried additional resistance genes. pMLST of the IncI1-bla(CMY) plasmids showed that 27 (65.8%) were sequence type (ST) 12, the most common ST among bla(CMY)-IncI1 plasmids from Heidelberg isolated from humans. Ten plasmids had a new ST profile, ST66, a type very similar to ST12. This work showed that the 2009 increase in ESC resistance among Salmonella Heidelberg was caused mainly by the dissemination of bla(CMY) on IncI1 and IncA/C plasmids in a variety of genetic backgrounds, and is likely not the result of clonal expansion.