Wattmeter based on tunnel-effect magnetoresistance sensor.

This work shows how the tunnel-effect based magnetoresistance (TMR) technology can be used as a competitive sensing method in electrical current and power processors. The sensor is arranged in a Wheatstone bridge topology, and each magnetoresistance was composed of a series connection of 360 magnetic tunnel junction elements with the following structure (thickness in nm): 100 SiO2/5 Ta/15 Ru/5 Ta/15 Ru/5 Ta/5 Ru/20 IrMn/2 CoFe30/0.85 Ru/2.6 CoFe40B20/1.2 MgO/2 CoFe40B20/0.21 Ta/4 NiFe/0.20 Ru/6 IrMn/2 Ru/5 Ta/10 Ru. First, the electrical and thermal characteristics of the sensor were evaluated by analyzing its response to DC current sweeps at various temperatures, controlled using a climatic chamber. Nominal values of current sensitivity S (0.324 mV/A), bridge output offset voltage Vo,s,o (-37.1 mV), bridge input resistance Rinp,bridge (0.958 kΩ), and their thermal behavior were obtained (0.0036 mV/A°C, 0.079 mV/°C, and -0.31 Ω/°C). Second, an instrumentation system is introduced to characterize the sensor, measuring its sensitivity to AC line currents from the mains up to 10 Arms. Finally, an electronic wattmeter was developed showing the relevant quantities of its design. The circuit is able to interface a TMR Wheatstone bridge to an analog processor. Power and current measurements were obtained from a 150 Vrms AC mains 1.5 kW load with resistive and capacitive components, achieving less than 1% deviation over the expected values. The circuit shown can be used to interface these signals to more complex smart digital engines with active or reactive energy processing capabilities, while providing inherent high voltage isolation, thanks to its TMR measurement technology.

Imaging findings of the postoperative chest: What the radiologist should know.

Thoracic surgical procedures are increasing in recent years, and there are different types of lung resections. Postsurgical complications vary depending on the type of resection and the time elapsed, with imaging techniques being key in the postoperative follow-up. Multidisciplinary management of these patients throughout the perioperative period is essential to ensure an optimal surgical outcome. This pictorial review will review the different thoracic surgical techniques, normal postoperative findings and postsurgical complications.

Microscopic fractional anisotropy outperforms multiple sclerosis lesion assessment and clinical outcome associations over standard fractional anisotropy tensor.

We aimed to compare the ability of diffusion tensor imaging and multi-compartment spherical mean technique to detect focal tissue damage and in distinguishing between different connectivity patterns associated with varying clinical outcomes in multiple sclerosis (MS). Seventy-six people diagnosed with MS were scanned using a SIEMENS Prisma Fit 3T magnetic resonance imaging (MRI), employing both conventional (T1w and fluid-attenuated inversion recovery) and advanced diffusion MRI sequences from which fractional anisotropy (FA) and microscopic FA (µFA) maps were generated. Using automated fiber quantification (AFQ), we assessed diffusion profiles across multiple white matter (WM) pathways to measure the sensitivity of anisotropy diffusion metrics in detecting localized tissue damage. In parallel, we analyzed structural brain connectivity in a specific patient cohort to fully grasp its relationships with cognitive and physical clinical outcomes. This evaluation comprehensively considered different patient categories, including cognitively preserved (CP), mild cognitive deficits (MCD), and cognitively impaired (CI) for cognitive assessment, as well as groups distinguished by physical impact: those with mild disability (Expanded Disability Status Scale [EDSS] <=3) and those with moderate-severe disability (EDSS >3). In our initial objective, we employed Ridge regression to forecast the presence of focal MS lesions, comparing the performance of µFA and FA. µFA exhibited a stronger association with tissue damage and a higher predictive precision for focal MS lesions across the tracts, achieving an R-squared value of .57, significantly outperforming the R-squared value of .24 for FA (p-value <.001). In structural connectivity, µFA exhibited more pronounced differences than FA in response to alteration in both cognitive and physical clinical scores in terms of effect size and number of connections. Regarding cognitive groups, FA differences between CP and MCD groups were limited to 0.5% of connections, mainly around the thalamus, while µFA revealed changes in 2.5% of connections. In the CP and CI group comparison, which have noticeable cognitive differences, the disparity was 5.6% for FA values and 32.5% for µFA. Similarly, µFA outperformed FA in detecting WM changes between the MCD and CI groups, with 5% versus 0.3% of connections, respectively. When analyzing structural connectivity between physical disability groups, µFA still demonstrated superior performance over FA, disclosing a 2.1% difference in connectivity between regions closely associated with physical disability in MS. In contrast, FA spotted a few regions, comprising only 0.6% of total connections. In summary, µFA emerged as a more effective tool than FA in predicting MS lesions and identifying structural changes across patients with different degrees of cognitive and global disability, offering deeper insights into the complexities of MS-related impairments.

External validation of the EFFECT mortality prediction scale in patients admitted for acute heart failure in Araba, Spain.

AIM: To validate the EFFECT (Enhanced Feedback for Effective Cardiac Treatment) scales, which predict mortality at 1 month and 1 year after admission, in a defined cohort of patients admitted to the Araba University Hospital (HUA) with a diagnosis of acutely decompensated heart failure. METHOD: External validation study of a predictive model, in a retrospective cohort of patients admitted between October 1, 2020 and September 30, 2021. RESULTS: A total of 550 patients were included. The two scales demonstrated good overall discriminatory ability in our series, with an area under ROC (0.755 y 0.756) and values in Brier score (0.094 y 0.194) similar to the original series. Calibration was assessed using the Hosmer-Lemeshow test and calibration plots and was also adequate. All this despite the fact that significant differences were observed in many clinical characteristics between our series and the original one. CONCLUSIONS: The EFFECT scales showed good predictive ability and transportability. The one-month prediction scale was also useful for predicting mortality at one year. For both time periods, mortality was similar in the groups established in the original as low and very low risk.

Mapping Bovine Tuberculosis in Colombia, 2001-2019.

INTRODUCTION: Bovine tuberculosis is a zoonotic disease of significant impact, particularly in countries where a pastoral economy is predominant. Despite its importance, few studies have analysed the disease's behaviour in Colombia, and none have developed maps using geographic information systems (GIS) to characterise it; as such, we developed this study to describe the temporal-spatial distribution of bovine tuberculosis in Colombia over a period of 19 years. METHODS: A retrospective cross-sectional descriptive study, based on reports by the Colombian Agricultural Institute (ICA), surveillance of tuberculosis on cattle farms in Colombia from 2001 to 2019 was carried out. The data were converted into databases using Microsoft Access 365®, and multiple epidemiological maps were generated with the QGIS® version 3.36 software coupled to shape files of all the country's departments. RESULTS: During the study period, 5273 bovine tuberculosis cases were identified in multiple different departments of Colombia (with a mean of 278 cases/year). Regarding its temporal distribution, the number of cases varied from a maximum of 903 cases (17.12% of the total) in 2015 to a minimum of 0 between 2001 and 2004 and between 2017 and 2019 (between 2005 and 2016, the minimum was 46 cases, 0.87%). CONCLUSIONS: GIS are essential for understanding the temporospatial behaviour of zoonotic diseases in Colombia, as is the case for bovine tuberculosis, with its potential implications for the Human and One Health approaches.

Cognitive rehabilitation program in patients with multiple sclerosis: A pilot study.

INTRODUCTION: In recent years, there has been an increase of studies dedicated to cognitive rehabilitation in patients with multiple sclerosis (MS); however, few of these analyze the impact on such variables as cognitive reserve. The study aims to explore the effects of a cognitive rehabilitation program comprising a combination of cognitive and physical exercises, as well as group sessions to improve cognitive performance, emotional state, and cognitive reserve index. METHOD: Fifty patients with MS were subdivided into 2 groups: the control group, which performed aerobic exercise (n=25), and the experimental group (n=25), which participated in the integrated cognitive rehabilitation program (ICRP). All participants were evaluated 3 times (baseline, post-treatment, and long-term) with the Brief Repeatable Battery of Neuropsychological Tests, Cognitive Reserve Scale, Beck Depression Inventory, and a scale evaluating trait and state anxiety. RESULTS: Compared with the control group, patients in the experimental group showed improvements in cognitive function, with significant changes in measures of information processing speed, attention, memory, cognitive reserve index, and long-term mood. CONCLUSIONS: The ICRP was effective in improving cognitive and emotional function in MS, and increased the cognitive reserve index.

Design and baseline characteristics of SALT-HF trial: hypertonic saline therapy in ambulatory heart failure.

AIMS: Hypertonic saline solution (HSS) plus intravenous (IV) loop diuretic appears to enhance the diuretic response in patients hospitalized for heart failure (HF). The efficacy and safety of this therapy in the ambulatory setting have not been evaluated. We aimed to describe the design and baseline characteristics of the SALT-HF trial participants. METHODS AND RESULTS: 'Efficacy of Saline Hypertonic Therapy in Ambulatory Patients with HF' (SALT-HF) trial was a multicenter, double-blinded, and randomized study involving ambulatory patients who experienced worsening heart failure (WHF) without criteria for hospitalization. Enrolled patients had to present at least two signs of volume overload, use ≥ 80 mg of oral furosemide daily, and have elevated natriuretic peptides. Patients were randomized 1:1 to treatment with a 1-h infusion of IV furosemide plus HSS (2.6-3.4% NaCl depending on plasmatic sodium levels) versus a 1-h infusion of IV furosemide at the same dose (125-250 mg, depending on basal loop diuretic dose). Clinical, laboratory, and imaging parameters were collected at baseline and after 7 days, and a telephone visit was planned after 30 days. The primary endpoint was 3-h diuresis after treatment started. Secondary endpoints included (a) 7-day changes in congestion data, (b) 7-day changes in kidney function and electrolytes, (c) 30-day clinical events (need of IV diuretic, HF hospitalization, cardiovascular mortality, all-cause mortality or HF-hospitalization). RESULTS: A total of 167 participants [median age, 81 years; interquartile range (IQR), 73-87, 30.5% females] were randomized across 13 sites between December 2020 and March 2023. Half of the participants (n = 82) had an ejection fraction >50%. Most patients showed a high burden of comorbidities, with a median Charlson index of 3 (IQR: 2-4). Common co-morbidities included diabetes mellitus (41%, n = 69), atrial fibrillation (80%, n = 134), and chronic kidney disease (64%, n = 107). Patients exhibited a poor functional NYHA class (69% presenting NYHA III) and several signs of congestion. The mean composite congestion score was 4.3 (standard deviation: 1.7). Ninety per cent of the patients (n = 151) presented oedema and jugular engorgement, and 71% (n = 118) showed lung B lines assessed by ultrasound. Median inferior vena cava diameter was 23 mm, (IQR: 21-25), and plasmatic levels of N-terminal-pro-B-type natriuretic peptide (NTproBNP) and antigen carbohydrate 125 (CA125) were increased (median NT-proBNP 4969 pg/mL, IQR: 2508-9328; median CA125 46 U/L, IQR: 20-114). CONCLUSIONS: SALT-HF trial randomized 167 ambulatory patients with WHF and will determine whether an infusion of hypertonic saline therapy plus furosemide increases diuresis and improves decongestion compared to equivalent furosemide administration alone.

[Efficacy of high-intensity exercise in people with chronic low back pain: A systematic review]. / Eficacia del ejercicio de alta intensidad en personas con dolor lumbar crónico: una revisión sistemática.

Chronic low back pain causes disability and socioeconomic impact. High-intensity exercise shows positive results in other diseases, but there is no evidence on this pathology. The aim is to determine its efficacy on health-related quality of life, disability, pain intensity and adherence to treatment in people with chronic low back pain. A literature review is conducted in Pubmed, PEDro and Scopus, including randomized clinical trials, clinical practice guidelines and systematic reviews in Spanish, English or Portuguese (2012-2022). In addition, a snowball search is performed. Eight randomized clinical trials (n=379) are incorporated. Different high-intensity exercise modalities are analyzed, which seem to improve health-related quality of life and reduce disability and pain intensity. These data should be taken with caution given the small number of studies and the risk of bias presented.

ß-hydroxybutyrate is a metabolic regulator of proteostasis in the aged and Alzheimer disease brain.

Loss of proteostasis is a hallmark of aging and Alzheimer disease (AD). Here, we identify ß-hydroxybutyrate (ßHB), a ketone body, as a regulator of protein solubility in the aging brain. ßHB is a small molecule metabolite which primarily provides an oxidative substrate for ATP during hypoglycemic conditions, and also regulates other cellular processes through covalent and noncovalent protein interactions. We demonstrate ßHB-induced protein insolubility across in vitro, ex vivo, and in vivo mouse systems. This activity is shared by select structurally similar metabolites, is not dependent on covalent protein modification, pH, or solute load, and is observable in mouse brain in vivo after delivery of a ketone ester. Furthermore, this phenotype is selective for pathological proteins such as amyloid-ß, and exogenous ßHB ameliorates pathology in nematode models of amyloid-ß aggregation toxicity. We have generated a comprehensive atlas of the ßHB-induced protein insolublome ex vivo and in vivo using mass spectrometry proteomics, and have identified common protein domains within ßHB target sequences. Finally, we show enrichment of neurodegeneration-related proteins among ßHB targets and the clearance of these targets from mouse brain, likely via ßHB-induced autophagy. Overall, these data indicate a new metabolically regulated mechanism of proteostasis relevant to aging and AD.

Arrhythmias in patients with X-linked myotubular myopathy. / Arritmias en pacientes con miopatía miotubular ligada al cromosoma X.

INTRODUCTION: Myotubular myopathy is a congenital muscle disease caused by a mutation in the myotubularin (MTM1) gene. The X-linked myotubular myopathy (XLMTM) affects males with early-onset symptoms such as muscle weakness, hypotonia, and respiratory distress. To our knowledge, cardiac involvement has not been previously described in this condition, in contrast to other types of congenital myopathies such as nemaline myopathy or core myopathy. CASE REPORTS: We report two clinical cases of XLMTM that started with severe sinus bradycardia or auriculoventricular block from the first days of life, with pathologic 24-hours Holter monitoring in both cases. A primary cardiac affection was excluded by electrophysiological studies and normal heart rate was recovered with proper respiratory support. DISCUSSION: These cases with sever bradyarrhythmia in a well know pathology such the XLMTM represents a nuance on the usual differential diagnostics of congenital myopathies.

TITLE: Arritmias en pacientes con miopatía miotubular ligada al cromosoma X.Introducción. La miopatía miotubular es una enfermedad muscular congénita causada por una mutación en el gen de la miotubularina (MTM1). La miopatía miotubular ligada al cromosoma X (XLMTM) afecta a los hombres con síntomas de aparición temprana como debilidad muscular, hipotonía y dificultad respiratoria. Hasta donde sabemos, la afectación cardíaca en estos pacientes no se ha descrito previamente, a diferencia de otros tipos de miopatías congénitas, como la miopatía nemalínica o la miopatía con cores. Casos clínicos. Presentamos dos casos clínicos de XLMTM que comenzaron con bradicardia sinusal grave o bloqueo auriculoventricular desde los primeros días de vida, con Holter patológico en ambos casos. Se descartó una afectación cardíaca primaria por estudios electrofisiológicos y se recuperó la frecuencia cardíaca normal con soporte respiratorio adecuado. Conclusión. Estos casos con bradicardia grave en una patología bien conocida, como la XLMTM, suponen un matiz en el diagnóstico diferencial habitual de las miopatías congénitas.

[Impact of COVID-19 on a rare disease (uveal melanoma) in a national reference unit of intraocular tumors in Spain]. / Impacto del COVID-19 en una enfermedad rara (melanoma uveal) en una unidad de referencia nacional de tumores intraoculares en España.

Objective: To analyze the impact of the COVID-19 pandemic on the diagnosis and management of uveal melanoma (a tumor included in the Orphanet catalog of rare diseases) in a Spanish national reference unit for intraocular tumors during the first year of the pandemic. Material and methods: An observational retrospective study of patients with uveal melanoma in the National Reference Unit for Adult Intraocular Tumors of the Hospital Clínico Universitario de Valladolid (Spain) was performed, analyzing the pre- and post-COVID-19 periods: from March 15, 2019 to March 15, 2020 and from March 16, 2020 to March 16, 2021. Demographic data, diagnostic delay, tumor size, extraocular extension, treatment and evolution were collected. A multivariable logistic regression model was used to identify factors that were associated with the variable: enucleation. Results: Eighty-two patients with uveal melanoma were included, of which 42(51.21%) belonged to the pre-COVID-19 period and 40(40.78%) to the post-COVID-19 period. An increase in tumor size at diagnosis and in the number of enucleations was observed during the post-COVID-19 period (p < 0.05). Multivariable logistic regression demonstrated that both medium-large tumor size and patients diagnosed in the post-COVID-19 period were independently related to an increased risk of enucleation (OR 250, 95%CI, 27.69-2256.37; p < 0.01 and OR 10; 95% CI,1.10-90.25; p = 0.04, respectively). Conclusions: The increase in tumor size observed in uveal melanomas diagnosed during the first year of the COVID-19 pandemic may have favored the increase in the number of enucleations performed during that period.

Issue 2 - "Update on adverse respiratory effects of indoor air pollution". Part 2): Indoor air pollution and respiratory diseases: Perspectives from Italy and some other GARD countries.

OBJECTIVE: to synthesize the Italian epidemiological contribution to knowledge on indoor pollution respiratory impact, and to analyze the perspective of some GARD countries on the health effects of indoor air pollution. RESULTS: Italian epidemiological analytical studies confirmed a strong relationship between indoor air pollution and health in general population. Environmental tobacco smoke, biomass (wood/coal) fuel for cooking/heating and indoor allergens (house dust mites, cat and dog dander, mold/damp) are the most relevant indoor pollution sources and are related to respiratory and allergic symptoms/diseases in Italy and in other GARD countries such as Mexico, Brazil, Vietnam, India, Nepal and Kyrgyzstan. Community-based global health collaborations are working to improve prevention, diagnosis and care of respiratory diseases around the world, specially in low- and middle-income countries, through research and education. CONCLUSIONS: in the last thirty years, the scientific evidence produced on respiratory health effects of indoor air pollution has been extensive, but the necessity to empower the synergies between scientific community and local administrations remains a challenge to address in order to implement effective interventions. Based on abundant evidence of indoor pollution health effect, WHO, scientific societies, patient organizations and other members of the health community should work together to pursue the GARD vision of "a world where all people breathe freely" and encourage policy makers to increase their engagement in advocacy for clean air.

Impact of COVID-19 on a rare disease (uveal melanoma) in a national reference unit of intraocular tumors in Spain.

OBJECTIVE: To analyse the impact of the COVID-19 pandemic on the diagnosis and management of uveal melanoma (a tumour included in the Orphanet catalogue of rare diseases) in a Spanish national reference unit for intraocular tumours during the first year of the pandemic. METHOD: An observational retrospective study of patients with uveal melanoma in the National Reference Unit for Adult Intraocular Tumors of the Hospital Clínico Universitario de Valladolid (Spain) was performed, analysing the pre- and post-COVID-19 periods: from March 15, 2019 to March 15, 2020 and from March 16, 2020 to March 16, 2021. Demographic data, diagnostic delay, tumour size, extraocular extension, treatment and evolution were collected. A multivariable logistic regression model was used to identify factors that were associated with the variable: enucleation. RESULTS: Eighty-two patients with uveal melanoma were included, of which 42 (51.21%) belonged to the pre-COVID-19 period and 40(40.78%) to the post-COVID-19 period. An increase in tumour size at diagnosis and in the number of enucleations was observed during the post-COVID-19 period (p < 0.05). Multivariable logistic regression demonstrated that both medium-large tumour size and patients diagnosed in the post-COVID-19 period were independently related to an increased risk of enucleation (OR 250, 95%CI, 27.69-2256.37; p < 0.01 and OR 10; 95%CI, 1.10-90.25; p = 0.04, respectively). CONCLUSIONS: The increase in tumour size observed in uveal melanomas diagnosed during the first year of the COVID-19 pandemic may have favored the increase in the number of enucleations performed during that period.

Synergistic Effect of SOS Response and GATC Methylome Suppression on Antibiotic Stress Survival in Escherichia coli.

The suppression of the SOS response has been shown to enhance the in vitro activity of quinolones. Furthermore, Dam-dependent base methylation has an impact on susceptibility to other antimicrobials affecting DNA synthesis. Here, we investigated the interplay between these two processes, alone and in combination, in terms of antimicrobial activity. A genetic strategy was used employing single- and double-gene mutants for the SOS response (recA gene) and the Dam methylation system (dam gene) in isogenic models of Escherichia coli both susceptible and resistant to quinolones. Regarding the bacteriostatic activity of quinolones, a synergistic sensitization effect was observed when the Dam methylation system and the recA gene were suppressed. In terms of growth, after 24 h in the presence of quinolones, the Δdam ΔrecA double mutant showed no growth or delayed growth compared to the control strain. In bactericidal terms, spot tests showed that the Δdam ΔrecA double mutant was more sensitive than the ΔrecA single mutant (about 10- to 102-fold) and the wild type (about 103- to 104-fold) in both susceptible and resistant genetic backgrounds. Differences between the wild type and the Δdam ΔrecA double mutant were confirmed by time-kill assays. The suppression of both systems, in a strain with chromosomal mechanisms of quinolone resistance, prevents the evolution of resistance. This genetic and microbiological approach demonstrated the enhanced sensitization of E. coli to quinolones by dual targeting of the recA (SOS response) and Dam methylation system genes, even in a resistant strain model.

Midbrain and pons MRI shape analysis and its clinical and CSF correlates in degenerative parkinsonisms: a pilot study.

OBJECTIVES: To conduct brainstem MRI shape analysis across neurodegenerative parkinsonisms and control subjects (CS), along with its association with clinical and cerebrospinal fluid (CSF) correlates. METHODOLOGY: We collected demographic and clinical variables, performed planimetric and shape MRI analyses, and determined CSF neurofilament-light chain (NfL) levels in 84 participants: 11 CS, 12 with Parkinson's disease (PD), 26 with multiple system atrophy (MSA), 21 with progressive supranuclear palsy (PSP), and 14 with corticobasal degeneration (CBD). RESULTS: MSA featured the most extensive and significant brainstem shape narrowing (that is, atrophy), mostly in the pons. CBD presented local atrophy in several small areas in the pons and midbrain compared to PD and CS. PSP presented local atrophy in small areas in the posterior and upper midbrain as well as the rostral pons compared to MSA. Our findings of planimetric MRI measurements and CSF NfL levels replicated those from previous literature. Brainstem shape atrophy correlated with worse motor state in all parkinsonisms and with higher NfL levels in MSA, PSP, and PD. CONCLUSION: Atypical parkinsonisms present different brainstem shape patterns which correlate with clinical severity and neuronal degeneration. In MSA, shape analysis could be further explored as a potential diagnostic biomarker. By contrast, shape analysis appears to have a rather limited discriminant value in PSP. KEY POINTS: • Atypical parkinsonisms present different brainstem shape patterns. • Shape patterns correlate with clinical severity and neuronal degeneration. • In MSA, shape analysis could be further explored as a potential diagnostic biomarker.

Interactions between epiphytes during canopy soil formation: an experiment in a lower montane cloud forest of southeast Mexico.

In several montane forests around the world, epiphytes coexist in mats, sharing the rhizosphere and forming histosol-type soils rich in nutrients. The role of these epiphytes in the formation of canopy soil and the fitness costs that epiphytes face when cohabiting in these mats are unknown. In a lower montane cloud forest in central Veracruz, Mexico, a 2-year factorial experiment was carried out with the presence/absence of ramets of Phlebodium areolatum (Polypodiaceae), Tillandsia kirchhoffiana, T. multicaulis and T. punctulata (Bromeliaceae). We examined (i) which epiphyte species contribute to the formation of canopy soil, (ii) the role of epiphyte composition in the soil nutrient composition, and (iii) the fitness costs faced by epiphytes when cohabiting. Canopy soil formation highest when P. areolatum is present. Soil nutrient content does not change with epiphyte composition, is influenced by the microbiota, and P content decreases with the presence of epiphytes. The fitness costs show that the species compete, decreasing their survival and growth, but the competitive capacity differs between the species. We conclude that P. areolatum is an ecosystem engineer that promotes the creation of canopy soil but is a poor competitor. The results coincide with the model of succession by facilitation. Canopy soil is a slow-created component whose nutrient content does not depend on the epiphytic flora. In epiphyte mats, the dominant interactions are competitive, but there is also facilitation.

RecA inactivation as a strategy to reverse the heteroresistance phenomenon in clinical isolates of Escherichia coli.

RecA inhibition could be an important strategy to combat antimicrobial resistance because of its key role in the SOS response, DNA repair and homologous recombination contributing to bacterial survival. This study evaluated the impact of RecA inactivation on heteroresistance in clinical isolates of Escherichia coli and their corresponding recA-deficient isogenic strains to multiple classes of antimicrobial agents. A high frequency (>30%) of heteroresistance was observed in this collection of clinical isolates. Deletion of the recA gene led to a marked reduction in heteroresistant subpopulations, especially against quinolones or ß-lactams. The molecular basis of heteroresistance was associated with an increase in copy number of plasmid-borne resistance genes (blaTEM-1B) or tandem gene amplifications (qnrA1). Of note, in the absence of the recA gene, the increase in copy number of resistance genes was suppressed. This makes the recA gene a promising target for combating heteroresistance.