Imaging demyelinated axons after spinal cord injuries with PET tracer [ 18 F]3F4AP.

Spinal cord injuries (SCI) often lead to lifelong disability. Among the various types of injuries, incomplete and discomplete injuries, where some axons remain intact, offer potential for recovery. However, demyelination of these spared axons can worsen disability. Demyelination is a reversible phenomenon, and drugs like 4-aminopyridine (4AP), which target K+ channels in demyelinated axons, show that conduction can be restored. Yet, accurately assessing and monitoring demyelination post-SCI remains challenging due to the lack of suitable imaging methods. In this study, we introduce a novel approach utilizing the positron emission tomography (PET) tracer, [ 18 F]3F4AP, specifically targeting K+ channels in demyelinated axons for SCI imaging. Rats with incomplete contusion injuries were imaged up to one month post-injury, revealing [ 18 F]3F4AP's exceptional sensitivity to injury and its ability to detect temporal changes. Further validation through autoradiography and immunohistochemistry confirmed [ 18 F]3F4AP's targeting of demyelinated axons. In a proof-of-concept study involving human subjects, [ 18 F]3F4AP differentiated between a severe and a largely recovered incomplete injury, indicating axonal loss and demyelination, respectively. Moreover, alterations in tracer delivery were evident on dynamic PET images, suggestive of differences in spinal cord blood flow between the injuries. In conclusion, [ 18 F]3F4AP demonstrates efficacy in detecting incomplete SCI in both animal models and humans. The potential for monitoring post-SCI demyelination changes and response to therapy underscores the utility of [ 18 F]3F4AP in advancing our understanding and management of spinal cord injuries.

Common anesthetic used in preclinical PET imaging inhibits metabolism of the PET tracer [18F]3F4AP.

Positron emission tomography (PET) imaging studies in laboratory animals are almost always performed under isoflurane anesthesia to ensure that the subject stays still during the image acquisition. Isoflurane is effective, safe, and easy to use, and it is generally assumed to not have an impact on the imaging results. Motivated by marked differences observed in the brain uptake and metabolism of the PET tracer 3-[18F]fluoro-4-aminopyridine [(18F]3F4AP) between human and nonhuman primate studies, this study investigates the possible effect of isoflurane on this process. Mice received [18F]3F4AP injection while awake or under anesthesia and the tracer brain uptake and metabolism was compared between groups. A separate group of mice received the known cytochrome P450 2E1 inhibitor disulfiram prior to tracer administration. Isoflurane was found to largely abolish tracer metabolism in mice (74.8 ± 1.6 vs. 17.7 ± 1.7% plasma parent fraction, % PF) resulting in a 4.0-fold higher brain uptake in anesthetized mice at 35 min post-radiotracer administration. Similar to anesthetized mice, animals that received disulfiram showed reduced metabolism (50.0 ± 6.9% PF) and a 2.2-fold higher brain signal than control mice. The higher brain uptake and lower metabolism of [18F]3F4AP observed in anesthetized mice compared to awake mice are attributed to isoflurane's interference in the CYP2E1-mediated breakdown of the tracer, which was confirmed by reproducing the effect upon treatment with the known CYP2E1 inhibitor disulfiram. These findings underscore the critical need to examine the effect of isoflurane in PET imaging studies before translating tracers to humans that will be scanned without anesthesia.

Complete remission with histamine blocker in a patient with intractable hyperadrenergic postural orthostatic tachycardia syndrome secondary to long coronavirus disease syndrome.

The COVID-19 pandemic caused by the novel severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), has emerged as a global public health concern and its sequels have barely started to outcrop. A good percentage of patients who suffered from COVID-19 are prone to develop long-COVID or post-COVID condition (PCC), a multisystemic, heterogeneous, chronic disorder. Patients with PCC may experience diverse manifestations, of which cardiovascular and neurological symptoms are among the most frequently reported. Indeed, dysautonomia presented as orthostatic intolerance has gained room following recent reports linking postural orthostatic tachycardia syndrome (POTS) with PCC. Disturbances in heart rate (HR) and blood pressure (BP) during postural changes are the cornerstones of orthostatic intolerance seen in patients suffering from PCC. A subtype of POTS, hyperadrenergic POTS, has been widely studied because of its association with mast cell activation syndrome (MCAS). Although a causative relationship between PCC, hyperadrenergic POTS, and MCAS remains unrevealed, these syndromes can overlap. We want to propose here a correlation produced by a close-loop mechanism with positive feedback established after SARS-CoV-2 infection in a previously healthy young patient.

Nirmatrelvir/ritonavir and remdesivir against symptomatic treatment in high-risk COVID-19 outpatients to prevent hospitalization or death during the Omicron era: a propensity score-matched study.

Background: Even though worldwide death rates from coronavirus disease 2019 (COVID-19) have decreased, the threat of disease progression and death for high-risk groups continues. Few direct comparisons between the available severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antivirals have been made. Objective: We aimed to compare two SARS-CoV-2 antivirals (nirmatrelvir/ritonavir and remdesivir) against all-cause hospitalization or death. Design: This is a propensity score-matched cohort study. Methods: We included all high-risk outpatients with COVID-19 in a tertiary referral center in Mexico City from 1 January 2022 to 31 July 2023. The primary outcome was all-cause hospitalization or death 28 days after symptom onset. The secondary outcome was COVID-19-associated hospitalization or death 28 days after symptom onset. Logistic regression analysis for characteristics associated with the primary outcome and a multi-group comparison with Kaplan-Meier survival estimates were performed. Results: Of 1566 patients analyzed, 783 did not receive antiviral treatment, 451 received remdesivir, and 332 received nirmatrelvir/ritonavir. The median age was 60 years (interquartile range: 46-72), 62.5% were female and 97.8% had at least one comorbidity. The use of nirmatrelvir/ritonavir was associated with an absolute risk reduction of 8.8% and a relative risk reduction of 90% for all-cause hospitalization or death. The use of remdesivir was associated with an absolute risk reduction of 6.4% and a relative risk reduction of 66% for all-cause hospitalization or death. In multivariable analysis, both antivirals reduced the odds of 28-day all-cause hospitalization or death [nirmatrelvir/ritonavir odds ratio (OR) 0.08 - 95% confidence interval (CI): 0.03-0.19, remdesivir OR 0.29 - 95% CI: 0.18-0.45]. Conclusion: In high-risk COVID-19 outpatients, early antiviral treatment with nirmatrelvir/ritonavir or remdesivir was associated with lower 28-day all-cause hospitalization or death.

Nirmatrelvir/ritonavir and remdesivir against symptomatic treatment in high-risk COVID-19 outpatients In this study, we included high-risk non-hospitalized patients with confirmed mild COVID-19. We compared those who received antiviral treatment (nirmatrelvir/ritonavir or remdesivir) against those who only received symptomatic treatment. The aim was to detect differences in hospitalization or death 28 days after symptom onset. We analyzed 1566 patients: 783 did not receive antiviral treatment, 451 received remdesivir, and 332 received nirmatrelvir/ritonavir. Most patients were female and over 60 years old. The most common comorbidities were chronic hypertension (44%), diabetes mellitus (26%), and autoimmune diseases (25%); systemic immunosuppression was registered in 35% of patients. Hospitalization or death 28 days after symptom onset occurred in 168 patients (136 in the symptomatic treatment group, 27 in the remdesivir group, and 5 in the nirmatrelvir/ritonavir group). Considering multiple variables like age, sex, comorbidities, and previous vaccination, both antivirals significantly reduced the odds of hospitalization or death (nirmatrelvir/ritonavir odds ratio 0.08, 95% confidence interval 0.03-0.19; remdesivir odds ratio 0.29, 95% confidence interval 0.18-0.45).

Cephalotin Versus Dicloxacillin for the Treatment of Methicillin-Susceptible Staphylococcus aureus Bacteraemia: A Retrospective Cohort Study.

BACKGROUND: First-line treatments for methicillin-susceptible S. aureus (MSSA) bacteraemia are nafcillin, oxacillin, or cefazolin. Regional shortages of these antibiotics force clinicians to use other options like dicloxacillin and cephalotin. This study aims to describe and compare the safety and efficacy of cephalotin and dicloxacillin for the treatment of MSSA bacteraemia. METHODS: This retrospective study was conducted in a referral centre in Mexico City. We identified MSSA isolates in blood cultures from 1 January 2012 to 31 December 2022. Patients ≥ 18 years of age, with a first episode of MSSA bacteraemia, who received cephalotin or dicloxacillin as the definitive antibiotic treatment, were included. The primary outcome was in-hospital all-cause mortality. RESULTS: We included 202 patients, of which 48% (97/202) received cephalotin as the definitive therapy and 52% (105/202) received dicloxacillin. In-hospital all-cause mortality was 20.7% (42/202). There were no differences in all-cause in-hospital mortality between patients receiving cephalotin or dicloxacillin (20% vs. 21%, p = 0.43), nor in 30-day all-cause mortality (14% vs. 18%, p = 0.57) or 90-day all-cause mortality (24% vs. 22%, p = 0.82). No severe adverse reactions were associated with either antibiotic. CONCLUSIONS: Cephalotin and dicloxacillin were equally effective for treating MSSA bacteraemia, and both showed an adequate safety profile.

LC-MS Fingerprinting Development for Standardized Precipitate from Agastache mexicana, Which Induces Antihypertensive Effect through NO Production and Calcium Channel Blockade.

The aim of this work was to evaluate the vasorelaxant and antihypertensive effects of a standardized precipitate of the hydroalcoholic extract from Agastache mexicana (PPAm), comprising ursolic acid, oleanolic acid, acacetin, luteolin and tilianin, among others. In the ex vivo experiments, preincubation with L-NAME (nonspecific inhibitor of nitric oxide synthases) reduced the relaxation induced by PPAm; nevertheless, preincubation with indomethacin (nonspecific inhibitor of cyclooxygenases) did not generate any change in the vasorelaxation, and an opposed effect was observed to the contraction generated by CaCl2 addition. Oral administration of 100 mg/kg of PPAm induced a significant acute decrease in diastolic (DBP) and systolic (SBP) blood pressure in spontaneously hypertensive rats, without changes in heart rate. Additionally, PPAm showed a sustained antihypertensive subacute effect on both DBP and SBP for 10 days compared to the control group. On the other hand, human umbilical vein cells treated with 10 µg/mL of PPAm showed a significant reduction (p < 0.05) in intracellular adhesion molecule-1, compared to the control, but not on vascular cell adhesion molecule-1. In conclusion, PPAm induces a significant antihypertensive effect in acute- and subacute-period treatments, due to its direct vasorelaxant action on rat aortic rings through NO production and Ca2+ channel blockade.

Safety and Tolerability of Six Months of Isoniazid Plus Pyridoxine or Three Months of Rifampicin for Tuberculosis among Subjects with Diabetes Mellitus: A Randomized Trial.

Tuberculosis (TB) associated with diabetes mellitus (DM) is a growing problem, particularly in low- and medium-resource countries. We conducted an open-label, parallel-group, randomized, and controlled trial in a tertiary care center in Mexico City to assess TB preventive treatment (TPT) with isoniazid (INH) or rifampicin (RIF) in people with type 2 DM. Participants were assigned six months of INH 300 mg/day plus pyridoxine 75 mg or three months of RIF 600 mg/day. The primary outcomes were adverse events resulting in permanent treatment cessation and considered possibly or probably related to study drugs. We included 130 subjects, 68 randomized to INH and 62 to RIF. We prematurely halted the study based on recommendations of the Adverse Event Safety Panel. There was no difference between arms in the overall frequency of adverse events. However, the INH group had significantly more permanent treatment interruptions due to grade 2 recurrent or grade 3 or 4 hepatoxicity. In comparison, the RIF arm had more treatment interruptions due to grade 3 or 4 gastrointestinal intolerance. TPT using INH or RIF is not safe enough to be considered a universal indication to patients with type 2 DM and TB infection. These results underline the need to search for alternative TB preventions with better safety profiles for type 2 DM patients.

Risk Factors Associated with the Development of Hospital-Acquired Infections in Hospitalized Patients with Severe COVID-19.

Recognition of risk factors for hospital-acquired infections (HAI) in patients with COVID-19 is warranted. We aimed to describe factors associated with the development of HAI in patients with severe COVID-19. We conducted a retrospective cohort study including all adult patients admitted with severe COVID-19 between March 2020 and November 2020. The primary outcome was HAI development. Bivariate and multiple logistic regression models were constructed. Among 1540 patients, HAI occurred in 221 (14%). A total of 299 episodes of HAI were registered. The most common HAI were hospital-acquired/ventilation-associated pneumonia (173 episodes) and primary bloodstream infection (66 episodes). Death occurred in 387 (35%) patients and was more frequent in patients with HAI (38% vs. 23%, p < 0.01). Early mechanical ventilation (aOR 18.78, 95% CI 12.56-28.07), chronic kidney disease (aOR 3.41, 95% CI 1.4-8.27), use of corticosteroids (aOR 2.95, 95% CI 1.92-4.53) and tocilizumab (aOR 2.68, 95% CI 1.38-5.22), age ≥ 60 years (aOR 1.91, 95% CI 1.27-2.88), male sex (aOR 1.52, 95% CI 1.03-2.24), and obesity (aOR 1.49, 95% CI 1.03-2.15) were associated with HAI. In patients with severe COVID-19, mechanical ventilation within the first 24 h upon admission, chronic kidney disease, use of corticosteroids, use of tocilizumab, age ≥ 60 years, male sex, and obesity were associated with a higher risk of HAI.

Predictors of Mortality in Patients with Infections Due to Carbapenem-Resistant Gram-Negative Bacteria.

INTRODUCTION: Infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB) are a significant cause of mortality and represent a serious challenge to health systems. The early identification of mortality predictors could guide appropriate treatment and follow-up. We aimed to identify the factors associated with 90-day all-cause mortality in patients with CR-GNB infections. METHODS: We conducted a cohort study from 1 January 2019 to 30 April 2022. The primary outcome was death from any cause during the first 90 days after the date of the first CR-GNB-positive culture. Secondary outcomes included infection relapse, invasive mechanical ventilation during follow-up, need for additional source control, acute kidney injury, Clostridioides difficile infection, and all-cause hospital admission after initial discharge. Bivariate and multivariate Cox-proportional hazards models were constructed to identify the factors independently associated with 90-day all-cause mortality. RESULTS: A total of 225 patients with CR-GNB infections were included. Death occurred in 76 (34%) cases. The most-reported comorbidities were immunosuppression (43%), arterial hypertension (35%), and COVID-19 (25%). The median length of stay in survivors was 18 days (IQR 10-34). Mechanical ventilation and ICU admission after diagnosis occurred in 8% and 11% of cases, respectively. Both infection relapse and rehospitalisation occurred in 18% of cases. C. difficile infection was diagnosed in 4% of cases. Acute kidney injury was documented in 22% of patients. Mechanical ventilation after diagnosis, ICU admission after diagnosis, and acute kidney injury in the first ten days of appropriate treatment were more frequently reported among non-survivors. In the multivariate analysis, age (HR 1.19 (95%CI 1.00-1.83)), immunosuppression (HR 1.84 (95%CI 1.06-3.18)), and septic shock at diagnosis (HR 2.40 (95% 1.41-4.08)) had an independent association with death during the first 90 days after the CR-GNB infection diagnosis. Receiving antibiogram-guided appropriate treatment was independently associated with a lower risk of death (HR 0.25 (95%CI 0.14-0.46)). CONCLUSIONS: The presence of advanced age, immunosuppression, septic shock at diagnosis, and inappropriate treatment are associated with higher 90-day all-cause mortality in hospitalised patients with infections due to CR-GNB. Recognition of the risk factors for adverse outcomes could further assist in patient care and the design of interventional studies that address the severe and widespread problem that is carbapenem resistance.

Fungal Infections in the ICU during the COVID-19 Pandemic in Mexico.

Background: Invasive Fungal Infections (IFI) are emergent complications of COVID-19. In this study, we aim to describe the prevalence, related factors, and outcomes of IFI in critical COVID-19 patients. Methods: We conducted a nested case-control study of all COVID-19 patients in the intensive care unit (ICU) who developed any IFI and matched age and sex controls for comparison (1:1) to evaluate IFI-related factors. Descriptive and comparative analyses were made, and the risk factors for IFI were compared versus controls. Results: We found an overall IFI prevalence of 9.3% in COVID-19 patients in the ICU, 5.6% in COVID-19-associated pulmonary aspergillosis (CAPA), and 2.5% in invasive candidiasis (IC). IFI patients had higher SOFA scores, increased frequency of vasopressor use, myocardial injury, and more empirical antibiotic use. CAPA was classified as possible in 68% and 32% as probable by ECMM/ISHAM consensus criteria, and 57.5% of mortality was found. Candidemia was more frequent for C. parapsilosis Fluconazole resistant outbreak early in the pandemic, with a mortality of 28%. Factors related to IFI in multivariable analysis were SOFA score > 2 (aOR 5.1, 95% CI 1.5-16.8, p = 0.007) and empiric antibiotics for COVID-19 (aOR 30, 95% CI 10.2-87.6, p = <0.01). Conclusions: We found a 9.3% prevalence of IFIs in critically ill patients with COVID-19 in a single center in Mexico; factors related to IFI were associated with higher SOFA scores and empiric antibiotic use for COVID-19. CAPA is the most frequent type of IFI. We did not find a mortality difference.

Post-COVID-19 syndrome and quality of life impairment in severe COVID-19 Mexican patients.

Introduction: Post-COVID-19 syndrome (PCS) usually occurs 3 months after the onset of COVID-19 with a symptom duration of at least 2 months without an alternative diagnosis. Objective: This study aimed to describe the prevalence, characteristics, and impact on the quality of life (QoL) of post-COVID-19 syndrome in patients with a history of hospitalization for COVID-19. Materials and methods: We conducted a cross-sectional study. Patients who required hospitalization due to COVID-19 between March 2020 and October 2021 were invited to answer a PCS questionnaire and the EQ-5D instrument. A total of 246 patients were included: 187 (76%) met the definition of PCS and 54% were men, with a median age of 50 years (IQR 41-63). Results: From 187 patients with PCS, the median time to symptom onset after hospital discharge was 1 day (IQR 1-20), and the median symptom duration was 150 days (IQR 90-225). A total of 27 different symptoms were reported; the most frequent were difficulty concentrating (81%), dyspnea (75%), arthralgia (71%), fatigue (68%), and hair loss (60%). Some symptoms, such as difficulty concentrating, arthralgia/myalgia, and hair loss, were more prevalent in women with PCS. Patients with PCS had a higher frequency of tobacco smoking (37 vs. 4%, p = 0.02) and increased severity of lung involvement in the initial chest tomography (75 vs. 58%, p = 0.01) than those without PCS. Patients with PCS were less likely to receive antivirals (15.5 vs. 27%, p = 0.04). No difference between ICU admission, mechanical ventilation, and length of hospital stay was found. Patients with PCS had a lower visual analog scale result for EQ-5D vs. those without (80 [IQR 70-90] vs. 89.5 [IQR 75-90], p = 0.05). All five QoL dimensions were affected in PCS patients, showing increased pain/discomfort (67 vs. 39%, p = < 0.001), difficulties in performing usual activities (39.2 vs. 20.3%, p = 0.03), and anxiety/depression (57.5 vs. 37%, p = 0.02). Conclusion: PCS occurred in 76% of hospitalized patients with prolonged duration and QoL impairment. Neurological symptoms such as difficulty concentrating were the most frequent symptoms. Timely diagnostic and therapeutic interventions are required.

Metabolic Stability of the Demyelination Positron Emission Tomography Tracer [18F]3-Fluoro-4-Aminopyridine and Identification of Its Metabolites.

[18F]3-fluoro-4-aminopyridine ([18F]3F4AP) is a positron emission tomography (PET) tracer for imaging demyelination based on the multiple sclerosis drug 4-aminopyridine (4AP, dalfampridine). This radiotracer was found to be stable in rodents and nonhuman primates imaged under isoflurane anesthesia. However, recent findings indicate that its stability is greatly decreased in awake humans and mice. Since both 4AP and isoflurane are metabolized primarily by cytochrome P450 enzymes, particularly cytochrome P450 family 2 subfamily E member 1 (CYP2E1), we postulated that this enzyme may be responsible for the metabolism of 3F4AP. Here, we investigated the metabolism of [18F]3F4AP by CYP2E1 and identified its metabolites. We also investigated whether deuteration, a common approach to increase the stability of drugs, could improve its stability. Our results demonstrate that CYP2E1 readily metabolizes 3F4AP and its deuterated analogs and that the primary metabolites are 5-hydroxy-3F4AP and 3F4AP N-oxide. Although deuteration did not decrease the rate of the CYP2E1-mediated oxidation, our findings explain the diminished in vivo stability of 3F4AP compared with 4AP and further our understanding of when deuteration may improve the metabolic stability of drugs and PET ligands. SIGNIFICANCE STATEMENT: The demyelination tracer [18F]3F4AP was found to undergo rapid metabolism in humans, which could compromise its utility. Understanding the enzymes and metabolic products involved may offer strategies to reduce metabolism. Using a combination of in vitro assays and chemical syntheses, this report shows that cytochrome P450 enzyme CYP2E1 is likely responsible for [18F]3F4AP metabolism, that 4-amino-5-fluoroprydin-3-ol (5-hydroxy-3F4AP, 5OH3F4AP) and 4-amino-3-fluoropyridine 1-oxide (3F4AP N-oxide) are the main metabolites, and that deuteration is unlikely to improve the stability of the tracer in vivo.

Broad-scope Syntheses of [11 C/18 F]Trifluoromethylarenes from Aryl(mesityl)iodonium Salts.

Efficient methods for labeling aryl trifluoromethyl groups to provide novel radiotracers for use in biomedical research with positron emission tomography (PET) are keenly sought. We report a broad-scope method for labeling trifluoromethylarenes with either carbon-11 (t1/2 =20.4 min) or fluorine-18 (t1/2 =109.8 min) from readily accessible aryl(mesityl)iodonium salts. In this method, the aryl(mesityl)iodonium salt is treated rapidly with no-carrier-added [11 C]CuCF3 or [18 F]CuCF3 . The mesityl group acts as a spectator allowing radiolabeled trifluoromethylarenes to be obtained with very high chemoselectivity. Radiochemical yields from aryl(mesityl)iodonium salts bearing either electron-donating or electron-withdrawing groups at meta- or para- position are good to excellent (67-96 %). Ortho-substituted and otherwise sterically hindered trifluoromethylarenes still give good yields (15-34 %). Substituted heteroaryl(mesityl)iodonium salts are also viable substrates. The broad scope of this method was further exemplified by labeling a previously inaccessible target, [11 C]p-trifluoromethylphenyl boronic acid, as a potentially useful labeling synthon. In addition, fluoxetine, leflunomide, and 3-trifluoromethyl-4-aminopyridine, as examples of small drug-like molecules and candidate PET radioligands, were successfully labeled in high yields (69-81 %).

Human biodistribution and radiation dosimetry of the demyelination tracer [18F]3F4AP.

PURPOSE: [18F]3F4AP is a novel PET radiotracer that targets voltage-gated potassium (K+) channels and has shown promise for imaging demyelinated lesions in animal models of neurological diseases. This study aimed to evaluate the biodistribution, safety, and radiation dosimetry of [18F]3F4AP in healthy human volunteers. METHODS: Four healthy volunteers (2 females) underwent a 4-h dynamic PET scan from the cranial vertex to mid-thigh using multiple bed positions after administration of 368 ± 17.9 MBq (9.94 ± 0.48 mCi) of [18F]3F4AP. Volumes of interest for relevant organs were manually drawn guided by the CT, and PET images and time-activity curves (TACs) were extracted. Radiation dosimetry was estimated from the integrated TACs using OLINDA software. Safety assessments included measuring vital signs immediately before and after the scan, monitoring for adverse events, and obtaining a comprehensive metabolic panel and electrocardiogram within 30 days before and after the scan. RESULTS: [18F]3F4AP distributed throughout the body with the highest levels of activity in the kidneys, urinary bladder, stomach, liver, spleen, and brain and with low accumulation in muscle and fat. The tracer cleared quickly from circulation and from most organs. The clearance of the tracer was noticeably faster than previously reported in nonhuman primates (NHPs). The average effective dose (ED) across all subjects was 12.1 ± 2.2 µSv/MBq, which is lower than the estimated ED from the NHP studies (21.6 ± 0.6 µSv/MBq) as well as the ED of other fluorine-18 radiotracers such as [18F]FDG (~ 20 µSv/MBq). No differences in ED between males and females were observed. No substantial changes in safety assessments or adverse events were recorded. CONCLUSION: The biodistribution and radiation dosimetry of [18F]3F4AP in humans are reported for the first time. The average total ED across four subjects was lower than most 18F-labeled PET tracers. The tracer and study procedures were well tolerated, and no adverse events occurred.

Common anesthetic used in preclinical PET imaging inhibits metabolism of the PET tracer [ 18 F]3F4AP.

PET imaging studies in laboratory animals are almost always performed under isoflurane anesthesia to ensure that the subject stays still during the image acquisition. Isoflurane is effective, safe, and easy to use, and it is generally assumed to not have an impact on the imaging results. Motivated by marked differences observed in [ 18 F]3F4AP brain uptake and metabolism between human and nonhuman primate studies, this study investigates the possible effect of isoflurane on [ 18 F]3F4AP metabolism and brain uptake. Isoflurane was found to largely abolish tracer metabolism in mice resulting in a 3.3-fold higher brain uptake in anesthetized mice at 35 min post radiotracer administration, which replicated the observed effect in unanesthetized humans and anesthetized monkeys. This effect is attributed to isoflurane's interference in the CYP2E1-mediated breakdown of [ 18 F]3F4AP, which was confirmed by reproducing a higher brain uptake and metabolic stability upon treatment with the known CYP2E1 inhibitor disulfiram. These findings underscore the critical need to examine the effect of isoflurane in PET imaging studies before translating tracers to humans that will be scanned without anesthesia.

Predictors of Poor Outcomes in Young Non-Comorbid Patients with COVID-19.

Background: Prognostic factors in previously healthy young patients with COVID-19 remained understudied. Objectives: The objective of the study was to identify factors associated with in-hospital death or need for invasive mechanical ventilation (IMV) in young (aged ≤ 65 years) and previously healthy patients with COVID-19. Methods: We conducted a prospective cohort study that included patients admitted with COVID-19. The primary outcome was in-hospital death/need for IMV. Secondary outcomes included need for IMV during follow-up, days on IMV, length of stay (LOS), hospital-acquired pneumonia/ventilator-associated pneumonia (HAP/VAP), and pulmonary embolism (PE). Bivariate and multivariate analyses were performed. Results: Among 92 patients, primary outcome occurred in 16 (17%), death in 12 (13%), need for IMV in 16 (17%), HAP/VAP in 7 (8%), and PE in 2 (2%). Median LOS and IMV duration were 7 and 12 days, respectively. Independent associations were found between the primary outcome and male sex (Adjusted odds ratio [aOR] 7.1, 95%CI 1.1-46.0, p < 0.05), D-dimer levels > 1000ng/mL (aOR 9.0, 95%CI 1.6-49.1, p < 0.05), and RT-PCR Ct-value ≤ 24 on initial swab samples (aOR 14.3, 95%CI 2.0-101.5, p < 0.01). Conclusions: In young and non-comorbid COVID-19 patients, male sex, higher levels of D-dimer, and low SARS-CoV-2 RT-PCR Ct-value on an initial nasopharyngeal swab were independently associated with increased in-hospital mortality or need for IMV. (Rev Invest Clin. 2022;74(5):268-75).

Epidemiologic and economic considerations regarding persistently infected cattle during vaccinate-to-live strategies for control of foot-and-mouth disease in FMD-free regions.

Development of a foot-and-mouth disease (FMD) carrier state following FMD virus (FMDV) infection is a well-established phenomenon in cattle. However, the proportion of cattle likely to become carriers and the duration of the carrier state at a herd or population-level are incompletely understood. The objective of this study was to examine the epidemiologic and economic impacts of vaccination-to-live strategy in a disease-free region or country. We developed and simulated scenarios of FMD spread and control in the US livestock population, which included depopulation for a limited period, followed by a vaccinate-to-live strategy with strong biosecurity and movement restrictions. Six scenarios of FMD spread and control were simulated in the InterSpread Plus (ISP) modeling tool. Data on the number of infected and depopulated cattle (by operation types) from ISP model runs were used to estimate the monthly number of infected but not depopulated (potential carrier) cattle after the infection. Using available literature data on the FMD carrier state, we estimated the monthly proportion of carrier cattle (from infected but not depopulated cattle) over time following infection. Among the simulated scenarios, the median (25th, 75th percentile) number of infected cattle ranged from 43,217 (42,819, 55,274) head to 148,907 (75,819, 205,350) head, and the epidemic duration ranged from 20 (11, 30) to 76 (38, 136) days. In general, larger outbreaks occurred when depopulation was carried out through longer periods, and the onset of the vaccination was late (p > 0.05). The estimated proportion of surviving cattle, which were infected and not depopulated and had the potential to become persistently infected ranged from 14 to 35% of total infected cattle. Production losses in beef and dairy sectors were higher when outbreaks started in multiple states simultaneously, but production losses were small compared to trade losses and consumer avoidance losses. These results can be used to inform the consideration of a vaccinate-to-live strategy for FMD outbreaks and the development of appropriate post-outbreak management strategies. Furthermore, this output will enable a more detailed examination of the epidemiologic and economic implications of allowing convalescent cattle to survive and remain in production chains after FMD outbreaks in FMD-free regions.

Early Outpatient Treatment With Remdesivir in Patients at High Risk for Severe COVID-19: A Prospective Cohort Study.

Background: Early treatment of coronavirus disease 2019 (COVID-19) with remdesivir in high-risk patients, including those with immunosuppression of different causes, has not been evaluated. The objective of this study was to assess the clinical effectiveness of early remdesivir treatment among patients with mild to moderate COVID-19 at high risk of progression. Methods: This prospective cohort comparative study was conducted in a tertiary referral center in Mexico City. Patients with mild to moderate COVID-19 at high risk for progression were treated with an ambulatory 3-day course of remdesivir. The primary efficacy composite outcome was hospitalization or death at 28 days after symptom onset. A Cox proportional hazards regression model was used to identify associations with the primary outcome. Results: From December 1, 2021, to April 30, 2022, a total of 196 high-risk patients were diagnosed with COVID-19, of whom 126 were included in this study (43%, 54/126, received remdesivir; 57%, 72/126, did not receive remdesivir). Baseline clinical characteristics were similar between groups; autoimmune diseases (39/126), solid organ transplant (31/126), and malignant neoplasms (24/126) were the most common immunocompromising conditions. Diabetes mellitus was strongly associated with the primary outcome in both groups. Prior severe acute respiratory syndrome coronavirus 2 infection or vaccination was not independently associated with COVID-19 progression. Treatment with remdesivir significantly reduced the odds of hospitalization or death (adjusted hazard ratio, 0.16; 95% CI, 0.06-0.44; P < .01). Conclusions: Early outpatient treatment with remdesivir significantly reduces hospitalization or death by 84% in high-risk, majority immunosuppressed patients with Omicron variant COVID-19.

Predictors of poor outcomes in young non-comorbid patients with COVID-19

ABSTRACT Background: Prognostic factors in previously healthy young patients with COVID-19 remained understudied. Objective: The objective of the study was to identify factors associated with in-hospital death or need for invasive mechanical ventilation (IMV) in young (aged ≤ 65 years) and previously healthy patients with COVID-19. Methods: We conducted a prospective cohort study that included patients admitted with COVID-19. The primary outcome was in-hospital death/need for IMV. Secondary outcomes included need for IMV during follow-up, days on IMV, length of stay (LOS), hospital-acquired pneumonia/ventilator-associated pneumonia (HAP/VAP), and pulmonary embolism (PE). Bivariate and multivariate analyses were performed. Results: Among 92 patients, primary outcome occurred in 16 (17%), death in 12 (13%), need for IMV in 16 (17%), HAP/VAP in 7 (8%), and PE in 2 (2%). Median LOS and IMV duration were 7 and 12 days, respectively. Independent associations were found between the primary outcome and male sex (Adjusted odds ratio [aOR] 7.1, 95%CI 1.1-46.0, p < 0.05), D-dimer levels > 1000ng/mL (aOR 9.0, 95%CI 1.6-49.1, p < 0.05), and RT-PCR Ct-value ≤ 24 on initial swab samples (aOR 14.3, 95%CI 2.0-101.5, p < 0.01). Conclusions: In young and non-comorbid COVID-19 patients, male sex, higher levels of D-dimer, and low SARS-CoV-2 RT-PCR Ct-value on an initial nasopharyngeal swab were independently associated with increased in-hospital mortality or need for IMV.