Impact of mothers' distress and emotional eating on calories served to themselves and their young children: An experimental study

BACKGROUND

Parents play a significant role in children's eating behaviours and food environment. Emotional eating (i.e., eating due to/to cope with emotions regardless of hunger) can contribute to excess energy consumption and subsequent weight gain. Yet, there is a paucity of research examining mothers' feeding and eating behaviours in the presence of their young children during times of acute distress.

OBJECTIVE

The current study examined whether manipulated maternal mood impacted subsequent eating and parental-feeding in mothers with overweight or obesity with their preschool aged children in a laboratory-based experiment.

METHODS

Mothers (n = 47) with overweight or obesity and their preschool aged children were randomized to either an acute distress or control group. After completing a task which manipulated mothers' moods, respectively, dyads were offered a buffet of snack foods. Measures of mothers' reported emotional eating and distress were collected, and calories served and consumed were objectively measured.

RESULTS

There were no between-group differences regarding calories served or consumed. Mothers across both groups who reported higher emotional eating served themselves (p = 0.014) and their children (p = 0.007) less food, and mothers consumed less food (p = 0.045). Mothers who reported higher emotional eating and increased acute distress fed their children less food (p = 0.02) and both children and mothers ate less food (p < 0.05).

CONCLUSIONS

Results suggest that mothers who report emotional eating tendencies may feed their children less food during periods of acute distress.

Feasibility/Acceptability of an Acceptance-Based Therapy Intervention for Diverse Adolescent Cisgender Girls With Overweight/Obesity

Objectives

This study assessed the feasibility and acceptability of an ABT healthy lifestyle intervention among diverse adolescent cisgender girls with overweight/obesity (OW/OB).

Methods

Adolescent cisgender girls ages 14 to 19 with a BMI ≥ 85th percentile-for-sex-and-age were recruited for participation in a single-arm feasibility study. The primary outcomes were recruitment and retention while the secondary outcome was change in BMI Z-score over the 6-month intervention. Exploratory outcomes included obesity-related factors, health-related behaviors, and psychological factors.

Results

Recruitment goals were achieved; thirteen adolescents (&gt;60% racial/ethnic minorities) participated in the intervention, and eleven completed the intervention (85% retention). In completers (n = 11), a mean decrease in BMI Z-score of −0.15 (SD = 0.34, Cohen's d = −0.44) was observed. Improvements were also noted for change in percentage of 95th percentile (d = −0.35), % body fat (d = −0.35), quality of life (d = 0.71), psychological flexibility (d = −0.86), and depression (d = −0.86).

Conclusions

These preliminary findings suggest an ABT healthy lifestyle intervention tailored for adolescent cisgender girls with OW/OB may be an acceptable treatment that could lead to improvements in BMI Z-score, obesity-related measures, and psychological outcomes.

Funding Sources

This work is supported by the National Center for Advancing Translational Sciences of the National Institutes of Health (NIH; UL1TR001427) and WellCare Health Plans, Inc. Dr. Cardel is also supported by the National Institutes of Health National Heart, Lung, and Blood Institute (K01HL141535 and R25HL126146).

Experimentally Manipulated Low Social Status and Food Insecurity Alter Eating Behavior Among Adolescents: A Randomized Controlled Trial

OBJECTIVE

This randomized trial experimentally manipulated social status to assess effects on acute eating behavior and 24-hour energy balance.

METHODS

Participants (n = 133 Hispanics; age 15-21 years; 60.2% females) were randomized to low social status ("LOW") or high social status ("HIGH") conditions in a rigged game of Monopoly (Hasbro, Inc.). Acute energy intake in a lunchtime meal was measured by food scales. Twenty-four-hour energy balance was assessed via summation of resting metabolic rate (metabolic cart), physical activity energy expenditure (accelerometer), thermic effect of food, and subtraction of twenty-four-hour energy intake (food diary).

RESULTS

In the total sample, no significant differences were observed by study condition at lunchtime. LOW females consumed a greater percent of lunchtime daily energy needs (37.5%) relative to HIGH females (34.3%); however, this difference was not statistically significant (P = 0.291). In males, however, LOW consumed significantly less (36.5%) of their daily energy needs relative to HIGH males (45.8%; P = 0.001). For 24-hour energy balance, sex differences were nearly significant (P = 0.057; LOW females: surplus +200 kcal; HIGH males: surplus +445 kcal). Food-insecure individuals consumed a nearly significant greater lunchtime percent daily energy than those with food security (40.7% vs. 36.3%; P = 0.0797).

CONCLUSIONS

The data demonstrate differential acute and 24-hour eating behavior responses between Hispanic male and female adolescents in experimentally manipulated conditions of low social status.

Executive function phenotypes in pediatric obesity

OBJECTIVE

To comprehensively examine the behavioral phenotypes of children with and without executive function (EF) impairments in a clinical sample of youth with obesity.

METHODS

Youth aged 8 to 17 years (Mean age = 12.97) attending a medical clinic for obesity and their caregivers (N = 195 dyads) completed a battery of behavioral questionnaires. Caregiver-proxy report of EF was assessed using the Behavior Rating Inventory of Executive Function. Latent Class Analysis was conducted to identify EF groupings. Analysis of variance and chi-square tests were conducted to examine associations between EF groups and behavioral phenotypes.

RESULTS

Four latent classes of EF impairment were identified (No/Low Impairment; Behavioral Regulation Impairment; Metacognition Impairment; Global Impairment). There was an overall positive pattern of associations between these EF groups and behavioral/emotional symptoms, such that behavioral/emotional symptoms tended to increase with EF impairment.

CONCLUSIONS

Children with obesity and EF impairment demonstrate a dysregulated behavioral phenotype ranging from internalizing to externalizing behavioral and weight-related symptoms. This phenotype framework may be clinically beneficial for utilizing screening/assessment results to develop, tailor, and/or match treatment approaches in pediatric obesity.

Perceived Barriers and Facilitators to Healthy Lifestyles and Weight Loss Among Adolescents with Overweight and Obesity: A Qualitative Study

Objectives

Obesity in adolescence has reached epidemic proportions around the world, with the prevalence of severe obesity increasing at least four-fold over the last 35 years. Provision of evidence-based treatment options that are tailored and relevant to the needs of adolescents is paramount, yet difficult to tailor because little is known regarding barriers and facilitators to adolescent weight loss. Thus, identification of barriers and facilitators to weight loss among adolescents with overweight/obesity (OW/OB) is needed. The objective of this qualitative study was to assess perceived barriers and facilitators to a healthy lifestyle and weight loss among adolescents with OW/OB.

Methods

Using 2018–2019 data from eleven focus groups among adolescents aged 14–19 with OW/OB (n = 41; n = 11 boys and n = 30 girls), a moderated, semi-structured focus group guide was used to identify perceived barriers and facilitators to a healthy lifestyle and weight loss.

Results

Adolescents reported time, access to healthful foods, food cravings, stress, and weight stigma/shaming as barriers to weight loss. Themes around internal and external psychosocial states (support, motivation) and behaviors including modeling, sports, and other physical activities were identified as both barriers and facilitators. Parents were recognized by teens as both helping and hindering weight loss, but overall teens felt their parents were more so facilitators than barriers, particularly as it related to modeling behaviors. Differences were noted by sex, among which girls reported experiencing weight struggles, whereas boys generally stated they did not struggle with weight, despite all participants meeting criterion for OW/OB.

Conclusions

Adolescent boys and girls with OW/OB perceive their weight status differently and identify a variety of barriers and facilitators to a healthy lifestyle and weight loss. Tailoring adolescent weight management interventions to address these perceived barriers and facilitators, along with noted sex differences, has the potential to improve the quality and effectiveness of adolescent obesity interventions.

Funding Sources

National Heart, Lung, and Blood Institute, National Institute of Health, WellCare Health Plans.

Diagnosis, Treatment and Follow Up of Acute Pulmonary Embolism: Consensus Practice from the PERT Consortium

Pulmonary embolism (PE) is a life-threatening condition and a leading cause of morbidity and mortality. There have been many advances in the field of PE in the last few years, requiring a careful assessment of their impact on patient care. However, variations in recommendations by different clinical guidelines, as well as lack of robust clinical trials, make clinical decisions challenging. The Pulmonary Embolism Response Team Consortium is an international association created to advance the diagnosis, treatment, and outcomes of patients with PE. In this consensus practice document, we provide a comprehensive review of the diagnosis, treatment, and follow-up of acute PE, including both clinical data and consensus opinion to provide guidance for clinicians caring for these patients.

Protocol for the Development of a Behavioral Family Lifestyle Intervention Supported by Mobile Health to Improve Weight Self-Management in Children With Asthma and Obesity

BACKGROUND

Asthma is the most common chronic childhood illness and is a leading cause of emergency department visits in the United States. Obesity increases the risk of poor health outcomes, reduced quality of life, and increased health care expenditures among youth with asthma. Weight loss is crucial for improving asthma outcomes in children with obesity. Our study team developed the Childhood Health and Asthma Management Program (CHAMP), a 16-session behavioral family lifestyle intervention (BFI) for school-age children with asthma and obesity and evaluated CHAMP in a randomized controlled trial compared with attention control. There were medium effect sizes favoring CHAMP for changes in body mass index z-scores, asthma control, and lung function among completers (ie, those who attended ≥9 of 16 sessions). Despite high rates of satisfaction reported by families, attendance and trial attrition were suboptimal, which raised concerns regarding the feasibility of CHAMP. Qualitative feedback from participants indicated 3 areas for refinement: (1) a less burdensome intervention modality, (2) a more individually tailored intervention experience, and (3) that interventionists can better answer health-related questions.

OBJECTIVE

We propose to improve upon our pilot intervention by developing the Mobile Childhood Health and Asthma Management Program (mCHAMP), a nurse-delivered BFI, delivered to individual families, and supported by a mobile health (mHealth) app. This study aims to (1) identify structural components of mCHAMP and (2) develop and test the usability of our mCHAMP app.

METHODS

Participants will be recruited from an outpatient pediatric pulmonary clinic. We will identify the structural components of mCHAMP by conducting a needs assessment with parents of children with asthma and obesity. Subsequently, we will develop and test our mCHAMP app using an iterative process that includes usability testing with target users and pediatric nurses.

RESULTS

This study was funded in 2018; 13 parents of children with asthma and obesity participated in the needs assessment. Preliminary themes from focus groups and individual meetings included barriers to engaging in health-promoting behaviors, perceived relationships between asthma and obesity, facilitators to behavior change, and intervention preferences. Participatory design sessions and usability testing are expected to conclude in late 2019.

CONCLUSIONS

Outcomes from this study are expected to include an mHealth app designed with direct participation from the target audience and usability data from stakeholders as well as potential end users.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/13549.

The Effects of Experimentally Manipulated Social Status and Food Insecurity on Acute Eating Behavior and Risk for Obesity Among Adolescents: A Randomized Controlled Study (P21-058-19)

Objectives

Subjective and objective social status is associated with weight status, but this relationship differs by sex and the mechanisms remain unclear.

Methods

This randomized study in Hispanic adolescents investigated the effects of experimentally manipulated social status on ad libitum acute and 24-hour dietary intakes and stress-related outcomes as potential mechanisms through which social status affects weight. Participants (n = 133; ages 15–21; 60.2% girls; BMI ≥18.5 and ≤40 kg/m2; 23.4% food insecure) consumed a standardized breakfast and then were randomized to a low (LOW) or high social status position (HIGH) in a rigged game of Monopoly™, in which the rules differed substantially by social status position. Following the game, the participants consumed an ad libitum lunchtime meal. Energy intake was assessed by pre- and post- food weighing. Stress-related markers were measured at baseline, before Monopoly™, after Monopoly™, and after lunch, with the exception of cortisol (measured before and after Monopoly™).

Results

There was a significant interaction between sex and experimentally manipulated social status (P = 0.0087), such that girls randomized to LOW consumed significantly more of their daily energy needs at the ad libitum lunchtime meal relative to those randomized to HIGH (37.5% vs. 34.3%, respectively). Individuals with food insecurity consumed a greater % of their daily energy needs at the lunchtime meal than those with food security, although the result was not quite statistically significant (40.7% vs. 36.3%, respectively; P = 0.08). In LOW, participants report decreased feelings of powerfulness following Monopoly™ (P = 0.0006). There were no significant differences between HIGH and LOW following Monopoly™ regarding perceived stress, cortisol, heart rate, or blood pressure. Social status condition was not related to 24-hour % of daily energy needs consumed.

Conclusions

Our data suggest a causal link between experimentally manipulated low social status and increased acute energy intakes among Hispanic girls, potentially influenced by decreased feelings of powerfulness, which is independent of stress. Low social status may play a causal role in the development of obesity by promoting excess calorie consumption. Further research is needed to identify the biobehavioral mechanisms contributing to this phenomenon.

Funding Sources

NIH.

Supporting Tables, Images and/or Graphs

Barriers to Recruitment in Pediatric Obesity Trials: Comparing Opt-in and Opt-out Recruitment Approaches

Objective

To compare the efficacy of opt-in versus opt-out recruitment methods in pediatric weight management clinical trials.

Methods

Recruitment of preschoolers and school-age children across two obesity randomized controlled trials (RCTs) were compared using the same opt-in recruitment approach (parents contact researchers in response to mailings). Opt-in and opt-out strategies (parents send decline postcard in response to mailings if they do not want to participate) were then compared across two preschool obesity RCTs.

Results

Opt-in strategies yielded a significantly lower overall recruitment rate among preschoolers compared with school-age children. Among preschoolers, an opt-out strategy demonstrated a significantly higher overall recruitment rate compared with an opt-in strategy with the main advantage in the number of families initially contacted.

Conclusions

Opt-out recruitment strategies may be more effective in overcoming the barriers of recruitment in the preschool age-group because it does not rely on parent recognition of obesity.

Exploring the contribution of maternal antibiotics and breastfeeding to development of the infant microbiome and pediatric obesity

Pediatric obesity, a significant public health concern, has been associated with adult premature mortality and the development of type 2 diabetes and cardiovascular disease. Evidence has suggested that the gut microbiota is associated with pediatric obesity. Establishment of the infant gut microbiome is dependent on a dynamic maternal-infant microbiota exchange during early life. The objective of this review is to describe maternal factors such as feeding practices and antibiotic use that may influence the infant gut microbiome and risk for obesity. The complex components in human milk have many nutritional benefits to the infant; however, the microbiome in human milk may be an important factor to help regulate the infant's weight. We discuss maternal antibiotics and the effects on breast milk as critical exposures that alter the infant's gut microbiome and influence the risk of pediatric obesity.

Relationship between Inflammation and Aspirin and Clopidogrel Antiplatelet Responses in Acute Ischemic Stroke

OBJECTIVE

We measured serum levels of proinflammatory/prothrombotic markers P-selectin, CD40L, matrix metalloproteinase 9 (MMP-9), intracellular adhesion molecule 1 (ICAM-1), and interleukin (IL)-6 in ischemic stroke patients, correlating their levels with the results of aspirin (ASA) and clopidogrel antiplatelet responses, using 3 "point of care" platelet function instruments, thromboelastograph (TEG), Accumetrics (ACU), and impedance aggregometer (IMP).

METHODS

Patients on chronic ASA regimen at the time of stroke were switched to 300 mg clopidogrel loading dose and 75 mg clopidogrel maintenance dose. Serum levels of the aforementioned inflammatory mediators were measured in 51 patients at baseline (on ASA regimen), and at 26 ± 5 hours and 64 ± 18 hours postclopidogrel administration by enzyme-linked immunosorbent assay.

RESULTS

P-selectin, CD40L, and MMP-9 serum levels were reduced; ICAM-1 and IL-6 serum levels showed no difference postclopidogrel administration relative to baseline. Patients' stratification based on ASA dose showed more significant reductions in P-selectin, CD40L, and MMP-9 serum levels postclopidogrel administration in patients who were on baseline 81 mg ASA, as compared to patients on 325 mg ASA. Measurement with TEG was sensitive for correlating ASA antiplatelet responses to serum levels of inflammatory markers, whereas measurements with ACU and IMP were sensitive for correlating clopidogrel antiplatelet responses to serum levels of inflammatory markers.

CONCLUSION

Clopidogrel exerts both platelet-dependent and platelet-independent anti-inflammatory effects. The association between platelet function and inflammation depends on the platelet function analyzer, the type of antiplatelet agent, the nature of the inflammatory marker, and the time of measurement relative to the time of drug administration.

Two novel mutations of SCN9A (Nav1.7) are associated with partial congenital insensitivity to pain

Insensitivity to pain is a rare disorder that is commonly associated with Hereditary Sensory and Autonomic Neuropathies (HSAN I-V) resulting often in autonomic dysfunction and premature death. Very few individuals have been reported with pain insensitivity lacking such autonomic neuropathies. We performed genetic, neurologic, psychological, and psychophysical evaluations in such an individual (OMIM 243000) and her first degree relatives. Sequence analysis of genomic DNA revealed two novel SCN9A mutations in this index case (IC). One was a non-conservative missense mutation (C1719R) in exon 26 present only in the IC and one parent. Further sequence analysis of the child's DNA revealed a 1-bp splice donor deletion in intron 17 which was also present in the other parent and one sibling. Detailed psychophysical testing was used to phenotypically characterize the IC, her family members, and 10 matched normal controls. Similar to family members and controls the IC showed normal somatosensory functioning for non-nociceptive mechanoreception and warmth. However, she demonstrated diminished ability to detect cool temperatures combined with profound deficits in heat and mechanical nociception. Congenital insensitivity to pain in our IC was associated with two novel SCN9A mutations which most likely resulted in a Nav1.7 channelopathy. However, in contrast to individuals with other SCN9A mutations, the observed pain insensitivity was relative and not absolute, which may be consistent with hypomorphic effects of one or both mutations. The ability to sense at least some danger signals may be advantageous and ameliorate the otherwise increased morbidity and mortality of some individuals with congenital insensitivity to pain.

Examining short-term stability of the Mealtime Interaction Coding System (MICS)

OBJECTIVE

This study assessed the stability of ratings on the McMaster Mealtime Interaction Coding System (MICS), an observational measure of family functioning, across three typical evening meals.

METHODS

Participants included families of infants and toddlers with cystic fibrosis (n = 33) and with no chronic illness (n = 33). Three meals were videotaped across a 3-week period (M = 17.4 days) and involved a secondary data analysis from a larger study.

RESULTS

Across both groups, test-retest reliability (paired correlation coefficients) was generally moderate, but significant, for all scales at each time point comparison. Analyses revealed no significant within-or between-group differences across time periods on healthy versus unhealthy ratings.

CONCLUSIONS

This study highlights the limitations of coding a single mealtime observation or interpreting multiple observations using the MICS. Findings highlight that family, meal, illness, and assessment factors may impact variability in ratings over time.

Anti-Inflammatory and Profibrinolytic Effect of Insulin in Acute ST-Segment–Elevation Myocardial Infarction

Background— The clinical benefits of insulin previously observed in acute ST-segment–elevation myocardial infarction (STEMI) may be partially explained by an anti-inflammatory effect. We assessed this potential effect of insulin in STEMI patients treated with fibrinolytics.

Methods and Results— Thirty-two patients receiving reteplase were randomly assigned infusions of either insulin at 2.5 U/h, dextrose, and potassium (GIK) or normal saline and potassium (C) for 48 hours. Plasma concentrations of high-sensitivity C-reactive protein (CRP), serum amyloid A (SAA), plasminogen activator inhibitor-1 (PAI-1), creatine kinase (CK), and CK-MB were measured at baseline and sequentially for 48 hours. Total p47 phox protein in mononuclear cells was measured in a subgroup of 13 subjects. Baseline CRP and SAA were significantly increased (2- to 4-fold) at 24 and 48 hours in each group ( P <0.01). However, in the insulin group, there was a significant ( P <0.05) attenuation of the absolute rise in concentration of CRP and SAA from baseline. The absolute increase of CRP and SAA was reduced by 40% (CRP) and 50% (SAA) at 24 hours and at 48 hours compared with the control group. The absolute increase in PAI-1 from baseline and the percentage increase in p47 phox over 48 hours were significantly ( P <0.05) lower in the insulin-treated group. CK-MB peaked earlier and tended to be lower in insulin-treated subjects, especially in patients with inferior MI.

Conclusions— Insulin has an anti-inflammatory and profibrinolytic effect in patients with acute MI. These effects may contribute to the clinical benefits of insulin in STEMI.

Evaluation of a screening protocol to exclude the diagnosis of deep venous thrombosis among emergency department patients

OBJECTIVE

The purpose of this study was to evaluate the efficacy and cost effectiveness of a deep venous thrombosis (DVT) screening protocol incorporating DVT pretest probability (PTP), selective D-dimer assay, and venous duplex imaging (VDI) to exclude the diagnosis of DVT among emergency department (ED) patients.

METHODS

A prospective study of all patients evaluated in the ED for suspected DVT during 1 year was undertaken. Patients were classified into PTP risk category by ED physicians before VDI. Correlation studies were completed using VDI as the gold standard. Charges associated with the protocol were calculated.

RESULTS

One hundred fourteen patients were included. The incidence of DVT was 9.6% (11). Thirty-six (55%) patients were classified as high risk, 23 (35%) as moderate, and 7 (10%) as low risk. All patients diagnosed with DVT were in the high-risk group (incidence, 16.7%). The sensitivity and negative predictive value were both 100% when PTP and D-dimer were used, but fell to 80% and 95%, respectively, when only D-dimer was considered. The true negative rates were 23% and 37%, respectively. Based on this study, we propose the following screening: for high-risk patients, use direct VDI (no D-dimer); for low-risk or moderate-risk patients, obtain D-dimer, and if it is positive, use VDI, and if it is negative, no further action is required. The average charge associated with the protocol was 170.50 dollars as opposed to 202.00 dollars for global VDI.

CONCLUSION

A screening protocol using PTP along with selective D-dimer and VDI to exclude the diagnosis of DVT among ED patients is efficacious and cost efficient. This screening approach establishes criteria to satisfy billing requirements, can eliminate unnecessary VDI in 23% of ED referrals, and can reduce charges by 16%.

A multisite survey of factors contributing to medically unnecessary ambulance transports

OBJECTIVES

To determine the social and demographic factors associated with medically unnecessary ambulance utilization, and to determine the willingness of patients to use alternate modes of transportation to the ED.

METHODS

A multisite prospective survey was conducted of all patients arriving by ambulance to 1 suburban and 4 urban EDs in New York State during a 1-week period.

RESULTS

For 626 patients surveyed, 71 (11.3%) transports were judged medically unnecessary by the receiving emergency physicians using preestablished guidelines. The patient's type of medical insurance and age were significant predictors of unnecessary ambulance transport (stepwise forward logistic regression analysis). Of the 71 patients whose ambulance transports were deemed medically unnecessary, 42 (59%) were Medicaid recipients and 53 (74%) were < 40 years of age. The most common reason for using ambulance transport was lack of an alternate mode of transportation (38.5%), although 82% would have been willing to use an alternate mode of transportation if it had been available. Of those who had medically unnecessary ambulance use, 30% indicated that they would not pay for the ambulance service if billed and 50% believed the cost of their ambulance transports was < $100. More than 85% of the patients whose ambulance transports were deemed medically unnecessary were unemployed; and nearly 85% reported a net annual income of < $20,000. While 33% had a primary care provider, only 22% had attempted to contact their doctors before requesting an ambulance.

CONCLUSIONS

Patient age < 40 years and Medicaid coverage were associated with medically unnecessary ambulance use. Those patients for whom ambulance use was considered medically unnecessary commonly had no alternate means of transportation. Providing alternate means of unscheduled transportation may reduce the incidence of unnecessary ambulance use.

Moxalactam epimer disposition in patients undergoing continuous ambulatory peritoneal dialysis

The kinetics of the epimers of moxalactam (R-MOX, S-MOX) were investigated in patients without infections who were receiving continuous ambulatory peritoneal dialysis after both intravenous and intraperitoneal injections of moxalactam. R-MOX and S-MOX were well absorbed from the peritoneal cavity, with mean systemic availability of 0.71 +/- 0.18 and 0.79 +/- 0.18, respectively. After intravenous MOX, serum clearance was 10.2 +/- 3.4 (R-MOX) and 10.9 +/- 3.2 (S-MOX) ml/hr/kg. Net time-averaged peritoneal dialysis clearance of both epimers was minimal, about 10% of serum clearance. Serum and dialysate MOX concentrations were above the minimum inhibitory concentrations for susceptible bacteria for 24 hours after a 2.0 or 1.0 gm intravenous or intraperitoneal dose. Gastrointestinal side effects occurred after a 2.0 gm dose (both intravenous and intraperitoneal) but not after a 1.0 gm dose. There were no significant differences in the kinetics of R-MOX and S-MOX. A single 1.0 gm ip dose leads to serum and dialysate MOX concentrations above the minimum inhibitory concentration for susceptible pathogens for 24 hours.