A Descriptive Study Using Rasch Analysis and Hypothesis Testing to Evaluate the Psychometric Properties of the UMOVE Mobility Screen Tested With Hospitalized Older Adults

The purpose of this study was to test the reliability and validity of the UMOVE Mobility Screen in older adults living with dementia using a Rasch analysis and hypothesis testing. The UMOVE Mobility Screen (UMOVE) focuses on nine activities: following commands, muscle strength, and basic functional mobility tasks. Trained evaluators completed assessments on 244 patients, the majority of whom were female (62%), and White (71%). Based on Rasch Analysis, there was evidence of good item and person reliability (indexes > 0.80), good INFIT statistics, and only one item fitting the model based on OUTFIT statistics. Validity was supported based on hypothesis testing. There was no evidence of Differential Item Functioning between races and genders. Item mapping raised concerns about the spread of the items across the full spectrum of mobility assessed in the UMOVE Mobility Screen. Future testing should consider adding some easier and some more difficult items.

Implementation of the UMove Mobility Program to Promote Safe Patient Mobility and Reduce Falls in the Hospital Setting

The purpose of the current quality improvement (QI) project was to implement the UMove Early Mobility Program to engage patients in safe out of bed (OOB) activities and reduce falls, specifically focusing on toileting-related falls, during the hospital stay. Eight nursing units implemented the UMove program, including the UMove Mobility Screen (UMove MS), to select strategies to reduce toileting-related falls while increasing mobility. De-identified, unit-based data were collected from hospital reports. Nursing had a 95% documentation compliance rate for the UMove MS, and OOB activities and ambulation were documented at 50% and 57%, respectively. There was no statistical difference found in reducing toileting-related falls or sustaining increased OOB activities across the 15-month QI project. Toileting-related falls approached significance with a rate reduction from 1.77 pre-implementation to 0.23 at 6 months and no toileting-related falls at 12 months. Despite no significant findings, there is evidence that clinical changes occurred with nurses assessing and promoting mobility, while implementing strategies to reduce toileting-related falls. [Research in Gerontological Nursing, 17(1), 19-29.].

Differences in Medication Use by Gender and Race in Hospitalized Persons Living with Dementia

The purpose of this study was to describe differences in treatment of White versus Black older adults, males versus females, and those living at home, assisted living, or nursing home communities with regard to the use of psychotropic, pain, and cardiovascular medications. Baseline data from the first 352 participants in the study, implementation of Function-Focused Care for Acute Care Using the Evidence Integration Triangle, were used. Data included age, gender, race, comorbidities, admission diagnosis, and living location prior to hospitalization, the Saint Louis University Mental Status exam, the modified Charlson Comorbidity Index, the Pain Assessment in Advanced Dementia scale, the Confusion Assessment Method, and medications prescribed. Generalized linear mixed model analyses were done, controlling for race or gender (depending on which comparison analysis was being done), age, cognitive status, hospital, delirium, and comorbidities. Medication use was significantly higher for White older adults, compared to Black older adults, for antidepressants, anxiolytics, non-opioid pain medications, and opioids and lower for antihypertensives. Females received more anxiolytics than their male counterparts. There were differences in medication use by living location with regard to non-opioid pain medication, antipsychotics, statins, and anticoagulants. The findings provide some current information about differences in medication use across groups of individuals and can help guide future research and hypothesis testing for approaches to minimizing these differences in treatment.

Factors Associated With Function-Focused Care Among Hospitalized Older Adults Living With Dementia

This article reports a study that was designed to describe the incidence of pain among older hospitalized patients with dementia and to evaluate the factors that influence pain among these individuals. It was hypothesized that function, behavioral and psychological symptoms of dementia, delirium, pain treatment, and patient exposure to care interventions would be associated with pain. Patients who performed more functional activities had less delirium. They also experienced higher quality-of-care interactions and were less likely to have pain. The findings from this study support the relationship between function, delirium, and quality-of-care interactions and pain. It suggests that it may be useful to encourage patients with dementia to engage in functional and physical activity to prevent or manage pain. This study serves as a reminder to avoid neutral or negative care interactions among patients with dementia as a strategy to mediate delirium and pain.

Factors Associated With Function-Focused Care Among Hospitalized Older Adults With Dementia

BACKGROUND

Function-focused care is an approach used to increase physical activity in hospitalized older adults with dementia.

OBJECTIVE

To explore factors associated with participation in function-focused care in this patient population.

METHODS

This was a cross-sectional descriptive study using baseline data from the first 294 participants in an ongoing study on testing function-focused care for acute care using the evidence integration triangle. Structural equation modeling was used for model testing.

RESULTS

The mean (SD) age of the study participants was 83.2 (8.0) years, and the majority were women (64%) and White (69%). Sixteen of the 29 hypothesized paths were significant and explained 25% of the variance in participation in function-focused care. Cognition, quality of care interactions, behavioral and psychological symptoms associated with dementia, physical resilience, comorbidities, tethers, and pain were all indirectly associated with function-focused care through function and/or pain. Tethers, function, and quality of care interactions were all directly associated with function-focused care. The χ2/df was 47.7/7, the normed fit index was 0.88, and the root mean square error of approximation was 0.14.

CONCLUSION

For hospitalized patients with dementia, the focus of care should be on treating pain and behavioral symptoms, reducing the use of tethers, and improving the quality of care interactions in order to optimize physical resilience, function, and participation in function-focused care.

Combining exercise, protein supplementation and electric stimulation to mitigate muscle wasting and improve outcomes for survivors of critical illness-The ExPrES study

BACKGROUND

Neuromuscular electrical stimulation (NMES) with high protein supplementation (HPRO) to preserve muscle mass and function has not been assessed in ICU patients. We compared the effects of combining NMES and HPRO with mobility and strength rehabilitation (NMES+HPRO+PT) to standardized ICU care.

OBJECTIVES

To assess the effectiveness of combined NMES+HPRO+PT in mitigating sarcopenia as evidenced by CT volume and cross-sectional area when compared to usual ICU care. Additionally, we assessed the effects of the combined therapy on select clinical outcomes, including nutritional status, nitrogen balance, delirium and days on mechanical ventilation.

METHODS

Participants were randomized by computer generated assignments to receive either NMES+HPRO+PT or standard care. Over 14 days the standardized ICU care group (N = 23) received usual critical care and rehabilitation while the NMES+HPRO+PT group (N = 16) received 30 min neuromuscular electrical stimulation of quadriceps and dorsiflexors twice-daily for 10 days and mean 1.3 ± 0.4 g/kg body weight of high protein supplementation in addition to standard care. Nonresponsive participants received passive exercises and, once responsive, were encouraged to exercise actively. Primary outcome measures were muscle volume and cross-sectional area measured using CT-imaging. Secondary outcomes included nutritional status, nitrogen balance, delirium and days on mechanical ventilation.

RESULTS

The NMES+HPRO+PT group (N = 16) lost less lower extremity muscle volume compared to the standard care group (N = 23) and had larger mean combined thigh cross-sectional area. The nitrogen balance remained negative in the standard care group, while positive on days 5, 9, and 14 in the NMES+HPRO+PT group. Standard care group participants experienced more delirium than the NMES+HPRO+PT group. No differences between groups when comparing length of stay or mechanical ventilation days.

CONCLUSIONS

The combination of neuromuscular electrical stimulation, high protein supplementation and mobility and strength rehabilitation resulted in mitigation of lower extremity muscle loss and less delirium in mechanically ventilated ICU patients.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02509520. Registered July 28, 2015.

The Effect of High Protein and Mobility-Based Rehabilitation on Clinical Outcomes in Survivors of Critical Illness

BACKGROUND

Protein supplementation and mobility-based rehabilitation programs (MRP) individually improve functional outcomes in survivors of critical illness. We hypothesized that combining MRP therapy with high protein supplementation is associated with greater weaning success from prolonged mechanical ventilation (PMV) and increased discharge home in this population.

METHODS

We conducted a retrospective analysis assessing the effects of an MRP on a cohort of survivors of critical illness. All received usual care (UC) rehabilitation. The MRP group received 3 additional MRP sessions each week for a maximum of 8 weeks. Subjects were prescribed nutrition and classified as receiving high protein (HPRO) or low protein (LPRO), based on a recommended 1.0 g/kg/d, and then the subjects were categorized into 4 groups: MRP+HPRO, MRP+LPRO, UC+HPRO, and UC+LPRO.

RESULTS

A total of 32 subjects were enrolled. The MRP+HPRO group had greater weaning success (90% vs 38%, P = .045) and a higher rate of discharge home (70% vs 13%, P = .037) compared to UC+LPRO group. The MRP+HPRO group had a higher, nonsignificant rate of discharge home compared to the MRP+LPRO (70% vs 20%, P = .10).

CONCLUSIONS

Combining high protein with mobility-based rehabilitation was associated with increased rates of discharge home and ventilator weaning success in survivors of critical illness. Further studies are needed to evaluate the role of combined exercise and nutrition interventions in this population.

A multimodal rehabilitation program for patients with ICU acquired weakness improves ventilator weaning and discharge home

PURPOSE

To compare the effects of adding a progressive multimodal rehabilitation program to usual care (MRP + UC) versus UC alone on 1) functional mobility, strength, endurance and 2) ventilator weaning and discharge status of patients with ICU-acquired weakness (ICUAW) receiving prolonged mechanical ventilation (PMV).

METHODS

Randomized pilot trial of an individualized MRP + UC versus UC in middle-aged and older ICU survivors with ICUAW receiving PMV. Outcomes compare changes in strength, mobility, weaning success and discharge home from a long-term acute care hospital (LTACH) between the groups.

RESULTS

Eighteen males and 14 females (age 60.3 ± 11.9 years) who received PMV for ≥14 days were enrolled. Despite no significant differences between groups in the changes in handgrip, gait speed, short physical performance battery or 6-min walk distance after treatment, the MRP + UC group had greater weaning success (87% vs. 41%, p < 0.01), and more patients discharged home than UC (53 vs. 12%, p = 0.05). Post hoc analyses, combining patients based on successful weaning or discharge home, demonstrated significant improvements in strength, ambulation and mobility.

CONCLUSION

The addition of an MRP that improves strength, physical function and mobility to usual physical therapy in LTACH patients with ICUAW is associated with greater weaning success and discharge home than UC alone.

A dietary intervention for chronic diabetic neuropathy pain: a randomized controlled pilot study

Background:

Diabetic neuropathy is a common and often debilitating condition for which available treatments are limited. Because a low-fat plant-based diet has been shown to improve glycemic control in individuals with type 2 diabetes, we hypothesized that such a diet would reduce painful symptoms of diabetic neuropathy.

Methods:

In this 20-week pilot study, individuals with type 2 diabetes and painful diabetic neuropathy were randomly assigned to two groups. The intervention group was asked to follow a low-fat, plant-based diet, with weekly classes for support in following the prescribed diet, and to take a vitamin B12 supplement. The control group was asked to take the same vitamin B12 supplement, but received no other intervention. At baseline, midpoint and 20 weeks, clinical, laboratory and questionnaire data were collected. Questionnaires included an analog ‘worst pain' scale, Michigan Neuropathy Screening Instrument, global impression scale, Short Form McGill Pain Questionnaire, Neuropathy Total Symptom Score, a weekly pain diary and Norfolk Quality of Life Questionnaire.

Results:

After 20 weeks, body weight change with the intervention was −6.4 kg (95% confidence interval (CI) −9.4 to −3.4, P<0.001) in an effect size analysis. Electrochemical skin conductance in the foot improved by an average of 12.4 microseimens (95% CI 1.2–23.6, P=0.03) with the intervention in an effect size analysis. The between-group difference in change in pain, as measured by the McGill pain questionnaire, was −8.2 points (95% CI −16.1 to −0.3, P=0.04). Michigan Neuropathy Screening Instrument questionnaire score change was −1.6 points (95% CI −3.0 to −0.2, P=0.03).

Conclusions:

Improvements were seen in some clinical and pain measures. This pilot study suggests the potential value of a plant-based diet intervention, including weekly support classes, for treating painful diabetic neuropathy.

Psychomotor performance in lung transplant recipients: simple reaction time

BACKGROUND

Many transplant recipients report difficulty completing fine motor activities such as eating, writing and manipulating buttons. These impairments are thought to stem from the immunosuppressive medications being taken by these patients. The purpose of this study was to examine central and peripheral processes and the force regulation involved in producing appropriate and quality movement in lung transplant recipients.

METHODS

Fifty-one right-handed subjects were recruited from 3 study groups (17 in each group): Group 1, lung transplant recipients (LTR); Group 2, subjects with advanced emphysema; and Group 3, healthy adult controls. Each subject completed a fine motor and gross motor simple reaction time task. Central processing was examined by measuring pre-motor time, peripheral processing was measured by motor time, and force regulation was measured using movement time. A 3 x 5 multivariate analysis of co-variance (MANCOVA) was utilized to examine group differences, with the performance on the 6-minute walk test serving as co-variant. Correlation analyses were conducted to examine the relationship between medication and psychomotor performance.

RESULTS

The lung transplant recipient group exhibited a longer movement time and a trend toward longer pre-motor times. There was also a significant relationship between medication and movement time.

CONCLUSIONS

The results support the hypothesis that lung transplant recipients have deficits in psychomotor performance, which is consistent with the literature showing that immunosuppressive medications and hypoxia have adverse effects on skeletal muscle. This line of research is relevant to the restoration of function and improvement in quality of life of LTR.

Pattern and predictors of early rejection after lung transplantation

BACKGROUND

Most lung transplant recipients experience improvement in their underlying pulmonary condition but are faced with the threat of allograft rejection, the primary determinant of long-term survival. Several studies examined predictors of rejection, but few focused on the early period after transplantation.

OBJECTIVES

To describe the pattern and predictors of early rejection during the first year after transplantation to guide the development of interventions to facilitate earlier detection and treatment of rejection.

METHODS

Data for donor, recipient, and posttransplant variables were retrieved retrospectively for 250 recipients of single or double lung transplants.

RESULTS

Most recipients (85%) had at least 1 episode of acute rejection; 33% had a single episode; 23% had recurrent rejection; 3% had persistent rejection; 13% had refractory rejection; and 14% had clinicopathological evidence of chronic rejection. Serious rejection (refractory acute rejection or chronic rejection) developed in 27% of recipients. Compared with other recipients, recipients who had serious rejection had more episodes of acute rejection (P = .004), and the first acute episodes occurred sooner after transplantation (P = .01) and were of a higher grade (P = .002).

CONCLUSIONS

Recipients who experienced higher grades for their first episode of acute rejection (P = .03) and higher cumulative rejection scores (P = .004) were significantly more likely than other recipients to have serious rejection during the first year after transplantation.

Pattern and Predictors of Early Rejection After Lung Transplantation

• Background Most lung transplant recipients experience improvement in their underlying pulmonary condition but are faced with the threat of allograft rejection, the primary determinant of long-term survival. Several studies examined predictors of rejection, but few focused on the early period after transplantation.

• Objectives To describe the pattern and predictors of early rejection during the first year after transplantation to guide the development of interventions to facilitate earlier detection and treatment of rejection.

• Methods Data for donor, recipient, and posttransplant variables were retrieved retrospectively for 250 recipients of single or double lung transplants.

• Results Most recipients (85%) had at least 1 episode of acute rejection; 33% had a single episode; 23% had recurrent rejection; 3% had persistent rejection; 13% had refractory rejection; and 14% had clinicopathological evidence of chronic rejection. Serious rejection (refractory acute rejection or chronic rejection) developed in 27% of recipients. Compared with other recipients, recipients who had serious rejection had more episodes of acute rejection (P = .004), and the first acute episodes occurred sooner after transplantation (P = .01) and were of a higher grade (P = .002).

• Conclusions Recipients who experienced higher grades for their first episode of acute rejection (P=.03) and higher cumulative rejection scores (P = .004) were significantly more likely than other recipients to have serious rejection during the first year after transplantation.

Intracellular survival of Staphylococcus aureus within cultured enterocytes

BACKGROUND

Little is known about the mechanisms involved in bacterial translocation from the intestinal lumen to extraintestinal sites. Because Staphylococcus aureus can colonize the intestinal tract, and because the intestinal tract is a reservoir for antibiotic resistant S. aureus, experiments were designed to clarify the interactions of S. aureus with cultured intestinal epithelial cells, and assays included measurements of bacterial internalization, enterocyte apoptosis, and epithelial barrier function.

METHODS AND RESULTS

Mature, confluent enterocytes were incubated 1 h with S. aureus, and the gentamicin protection assay was used to quantify intracellular bacterial survival at various time intervals up to 120 h later. Enterocyte apoptosis was assessed using Annexin V, and the permeability of confluent enterocyte cultures was measured by transepithelial electrical resistance and by transmigration of Escherichia coli across confluent enterocytes.S. aureus was internalized by cultured enterocytes and remained viable for up to 120 h within both HT-29 and Caco-2 enterocytes. S. aureus intracellular survival was associated with enterocyte apoptosis and with decreased transepithelial electrical resistance across confluent Caco-2 enterocytes. S. aureus intracellular survival over time was also associated with increased E. coli transmigration across confluent Caco-2, but not HT-29, enterocytes.

CONCLUSIONS

S. aureus appeared to survive within cultured enterocytes for prolonged time periods, up to several days. Survival of S. aureus within host eukaryotic cells, such as enterocytes, might facilitate persistence of S. aureus in infected tissue despite appropriate antibiotic therapy.

Liver and circulating NK1.1(+)CD3(-) cells are increased in infection with attenuated Salmonella typhimurium and are associated with reduced tumor in murine liver cancer

An attenuated (DeltacyA, Deltacrp) strain of Salmonella typhimurium (chi4550) containing a gene for human IL-2 (chi4550pIL2) reduces hepatic tumor burden when orally inoculated into mice with liver cancer; however, wild-type S. typhimurium is also associated with cancer regression. Therefore, experiments were designed to clarify the invasiveness and the anti-tumor properties of three strains of S. typhimurium. S. typhimurium chi4550pIL2, chi4550, or wild type (WT) was incubated with mature Caco-2 and HT-29 enterocytes, and S. typhimurium internalization was assessed. For infectivity experiments, mice were orally inoculated with saline or 10(9)S. typhimurium chi4550pIL2, chi4550, or WT; 48 h later mice were sacrificed for analysis of cecal bacteria and S. typhimurium translocation to mesenteric lymph nodes. For experiments involving tumor implantation, four groups were studied: saline control, tumor alone, chi4550pIL2+tumor, and chi4550+tumor. Mice were orally inoculated with saline or S. typhimurium and underwent laparotomy 24 h later with 5 x 10(4) MCA38 murine adenocarcinoma cells injected into the spleen. On day 14, liver tumors were counted and peripheral blood and hepatic lymphocyte populations were analyzed by FACScan. Attenuated S. typhimurium exhibited decreased internalization by cultured enterocytes and decreased infectivity after oral inoculation. Mice treated with chi4550pIL2 or chi4550 had fewer liver tumors and increased populations of hepatic and circulating NK1.1(+)CD3(-) lymphocytes compared to mice treated with saline (P < 0.01). These data suggest that attenuated S. typhimurium may have an application as an anti-tumor agent.

Effect of tumor necrosis factor alpha, interferon gamma, and interleukin-4 on bacteria-enterocyte interactions

BACKGROUND

Little is known about the mechanisms involved in bacterial translocation from the intestinal lumen to extraintestinal sites. Because the cytokine cascade associated with sepsis, inflammation, and trauma has been shown to affect intestinal epithelial permeability, experiments were designed to clarify the effects of selected cytokines on bacterial adherence to and internalization by cultured HT-29 and Caco-2 enterocytes.

METHODS

Mature, confluent enterocytes were pretreated 48 to 72 h with tumor necrosis factor alpha (TNF-alpha), interferon gamma, (IFN-gamma), or interleukin-4 (IL-4). Adherence of Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, and Escherichia coli was measured by enzyme-linked immunosorbent assay and bacterial internalization was quantified by the gentamicin protection assay. Enterocyte permeability was measured by transepithelial electrical resistance and by flux of 40-kDa fluorescent dextran. Bacterial transmigration across confluent enterocytes was measured using enterocytes cultivated on permeable supports.

RESULTS

TNF-alpha, IFN-gamma, and IL-4 had variable effects on bacterial adherence to HT-29 and Caco-2 enterocytes, although the most consistent finding was increased bacterial adherence associated with INF-gamma. However, none of these cytokines had a noticeable effect on bacterial internalization by either Caco-2 or HT-29 enterocytes. In addition, none of these cytokines had a noticeable effect on the permeability of confluent enterocytes as measured by transepithelial electrical resistance or dextran flux. Bacterial transmigration across confluent HT-29 enterocytes was not altered by TNF-alpha, IFN-gamma, or IL-4; however, IL-4 consistently decreased bacterial transmigration across confluent Caco-2 enterocytes.

CONCLUSIONS

IFN-gamma may augment the epithelial adherence of selected species of enteric bacteria, and IL-4 may act as a barrier-sustaining agent to decrease bacterial migration across the intestinal epithelium.

Integrin expression, enterocyte maturation, and bacterial internalization

BACKGROUND

Little is known about the molecular mechanisms involved in the translocation of enteric bacteria. Adhesion molecules mediate interactions between some enteric pathogens and mammalian cells, but no such interactions have been identified for enterocytes and normal enteric bacteria. Using enteric pathogens, adhesion molecule expression has been linked to bacterial internalization and to enterocyte differentiation. Therefore, experiments were designed to study enterocyte integrin expression and differentiation, as well as enterocyte internalization of Salmonella typhimurium, Proteus mirabilis, and Escherichia coli.

MATERIALS AND METHODS

Relative expression of the alpha2, alpha3, and beta1 integrin subunits on Caco-2 and HT-29 enterocytes (mature and immature) was measured by ELISA. Bacteria-enterocyte surface interactions were observed by light and scanning electron microscopy. Bacterial internalization by enterocytes was quantified using the gentamicin protection assay.

RESULTS

Expression of the alpha2, alpha3, and beta1 integrin subunits was consistently increased in immature compared to mature Caco-2 enterocytes; however, compared to mature enterocytes, immature HT-29 enterocytes had similar expression of alpha3 and beta1 but decreased alpha2. Compared to untreated mature enterocytes, bacterial internalization was increased in immature enterocytes as well as mature enterocytes with lateral membranes artifactually exposed. However, there was no difference in bacterial internalization between immature enterocytes and mature enterocytes treated to expose the lateral membrane.

CONCLUSIONS

Bacterial internalization by enterocytes appeared to be due to factors other than integrin expression or enterocyte differentiation. Exposure of the lateral enterocyte membrane may play an important role in facilitating bacterial internalization by enterocytes.

Clostridium difficile toxins and enterococcal translocation in vivo and in vitro

BACKGROUND

Clostridium difficile toxins alter permeability in cultured enterocytes and may alter intestinal epithelial permeability to bacteria in vivo. Experiments were designed to test the effects of C. difficile toxins on in vitro interactions of Enterococcus gallinarum with cultured enterocytes, as well as on translocation of E. gallinarum in mice.

MATERIALS AND METHODS

Mature Caco-2 and HT-29 enterocytes were pretreated with C. difficile toxin A or toxin B followed by incubation with E. gallinarum. E. gallinarum-enterocyte interactions were assessed by quantitative culture. For in vivo experiments, antibiotic-treated mice were orally inoculated with C. difficile or saline, and all mice were orally inoculated 24 h later with E. gallinarum and sacrificed after another 24 h for analysis of cecal bacteria, cecal C. difficile toxin, and enterococcal translocation. Cecal C. difficile toxin was assayed as cytopathic effects on human foreskin fibroblasts.

RESULTS

Although neither toxin had a noticeable effect on bacterial internalization by cultured enterocytes, C. difficile toxins were associated with increased E. gallinarum transmigration across confluent enterocyte cultures. Mice orally inoculated with saline rather than C. difficile (n = 29) had no detectable cecal toxin, while mice orally inoculated with C. difficile (n = 30) had detectable cecal toxin. Viable E. gallinarum was recovered from the mesenteric lymph nodes of 97% of mice orally inoculated with saline followed by oral E. gallinarum, but only 37% of mice orally inoculated with C. difficile followed by oral E. gallinarum (P < 0.01).

CONCLUSIONS

These results suggested that observations with cultured enterocytes, demonstrating that C. difficile toxins facilitated bacterial migration across the intestinal epithelium, might have little in vivo relevance in a mouse model of antibiotic-induced C. difficile overgrowth.

Gastrointestinal colonization by Candida albicans mutant strains in antibiotic-treated mice

Antibiotic-treated mice orally inoculated with one of three Candida albicans strains (including two mutant strains) or indigenous Candida pelliculosa showed levels of candidal gastrointestinal colonization that were strain specific. However, regardless of strain, the numbers of viable candida were intermediate to high in the stomach, were consistently lowest in the upper small intestine, and increased progressively down the intestinal tract.

Clostridium difficile toxins A and B can alter epithelial permeability and promote bacterial paracellular migration through HT-29 enterocytes

Clostridium difficile toxins A and B are the widely recognized etiologic agents of antibiotic-associated diseases ranging from diarrhea to pseudomembranous colitis. We hypothesized that C. difficile toxins may alter intestinal epithelial permeability and facilitate bacterial penetration of the intestinal epithelial barrier. Experiments were designed to clarify the effects of C. difficile toxins A and B on the flux of inert particles across HT-29 enterocyte monolayers, and to correlate these results with bacteria-enterocyte interactions. In all experiments, mature, confluent HT-29 cultures were preincubated 16 h with toxin A or B (1-100 ng/mL). To study alterations in epithelial permeability, toxin-treated enterocytes were incubated with 5 pM solutions of 10- and 40-kD inert dextran particles. Toxin A, but not toxin B, was associated with increased dextran flux through enterocyte monolayers. To study bacteria-enterocyte interactions, toxin-treated enterocytes were incubated with 10(8) Salmonella typhimurium, Proteus mirabilis, or Escherichia coli. Although numbers of internalized bacteria were generally unaffected, both toxins were associated with increased bacterial adherence, as well as increased bacterial transmigration through enterocyte monolayers. Bacterial transmigration was significantly greater using toxin A- compared to toxin B-treated enterocytes, consistent with the observation that dextran flux was significantly greater using toxin A- compared to toxin B-treated enterocytes. Thus intestinal colonization with toxigenic C. difficile may facilitate bacterial penetration of the intestinal epithelium by a mechanism involving increased permeability of the intestinal epithelial barrier.

Inducible expression of Enterococcus faecalis aggregation substance surface protein facilitates bacterial internalization by cultured enterocytes

Aggregation substance (AS) is an Enterococcus faecalis surface protein that may contribute to virulence. Using a recently described system for controlled expression of AS in E. faecalis and the heterologous host Lactococcus lactis, experiments were designed to assess the effect of AS on bacterial internalization by HT-29 and Caco-2 enterocytes. AS expression was associated with increased internalization of E. faecalis by HT-29 enterocytes and of L. lactis by HT-29 and Caco-2 enterocytes. Compared to enterocytes cultivated under standard conditions, either cultivation in hypoxia or 1-h pretreatment of enterocytes with calcium-free medium resulted in increased internalization of both E. faecalis and L. lactis (with and without AS expression). Also, AS expression augmented these increases when E. faecalis was incubated with pretreated HT-29 enterocytes and when L. lactis was incubated with pretreated Caco-2 and HT-29 enterocytes. These data indicated that AS might facilitate E. faecalis internalization by cultured enterocytes.

The Candida albicans INT1 gene facilitates cecal colonization in endotoxin-treated mice

Increased intestinal colonization with Candida albicans is believed to be a major predisposing factor to systemic candidiasis. Previous evidence has implicated the C. albicans INT1 gene in hyphal development, epithelial adherence, and mouse virulence. The effect of INT1 on mouse cecal colonization was measured using a parent strain (CAF2, INT1/INT1), an int1 deletion homozygote (CAG3, int1/int1), and a heterozygous reintegrant (CAG5, int1/int1 + INT1). Forty-eight hours after oral inoculation of 10(7) C. albicans into normal mice, only low numbers of each strain were recovered from the cecal flora. In mice pretreated with oral bacitracin/streptomycin, cecal colonization of each C. albicans strain was increased compared to the corresponding strain inoculated into untreated mice, with the CAF2 parent strain greater (P < 0.01) than the two mutant strains, and with the heterozygous and homozygous mutants not different from each other. In mice pretreated with parenteral lipopolysaccharide (LPS), in addition to oral antibiotics, numbers of cecal CAF2, CAG5, and CAG3 were increased (P < 0.01) compared to the corresponding strain inoculated into mice treated with antibiotics alone. In LPS-treated mice, numbers of cecal C. albicans CAF2 (INT1/INT1) were greater (P < 0.05) than C. albicans CAG3 (int1/int1). Thus, parenteral LPS had an additive effect on C. albicans cecal colonization in antibiotic-treated mice, and the presence of two functional copies of the INT1 gene appeared to facilitate colonization in both antibiotic-treated mice and in mice treated with antibiotics plus parenteral endotoxin.

Pathogenic role of SEF14, SEF17, and SEF21 fimbriae in Salmonella enterica serovar enteritidis infection of chickens

Very little is known about the contribution of surface appendages of Salmonella enterica serovar Enteritidis to pathogenesis in chickens. This study was designed to clarify the role of SEF14, SEF17, and SEF21 fimbriae in serovar Enteritidis pathogenesis. Stable, single, defined sefA (SEF14), agfA (SEF17), and fimA (SEF21) insertionally inactivated fimbrial gene mutants of serovar Enteritidis were constructed. All mutant strains invaded Caco-2 and HT-29 enterocytes at levels similar to that of the wild type. Both mutant and wild-type strains were ingested equally well by chicken macrophage cell lines HD11 and MQ-NCSU. There were no significant differences in the abilities of these strains to colonize chicken ceca. The SEF14(-) strain was isolated in lower numbers from the livers of infected chickens and was cleared from the spleens faster than other strains. No significant differences in fecal shedding of these strains were observed.

Effect of oral genistein and isoflavone-free diet on cecal flora and bacterial translocation in antibiotic-treated mice

BACKGROUND

There are several reports indicating that the isoflavone genistein may augment the integrity of the intestinal epithelial barrier as well inhibit bacterial internalization by cultured enterocytes. We speculated that oral genistein might enhance the integrity of the intestinal epithelial barrier as monitored by the extraintestinal dissemination of intestinal bacteria.

METHODS

Mice were treated with oral antibiotics to induce cecal bacterial overgrowth accompanied by bacterial translocation of antibiotic-resistant enterobacteria, especially Escherichia coli. These mice were divided into separate groups that included chow-fed mice orally inoculated either with saline, vehicle, or genistein, and mice fed isoflavone-free diet and orally inoculated with either saline, vehicle, or genistein. Intestinal bacterial overgrowth was monitored by quantitative culture of excised ceca and bacterial translocation was monitored by quantitative culture of draining mesenteric lymph nodes.

RESULTS

Mice fed the isoflavone-free diet had decreased populations of cecal bacteria compared with chow-fed mice, and bacterial translocation was reduced in chow-fed mice compared with mice fed isoflavone-free diet. However, bacterial translocation was similar in mice given oral genistein compared with appropriate control mice.

CONCLUSIONS

Oral genistein had no noticeable effect on bacterial translocation in this model. However, the isoflavone-free diet had an antibacterial effect on cecal flora, and the isoflavone-free diet was associated with decreased numbers of cecal bacteria and decreased incidence of bacterial translocation.

Effect of INT1 gene on Candida albicans murine intestinal colonization

BACKGROUND

Increased intestinal colonization with Candida albicans is believed to be a major factor predisposing immunocompromised and postsurgical patients to systemic candidiasis, although the mechanisms facilitating C. albicans colonization remain unclear. Because previous studies have linked the C. albicans INT1 gene to filament formation, epithelial adherence, and mouse virulence, experiments were designed to evaluate the effect of INT1 on intestinal colonization.

MATERIALS AND METHODS

Mice were orally inoculated with either the parent strain (CAF2, INT/INT1), an int1 heterozygote (CAG1, INT1/int1), an int1 homozygote (CAG3, int1/int1), or a reintegrant (CAG5, int1/int1 + INT1), and sacrificed 3 and 7 days later for quantitative analysis of cecal C. albicans.

RESULTS

Following oral inoculation with 10(3) C. albicans, only small numbers of each strain were recovered from the cecal flora of normal mice. However, in mice pretreated with oral antibiotics, cecal colonization of each strain was increased (P < 0.01). In addition, cecal colonization was reduced for all int1 mutant strains compared with the parent strain (P < 0.05). By light microscopy, all four C. albicans strains were easily observed in the ileal lumen as both budding yeast and filamentous forms, although only occasional yeast forms appeared adherent to the intestinal epithelium.

CONCLUSIONS

C. albicans readily colonized and replicated in the ceca of antibiotic-treated mice. The presence of two functional copies of INT1 appeared to facilitate C. albicans cecal colonization, suggesting that intestinal colonization may be another virulence factor associated with INT1 and that the gene product may be an attractive target to control C. albicans intestinal colonization.

Clostridium difficile toxins may augment bacterial penetration of intestinal epithelium

BACKGROUND

Clostridium difficile can be recovered from many high-risk hospitalized patients receiving broad-spectrum antibiotic therapy. Clostridium difficile toxins A and B have been associated with increased intestinal permeability in vitro and there is growing evidence that increased intestinal permeability may be a common mechanism whereby enteric bacteria penetrate the intestinal epithelium.

HYPOTHESIS

Clostridium difficile-induced alterations in the intestinal barrier facilitate microbial penetration of the intestinal epithelium, which in turn facilitates the translocation of intestinal bacteria.

DESIGN

Mature Caco-2 enterocytes were pretreated with varying concentrations of toxin A or toxin B followed by 1 hour of incubation with pure cultures of either Salmonella typhimurium, Escherichia coli, or Proteus mirabilis. The effects of toxins A and B on enterocyte viability, cytoskeletal actin, and ultrastructural topography were assessed using vital dyes, fluorescein-labeled phalloidin, and scanning electron microscopy, respectively. The toxins' effects on bacterial adherence and bacterial internalization by cultured enterocytes were assessed using enzyme-linked immunosorbent assay and quantitative culture, respectively. Epithelial permeability was assessed by changes in transepithelial electrical resistance and by quantifying paracellular bacterial movement through Caco-2 enterocytes cultivated on permeable supports.

RESULTS

Neither toxin A nor toxin B had a measurable effect on the numbers of enteric bacteria internalized by Caco-2 enterocytes; however, both toxins were associated with alterations in enterocyte actin, decreased transepithelial electrical resistance, and increased bacterial adherence and paracellular transmigration.

CONCLUSION

Clostridium difficile toxins A or B may facilitate bacterial adherence and penetration of the intestinal epithelial barrier.

Systemic infection following intravenous inoculation of mice with Candida albicans int1 mutant strains

The Candida albicans gene INT1 is associated with epithelial adhesion, hyphal formation, and virulence. C. albicans strains carrying two, one, or no functional INT1 alleles were used to assess the association between mortality and C. albicans persistence in the liver and kidney of intravenously inoculated mice. Mice were injected with 10(5) C. albicans CAF2 (parent strain, INT1/INT1), C. albicans CAG3 (homozygous disruptant, Int1/int1), or C. albicans CAG5 (heterozygous reintegrant, int1/int1 + INT1). Mortality was monitored and mice were sacrificed on Days 1, 7, 14, and 21 for quantitative analysis of kidney and liver microbes, with histologic analysis of these tissues as well. Mortality was highest for mice injected with the wild-type strain CAF2 (INT1/INT1) and lowest for mice injected with the homozygous disruptant CAG3 (int/int1). Yeast were readily cleared from the liver of all mice injected with any of the three C. albicans strains. Although the mutant strains CAG3 and CAG5 are defective for hyphal formation in vitro, there was histological evidence of abundant hyphal formation in the renal pelvis of mice injected with these strains. Compared to the wild-type strain, mutant strains were associated with reduced mortality but increased C. albicans persistence in the kidney. Thus, the absolute ability to form hyphae in the kidney did not appear to modulate either C. albicans-induced mortality or the course of progressive infection in the kidney. In addition, reduced virulence was paradoxically associated with increased, not decreased, persistence of C. albicans in the kidney.

The isoflavone genistein inhibits internalization of enteric bacteria by cultured Caco-2 and HT-29 enterocytes

The dietary isoflavone genistein is the focus of much research involving its role as a potential therapeutic agent in a variety of diseases, including cancer and heart disease. However, there is recent evidence that dietary genistein may also have an inhibitory effect on extraintestinal invasion of enteric bacteria. To study the effects of genistein on bacterial adherence and internalization by confluent enterocytes, Caco-2 and HT-29 enterocytes (cultivated for 15-18 d and 21-24 d, respectively) were pretreated for 1 h with 0, 30, 100, or 300 micromol/L genistein, followed by 1-h incubation with pure cultures of Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, or Escherichia coli. Pretreatment of Caco-2 and HT-29 enterocytes with genistein inhibited bacterial internalization in a dose-dependent manner (r = 0.60-0.79). Compared to untreated enterocytes, 1-h pretreatment with 300 micromol/L genistein was generally associated with decreased bacterial internalization (P < 0. 05) without a corresponding decrease in bacterial adherence. Using Caco-2 cell cultures, decreased bacterial internalization was associated with increased integrity of enterocyte tight junctions [measured by increased transepithelial electrical resistance (TEER)], with alterations in the distribution of enterocyte perijunctional actin filaments (visualized by fluorescein-labeled phalloidin), and with abrogation of the decreased TEER associated with S. typhimurium and E. coli incubation with the enterocytes (P < 0.01). Thus, genistein was associated with inhibition of enterocyte internalization of enteric bacteria by a mechanism that might be related to the integrity of the enterocyte tight junctions, suggesting that genistein might function as a barrier-sustaining agent, inhibiting extraintestinal invasion of enteric bacteria.

Social physique anxiety in postmenopausal women

Social physique anxiety (SPA), the degree to which individuals become anxious when others observe their bodies, is an important concept for postmenopausal women because it may be directly related to their physical activity behavior. Women with high levels of social physique anxiety may not participate in health-enhancing physical activity. Therefore, the main purpose of this study was to examine SPA in postmenopausal women relative to leisure time physical activity (LTPA, activities such as exercise, recreation, and sports). Other factors, such as percent body fat, body fat distribution, age, and hormone replacement therapy status were also examined for their relationship to SPA. Women who expended < or = 500 kcal.wk-1 in LTPA had significantly higher SPA than women who expended > or = 2,000 kcal.wk-1, independent of percent body fat. Women with more than 37.5% body fat had significantly higher SPA than those with less than 37.5% body fat. Women with upper BFD (waist-to-hip ratio or WHR > 0.85) had higher SPA than women with lower BFD (WHR < 0.75). There were no differences in SPA relative to age or HRT status. It appears that a sedentary lifestyle, high percent body fat, and upper body fat distribution are associated with increased SPA in postmenopausal women, thus health promotion professionals should be aware of these concerns when developing physical activity interventions for postmenopausal women.

Physical activity in urban white, African-American, and Mexican-American women

PURPOSE AND METHODS

The purpose of this study was to analyze physical activity in a large, diverse sample of urban women (N = 521; X = 40.5 +/- 10.5 yr) relative to race/ethnicity, income, age, and education, using a sex-specific physical activity questionnaire. We also examined demographic and behavioral predictors of high levels (> or = 2000 kcal.wk-1) of leisure-time physical activity (LTPA; exercise, sports, recreational activities) in this population.

RESULTS

The majority of women were sedentary (0-666 kcal.wk-1 in LTPA), and only 8% of African-American women (N = 6), 11% of Mexican-American women (N = 4), and 13% of white women (N = 55) participated in the level of physical activity recommended by the surgeon general (i.e., moderate to vigorous physical activity most days of the week for at least 30 min). Women of color, women over 40, and women without a college education had the lowest levels of participation in LTPA. Logistic regression analysis indicated that education was the only significant predictor of high LTPA in white women (P < 0.01) and marital status was the only significant predictor of high LTPA in minority women (P < 0.001). Age, body mass index (BMI; kg.m-2), income, self-rated health, alcohol intake, and smoking were not significant predictors of high LTPA for any of the women. Because the majority of adult women from this sample do not participate in adequate amounts of physical activity as recommended by the surgeon general, they may be at increased risk for hypokinetic diseases.

CONCLUSIONS

These results indicate that public health efforts to increase physical activity in women should be focused on women of color, women over 40, and women without a college degree. More attention to predictors of physical activity that are specific to race or ethnicity may improve intervention program design and implementation.

Cytochalasin-induced actin disruption of polarized enterocytes can augment internalization of bacteria

Cytochalasin-induced actin disruption has often been associated with decreased bacterial internalization by cultured epithelial cells, although polarized enterocytes have not been systematically studied. In assays using confluent polarized HT-29 enterocytes, cytochalasin D appeared to increase internalization of wild-type Salmonella typhimurium, Proteus mirabilis, and Escherichia coli. HeLa and HEp-2 epithelial cells, as well as HT-29 and Caco-2 enterocytes, were used to clarify this unexpected observation. Resulting data showed that cytochalasin D was associated with increased internalization of S. typhimurium and P. mirabilis by both HT-29 and Caco-2 enterocytes and with increased internalization of E. coli by HT-29 enterocytes; with either HeLa or HEp-2 cells, cytochalasin was associated with no change or a decrease in internalization of these same bacterial strains. Cytochalasin caused decreased internalization of Listeria monocytogenes by HT-29, Caco-2, HeLa, and HEp-2 cells, indicating that cytochalasin did not consistently augment bacterial internalization by polarized enterocytes. Fluorescein-labeled phalloidin confirmed marked disruption of filamentous actin in cytochalasin-treated HT-29, Caco-2, HeLa, and HEp-2 cells. Cytochalasin had no noticeable effect on epithelial viability but caused distorted apical microvilli, cell rounding, and separation of adjacent enterocytes in confluent cultures (with a corresponding decrease in transepithelial electrical resistance). Scanning electron microscopy showed that cytochalasin-induced enhanced bacterial internalization was associated with preferential bacterial adherence on the exposed enterocyte lateral surface. Colchicine, used to disrupt microtubules, had no noticeable effect on bacterial internalization by HT-29 or Caco-2 enterocytes. These data indicated that for HT-29 and Caco-2 enterocytes, cytochalasin-induced disruption of filamentous actin might augment internalization of some bacterial species by a mechanism that appeared to involve exposure of the enterocyte lateral surface.

Bacterial translocation in multiple organ failure: cause or epiphenomenon still unproven

BACKGROUND

A body of evidence exists for the occurrence of bacterial translocation and its relationship to multiple organ failure (MOF).

METHODS

Relevant articles on bacterial translocation (the phenomenon defined as the passage of microbes and endotoxin across the intestinal barrier) in patients prone to develop MOF and in representative animal studies were selected. To interpret and evaluate the evidence for bacterial translocation in current literature, the endpoints generally used are discussed.

RESULTS

Fractional data from individual manuscripts were tabulated and assessed for statistical significance with chi 2 analysis. Various clinically relevant stimuli, postulated as important causative factors for the development of MOF, appeared to be interrelated and related to bacterial translocation itself.

CONCLUSIONS

Convincing evidence exists that bacterial translocation can occur in humans during various disease processes. However, it remains to be determined whether a causal relationship between bacterial translocation and MOF exists. MOF is probably multifactorial and not uniform in origin; when evaluating translocation as a causative factor in the absence of an infective focus, the type of initiating event and the period of time after which MOF develops should be taken into account. The origin of early MOF is probably a non-bacterial, extensive, inflammatory response resulting in massive generalized endothelial cell activation. Late MOF may be caused primarily by bacterial translocation inducing an imbalance between proinflammatory and anti-inflammatory cytokines.

Surgical Infection Society position on vancomycin-resistant Enterococcus

The risk of transfer of vancomycin resistance to staphylococci is a real possibility and has been achieved in the laboratory. Prolonged colonization occurs with vancomycin-resistant Enterococcus (VRE), and many more patients are colonized than infected. The failure to identify, isolate, and adhere to infection control measures when caring for VRE-colonized patients dooms to failure any means to control its spread. Control of vancomycin use alone is unlikely to greatly affect the number of patients at risk for VRE colonization. The global spread of VRE may be impossible to stop, but infection control measures are the most important line of defense inside hospitals.

Intracellular survival of enteric bacteria in cultured human enterocytes

Translocating enteric bacteria have been visualized within intact intestinal epithelial cells in animal models of bacterial translocation. Although the ability of the enterocyte to engulf bacteria has been well documented in both in vivo and in vitro experimental models, relatively little is known about the enterocyte's ability to degrade internalized bacteria. Intracellular survival of eight strains of enteric bacteria (two strains of Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, two strains of Escherichia coli, and two strains of Enterococcus faecalis) was quantified over a 20 h period using two different types of terminally differentiated polarized enterocytes considered relevant in vitro models of human small intestinal epithelium, namely Caco-2 and HT-29 cells. Caco-2 enterocytes were generally more permissive for bacterial uptake when compared with HT-29 enterocytes. However, bacterial survival was similar within each type of enterocyte, and most strains of enteric bacteria remained viable within enterocytes for the 20 h duration of the assay. In addition, with the exception of one strain of L. monocytogenes in Caco-2 cells, intracellular enteric bacteria had no noticeable effect on host enterocyte viability for this 20 h duration. Transmission electron microscopy was used to visualize both intact and degraded bacteria within individual enterocytes, suggesting that prolonged bacterial survival might have resulted from simultaneous bacterial degradation and replication. Thus, although enterocytes internalize enteric bacteria, enterocytes might not kill internalized bacteria as efficiently as leukocytes. Observations of bacterial intracellular survival supported the hypothesis that the enterocyte might be a portal of entry for translocating microbes, and observations of intracellular bacterial degradation might have implications for the role of the enterocyte as an antigen-presenting cell.

Effect of hypoxia on enterocyte endocytosis of enteric bacteria

OBJECTIVE

To clarify the effect of hypoxia on bacteria-enterocyte interactions.

DESIGN

Randomized.

SETTING

Research laboratory.

SUBJECTS

Enteric bacterial and cultured human intestinal epithelial cells, HT-29 cells.

INTERVENTIONS

The effect of hypoxia on bacterial internalization and intracellular survival was studied, using enterocytes cultured for 21 days in either 20%, 10%, or 5% oxygen. The effect of bacterial growth conditions on bacterial internalization by enterocytes was studied, using bacterial cells in either the log phase or stationary phase of aerobic growth, and using bacterial cells in stationary phase, grown either under low oxygen conditions or under anaerobic conditions.

MEASUREMENTS AND MAIN RESULTS

Individual strains of enteric bacteria were incubated with HT-29 cells for 1 hr. Numbers of internalized bacteria were subsequently quantified after enterocyte lysis. Bacterial growth conditions (anaerobic vs. aerobic and log-phase vs. stationary-phase bacterial cells) had no noticeable effect on the numbers of Salmonella typhimurium, Proteus mirabilis, and Escherichia coli internalized by enterocytes. Enterocytes cultivated in 20%, 10%, or 5% oxygen were >95% viable. Enterocytes cultivated in 20% oxygen were confluent, but those enterocytes cultivated in hypoxia were not confluent and were fewer in number compared with enterocytes cultivated in normoxia. Compared with enterocytes grown in normoxia, enterocytes cultivated in 5% and 10% oxygen internalized greater numbers of each of seven strains of enteric bacteria, including Listeria monocytogenes (two strains), Enterococcus faecalis (two strains), and P. mirabilis, E. coli (two strains), with statistically significant increases noted for five of these seven bacterial strains. Intracellular survival of L. monocytogenes and P. mirabilis was assayed. Both species survived intracellularly for 22 hrs, with no noticeable differences in the numbers of intracellular bacteria recovered from enterocytes cultivated in 20%, 10%, and 5% oxygen.

CONCLUSION

These in vitro results suggest that augmented bacterial endocytosis by enterocytes might at least partially explain the increased frequency of bacterial translocation associated with tissue ischemia.

Bacteroides fragilis enterotoxin modulates epithelial permeability and bacterial internalization by HT-29 enterocytes

BACKGROUND & AIMS

Enterotoxigenic Bacteroides fragilis has been associated with diarrheal disease, and the enterotoxin has a cytopathic effect on cultured HT-29 enterocytes. Experiments were designed to determine the effect of B. fragilis enterotoxin on bacteria-enterocyte interactions.

METHODS

Confluent HT-29 enterocytes were incubated for 1 hour with B. fragilis enterotoxin, followed by 1 hour of incubation with pure cultures of enteric bacteria, namely, Salmonella typhimurium (two strains), Listeria monocytogenes (three strains), Proteus mirabilis, Escherichia coli (three strains), and Enterococcus faecalis. Enterocyte viability was assessed using vital dyes, epithelial permeability was measured using transepithelial electrical resistance, enterocyte morphology and bacteria-enterocyte interactions were visualized using light and electron microscopy, and bacterial internalization was assessed using a quantitative culture of lysed enterocytes.

RESULTS

B. fragilis enterotoxin did not affect enterocyte viability but decreased transepithelial electrical resistance, and individual enterocytes pulled apart. Enterotoxin pretreatment decreased internalization of L. monocytogenes (P < 0.01) but increased (P < 0.01) internalization of the other strains of enteric bacteria. Augmented bacterial internalization was associated with preferential bacterial adherence on the exposed lateral surface of enterotoxin-treated enterocytes.

CONCLUSIONS

B. fragilis enterotoxin was associated with HT-29 cell rounding and with augmented internalization of selected strains of enteric bacteria that were preferentially adherent on the exposed enterocyte lateral surface.

Problems and priorities for controlling opportunistic pathogens with new antimicrobial strategies; an overview of current literature

An International Study Group on New Antimicrobial Strategies (ISGNAS) has been formed in response to the recognition that development of microbial resistance to antibiotics is becoming a serious, world-wide problem. The group met in 1993 for the first time to discuss the feasibility of developing rational alternatives to the use of antibiotics and prepared, as a result, a comprehensive overview of normal (physiological) mechanisms involved in the control of potentially pathogenic (oppotunistic) microorganisms. One objective of ISGNAS is to understand the conditions which allow opportunistic microbes present among the symbionts to cause an infection. There is a need for more coherent information concerning the habitat, growth requirements and host and pathogen properties which allow opportunistic pathogens to cause life-threatening infections. In particular, information is urgently being sought to understand the complexity of the interactions between the vast number of microbial species, and the interactions between the microbes and their host. Another goal is to inspire and enable basic and clinical research that will lead to the development of new therapies for regulating colonization, translocation and infection by opportunistic micro-organisms in patients during periods of decreased resistance. With a sufficient amount of knowledge of how healthy individuals keep opportunistic micro-organisms under control, it may become feasible for physicians to maintain host resistance and inter-microbial factors involved in the containment of opportunistic microbes. Therapies aimed at boostering natural resistance mechanisms will be of critical importance to individuals whose resistance has been compromised as a result of another clinical condition.

Does physical activity reduce risk of estrogen-dependent cancer in women?

The estrogen-dependent cancers (breast, endometrial, and ovarian) are among the leading causes of morbidity and mortality in American women. Increased incidence of these cancers is predicted in the future, and the need for primary prevention is clear. Sufficient evidence has accumulated to warrant an analysis of the relationship between physical activity and estrogen-dependent cancer. Recent epidemiological studies confirm an inverse relationship between physical activity and estrogen-dependent cancer, with stronger associations appearing for occupational activity than for leisure time or nonoccupational activity. Several hypothesized mechanisms are described for the prevention of estrogen-dependent cancer by physical activity: 1) maintenance of low body fat and moderation of extraglandular estrogen, 2) reduction in number of ovulatory cycles and subsequent diminution of lifetime exposure to endogenous estrogen, 3) enhancement of natural immune function, and 4) the association of other healthy lifestyle habits. Although the mechanisms are not well defined, several lines of evidence support the inclusion of low-to-moderate physical activity as a preventive strategy for estrogen-dependent cancer.

Bacterial translocation in a large-animal model of small-bowel transplantation. Portal vs systemic venous drainage and the effect of tacrolimus immunosuppression

OBJECTIVE

To study whether bacterial translocation is more prevalent after small-bowel transplantation with systemic venous drainage (SVD) vs portal venous drainage (PVD) and whether it is influenced by immunosuppression.

DESIGN

We performed 15 small-bowel transplantations in pigs. Group 1 (n = 5) had SVD and no immunosuppression; group 2 (n = 6), PVD and no immunosuppression; and group 3 (n = 4), PVD and immunosuppression with tacrolimus and methylprednisolone sodium succinate. Portal and systemic blood, portal and mesenteric lymph nodes, and liver were cultured in donors and recipients on postoperative day 0 (POD 0) and in recipients on postoperative day 3 (POD 3). Jejunal and ileal contents were also sampled at these times.

SUBJECTS

Outbred male Yorkshire-Landrace pigs.

MAIN OUTCOME MEASURES

(1) Blood and tissue bacterial cultures, (2) blood endotoxin levels, and (3) histopathologic examination.

RESULTS

Cultures were positive for bacteria in 32% (16/50) of samples on POD 0 and 88% (22/25) on POD 3 in group 1, in 18% (11/60) of samples on POD 0 and 97% (29/30) on POD 3 in group 2, and in 8% (3/40) of samples on POD 0 and 95% (19/20) on POD 3 in group 3. Systemic blood cultures were positive for bacteria on POD 3 in 60% (3/5) of pigs in group 1, 83% (5/6) in group 2, and 100% (4/4) in group 3. Significantly more bacteria were present in the ileum than in the jejunum on POD 0 in group 2; this difference approached significance in groups 1 and 3. Bacterial numbers were identical in the ileum and jejunum by POD 3 in all groups. Circulating endotoxin levels were significantly elevated on POD 3 vs POD 0 only in group 1. Endotoxin levels were not significantly different between the SVD group (group 1) and either PVD group (groups 2 and 3).

CONCLUSIONS

Bacterial translocation is prevalent after small-bowel transplantation in pigs whether PVD or SVD is used. Immunosuppression with tacrolimus does not prevent bacterial translocation but may reduce systemic endotoxemia.

Exposure of the lateral enterocyte membrane by dissociation of calcium-dependent junctional complex augments endocytosis of enteric bacteria

Intestinal bacterial translocation is facilitated in a variety of clinical conditions involving increased intestinal permeability, such as shock and trauma. Because there is both in vivo and in vitro evidence that enteric bacteria can be internalized by intestinal epithelial cells, experiments were designed to test the effect of increased intestinal permeability on enterocyte endocytosis of enteric bacteria. Mature, confluent cultures of HT-29 enterocytes were placed in a calcium-free solution for 1 h. Enterocyte viability was not noticeably altered, but transepithelial electrical resistance was significantly decreased (indicating a decrease in epithelial junctional integrity), and the enterocytes were pulled apart. Electron microscopic observations revealed enteric bacteria preferentially adherent on the exposed enterocyte lateral surface, and the numbers of viable enteric bacteria (Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, Escherichia coli, and Enterococcus faecalis) internalized by these enterocytes were significantly increased. Restoration of calcium restored confluency to enterocyte cultures, and bacterial internalization reverted to control levels. Thus, calcium-dependent junctional integrity might play a role in augmenting bacterial translocation in clinical conditions associated with increased intestinal permeability.

Stool carriage, clinical isolation, and mortality during an outbreak of vancomycin-resistant enterococci in hospitalized medical and/or surgical patients

During a nosocomial outbreak of infection due to vancomycin-resistant enterococci (VRE), rectal swabs that were collected weekly were used to identify and isolate VRE carriers. Over 6 months, 1,458 stool specimens from 724 high-risk patients were cultured, and 187 VRE isolates were recovered from 61 patients; 96% of the isolates were Enterococcus faecium. VRE tended to be isolated from clinical specimens from patients identified as VRE carriers by stool surveillance (P < .01). However, isolation of VRE from surveillance cultures preceded clinical isolation for only approximately 50% of the patients from whom a clinical VRE isolate was recovered. Mortality was greater (P < .05) among patients from whom a clinical VRE isolate was recovered than among patients from whom VRE was isolated only by stool surveillance. The mortality (1[17%] of 6) among patients for whom VRE was isolated from blood was similar to that (10 [27%] of 37) among patients for whom vancomycin-susceptible enterococcus was isolated from blood (P = .97). Despite prompt initiation of contact precautions for VRE carriers, the incidence of fecal carriage of VRE remained approximately 8% among this patient population for the 6-month period of the study.

Inhibitory effect of bile on bacterial invasion of enterocytes: possible mechanism for increased translocation associated with obstructive jaundice

OBJECTIVE

To clarify the effect of bile salts on internalization of enteric bacteria by intestinal epithelial cells.

DESIGN

Randomized study.

SETTING

Research laboratory.

SUBJECTS

Cultured human intestinal epithelial cells, namely HT-29 cells.

INTERVENTIONS

The effect of bile was studied by adding bile during the time period in which bacterial cells were permitted to interact with enterocytes. In subsequent experiments, bile was added to the culture medium used to grow bacteria, and bacterial cells were washed before adding bacteria to enterocytes. Three different concentrations of three different bile preparations were tested.

MEASUREMENTS AND MAIN RESULTS

Salmonella typhimurium and Proteus mirabilis were each incubated with HT-29 cells for 1 hr; the numbers of internalized bacteria were subsequently quantified following enterocyte lysis. The presence of bile during bacteria-enterocyte incubation had no effect on the numbers of internalized bacteria. However, if S. typhimurium or P. mirabilis were grown in the presence of bile, these washed bacterial cells were generally internalized by HT-29 cells in significantly fewer numbers, compared with bacterial cells grown in medium without bile supplementation. Enterocyte viability and morphologic ultrastructure did not appear to be affected by the presence of bile itself, or by the interaction with bacterial cells that had been cultivated in unsupplemented medium or in bile-supplemented medium.

CONCLUSIONS

Exposure to bile during bacterial growth resulted in bacterial cells with decreased invasiveness for cultured intestinal epithelial cells. This observation is consistent with previous in vivo studies of obstructive jaundice, where the absence of bile in the intestinal lumen, not bile duct ligation, appeared to facilitate bacterial translocation in obstructed animals. Thus, the presence of bile in the intestinal lumen may decrease bacterial translocation by a mechanism that involves decreased epithelial internalization of enteric bacteria.

A plasmid-encoded surface protein on Enterococcus faecalis augments its internalization by cultured intestinal epithelial cells

Aggregation substance, a plasmid-encoded Enterococcus faecalis surface protein, plays a role in mediating the formation of mating aggregates, resulting in plasmid transfer. The role of aggregation substance in the internalization of E. faecalis by cultured intestinal epithelial cells, namely HT-29 cells, was analyzed. It was associated with a significant increase in endocytosis of E. faecalis by HT-29 cells: Numbers of internalized enterococci were fewer than of an invasive strain of Listeria monocytogenes, similar to Salmonella typhimurium and another L. monocytogenes strain, and greater than relatively noninvasive strains of E. faecalis, Proteus mirabilis, and Escherichia coli. Electron microscopy confirmed aggregation substance on the surface of strains interacting with the enterocyte microvillous surface, and intracellular enterococci were localized within membrane-bound vacuoles in the enterocyte cytoplasm. Thus, aggregation substance may facilitate E. faecalis internalization by host epithelial cells.

Bacterial translocation and lipopolysaccharide-induced mortality in genetically macrophage-deficient op/op mice

Genetically macrophage-deficient op/op mice have a total absence of macrophage colony-stimulating factor (also known as colony-stimulating factor 1 or CSF-1), and therefore an absence of a population of macrophages dependent on CSF-1. op/op mice also have profound secondary deficiencies in certain cytokines secreted by this macrophage population, such as tumor necrosis factor, interleukin-1, and granulocyte colony-stimulating factor. In the present study, op/op mice were used to clarify the role of the macrophage in two clinical processes: (a) bacterial translocation in response to antibiotic-induced intestinal overgrowth, and (b) endotoxin-induced bacterial translocation, morbidity, and mortality. The results were unexpected, in that bacterial translocation and endotoxin-induced morbidity and mortality were similar in op/op mice and their functionally normal littermates. These data indicated either that a specific macrophage population and its cytokines (including tumor necrosis factor and interleukin 1) might not play pivotal roles in the pathogenesis of bacterial translocation and endotoxin-induced septic shock, or alternatively, as yet unknown redundancies in vivo might compensate for the genetic deficiencies associated with the op/op mutation.

Bacterial translocation in cultured enterocytes: magnitude, specificity, and electron microscopic observations of endocytosis

Previous in vivo evidence has shown that bacterial phagocytosis by enterocytes may be an initial step in bacterial translocation across the intestinal epithelium. This study analyzed the interactions of cultured enterocytes, namely Caco-2 cells, with nine strains of enteric bacteria, tested in pure culture and in mixed culture. These nine strains had a spectrum of invasive potential and included Salmonella typhimurium, Listeria monocytogenes (three strains), Escherichia coli (three strains), Proteus mirabilis, and Enterococcus faecalis. Numbers of viable intracellular bacteria recovered from Caco-2 cells were: L. monocytogenes > S. typhimurium > P. mirabilis > E. coli > E. faecalis. Uptake of a given microbe by enterocytes was strain-specific and was not influenced by the presence of another strain, regardless of the invasive ability of the coinfecting strain. Electron microscopic visualization of bacterial adherence and uptake by Caco-2 cells indicated that the epithelial interactions of normal enteric bacteria were similar to these observed with invasive strains of salmonella and listeria.

Contact with epithelial cells induces the formation of surface appendages on Salmonella typhimurium

The enteric bacteria Salmonella typhimurium has the ability to invade (enter) nonphagocytic cells. The internalization process occurs as a result of an intimate interaction between the bacteria and the host cell, in which S. typhimurium triggers a cascade of host cell-signaling events leading to the formation of host cell membrane ruffles and bacterial uptake. Using high resolution scanning electron microscopy, we have observed that contact with cultured epithelial cells results in the formation of appendages on the surface of S. typhimurium. The formation of such appendages did not require de novo protein synthesis, and it was transient, since these surface structures were no longer present on bacteria that had initiated the internalization event. Salmonella mutants defective in the transient formation of these surface organelles were unable to enter into cultured epithelial cells, indicating that such structures are required for bacterial internalization.