Inadequate physical activity and health care expenditures in the United States

This study estimates the percentage of health care expenditures in the non-institutionalized United States (U.S.) adult population associated with levels of physical activity inadequate to meet current guidelines. Leisure-time physical activity data from the National Health Interview Survey (2004-2010) were merged with health care expenditure data from the Medical Expenditure Panel Survey (2006-2011). Health care expenditures for inactive (i.e., no physical activity) and insufficiently active adults (i.e., some physical activity but not enough to meet guidelines) were compared with active adults (i.e., ≥150minutes/week moderate-intensity equivalent activity) using an econometric model. Overall, 11.1% (95% CI: 7.3, 14.9) of aggregate health care expenditures were associated with inadequate physical activity (i.e., inactive and insufficiently active levels). When adults with any reported difficulty walking due to a health problem were excluded, 8.7% (95% CI: 5.2, 12.3) of aggregate health care expenditures were associated with inadequate physical activity. Increasing adults' physical activity to meet guidelines may reduce U.S. health care expenditures.

Physical activity and health-related quality of life: US adults with and without limitations

PURPOSE

The purpose of this study was to examine the dose-response relationship between physical activity (PA) and health-related quality of life (HRQOL) among adults with and without limitations.

METHODS

We dichotomized HRQOL as ≥14 unhealthy (physical or mental) days (past 30 days), or <14 unhealthy days. By using a moderate-intensity minute equivalent, PA categories were as follows: inactive, 10-60, 61-149, 150-300, and >300 min/week. Persons with limitations reported having problems that limited their activities or required use of special equipment. Age-adjusted prevalence estimates and logistic regression analyses were performed with 2009 Behavioral Risk Factor Surveillance System data (n = 357,665), controlling for demographics, BMI, smoking, and heavy alcohol use.

RESULTS

For adults without limitations, the odds of ≥14 unhealthy days were lower among adults obtaining any PA (10-60 min/week, AOR = 0.79, 95 % CI 0.70, 0.88), compared with those inactive. A quadratic trend (P < 0.001) indicated enhanced HRQOL with each PA level, but improvements were less marked between lower and upper sufficient PA categories (150-300 and >300 min/week). Because of a significant age interaction, persons with limitations were stratified by age (18-34, 35-64, and 65+ years). Findings for persons aged 35 years or older with limitations were similar to those without limitations. Lower odds of poor HRQOL for persons aged 18-34 years with limitations were associated with recommended levels of PA (150-300 min/week; AOR = 0.61, 95 % CI 0.43, 0.88 and >300 min/week; AOR = 0.58, 95 % CI 0.43, 0.80).

CONCLUSIONS

PA is positively associated with HRQOL among persons with and without limitations.

TV watching and computer use in U.S. youth aged 12-15, 2012

Data from the National Health and Nutrition Examination Survey (NHANES) and the NHANES National Youth Fitness Survey, 2012. Nearly all (98.5%) youth aged 12-15 reported watching TV daily. More than 9 in 10 (91.1%) youth aged 12-15 reported using the computer daily outside of school. In 2012, 27.0% of youth aged 12-15 had 2 hours or less of TV plus computer use daily. Among youth aged 12-15, girls (80.4%) were more likely to use the computer 2 hours or less daily when compared with boys (69.4%). Fewer non-Hispanic black youth aged 12-15 (53.4%) reported watching 2 hours or less of TV daily than non-Hispanic white (65.8%) and Hispanic (68.7%) youth. Excessive screen-time behaviors, such as using a computer and watching TV, for more than 2 hours daily have been linked with elevated blood pressure, elevated serum cholesterol, and being overweight or obese among youth (1-3). Additionally, screen-time behavior established in adolescence has been shown to track into adulthood (4). The National Heart, Lung, and Blood Institute-supported Expert Panel and the American Academy of Pediatrics (AAP) recommend that children limit leisure screen time to 2 hours or less daily (5,6). This report presents national estimates of TV watching and computer use outside of the school day.

Leisure-time aerobic physical activity, muscle-strengthening activity and mortality risks among US adults: the NHANES linked mortality study

BACKGROUND

Regular physical activity elicits multiple health benefits in the prevention and management of chronic diseases. We examined the mortality risks associated with levels of leisure-time aerobic physical activity and muscle-strengthening activity based on the 2008 Physical Activity Guidelines for Americans among US adults.

METHODS

We analysed data from the 1999 to 2004 National Health and Nutrition Examination Survey with linked mortality data obtained through 2006. Cox proportional HRs with 95% CIs were estimated to assess risks for all-causes and cardiovascular disease (CVD) mortality associated with aerobic physical activity and muscle-strengthening activity.

RESULTS

Of 10 535 participants, 665 died (233 deaths from CVD) during an average of 4.8-year follow-up. Compared with participants who were physically inactive, the adjusted HR for all-cause mortality was 0.64 (95% CI 0.52 to 0.79) among those who were physically active (engaging in ≥150 min/week of the equivalent moderate-intensity physical activity) and 0.72 (95% CI 0.54 to 0.97) among those who were insufficiently active (engaging in >0 to <150 min/week of the equivalent moderate-intensity physical activity). The adjusted HR for CVD mortality was 0.57 (95% CI 0.34 to 0.97) among participants who were insufficiently active and 0.69 (95% CI 0.43 to 1.12) among those who were physically active. Among adults who were insufficiently active, the adjusted HR for all-cause mortality was 44% lower by engaging in muscle-strengthening activity ≥2 times/week.

CONCLUSIONS

Engaging in aerobic physical activity ranging from insufficient activity to meeting the 2008 Guidelines reduces the risk of premature mortality among US adults. Engaging in muscle-strengthening activity ≥2 times/week may provide additional benefits among insufficiently active adults.

Muscle-strengthening activities and participation among adults in the United States

PURPOSE

To describe those who reported meeting the 2008 Physical Activity Guidelines for Americans (2008 Guidelines) muscle-strengthening standard of 2 or more days per week, including all seven muscle groups, and to assess the type and location of muscle-strengthening activities performed.

METHOD

Data from HealthStyles 2009, a cross-sectional, consumer mail-panel survey, was used for analyses (n = 4,271). The prevalence estimates with 95% confidence intervals of those meeting the 2008 Guidelines standards were calculated. Pairwise t-tests were performed to examine differences between estimates, tests for linear trends were performed among age, education, and body mass index (BMI) groups, and differences and trends were considered statistically significant at p < .05.

RESULTS

Overall, 6.0% of participants reported meeting 2008 Guidelines, and there were no significant differences between sex and racial/ethnic groups. A significant linear increase was noted among education groups, with respondents who reported lower levels of educational attainment having lower levels of participation compared with respondents who reported higher levels of educational attainment. A significant linear decrease was noted among each BMI group, with those classified as underweight/normal reporting higher levels of participation, compared with those classified as obese. Free weights and calisthenics were the most common types of activities; the home was the most common location.

CONCLUSIONS

Few adults reported meeting current muscle-strengthening standards. Future public health efforts to increase participation should use the most frequently reported type and location of muscle-strengthening activities outlined in this study to guide interventions and communication campaigns.

Trends in no leisure-time physical activity--United States, 1988-2010

PURPOSE

The aim of this study was to examine trends in the prevalence of no leisure-time physical activity (LTPA) from 1988 to 2010.

METHOD

Using the Behavioral Risk Factor Surveillance System data, 35 states and the District of Columbia reported information on no LTPA from 1988 to 1994; all states reported no LTPA from 1996 to 2010.

RESULTS

No LTPA significantly declined over two decades. Prevalence for all states declined on an average of 0.6% per year from 29.1% in 1996 to 24.1% in 2004 and stabilized from 2005 to 2010, ranging from 24.0% to 25.4%. Prevalence declined for both sexes and all racial/ethnic groups.

CONCLUSION

While the no LTPA trends improved over two decades, one in four U.S. adults still report they do not engage in LTPA.

Non-typhoidal Salmonella encephalopathy involving lipopolysaccharide in cattle

This study assessed the involvement of lipopolysaccharide (LPS) in the non-typhoidal Salmonella encephalopathy (NTSE) caused by a unique isolate of Salmonella enterica serovar Saint-paul (SstpNPG). NTSE was prevented by genetic (deletion of murE) or pharmacologic (polymyxin) disruption of LPS on SstpNPG although the disruption of LPS did not deter brain penetration of the strain. This is the first study to demonstrate that LPS is involved in the manifestations of NTSE.

Household transmission of 2009 pandemic influenza A (H1N1) and nonpharmaceutical interventions among households of high school students in San Antonio, Texas

San Antonio, Texas, was one of the first metropolitan areas where 2009 pandemic influenza A (H1N1) virus (pH1N1) was detected. Identification of laboratory-confirmed pH1N1 in 2 students led to a preemptive 8-day closure of their high school. We assessed transmission of pH1N1 and changes in adoption of nonpharmaceutical interventions (NPIs) within households of students attending the affected school. Household secondary attack rates were 3.7% overall and 9.1% among those 0-4 years of age. Widespread adoption of NPIs was reported among household members. Respondents who viewed pH1N1 as very serious were more likely to adopt certain NPIs than were respondents who viewed pH1N1 as not very serious. NPIs may complement influenza vaccine prevention programs or be the only line of defense when pandemic vaccine is unavailable. The 2009 pandemic provided a unique opportunity to study NPIs, and these real-world experiences provide much-needed data to inform pandemic response policy.

Trend and prevalence estimates based on the 2008 Physical Activity Guidelines for Americans

BACKGROUND

According to the 2008 Physical Activity Guidelines for Americans, adults need to engage in at least 150 minutes/week of moderate-intensity activity or its equivalent (defined as aerobically active) to obtain substantial health benefits and more than 300 minutes/week (defined as highly active) to obtain more extensive health benefits. In addition to aerobic activity, the 2008 Guidelines recommend that adults participate in muscle-strengthening activities on 2 or more days/week.

PURPOSE

This study examined the prevalence and trends of meeting the activity criteria defined by the 2008 Guidelines among U.S. adults.

METHODS

Prevalence and trends of participation in leisure-time physical activity were estimated from the 1998-2008 National Health Interview Survey (analyzed in 2010).

RESULTS

In 2008, 43.5% of U.S. adults were aerobically active, 28.4% were highly active, 21.9% met the muscle-strengthening guideline, and 18.2% both met the muscle-strengthening guideline and were aerobically active. The likelihood of meeting each of these four activity criteria was similar and were associated with being male, being younger, being non-Hispanic white, having higher levels of education, and having a lower BMI. Trends over time were also similar for each part of the 2008 Guidelines, with the prevalence of participation exhibiting a small but significant increase when comparing 1998 to 2008 (difference ranging from 2.4 to 4.2 percentage points).

CONCLUSIONS

Little progress has been made during the past 10 years in increasing physical activity levels in the U.S. There is much room for improvement in achieving recommended levels of physical activity among Americans, particularly among relatively inactive subgroups.

Prevalence of highly active adults--Behavioral Risk Factor Surveillance System, 2007

BACKGROUND

The 2008 Physical Activity Guidelines for Americans (2008 Guidelines) included a novel aerobic physical activity standard, in excess of minimum standards, for more extensive health benefits (>300 minutes/week of moderate-intensity, 150 minutes/week of vigorous-intensity, or an equivalent combination). Prevalence estimates among US states have yet to be described for this new standard.

METHODS

Respondents self-reported physical activity in the 2007 Behavioral Risk Factor Surveillance System was used (n=398,397). Total weekly aerobic activity was calculated for each respondent and 2008 Guidelines standards guided classification.

RESULTS

In 2007, 43.5% (95% CI: 43.1%-43.8%) of adults met the new 2008 Guidelines standard and were classified as highly active (male, 48.3%; female, 38.9%). Linear patterns were noted by age and education, where younger age and higher levels of education had a higher proportion of highly active. Non-Hispanic whites (45.7%) had a significantly higher proportion of highly active compared with non-Hispanic blacks (37.5%) and Hispanics (37.6%). Variations in estimates were noted among those categorized as sufficiently active, insufficiently active, and inactive.

CONCLUSION

More than half of 2007 Behavioral Risk Factor Surveillance System respondents did not meet the new 2008 Guidelines standard. Aerobic activity levels commensurate with more extensive health benefits should be encouraged among US adults.

Influence of limit-setting and participation in physical activity on youth screen time

OBJECTIVES

To examine the associations of demographics, rules associated with television-viewing, and physical activity with daily screen time (including television, non-school-related computer use, and video games) in children and adolescents.

METHODS

We analyzed data from a telephone survey of 7415 youth aged 9 to 15 years from the Youth Media Campaign Longitudinal Survey. We used logistic regression models to calculate odds of exceeding recommended screen-time limits (>120 minutes/day) according to demographics, rules, and physical activity.

RESULTS

Odds that children would exceed recommended screen-time limits were positively associated with age and black race/ethnicity and negatively associated with income level. Children and adolescents who reported that they really agreed that their parents had rules about time spent watching television and playing video games were less likely to exceed recommended limits than those who strongly disagreed that their parents had rules. Similarly, when parents reported always or very often having limits on television watching (versus rarely or never) and when parents correctly identified the recommended limits, children were less likely to exceed recommended limits. Children whose parents reported consistent limits and who themselves reported consistent rules about time spent watching television had the lowest prevalence of exceeding recommended limits. Odds that children would exceed recommended limits decreased as physical activity in the previous week increased.

CONCLUSIONS

Parental rules regarding screen time and participation in physical activity play a role in the amount of screen time among children and adolescents. Programs that encourage limit-setting by parents and promote physical activity may reduce screen time among youth.

Racial/Ethnic differences in perceived access, environmental barriers to use, and use of community parks

INTRODUCTION

Community parks provide places for people to be physically active. Our objective was to determine how access to, barriers to use of, and use of community parks differ by race/ethnicity.

METHODS

Analyses are based on a cross-sectional national sample of adults (N = 5,157) participating in the 2006 HealthStyles mail survey. Community parks were defined as outdoor public areas within 10 miles or a 20-minute drive from where a person lives that include walking/bike paths, nature preserves, playgrounds, beaches, lakes, rivers, or similar places.

RESULTS

Overall, 12% of respondents reported not having a community park. Among those with a community park, 14% reported personal safety concerns and 14% reported inadequate or poorly maintained facilities as barriers to park use. Race/ethnicity was not associated with park access; however, Hispanics and non-Hispanic blacks were more likely than non-Hispanic whites to report barriers. Among those with access to a community park, 83% reported any park use in the previous year and, of these, 67% reported an active visit. Odds of any park use did not differ significantly by race/ethnicity. Odds of an active visit were significantly lower in non-Hispanic blacks than whites (odds ratio, 0.67) but did not significantly differ between Hispanics and non-Hispanic whites.

CONCLUSION

Parks are valuable community resources to all racial/ethnic groups. To promote and increase community park use, it is important to be aware that parks are used differently by different racial/ethnic groups and that barriers may differentially influence park use.

Relationships between body size satisfaction and weight control practices among US adults

CONTEXT

Few studies of US adults have specifically examined body size satisfaction

OBJECTIVES

Describe correlates of body size satisfaction and examine whether satisfaction was associated with trying to lose weight or specific weight control practices among US adults using a national sample of women and men.

DESIGN, SETTING & PARTICIPANTS

The National Physical Activity and Weight Loss Survey (NPAWLS) was a population-based, cross-sectional telephone survey of US adults (n = 9740).

MAIN OUTCOME MEASURES

Participants reported their weight, height, body size satisfaction, and weight loss practices. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each dependent variable.

RESULTS

Among women and men, higher body mass index (BMI) was significantly associated with body size dissatisfaction. Dissatisfaction, compared with being very satisfied, was positively associated with trying to lose weight among women and men. This association was modified by BMI for women (OR normal weight = 19.69, overweight = 8.79, obese = 4.05; P < .01 for interaction) but not men (OR normal weight = 8.72, overweight = 10.50, obese = 7.86; P = 0.93 for interaction). Compared with women who were very satisfied, dissatisfied women used diet more (OR = 2.03), but not physical activity/exercise (OR = 0.55) or both strategies (OR = 0.63), to try to lose weight. Men who were somewhat satisfied, compared with those who were very satisfied, were more likely to use physical activity/exercise (OR = 1.64) and both diet and physical activity/exercise (OR = 1.54) to try to lose weight.

CONCLUSION

These findings highlight the sex differences in body size satisfaction, actions taken to try to lose weight, and the importance of considering body size satisfaction when designing weight-management programs.

Physical education and academic achievement in elementary school: data from the early childhood longitudinal study

OBJECTIVES

We examined the association between time spent in physical education and academic achievement in a longitudinal study of students in kindergarten through fifth grade.

METHODS

We used data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998 to 1999, which employed a multistage probability design to select a nationally representative sample of students in kindergarten (analytic sample = 5316). Time spent in physical education (minutes per week) was collected from classroom teachers, and academic achievement (mathematics and reading) was scored on an item response theory scale.

RESULTS

A small but significant benefit for academic achievement in mathematics and reading was observed for girls enrolled in higher amounts (70-300 minutes per week) of physical education (referent: 0-35 minutes per week). Higher amounts of physical education were not positively or negatively associated with academic achievement among boys.

CONCLUSIONS

Among girls, higher amounts of physical education may be associated with an academic benefit. Physical education did not appear to negatively affect academic achievement in elementary school students. Concerns about adverse effects on achievement may not be legitimate reasons to limit physical education programs.

How active are older Americans?

INTRODUCTION

Regular physical activity can reduce age-related functional decline, as well people's risk for chronic diseases such as coronary heart disease, hypertension, colon cancer, and diabetes. The objective of this study was to estimate the level of participation in aerobic, muscle-strengthening, and flexibility activities among Americans aged 50 years or older.

METHODS

Using population-based data from the 2001 National Health Interview Survey, we classified qualified respondents (N = 11,969) according to whether they met the activity criteria used in Healthy People 2010 goals for leisure-time participation in regular aerobic physical activity, vigorous-intensity aerobic activity, strength-training activity, and flexibility activity. We also classified respondents according to their level of aerobic activity (i.e., inactive, insufficiently active, and regularly active).

RESULTS

We estimated that 46.4% of older Americans engaged in no leisure-time aerobic activity; that 26.1% were regularly active (participated in light- to moderate-intensity aerobic activities at least 5 days per week for at least 30 minutes or vigorous-intensity activities at least 3 days per week for at least 20 minutes); that 16.2% participated in vigorous-intensity aerobic activities at least 3 days per week for at least 20 minutes; that 13.7% participated in strength-training activities at least 2 days per week; and that 24.5% participated in flexibility activities at least 1 day per week. Among the 26.1% of older Americans who were regularly active, 30.5% engaged in strengthen-training activities at least 2 days per week. Overall, only 8.2% of older Americans met the criteria for both aerobic and strength-training activity.

CONCLUSION

As of 2001, the percentage of older Americans who met recommended activity levels of physical activity were well below the goals for U.S. adults in Healthy People 2010. Further efforts are needed to encourage older Americans to engage in aerobic activities and in strengthening and flexibility activities.

Fitness facilities for adults: differences in perceived access and usage

BACKGROUND

Perceived access to places for physical activity may play an important role in influencing physical activity behavior. Little is known about the prevalence of perceived access to facilities for physical activity.

METHODS

Cross-sectional analysis of a national sample of 27,894 adults from the 2002 National Health Interview Survey was performed to describe the characteristics of those who perceived that they have access to fitness facilities, and determine the prevalence of perceived access, reported use of fitness facilities, and reported barriers to the use of fitness facilities. Analyses were conducted in 2005 and 2006.

RESULTS

Approximately 61% of adults reported having access to fitness facilities. Perceived access was highest among adults aged 34 and younger, non-Hispanic whites, those with a college education, among adults with a body mass index of less than 35 kg/m(2), and among those with higher physical activity levels. The most commonly reported perceived barrier to access was cost. Almost 21% of U.S. adults (37.0% of active, 19.9% of intermittently active, 6.0% of inactive) reported having used a health club, wellness program, or fitness facility at least ten times during the past year.

CONCLUSIONS

Fitness facilities provide one option for increasing access to places to be physically active. Having access to fitness facilities is significantly associated with physical activity levels among U.S. adults.

Experimental reproduction of bovine Salmonella encephalopathy using a norepinephrine-based stress model

Neurological disease represents a sporadic but serious manifestation of bovine salmonellosis that is thought to be related to systemic infection. Salmonella enterica serovar Dublin (S. Dublin) is the serovar most associated with systemic infection in cattle, although reports of neurological disease associated with S. Dublin or any other serovar are rare and usually anecdotal. This study reports the involvement of three strains of S. enterica, serovars Saintpaul, Montevideo, and Enteritidis, in Salmonella encephalopathies. Encephalopathies were reproduced in calves using a norepinephrine-based stress model. Neurological signs were not observed in calves infected with control strains of S. enterica, including S. Dublin, or in calves infected with clinical strains in the absence of norepinephrine. Therefore, norepinephrine may play a role in Salmonella encephalopathies.

Self-reported Injury and Physical Activity Levels: United States 2000 to 2002

PURPOSE

The aim of the study is to compare national estimates of the incidence of self-reported all-cause and activity-specific injuries in adults with differing leisure-time physical activity levels.

METHODS

Data were analyzed from the 2000 to 2002 National Health Interview Survey. Leisure-time physical activity levels were categorized as active, insufficiently active, and inactive.

RESULTS

Age-adjusted incidences of all-cause injury did not differ by leisure-time physical activity level (active, 89.3/1000; 95% confidence interval [CI], 81.8-96.8; insufficiently active, 81.6/1000; 95% CI, 73.1-90.1; and inactive, 86.3/1000; 95% CI, 78.6-93.9). Active respondents (29.4/1000; 95% CI, 25.2-33.6) had a greater incidence of injury related to sport and leisure-time activities than inactive respondents (15.2/1000; 95% CI, 12.1-18.3), whereas inactive respondents (71.1/1000; 95% CI, 63.9-78.2) had a greater incidence of injury related to nonsport and non-leisure-time activities than active respondents (59.9/1000; 95% CI, 53.6-66.2). Results were unchanged after multivariate control for confounding factors.

CONCLUSIONS

Although the incidence of sport and leisure-time injuries is associated with participation in leisure-time physical activity, no association was observed between leisure-time physical activity and overall injuries.

Klebsiella to Salmonella gene transfer within rumen protozoa: implications for antibiotic resistance and rumen defaunation

The rumen has long been thought to be a site of gene transfer for microorganisms. Rumen protozoa (RPz) are active predators of bacteria that can harbor antibiotic resistance genes. In this study, RPz were assessed as sites of gene transfer between two bacterial species, Salmonella and Klebsiella. One Klebsiella isolate carried a plasmid bearing bla(CMY-2), encoding an extended-spectrum beta-lactamase conferring ceftriaxone resistance, while the Salmonella was susceptible to ceftriaxone yet capable of thriving within protozoa. In vitro studies revealed that ceftriaxone-resistant Salmonella could be isolated following co-incubation of Salmonella and Klebsiella with RPz obtained from adult cattle and goats. Ceftriaxone-resistant Salmonella were not recovered in the presence of an inhibitor of protozoa engulfment or when a protozoa-sensitive Salmonella was part of the co-incubation. This transfer event was additionally observed in vitro for protozoa-independent stressors although at a significantly lower frequency. The gene transfer event was related to bacterial conjugation since a conjugation inhibitor, nalidixic acid, perturbed the phenomenon. Ceftriaxone-resistant Salmonella were recovered from calves, sheep, and goats co-challenged with ceftriaxone-resistant Klebsiella and ceftriaxone-sensitive Salmonella. However, the transfer event was not observed in calves and sheep that were defaunated prior to the co-challenge. Moreover, Salmonella transconjugants were isolated from separate bovine in vivo studies involving a Klebsiella donor carrying a plasmid conferring colicin activity while no such transconjugants were obtained from defaunated calves. These results provide an important basis for evaluating and preventing the spread of antibiotic resistance and other selective advantages for pathogens present in ruminants.

Early epithelial invasion by Salmonella enterica serovar Typhimurium DT104 in the swine ileum

Salmonella enterica serovar Typhimurium is an important intestinal pathogen in swine. This study was performed to document the early cellular invasion of Salmonella serovar Typhimurium in swine ileum. Ileal gut-loops were surgically prepared in ten 4- to 5-week-old mixed-breed pigs and inoculated for 0-60 minutes. Loops were harvested and prepared for both scanning and transmission electron microscopy (SEM and TEM, respectively). Preferential bacterial adherence to microfold cells (M cells) was seen within 5 minutes, and by 10 minutes bacterial invasion of the apical membrane was seen in M cells, goblet cells, and enterocytes. This multicellular invasion was observed throughout the course of infection. In addition, SEM revealed a specific affinity of Salmonella serovar Typhimurium to sites of cell extrusion. Using TEM, bacteria in these areas were focused in the crevices formed by the extruding cell and the adjacent cells and in the cytoplasm immediately beneath the extruding cell. Our results suggest that early cellular invasion by Salmonella serovar Typhimurium is nonspecific and rapid in swine. Furthermore, the combination of SEM and TEM data suggests that Salmonella serovar Typhimurium may use sites of cell extrusion as an additional mechanism for early invasion.

Abomasitis associated with multiple antibiotic resistant Salmonella enterica serotype Typhimurium phagetype DT104

Salmonella enterica serotype Typhimurium phagetype DT104 is a multiple antibiotic resistant pathogen that has been purported to be more pathogenic than other Salmonella. In this study, we evaluated the possibility that DT104 is the causative agent of veal calf abomasitis observed in four independent outbreaks of salmonellosis. This study was undertaken to determine if the outbreaks might be due to hypervirulent S. enterica serotype Typhimurium phagetype DT104 (DT104) since Salmonella does not usually cause abomasitis. Tissues and fluids from these calves were subjected to bacteriologic culture. Pure Salmonella cultures were then used in bovine challenge experiments. DT104 was identified as the causative agent of abomasitis in calves. Thus, abomasitis is a potential indicator of infection with multiple antibiotic resistant DT104 and adds credence to the apparent hypervirulence of this pathogen.

Secretion of a putative cytotoxin in multiple antibiotic resistant Salmonella enterica serotype Typhimurium phagetype DT104

Salmonella enterica serotype Typhimurium phagetype DT104 (DT104) is a multiple antibiotic-resistant pathogen. DT104 infections have been reported in a multitude of hosts including humans, companion animals, livestock and wildlife. Recently, several isolates of DT104 were recovered from veal calves exhibiting abomasitis, a finding that is inconsistent with classic salmonellosis. One of these isolates was used in murine ligated loop experiments where it was observed that multiresistant DT104 can elaborate a putative cytotoxin. Thus it appears that DT104 has the ability to evade pharmacologic interventions, via antibiotic resistance, and elaborate a toxin that can damage cells.

Antibiotic resistance in Salmonella enterica serovar Typhimurium exposed to microcin-producing Escherichia coli

Microcin 24 is an antimicrobial peptide secreted by uropathogenic Escherichia coli. Secretion of microcin 24 provides an antibacterial defense mechanism for E. coli. In a plasmid-based system using transformed Salmonella enterica, we found that resistance to microcin 24 could be seen in concert with a multiple-antibiotic resistance phenotype. This multidrug-resistant phenotype appeared when Salmonella was exposed to an E. coli strain expressing microcin 24. Therefore, it appears that multidrug-resistant Salmonella can arise as a result of an insult from other pathogenic bacteria.

Relative distribution and conservation of genes encoding aminoglycoside-modifying enzymes in Salmonella enterica serotype typhimurium phage type DT104

PCR was used to identify genes encoding aminoglycoside-modifying enzymes in 422 veterinary isolates of Salmonella enterica serotype Typhimurium. The identities of extra-integron genes encoding resistance to streptomycin, gentamicin, kanamycin, and apramycin were evaluated. Gentamicin resistance was conferred by the aadB gene. Kanamycin resistance was encoded by either the aphA1-Iab gene or the Kn gene. Apramycin resistance was determined by the aacC4 gene. Analysis of gene distribution did not reveal significant differences with regard to phage type, host species, or region except for the Kn gene, which was found mostly in nonclinical isolates. The data from this study indicate that pentaresistant DT104 does not acquire extra-integron genes in species- or geography-related foci, which supports the hypothesis that clonal expansion is the method of spread of this organism.

Simultaneous detection of Salmonella strains and Escherichia coli O157:H7 with fluorogenic PCR and single-enrichment-broth culture

A multiplex fluorogenic PCR assay for simultaneous detection of pathogenic Salmonella strains and Escherichia coli O157:H7 was developed and evaluated for use in detecting very low levels of these pathogens in meat and feces. Two sets of primers were used to amplify a junctional segment of virulence genes sipB and sipC of Salmonella and an intragenic segment of gene eae of E. coli O157:H7. Fluorogenic reporter probes were included in the PCR assay for automated and specific detection of amplified products. The assay could detect <10 CFU of Salmonella enterica serovar Typhimurium or E. coli O157:H7 per g of meat or feces artificially inoculated with these pathogens and cultured for 6 to 18 h in a single enrichment broth. Detection of amplification products could be completed in </=4 h after enrichment.

Evaluation of invasion-conferring genotypes and antibiotic-induced hyperinvasive phenotypes in multiple antibiotic resistant Salmonella typhimurium DT104

Antibiotic resistance in pathogenic bacteria is a problem in both industrialized and developing countries. This is especially evident in Salmonella typhimurium, a foodborne pathogen that causes gastrointestinal and systemic disease throughout the world. S. typhimurium DT104 further poses a major health concern due to its apparent enhanced ability to acquire multiple antibiotic resistance genes and its putative hypervirulent phenotype. Recently, we demonstrated that multiresistant S. typhimurium do not appear to be more invasive than non-resistant cohorts. In the present study, we evaluated the presence of Salmonella pathogenicity island 1 (SPI1) flanking and internal sequences in over 400 isolates of multiresistant S. typhimurium. With these same isolates, we also used a tissue culture invasion assay to evaluate a potential relationship between antibiotic exposure and a hyperinvasive phenotype. Our studies revealed that SPI1 flanking sequences are similar in multiresistant and non-resistant S. typhimurium. Furthermore, we failed to identify any isolates that were hyperinvasive in the presence of any of the 14 antibiotics evaluated. These results further indicate that the putative hypervirulence of multiresistant S. typhimurium is not likely to occur at the level of invasion.

Augmentation of antibiotic resistance in Salmonella typhimurium DT104 following exposure to penicillin derivatives

Antibiotic resistance in pathogenic bacteria has been a problem in both developed and developing countries. This problem is especially evident in Salmonella typhimurium, one of the most prevalent foodborne pathogens. While performing in vitro gentamicin protection-based invasion assays, we found that certain isolates of multiresistant S. typhimurium can be 'induced' to exhibit new resistance profiles. That is, bacteria become resistant to a wider range of antibiotics and they also exhibit quantitative increases in MIC values for antibiotics that were part of their pre-induction antibiograms. This 'induction' process involves growing the bacteria to stationary phase in the presence of antibiotics such as ampicillin, amoxicillin or ticarcillin. Since the isolates studied exhibited resistance to ampicillin, amoxicillin and ticarcillin prior to exposing the bacteria to these antibiotics, the observed phenomenon suggests that resistant Salmonella not only have a selective advantage over non-resistant Salmonella but their resistance phenotypes can be accentuated when an inappropriate antibiotic is used therapeutically.

Identification of diminished tissue culture invasiveness among multiple antibiotic resistant Salmonella typhimurium DT104

Salmonella infections continue to cause gastrointestinal and systemic disease throughout the world. Salmonella typhimurium further poses a major health concern due to its apparent enhanced ability to acquire multiple antibiotic resistance genes. Currently it is unclear if multiresistant S. typhimurium are more or less pathogenic than non-resistant counterparts. Using an in vitro invasion assay, we evaluated the relative pathogenicity of over 400 multiresistant S. typhimurium isolates. Our studies failed to identify any <<<<hyperinvasive>>>> isolates. However, we identified 12 isolates exhibiting invasive phenotypes that were constrained relative to controls. These <<<<hypoinvasive>>>> strains were found in a variety of phagetypes all possessing at least a hexaresistant profile. Further studies revealed that the alterations in invasion were not due to changes in adherence. Limited studies exploring in vivo virulence revealed a mildly decreased ability to cause murine lethality for the hypoinvasive strain examined. These results indicate that the ability to cause disease is not increased but is rather mildly attenuated for certain isolates of multiresistant S. typhimurium.

Detection of multiresistant Salmonella typhimurium DT104 using multiplex and fluorogenic PCR

Salmonella infections continue to cause gastrointestinal and systemic disease throughout the world. Salmonella typhimurium DT104 further poses a major health concern due to its acquisition of resistance to multiple antibiotics. The rapid detection of multiresistant S. typhimurium DT104 would facilitate strategies aimed at controlling this pathogen. We developed a specific and sensitive polymerase chain reaction (PCR) assay that amplifies a segment of DNA that is conserved in multiresistant S. typhimurium DT104. To provide further specificity for this PCR-based diagnostic test, we amplified two other gene fragments that are present in S. typhimurium DT104. A multiplex PCR containing primers for targeted sequences resulted in the amplification of predicted size fragments from S. typhimurium DT104 exhibiting the ACSSuT (ampicillin, chloramphenicol, streptomycin, sulphamethoxazole and tetracycline) or ASSuT resistance phenotypes. A minor modification of the multiplex PCR enabled the detection of other related multiresistant Salmonella such as S. typhimurium U302. To augment the detection process, we also designed a fluorogenic PCR assay that can detect the DNA of multiresistant S. typhimurium DT104 in the presence of excess contaminating bacterial DNA. These results provide a method by which multiresistant S. typhimurium DT104, or potentially the next emerging multiresistant Salmonella, can be accurately detected in only 3-4 h.

Inhibition of Salmonella typhimurium invasion by host cell expression of secreted bacterial invasion proteins

Pathogenic Salmonella species initiate infection of a host by inducing their own uptake into intestinal epithelial cells. An invasive phenotype is conferred to this pathogen by a number of proteins that are components of a type III secretion system. During the invasion process, the bacteria utilize this secretion system to release proteins that enter the host cell and apparently interact with unknown host cell components that induce alterations in the actin cytoskeleton. To investigate the role of secreted proteins as direct modulators of invasion, we have evaluated the ability of Salmonella typhimurium to enter mammalian cells that express portions of the Salmonella invasion proteins SipB and SipC. Plasma membrane localization of SipB and SipC was achieved by fusing carboxyl- and amino-terminal portions of each invasion protein to the intracellular carboxyl-terminal tail of a membrane-bound eukaryotic receptor. Expression of receptor chimeras possessing the carboxyl terminus of SipB or the amino terminus of SipC blocked Salmonella invasion, whereas expression of their chimeric counterparts had no effect on invasion. The effect on invasion was specific for Salmonella since the perturbation of uptake was not extended to other invasive bacterial species. These results suggest that Salmonella invasion can be competitively inhibited by preventing the intracellular effects of SipB or SipC. In addition, these experiments provide a model for examining interactions between bacterial invasion proteins and their host cell targets.