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1.  Optically Trapped Bacteria Pairs Reveal Discrete Motile Response to Control Aggregation upon Cell–Cell Approach 
Current Microbiology  2014;69(5):669-674.
Aggregation of bacteria plays a key role in the formation of many biofilms. The critical first step is cell–cell approach, and yet the ability of bacteria to control the likelihood of aggregation during this primary phase is unknown. Here, we use optical tweezers to measure the force between isolated Bacillus subtilis cells during approach. As we move the bacteria towards each other, cell motility (bacterial swimming) initiates the generation of repulsive forces at bacterial separations of ~3 μm. Moreover, the motile response displays spatial sensitivity with greater cell–cell repulsion evident as inter-bacterial distances decrease. To examine the environmental influence on the inter-bacterial forces, we perform the experiment with bacteria suspended in Tryptic Soy Broth, NaCl solution and deionised water. Our experiments demonstrate that repulsive forces are strongest in systems that inhibit biofilm formation (Tryptic Soy Broth), while attractive forces are weak and rare, even in systems where biofilms develop (NaCl solution). These results reveal that bacteria are able to control the likelihood of aggregation during the approach phase through a discretely modulated motile response. Clearly, the force-generating motility we observe during approach promotes biofilm prevention, rather than biofilm formation.
PMCID: PMC4201752  PMID: 24965235
2.  The Role of Support Services in Promoting Social Inclusion for the Disadvantaged Urban-dwelling Elderly 
Canadian Geriatrics Journal  2013;16(4):156-179.
Disadvantaged older adults living in non-family situations in Toronto are more likely than older adults living in family situations to have less economic security, less social support, and less choice in housing. Older adults who live in poverty and are precariously housed are more likely to be chronically ill, to live with multiple illnesses, to have poor nutrition, high stress and loneliness, all of which are strongly associated with the determinant of health social exclusion. The aim of this study is to: 1) evaluate the level of social disadvantage and exclusion experienced by low-income older adults 65 years of age and older living alone or in non-family situations; 2) assess the level of dependency on government and community services (support services) to maintain a reasonable standard of living (minimize effects of social exclusion); and 3) identify consequences of social exclusion not addressed by current available services.
Fifteen male older adult members of the Good Neighbours’ Club in downtown Toronto were interviewed. Semi-structured questionnaires assessed barriers to, utility of, and perceived impact of support services available to disadvantaged older adults living in the central core of southeast Toronto.
Support services for income, housing, food security, social support, and health care do mitigate the effects of social exclusion in the study participants. Data gathered from interviews identified factors that counter the efforts by support services to increase social inclusion in this population.
Support services reduce social isolation experienced by these older adults. Evidence of the detrimental impact of low financial literacy suggests a need to design and implement training programs to build the older adults’ capacity to manage their own finances effectively, and resist falling victim to financial fraud.
PMCID: PMC3837715  PMID: 24278093
social exclusion; social inclusion; financial literacy; social support; health resilience; urban-dwelling elderly
3.  Access to primary health care among homeless adults in Toronto, Canada: results from the Street Health survey 
Open Medicine  2011;5(2):e94-e103.
Despite experiencing a disproportionate burden of acute and chronic health issues, many homeless people face barriers to primary health care. Most studies on health care access among homeless populations have been conducted in the United States, and relatively few are available from countries such as Canada that have a system of universal health insurance. We investigated access to primary health care among a representative sample of homeless adults in Toronto, Canada.
Homeless adults were recruited from shelter and meal programs in downtown Toronto between November 2006 and February 2007. Cross-sectional data were collected on demographic characteristics, health status, health determinants and access to health care. We used multivariable logistic regression analysis to investigate the association between having a family doctor as the usual source of health care (an indicator of access to primary care) and health status, proof of health insurance, and substance use after adjustment for demographic characteristics.
Of the 366 participants included in our study, 156 (43%) reported having a family doctor. After adjustment for potential confounders and covariates, we found that the odds of having a family doctor significantly decreased with every additional year spent homeless in the participant’s lifetime (adjusted odds ratio [OR] 0.91, 95% confidence interval [CI] 0.86–0.97). Having a family doctor was significantly associated with being lesbian, gay, bisexual or transgendered (adjusted OR 2.70, 95% CI 1.04–7.00), having a health card (proof of health insurance coverage in the province of Ontario) (adjusted OR 2.80, 95% CI 1.61–4.89) and having a chronic medical condition (adjusted OR 1.91, 95% CI 1.03–3.53).
Less than half of the homeless people in Toronto who participated in our study reported having a family doctor. Not having a family doctor was associated with key indicators of health care access and health status, including increasing duration of homelessness, lack of proof of health insurance coverage and having a chronic medical condition. Increased efforts are needed to address the barriers to appropriate health care and good health that persist in this population despite the provision of health insurance.
PMCID: PMC3148004  PMID: 21915240
4.  Multidimensional Social Support and the Health of Homeless Individuals 
Homeless individuals often suffer from serious health problems. It has been argued that the homeless are socially isolated, with low levels of social support and social functioning, and that this lack of social resources contributes to their ill health. These observations suggest the need to further explore the relationship between social networks, social support, and health among persons who are homeless. The purpose of this study was to examine the association between multidimensional (cognitive/perceived and behavioral/received) social support and health outcomes, including physical health status, mental health status, and recent victimization, among a representative sample of homeless individuals in Toronto, Canada. Multivariate regression analyses were performed on social support and health outcome data from a subsample of 544 homeless adults, recruited from shelters and meal programs through multistage cluster sampling procedures. Results indicated that participants perceived moderately high levels of access to financial, emotional, and instrumental social support in their social networks. These types of perceived social supports were related to better physical and mental health status and lower likelihood of victimization. These findings highlight a need for more services that encourage the integration of homeless individuals into social networks and the building of specific types of social support within networks, in addition to more research into social support and other social contextual factors (e.g., social capital) and their influence on the health of homeless individuals.
PMCID: PMC2729873  PMID: 19629703
Homelessness; Social support; Physical health; Mental health; Victimization; Canada
5.  Drug problems among homeless individuals in Toronto, Canada: prevalence, drugs of choice, and relation to health status 
BMC Public Health  2010;10:94.
Drug use is believed to be an important factor contributing to the poor health and increased mortality risk that has been widely observed among homeless individuals. The objective of this study was to determine the prevalence and characteristics of drug use among a representative sample of homeless individuals and to examine the association between drug problems and physical and mental health status.
Recruitment of 603 single men, 304 single women, and 284 adults with dependent children occurred at homeless shelters and meal programs in Toronto, Canada. Information was collected on demographic characteristics and patterns of drug use. The Addiction Severity Index was used to assess whether participants suffered from drug problems. Associations of drug problems with physical and mental health status (measured by the SF-12 scale) were examined using regression analyses.
Forty percent of the study sample had drug problems in the last 30 days. These individuals were more likely to be single men and less educated than those without drug problems. They were also more likely to have become homeless at a younger age (mean 24.8 vs. 30.9 years) and for a longer duration (mean 4.8 vs. 2.9 years). Marijuana and cocaine were the most frequently used drugs in the past two years (40% and 27%, respectively). Drug problems within the last 30 days were associated with significantly poorer mental health status (-4.9 points, 95% CI -6.5 to -3.2) but not with poorer physical health status (-0.03 points, 95% CI -1.3 to 1.3)).
Drug use is common among homeless individuals in Toronto. Current drug problems are associated with poorer mental health status but not with poorer physical health status.
PMCID: PMC2841106  PMID: 20181248
6.  The effect of traumatic brain injury on the health of homeless people 
We sought to determine the lifetime prevalence of traumatic brain injury and its association with current health conditions in a representative sample of homeless people in Toronto, Ontario.
We surveyed 601 men and 303 women at homeless shelters and meal programs in 2004–2005 (response rate 76%). We defined traumatic brain injury as any self-reported head injury that left the person dazed, confused, disoriented or unconscious. Injuries resulting in unconsciousness lasting 30 minutes or longer were defined as moderate or severe. We assessed mental health, alcohol and drug problems in the past 30 days using the Addiction Severity Index. Physical and mental health status was assessed using the SF-12 health survey. We examined associations between traumatic brain injury and health conditions.
The lifetime prevalence among homeless participants was 53% for any traumatic brain injury and 12% for moderate or severe traumatic brain injury. For 70% of respondents, their first traumatic brain injury occurred before the onset of homelessness. After adjustment for demographic characteristics and lifetime duration of homelessness, a history of moderate or severe traumatic brain injury was associated with significantly increased likelihood of seizures (odds ratio [OR] 3.2, 95% confidence interval [CI] 1.8 to 5.6), mental health problems (OR 2.5, 95% CI 1.5 to 4.1), drug problems (OR 1.6, 95% CI 1.1 to 2.5), poorer physical health status (–8.3 points, 95% CI –11.1 to –5.5) and poorer mental health status (–6.0 points, 95% CI –8.3 to –3.7).
Prior traumatic brain injury is very common among homeless people and is associated with poorer health.
PMCID: PMC2553875  PMID: 18838453

Results 1-6 (6)