Staphylococcus Aureus Biofilms Interfere With Macrophage Antimicrobial Responses Through Differential Gene Regulation, Toxin Production, and Purine Metabolism

Staphylococcus aureus (S. aureus) is an opportunistic pathogen that is a leading cause of both nosocomial and community-associated infections. Armed with a myriad of virulence factors and the propensity to form a biofilm on native tissues and implanted medical devices alike, S. aureus infections represent a very real public health threat, the treatment of which results in an excessive economic burden. S. aureus biofilm infections are notoriously recalcitrant to antibiotic therapy and adept at evading and neutralizing the host immune antimicrobial response. Previous studies from our laboratory have shown that S. aureus biofilms are able to cause persistent infections, in part, through the reprogramming of the macrophage (MΦ) immune response. While macrophages are readily able to recognize and respond to S. aureus in a planktonic state, their ability to mount a functional antimicrobial attack is thwarted upon encountering S. aureus biofilm. We have observed that MΦs in close proximity to S. aureus biofilms are less phagocytic and skewed towards an anti-inflammatory profile typified by arginase and IL-10 production. We have demonstrated that the ability of S. aureus biofilms to cause chronic infections is due, in part, to TLR2 or TLR9 evasion. However, we have shown that MyD88 signaling does provide some benefit to the host in combating S. aureus biofilm infections, which may be attributed to IL-1 receptor signaling. To better understand how S. aureus biofilms subvert the MΦ antimicrobial response, the work described in this dissertation assessed S. aureus transcriptional activity during co-culture with MΦs, whether S. aureus biofilms inhibit MΦ activity through secreted molecules, and performed a high-throughput screen of the Nebraska Transposon Mutant Library to identify key genes involved in dampening the MΦ NF-κB-regulated proinflammatory response. We found that S. aureus biofilms attenuate their transcriptional activity following MΦ exposure, augment α-hemolysin (Hla) and leukocidin AB (LukAB) secretion to inhibit MΦ phagocytosis and induce cell death, and rely on a functional purine biosynthetic pathway to prevent MΦ invasion and phagocytosis, in part, through controlling the amount of eDNA available for MΦ recognition at the surface of the biofilm extracellular matrix (ECM). Collectively, these studies build upon our previous observations by identifying key mechanisms whereby S. aureus biofilms are able to thwart the MΦ antimicrobial response

The Dynamics of Students' Behaviors and Reasoning during Collaborative Physics Tutorial Sessions

We investigate the dynamics of student behaviors (posture, gesture, vocal register, visual focus) and the substance of their reasoning during collaborative work on inquiry-based physics tutorials. Scherr has characterized student activity during tutorials as observable clusters of behaviors separated by sharp transitions, and has argued that these behavioral modes reflect students' epistemological framing of what they are doing, i.e., their sense of what is taking place with respect to knowledge. We analyze students' verbal reasoning during several tutorial sessions using the framework of Russ, and find a strong correlation between certain behavioral modes and the scientific quality of students' explanations. We suggest that this is due to a dynamic coupling of how students behave, how they frame an activity, and how they reason during that activity. This analysis supports the earlier claims of a dynamic between behavior and epistemology. We discuss implications for research and instruction.Comment: 4 pages, PERC 200

Using Theory to Develop Healthy Choices in Motion, a Comprehensive, Experiential Physical Activity Curriculum.

Background: Research has shown that engaging in regular physical activity supports physiologic, metabolic, and immunologic processes, as well as quality of life. However, few youth in the United States meet the U.S. Department of Health and Human Services recommendation of 60 min of moderate-to-vigorous physical activity every day. School-based programs can be an effective avenue for engaging youth in physical activity, particularly when the design of the health education is based on theory, research, and practice. The purpose of this study was to design, implement, and evaluate a theory-driven physical activity curriculum for the Shaping Healthy Choices Program (SHCP) using a systematic approach. Methods: The experiential, inquiry-based physical activity curriculum, Healthy Choices in Motion (HCIM), was developed with an optional technology enhancement using Backward Design. A questionnaire to assess the curriculum's effect on physical activity knowledge was developed and assessed for content validity, internal consistency (α = 0.84), and test-retest reliability (r = 0.73). The curriculum was piloted in two phases among upper elementary-aged youth: to ensure the learning goals were met (Pilot I) and to determine the curriculum's impact on physical activity knowledge, behavior, and self-efficacy (Pilot II). Pilot II was implemented among eight 4th and 5th-grade classrooms participating in the UC CalFresh Nutrition Education Program: (1) Comparison (no intervention) (n = 25); (2) SHCP only (n = 22); (3) SHCP + HCIM (n = 42); (4) SHCP + HCIM with technology enhancement (n = 47). Analyses included unadjusted ANOVA and Bonferroni for multiple comparisons and paired t-test (p < 0.05). Results: Through the use of a methodical design approach, a comprehensive physical activity curriculum, called HCIM, was developed. Youth participating in HCIM improved physical activity knowledge compared to youth receiving no intervention (+2.8 points, p = 0.009) and youth only in the SHCP (+3.0 points, p = 0.007). Youth participating in HCIM with technology enhancement demonstrated improvements compared to youth only in the SHCP (+2.3 points, p = 0.05). Conclusion: Improvements in physical activity knowledge in youth participating in HCIM may contribute to improvements in physical activity and should be further explored in conjunction with behavioral measurements

Hiding in Plain Sight: Interplay between Staphylococcal Biofilms and Host Immunity.

Staphylococcus aureus and Staphylococcus epidermidis are notable for their propensity to form biofilms on implanted medical devices. Staphylococcal biofilm infections are typified by their recalcitrance to antibiotics and ability to circumvent host immune-mediated clearance, resulting in the establishment of chronic infections that are often recurrent in nature. Indeed, the immunomodulatory lifestyle of biofilms seemingly shapes the host immune response to ensure biofilm engraftment and persistence in an immune competent host. Here, we provide a brief review of the mechanisms whereby S. aureus and S. epidermidis biofilms manipulate host-pathogen interactions and discuss the concept of microenvironment maintenance in infectious outcomes, as well as speculate how these findings pertain to the challenges of staphylococcal vaccine development

Gesture analysis for physics education researchers

Systematic observations of student gestures can not only fill in gaps in students' verbal expressions, but can also offer valuable information about student ideas, including their source, their novelty to the speaker, and their construction in real time. This paper provides a review of the research in gesture analysis that is most relevant to physics education researchers and illustrates gesture analysis for the purpose of better understanding student thinking about physics.Comment: 14 page