Targeting of permissive entry sites is crucial for bacterial infection. The targeting mechanisms are incompletely understood. We have analyzed target-site selection by S . Typhimurium. This enteropathogenic bacterium employs adhesins (e.g. fim ) and the type III secretion system 1 (TTSS-1) for host cell binding, the triggering of ruffles and invasion. Typically, S . Typhimurium invasion is focused on a subset of cells and multiple bacteria invade via the same ruffle. It has remained unclear how this is achieved. We have studied target-site selection in tissue culture by time lapse microscopy, movement pattern analysis and modeling. Flagellar motility (but not chemotaxis) was required for reaching the host cell surface in vitro. Subsequently, physical forces trapped the pathogen for ∼1.5–3 s in “near surface swimming”. This increased the local pathogen density and facilitated “scanning” of the host surface topology. We observed transient TTSS-1 and fim -independent “stopping” and irreversible TTSS-1-mediated docking, in particular at sites of prominent topology, i.e. the base of rounded-up cells and membrane ruffles. Our data indicate that target site selection and the cooperative infection of membrane ruffles are attributable to near surface swimming. This mechanism might be of general importance for understanding infection by flagellated bacteria.

Children from refugee backgrounds often experience multiple traumatic events and schools are uniquely placed to support these students. This study examined the experiences of teachers in supporting students from refugee backgrounds who have experienced trauma. Six teachers participated in interviews which were analysed using thematic analysis. Teachers reported challenges related to limited sharing of relevant background information, uncertainty about presenting classroom lessons sensitively, when to refer students for specialised intervention, and how best to support refugee students when external factors create continued challenges. The effectiveness of existing practices and recommendations for tailoring trauma-informed practices for this student population are discussed. The results are also discussed in the context of social constructivism and how teachers use their interactions with students and colleagues to inform how they respond to refugee students exposed to trauma.

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