There is increasing evidence that Escherichia coli organisms are important in Crohn's disease (CD) pathogenesis. In CD tissue they are found within macrophages, and the adherent-invasive CD ileal E. coli isolate LF82 can replicate inside macrophage phagolysosomes. This study investigates replication and antibiotic susceptibility of CD colonic E. coli isolates inside macrophages. Replication of CD colonic E. coli within J774-A1 murine macrophages and human monocyte-derived macrophages (HMDM) was assessed by culture and lysis after gentamicin killing of noninternalized bacteria and verified by electron microscopy (EM). All seven CD colonic isolates tested replicated within J774-A1 macrophages by 3 h (6.36-fold ؎ 0.7-fold increase; n ‫؍‬ 7 isolates) to a similar extent to CD ileal E. coli LF82 (6.8-fold ؎ 0.8-fold) but significantly more than control patient isolates (5.2-fold ؎ 0.25-fold; n ‫؍‬ 6; P ‫؍‬ 0.006) and E. coli K-12 (1.0-fold ؎ 0.1-fold; P < 0.0001). Replication of CD E. coli HM605 within HMDM (3.9-fold ؎ 0.7-fold) exceeded that for K-12 (1.4-fold ؎ 0.2-fold; P ‫؍‬ 0.03). EM showed replicating E. coli within macrophage vacuoles. Killing of HM605 within J774-A1 macrophages following a 3-h incubation with antibiotics at published peak serum concentrations (C max ) was as follows: for ciprofloxacin, 99.5% ؎ 0.2%; rifampin, 85.1% ؎ 6.6%; tetracycline, 62.8% ؎ 6.1%; clarithromycin, 62.1% ؎ 5.6% (all P < 0.0001); sulfamethoxazole, 61.3% ؎ 7.0% (P ‫؍‬ 0.0007); trimethoprim, 56.3% ؎ 3.4% (P < 0.0001); and azithromycin, 41.0% ؎ 10.5% (P ‫؍‬ 0.03). Ampicillin was not effective against intracellular E. coli. Triple antibiotic combinations were assessed at 10% C max , with ciprofloxacin, tetracycline, and trimethoprim causing 97% ؎ 0.0% killing versus 86% ؎ 2.0% for ciprofloxacin alone. Colonic mucosaassociated E. coli, particularly CD isolates, replicate within macrophages. Clinical trials are indicated to assess the efficacy of a combination antibiotic therapy targeting intramacrophage E. coli.

Placements are often an extra-curricular activity of a science degree. This study reports on the outcomes of a final year credit-bearing 6-week placement module that was specifically designed to develop and enhance students' employability skills. A key element of this module was that the student placements were not only evaluated from a science perspective, but also with an emphasis on meaningful reflection and evaluation of employability skills development. Students recorded their levels of confidence in skills before, during and after the placement via an Online Reflective Log, as part of a module's summative assessment. The results showed that taking part in the placement and conducting their own independent research helped students to make connections between their scientific knowledge, otherwise constrained within the walls of the undergraduate science lab, and the wider impact of their research on society. Another theme that emerged concerned career choices and aspirations, and the placement experience either confirmed prior choices or opened new horizons. The Online Reflective Log helped students to feel supported by their university supervisor who were at a distance. Feedback on their tasks prompted students to reflect on the scientific and personal skills while being engaged in scientific activities during placement. Students agreed that they had further developed their employability skills during the placement and acknowledged that it was challenging to acquire evidence of skills development. However, students appreciated the usefulness of this reflection in relation to their future career development.

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