was evaluated when the polymer was applied as a coating to various surfaces using a paint-like procedure. Antimicrobial activity of PEIþ as a function of time was determined using an assay for long-term survival involving placement of single drops of various bacterial concentrations on dry surfaces. These data were compared with an assay method where bacteria were applied by spraying and surfaces were incubated overnight under agar. PEIþ-coated surfaces were found to be highly bactericidal after 30 min when bacteria were sprayed onto surfaces. However, when bacteria were applied as single drops, PEIþ-coated surfaces were less biocidal at short contact times particularly for A. baumannii and E. coli. The observations are explained in the context of the difference in drying time between drops deposited on uncoated surfaces and PEIþ-coated surfaces and the sensitivity of bacterial survival to dehydration. These results demonstrate that PEIþ-coated surfaces are not effectively biocidal for some types of bacteria under certain conditions and that the method of assaying bactericidal efficiency can greatly affect the results obtained.

Background Mentorship programs are perceived as valuable, yet little is known about the effect of program design on mentoring effectiveness. Intervention We developed a program focused on mentoring relationship quality and evaluated how subsequent relationships compared to preexisting informal pairings. Methods Faculty members were invited by e-mail to participate in a new mentoring program. Participants were asked to complete a biography, subsequently provided to second- and third-year internal medicine residents. Residents were instructed to contact available mentors, and ultimately designate a formal mentor. All faculty and residents were provided a half-day workshop training, written guidelines, and e-mails. Reminders were e-mailed and announced in conferences approximately monthly. Residents were surveyed at the end of the academic year. Results Thirty-seven faculty members completed the biography, and 70% (26 of 37) of residents responded to the survey. Of the resident respondents, 77% (20 of 26) chose a formal mentor. Of the remainder, most had a previous informal mentor. Overall, 96% (25 of 26) of the residents had identified a mentor of some kind compared to 50% (13 of 26) before the intervention (P < .001), and 70% (14 of 20) who chose formal mentors identified them as actual mentors. Similar numbers of residents described their mentors as invested in the mentorship, and there was no statistical difference in the number of times mentors and mentees met. Conclusions Facilitated selection of formal mentors produced relationships similar to preexisting informal ones. This model may increase the prevalence of mentorship without decreasing quality.

The ability of an antimicrobial, cationic polyethylenimine (PEI+) to induce the three known extracytoplasmic stress responses of Escherichia coli was quantified. Exposure of E. coli to PEI+ in solution revealed specific, concentration-dependent induction of the Cpx extracytoplasmic cellular stress response, ~2.0-2.5 fold at 320 μg/mL after 1.5 hours without significant induction of the σE or Bae stress responses. In comparison, exposure of E. coli to a non-antimicrobial polymer, polyethylene oxide (PEO), resulted in no induction of the three stress responses. The antimicrobial small molecule vanillin, a known membrane pore-forming compound, was observed to cause specific, concentration-dependent induction of the σE stress response, ~6-fold at 640 μg/mL after 1.5 hours, without significant induction of the Cpx or Bae stress responses. The different stress response induction profiles of PEI+ and vanillin suggest that although both are antimicrobial compounds, they interact with the bacterial membrane and extracytoplasmic area by unique mechanisms. EPR studies of liposomes containing spin-labeled lipids exposed to PEI+, vanillin, and PEO reveal that PEI+ and PEO increased membrane stability whereas vanillin was found to have no effect.