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Background: Increasing awareness of the burden of absenteeism and reduced performance at work highlights the importance of early identification of individuals experiencing work instability (WI), a mismatch between functional and cognitive abilities and job demands., Aims: To develop and validate a screening questionnaire to measure WI in manual workers., Methods: Questionnaire items were generated via qualitative interviews with manual workers and a draft survey instrument was completed by workers in a variety of fields. Rasch analysis was used interactively to assess the psychometric aspects of the emerging scale, including unidimensionality and absence of item bias (differential item functioning)., Results: A total of 17 qualitative interviews generated 110 potential items for the questionnaire. The item set resolved to a 25-item scale, which satisfied model expectations (item residual mean = -0.13, SD = 1.04; person residual mean = -0.29, SD = 0.75), had good reliability (alpha = 0.86) and strict unidimensionality (t-test 7.5% confidence interval 3.8-11.2)., Conclusions: The Manual Work Instability Scale is a short psychometrically robust questionnaire based on the concept of WI, which incorporates both musculoskeletal symptoms and relevant psychosocial factors. It may prove effective in screening and identifying WI in workers in predominantly physical occupations., (© The Author 2016. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Pasteurella multocida toxin is a potent mitogen that is believed to act intracellularly. On transverse urea gradient gels at pH 8.0 the toxin displayed one major unfolding transition at 4 M urea. However, at pH 6.1 the unfolding transition took place at 3.5 M urea. Circular dichroism spectra also indicated that a structural change took place at acidic pH. In addition it was found that the toxin that had been denatured in 8 M urea refolded in solution with a high recovery of biological activity. These findings are discussed in terms of the likely domain structure of the P. multocida toxin.