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A bacterial species is considered to be intrinsically resistant to an antimicrobial when nearly all of the wild-type isolates (i.e., those without acquired resistance) exhibit minimum inhibitory concentration (MIC) values that are sufficiently high such that susceptibility testing is unnecessary, and that the antimicrobial should not be considered for therapy. Accordingly, knowledge of intrinsic resistance influences both the selection of treatment regimens and the approach to susceptibility testing in the clinical laboratory, where unexpected results also facilitate the recognition of microbial identification or susceptibility testing errors. Previously, limited data have suggested that Hafnia spp. may be intrinsically resistant to colistin. We evaluated the in vitro activity of colistin against 119 Hafniaceae that were isolated from human samples: 75 (63%) from routine clinical cultures and 44 (37%) from stool samples of travelers undergoing screening for antimicrobial resistant organisms. Broth microdilution colistin MICs were ≥4 μg/mL for 117 of 119 (98%) isolates. Whole-genome sequencing of 96 of the isolates demonstrated that the colistin-resistant phenotype was not lineage-specific. 2 of the 96 (2%) isolates harbored mobile colistin resistance genes. Compared to whole-genome sequencing, VITEK MS matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and VITEK 2 GN ID failed to consistently distinguish between Hafnia alvei, Hafnia paralvei, and Obesumbacterium proteus. In conclusion, using a reference antimicrobial susceptibility testing method and a genetically diverse collection of isolates, we found Hafnia spp. to be intrinsically resistant to colistin. The recognition of this phenotype will help inform rational approaches by which to perform antimicrobial susceptibility testing and therapy for patients with infections that are caused by Hafnia spp., Competing Interests: The authors declare a conflict of interest. S.E.T., R.C.L., and V.M.P. receive royalties from UpToDate. R.C.L. also received payments for editorial services from the CDC Foundation. V.M.P. is a member of the Clinical and Laboratory Standards Institute Subcommittee on Antimicrobial Susceptibility Testing.

A frequently studied hypothesized cause of borderline personality disorder (BPD) is experiencing interpersonal trauma. A recent study by L. A. Kaehler and J. J. Freyd (2009 ) found a connection between betrayal trauma and BPD characteristics, with higher betrayal traumas associated with greater BPD characteristics. The present study seeks to expand upon that study by investigating relational health as a potential mediator for the association between betrayal trauma and BPD. A sample of 165 college students completed measures of betrayal trauma life events, relational health, and BPD traits. Mediation analyses showed significant partial mediation for total relational health (bootstrap coefficient = .0168) and its community subscale (bootstrap coefficient = .0204); however, significant mediating effects for the mentor and friend subscales were not found. Given the significant finding for only the community subscale, which may be driving the total relational health effect seen, the results suggest that connection with a valued community may be an important protective factor for BPD after one experiences betrayal trauma.