Assessing the risk of resistance associated with biocide exposure commonly involves exposing microorganisms to biocides at concentrations close to the MIC. With the aim of representing exposure to environmental biocide residues, Escherichia coli MG1655 was grown for 20 passages in the presence or absence of benzalkonium chloride (BAC) at 100 ng/liter and 1,000 ng/liter (0.0002% and 0.002% of the MIC, respectively). BAC susceptibility, planktonic growth rates, motility, and biofilm formation were assessed, and differentially expressed genes were determined via transcriptome sequencing. Planktonic growth rate and biofilm formation were significantly reduced (P < 0.001) following BAC adaptation, while BAC minimum bactericidal concentration increased 2-fold. Transcriptomic analysis identified 289 upregulated and 391 downregulated genes after long-term BAC adaptation compared with the respective control organism passaged in BAC-free medium. When the BAC-adapted bacterium was grown in BAC-free medium, 1,052 genes were upregulated and 753 were downregulated. Repeated passage solely in biocide-free medium resulted in 460 upregulated and 476 downregulated genes compared with unexposed bacteria. Long-term exposure to environmentally relevant BAC concentrations increased the expression of genes associated with efflux and reduced the expression of genes associated with outer-membrane porins, motility, and chemotaxis. This was manifested phenotypically through the loss of function (motility). Repeated passage in a BAC-free environment resulted in the upregulation of multiple respiration-associated genes, which was reflected by increased growth rate. In summary, repeated exposure of E. coli to BAC residues resulted in significant alterations in global gene expression that were associated with minor decreases in biocide susceptibility, reductions in growth rate and biofilm formation, and loss of motility. IMPORTANCE Exposure to very low concentrations of biocides in the environment is a poorly understood risk factor for antimicrobial resistance. Repeated exposure to trace levels of the biocide benzalkonium chloride (BAC) resulted in loss of function (motility) and a general reduction in bacterial fitness but relatively minor decreases in susceptibility. These changes were accompanied by widespread changes in the Escherichia coli transcriptome. These results demonstrate the importance of including phenotypic characterization in studies designed to assess the risks of biocide exposure.

Background Cancer cachexia (CC) is a debilitating syndrome severely impacting patients’ quality of life and survivorship. We aimed to investigate the health care professionals’ (HCPs’) experiences of dealing with CC. Methods Survey questions entailed definitions and guidelines, importance of CC management, clinician confidence and involvement, screening and assessment, interventions, psychosocial and food aspects. The online survey was disseminated through Australian and New Zealand palliative care, oncology, allied health and nursing organisations. Frequencies were reported using descriptive statistics accounting for response rates. Associations were examined between variables using Fisher’s exact and Pearson’s chi-square tests. Results Over 90% of the respondents (n = 192) were medical doctors or nurses. Over 85% of the respondents were not aware of any guidelines, with 83% considering ≥ 10% weight loss from baseline indicative of CC. CC management was considered important by 77% of HCPs, and 55% indicated that it was part of their clinical role to assess and treat CC. In contrast, 56% of respondents were not confident about managing CC, and 93% believed formal training in CC would benefit their clinical practice. Although formal screening tools were generally not used (79%), 75% of respondents asked patients about specific symptoms. Antiemetics (80%) and nutritional counselling (86%) were most prescribed or recommended interventions, respectively. Conclusion This study underlines the deficiencies in knowledge and training of CC which has implications for patients’ function, well-being and survival. HCP training and a structured approach to CC management is advocated for optimal and continued patient care.

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