Aims The objective of this study was to determine the effects of Ca‐dipicolinic acid (CaDPA), cortex‐lytic enzymes (CLEs), the inner membrane (IM) CaDPA channel and coat on spore killing by dodecylamine. Methods and Results Bacillus subtilis spores, wild‐type, CaDPA‐less due to the absence of DPA synthase or the IM CaDPA channel, or lacking CLEs, were dodecylamine‐treated and spore viability and vital staining were all determined. Dodecylamine killed intact wild‐type and CaDPA‐less B. subtilis spores similarly, and also killed intact Clostridiodes difficile spores ± CaDPA, with up to 99% killing with 1 mol l−1 dodecylamine in 4 h at 45°C with spores at ~108 ml−1. Dodecylamine killing of decoated wild type and CLE‐less B. subtilis spores was similar, but ~twofold faster than for intact spores, and much faster for decoated CaDPA‐less spores, with ≥99% killing in 5 min. Propidium iodide stained intact spores ± CaDPA minimally, decoated CaDPA‐replete spores or dodecylamine‐killed CLE‐less spores peripherally, and cores of decoated CaDPA‐less spores and dodecylamine‐killed intact spores with CLEs. The IM of some decoated CaDPA‐less spores was greatly reorganized. Conclusions Dodecylamine spore killing does not require CaDPA channels, CaDPA or CLEs. The lack of CaDPA in decoated spores allowed strong PI staining of the spore core, indicating loss of these spores IM permeability barrier. Significance and Impact of the Study This work gives new information on killing bacterial spores by dodecylamine, and how spore IM’s relative impermeability is maintained.

Bacteria have a repertoire of strategies to overcome antibiotics in clinical use, complicating our ability to treat and cure infectious diseases. In addition to evolving resistance, bacteria within genetically clonal cultures can undergo transient phenotypic changes and tolerate high doses of antibiotics. These cells, termed persisters, exhibit heterogeneous phenotypes: the strategies that a bacterial population deploys to overcome one class of antibiotics can be distinct from those needed to survive treatment with drugs with another mode of action. It was previously reported that fluoroquinolones, which target DNA topoisomerases, retain the capacity to kill non-growing bacteria that tolerate other classes of antibiotics. Here, we show that in Escherichia coli stationary-phase cultures and colony biofilms, persisters that survive treatment with the anionic fluoroquinolone Delafloxacin depend on the AcrAB-TolC efflux pump. In contrast, we did not detect this dependence on AcrAB-TolC in E. coli persisters that survive treatment with three other fluroquinolone compounds. We found that the loss of AcrAB-TolC activity via genetic mutations or chemical inhibition not only reduces Delafloxacin persistence in non-growing E. coli MG1655 or EDL933 (an E. coli O157:H7 strain), it limits resistance development in progenies derived from Delafloxacin persisters that were given the opportunity to recover in nutritive media following antibiotic treatment. Our findings highlight the heterogeneity in defense mechanisms that persisters use to overcome different compounds within the same class of antibiotics. They further indicate that efflux pump inhibitors can potentiate the activity of Delafloxacin against stationary-phase E. coli and block resistance development in Delafloxacin persister progenies.

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Glioblastoma (GB), an aggressive primary tumor of the central nervous system, represents about 60% of all adult primary brain tumors. It is notorious for its extremely low (~5%) 5-year survival rate which signals the unsatisfactory results of the standard protocol for GB therapy. This issue has become, over time, the impetus for the discipline of bringing novel therapeutics to the surface and challenging them so they can be improved. The cell-based approach in treating GB found its way to clinical trials thanks to a marvelous number of preclinical studies that probed various types of cells aiming to combat GB and increase the survival rate. In this review, we aimed to summarize and discuss the up-to-date preclinical studies that utilized stem cells or immune cells to treat GB. Likewise, we tried to summarize the most recent clinical trials using both cell categories to treat or prevent recurrence of GB in patients. As with any other therapeutics, cell-based therapy in GB is still hampered by many drawbacks. Therefore, we highlighted several novel techniques, such as the use of biomaterials, scaffolds, nanoparticles, or cells in the 3D context that may depict a promising future when combined with the cell-based approach.

Significance and Impact of the Study: Given potential deleterious effects of spores of Bacillales and Clostridiales, there is an ongoing interest in new ways of spore killing. A recent paper (mSphere 3: e00597-1, 2018) reported that glycerol monolaurate (GML) in a non-aqueous gel (GMLg) effectively killed spores of many species. We now find that (i) the Bacillus subtilis spores prepared as in the previous report were impure and (ii) GMLg gave no killing of purified spores of Bacillales and Clostridiales species in ≤5 h under the published conditions. Thus, GMLg is not an effective sporicide, though may prevent spore germination or kill germinated spores. AbstractInactivation of Bacillales and Clostridiales spores is of interest, since some cause food spoilage and human diseases. A recent publication (mSphere 3: e00597-1, 2018) reported that glycerol monolaurate (GML) in a non-aqueous gel (GMLg) effectively killed spores of Bacillus subtilis, Bacillus cereus and Clostridioides difficile, and Bacillus anthracis spores to a lesser extent. We now show that (i) the B. subtilis spores prepared as in the prior work were impure; (ii) if spore viability was measured by diluting spores 1/10 in GMLg, serially diluting incubations 10-fold and spotting aliquots on recovery plates, there was no colony formation from the 1/10 to 1/1000 dilutions due to GMLg carryover, although thorough ethanol washes of incubated spores eliminated this problem and (iii) GMLg did not kill highly purified spores of B. subtilis, B. cereus, Bacillus megaterium and C. difficile in 3-20 h in the conditions used in the recent publication. GMLg also gave no killing of crude B. subtilis spores prepared as in the recent publication in 5 h but gave~1Á5 log killing at 24 h. Thus, GMLg does not appear to be an effective sporicide, although the gel likely inhibits spore germination and could kill spores somewhat upon long incubations.