@article{kay_breidt_fratamico_baranzoni_kim_grunden_oh_2017, title={Escherichia coli O157:H7 Acid Sensitivity Correlates with Flocculation Phenotype during Nutrient Limitation}, volume={8}, ISSN={["1664-302X"]}, DOI={10.3389/fmicb.2017.01404}, abstractNote={Shiga toxin producing Escherichia coli (STEC) strains vary in acid resistance; however, little is known about the underlying mechanisms that result in strain specific differences. Among 25 STEC O157:H7 strains tested, 7 strains flocculated when grown statically for 18 h in minimal salts medium at 37°C, while 18 strains did not. Interestingly, the flocculation phenotype (cells came out of suspension) was found to correlate with degree of acid sensitivity in an assay with 400 mM acetic acid solution at pH 3.3 targeting acidified foods. Strains exhibiting flocculation were more acid sensitive and were designated FAS, for flocculation acid sensitive, while the acid resistant strain designated PAR for planktonic acid resistant. Flocculation was not observed for any strains during growth in complex medium (Luria Bertani broth). STEC strains B201 and B241 were chosen as representative FAS (2.4 log reduction) and PAR (0.15 log reduction) strains, respectively, due to differences in acid resistance and flocculation phenotype. Results from electron microscopy showed evidence of fimbriae production in B201, whereas fimbriae were not observed in B241.Curli fimbriae production was identified through plating on Congo red differential medium, and all FAS strains showed curli fimbriae production. Surprisingly, 5 PAR strains also had evidence of curli production. Transcriptomic and targeted gene expression data for B201 and B241indicated that csg and hde (curli and acid induced chaperone genes, respectively) expression positively correlated with the phenotypic differences observed for these strains. These data suggest that FAS strains grown in minimal medium express curli, resulting in a flocculation phenotype. This may be regulated by GcvB, which positively regulates curli fimbriae production and represses acid chaperone proteins. RpoS and other regulatory mechanisms may impact curli fimbriae production, as well. These findings may help elucidate mechanisms underlying differences among STEC strains in relating acid resistance and biofilm formation.}, journal={FRONTIERS IN MICROBIOLOGY}, author={Kay, Kathryn L. and Breidt, Frederick and Fratamico, Pina M. and Baranzoni, Gian M. and Kim, Gwang-Hee and Grunden, Amy M. and Oh, Deog-Hwan}, year={2017}, month={Jul} }
 @article{breidt_kay_cook_osborne_ingham_arritt_2013, title={Determination of 5-Log Reduction Times for Escherichia coli O157:H7, Salmonella enterica, or Listeria monocytogenes in Acidified Foods with pH 3.5 or 3.8}, volume={76}, ISSN={["1944-9097"]}, DOI={10.4315/0362-028x.jfp-12-528}, abstractNote={A critical factor in ensuring the safety of acidified foods is the establishment of a thermal process that assures the destruction of acid-resistant vegetative pathogenic and spoilage bacteria. For acidified foods such as dressings and mayonnaises with pH values of 3.5 or higher, the high water phase acidity (acetic acid of 1.5 to 2.5% or higher) can contribute to lethality, but there is a lack of data showing how the use of common ingredients such as acetic acid and preservatives, alone or in combination, can result in a 5-log reduction for strains of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in the absence of a postpackaging pasteurization step. In this study, we determined the times needed at 10° C to achieve a 5-log reduction of E. coli O157:H7, S. enterica, and L. monocytogenes in pickling brines with a variety of acetic and benzoic acid combinations at pH 3.5 and 3.8. Evaluation of 15 different acid-pH combinations confirmed that strains of E. coli O157:H7 were significantly more acid resistant than strains of S. enterica and L. monocytogenes. Among the acid conditions tested, holding times of 4 days or less could achieve a 5-log reduction for vegetative pathogens at pH 3.5 with 2.5% acetic acid or at pH 3.8 with 2.5% acetic acid containing 0.1% benzoic acid. These data indicate the efficacy of benzoic acid for reducing the time necessary to achieve a 5-log reduction in target pathogens and may be useful for supporting process filings and the determination of critical controls for the manufacture of acidified foods.}, number={7}, journal={JOURNAL OF FOOD PROTECTION}, author={Breidt, F., Jr. and Kay, K. and Cook, J. and Osborne, J. and Ingham, B. and Arritt, F.}, year={2013}, month={Jul}, pages={1245–1249} }
 @article{vitchuli_shi_nowak_kay_caldwell_breidt_bourham_mccord_zhang_2011, title={Multifunctional ZnO/Nylon 6 nanofiber mats by an electrospinning-electrospraying hybrid process for use in protective applications}, volume={12}, ISSN={["1468-6996"]}, url={https://publons.com/publon/3117882/}, DOI={10.1088/1468-6996/12/5/055004}, abstractNote={Abstract ZnO/Nylon 6 nanofiber mats were prepared by an electrospinning–electrospraying hybrid process in which ZnO nanoparticles were dispersed on the surface of Nylon 6 nanofibers without becoming completely embedded. The prepared ZnO/Nylon 6 nanofiber mats were evaluated for their abilities to kill bacteria or inhibit their growth and to catalytically detoxify chemicals. Results showed that these ZnO/Nylon 6 nanofiber mats had excellent antibacterial efficiency (99.99%) against both the Gram-negative Escherichia coli and Gram-positive Bacillus cereus bacteria. In addition, they exhibited good detoxifying efficiency (95%) against paraoxon, a simulant of highly toxic chemicals. ZnO/Nylon 6 nanofiber mats were also deposited onto nylon/cotton woven fabrics and the nanofiber mats did not significantly affect the moisture vapor transmission rates and air permeability values of the fabrics. Therefore, ZnO/Nylon 6 nanofiber mats prepared by the electrospinning–electrospraying hybrid process are promising material candidates for protective applications.}, number={5}, journal={SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS}, author={Vitchuli, Narendiran and Shi, Quan and Nowak, Joshua and Kay, Kathryn and Caldwell, Jane M. and Breidt, Frederick and Bourham, Mohamed and McCord, Marian and Zhang, Xiangwu}, year={2011}, month={Oct} }