@article{lu_perez-diaz_hayes_breidt_2020, title={Bacteriophages Infecting Gram-Negative Bacteria in a Commercial Cucumber Fermentation}, volume={11}, ISSN={["1664-302X"]}, DOI={10.3389/fmicb.2020.01306}, abstractNote={Cucumber fermentations are one of the most important vegetable fermentations in the United States. The fermentation is usually driven by lactic acid bacteria (LAB) indigenous to fresh cucumbers. But LAB are greatly outnumbered by many Gram-negative bacteria on fresh cucumbers, which may influence the growth of LAB and the incidence of bloater defect (hollow cavities formed inside fermented cucumbers) leading to serious economic loss to the pickle industry. Rapid elimination of Gram-negative bacteria is crucial to the dominance of LAB and the reduction of bloater defect in the fermentation. Various factors can affect the viability of Gram-negative bacteria in cucumber fermentation. Bacteriophages (phages) may be one of such factors. This study explored the abundance, diversity, and functional role of phages infecting Gram-negative bacteria in a commercial cucumber fermentation. Cover brine samples were taken from a commercial fermentation tank over a 30-day period. On day 1 and day 3 of the fermentation, 39 Gram-negative bacteria and 26 independent phages were isolated. Nearly 67% of Gram-negative bacterial isolates were susceptible to phage infection. Phage hosts include Enterobacter, Citrobacter, Escherichia, Pantoea, Serratia, Leclercia, Providencia, and Pseudomonas species. About 88% of the isolated phages infected the members in the family Enterobacteriaceae and 58% of phages infected Enterobacter species. Eight phages with unique host ranges were characterized. These phages belong to the Myoviridae, Siphoviridae, or Podoviridae family and showed distinct protein profiles and DNA fingerprints. The infectivity of a phage against Enterobacter cancerogenus was evaluated in cucumber juice as a model system. The phage infection at the multiplicity of infection 1 or 100 resulted in a 5-log reduction in cell concentration within 3 h and rapidly eliminated its host. This study revealed the abundance and variety of phages infecting Gram-negative bacteria, particularly Enterobacteriaceae, in the commercial cucumber fermentation, suggesting that phages may play an important role in the elimination of Gram-negative bacteria, thereby facilitating the dominance of LAB and minimizing bloater defect. To our knowledge, this is the first report on the ecology of phages infecting Gram-negative bacteria in commercial cucumber fermentations.}, journal={FRONTIERS IN MICROBIOLOGY}, author={Lu, Zhongjing and Perez-Diaz, Ilenys M. and Hayes, Janet S. and Breidt, Fred}, year={2020}, month={Jun} }
 @article{perez-diaz_mcfeeters_moeller_johanningsmeier_hayes_fornea_rosenberg_gilbert_custis_beene_et al._2015, title={Commercial Scale Cucumber Fermentations Brined with Calcium Chloride Instead of Sodium Chloride}, volume={80}, ISSN={["1750-3841"]}, DOI={10.1111/1750-3841.13107}, abstractNote={Abstract}, number={12}, journal={JOURNAL OF FOOD SCIENCE}, author={Perez-Diaz, I. M. and McFeeters, R. F. and Moeller, L. and Johanningsmeier, S. D. and Hayes, J. and Fornea, D. S. and Rosenberg, L. and Gilbert, C. and Custis, N. and Beene, K. and et al.}, year={2015}, month={Dec}, pages={M2827–M2836} }
 @article{breidt_hayes_mcfeeters_2007, title={Determination of 5-log reduction times for food pathogens in acidified cucumbers during storage at 10 and 25 degrees C}, volume={70}, ISSN={["0362-028X"]}, DOI={10.4315/0362-028X-70.11.2638}, abstractNote={Outbreaks of acid-resistant foodborne pathogens in acid foods with pH values below 4.0, including apple cider and orange juice, have raised concerns about the safety of acidified vegetable products. For acidified vegetable products with pH values between 3.3 and 4.6, previous research has demonstrated that thermal treatments are needed to achieve a 5-log reduction in the numbers of Escherichia coli O157:H7, Listeria monocytogenes, or Salmonella enterica. For some acidified vegetable products with a pH of 3.3 or below, heat processing can result in unacceptable product quality. The purpose of this study was to determine the holding times needed to achieve a 5-log reduction in E. coli O157:H7, L. monocytogenes, and S. enterica strains in acidified vegetable products with acetic acid as the primary acidulant, a pH of 3.3 or below, and a minimum equilibrated temperature of 10 degrees C. We found E. coli O157:H7 to be the most acid-resistant microorganism for the conditions tested, with a predicted time to achieve a 5-log reduction in cell numbers at 10 degrees C of 5.7 days, compared with 2.1 days (51 h) for Salmonella or 0.5 days (11.2 h) for Listeria. At 25 degrees C, the E. coli O157:H7 population achieved a 5-log reduction in 1.4 days (34.3 h).}, number={11}, journal={JOURNAL OF FOOD PROTECTION}, author={Breidt, Fred, Jr. and Hayes, Janet and McFeeters, Roger F.}, year={2007}, month={Nov}, pages={2638–2641} }
 @article{breidt_hayes_osborne_mcfeeters_2005, title={Determination of 5-log pathogen reduction times for heat-processed, acidified vegetable brines}, volume={68}, ISSN={["0362-028X"]}, DOI={10.4315/0362-028X-68.2.305}, abstractNote={Recent outbreaks of acid-resistant food pathogens in acid foods, including apple cider and orange juice, have raised concerns about the safety of acidified vegetable products. We determined pasteurization times and temperatures needed to assure a 5-log reduction in the numbers of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella strains in acidified cucumber pickle brines. Cocktails of five strains of each pathogen were (separately) used for heat-inactivation studies between 50 and 60 degrees C in brines that had an equilibrated pH value of 4.1. Salmonella strains were found to be less heat resistant than E. coli O157:H7 or L. monocytogenes strains. The nonlinear killing curves generated during these studies were modeled using a Weibull function. We found no significant difference in the heat-killing data for E. coli O157:H7 and L. monocytogenes (P = 0.9709). The predicted 5-log reduction times for E. coli O157:H7 and L. monocytogenes were found to fit an exponential decay function. These data were used to estimate minimum pasteurization times and temperatures needed to ensure safe processing of acidified pickle products and show that current industry pasteurization practices offer a significant margin of safety.}, number={2}, journal={JOURNAL OF FOOD PROTECTION}, author={Breidt, F and Hayes, JS and Osborne, JA and McFeeters, RF}, year={2005}, month={Feb}, pages={305–310} }
 @article{breidt_hayes_mcfeeters_2004, title={Independent effects of acetic acid and pH on survival of Escherichia coli in simulated acidified pickle products}, volume={67}, ISSN={["1944-9097"]}, DOI={10.4315/0362-028x-67.1.12}, abstractNote={Our objective was to determine the effects of organic acids and pH on the rate at which selected strains of Escherichia coli O157:H7 die in acid solutions representative of acidified pickle products (pH < 4.6). We used gluconic acid/sodium gluconate (pKa = 3.7) as a noninhibitory buffer to maintain pH at selected values in the absence of other organic acids. This was possible because we found that the inhibitory effects of this acid on E. coli strains at pH 3.1 were independent of acid concentration over a range of 2 to 200 mM. By this method, the lethal effects of acetic acid solutions (100 to 400 mM) at selected pH values between 3.1 and 4.1 were compared with the effects of pH alone (as determined using gluconate buffer). We found D-values were two- to fourfold lower with acetic acid compared with the effect of pH alone for simulated pickle brines in this pH range. Glutamic acid, an amino acid that is known to enhance acid resistance in E. coli and is a component of pickle brines, protected the E. coli strains from the specific effects of acetic acid.}, number={1}, journal={JOURNAL OF FOOD PROTECTION}, author={Breidt, F and Hayes, JS and McFeeters, RF}, year={2004}, month={Jan}, pages={12–18} }