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2. Listeriosis Associated with Stone Fruit — United States, 2014

Author

Jackson, Brendan R., Salter, Monique, Tarr, Cheryl, Conrad, Amanda, Harvey, Emily, Steinbock, Lisa, Saupe, Amy, Sorenson, Alida, Katz, Lee, Stroika, Steven, Jackson, Kelly A., Carleton, Heather, Kucerova, Zuzana, Melka, David, Strain, Errol, Parish, Mickey, and Mody, Rajal K.

Published
2015

3. Multistate Outbreak of Listeriosis Linked to Soft-Ripened Cheese — United States, 2013

Author

Choi, Mary J., Jackson, Kelly A., Medus, Carlota, Beal, Jennifer, Rigdon, Carrie E., Cloyd, Tami C., Forstner, Matthew J., Ball, Jill, Bosch, Stacy, Bottichio, Lyndsay, Cantu, Venessa, Melka, David C., Ishow, Wilete, Slette, Sarah, Irvin, Kari, Wise, Matthew, Tarr, Cheryl, Mahon, Barbara, Smith, Kirk E., and Silk, Benjamin J.

Published
2014

5. Survey of Salmonella in raw tree nuts at retail in the United States

Author

Zhang, Guodong, primary, Hu, Lijun, additional, Luo, Yan, additional, Santillana Farakos, Sofia M, additional, Johnson, Rhoma, additional, Scott, Virginia N., additional, Curry, Phillip, additional, Melka, David, additional, Brown, Eric W., additional, Strain, Errol, additional, Bunning, Vincent K., additional, Musser, Steven M., additional, and Hammack, Thomas S., additional

Published
2021
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7. Whole genome sequencing uses for foodborne contamination and compliance: Discovery of an emerging contamination event in an ice cream facility using whole genome sequencing

Author

Allard, Marc W., primary, Strain, Errol, additional, Rand, Hugh, additional, Melka, David, additional, Correll, William A., additional, Hintz, Leslie, additional, Stevens, Eric, additional, Timme, Ruth, additional, Lomonaco, Sara, additional, Chen, Yi, additional, Musser, Steven M., additional, and Brown, Eric W., additional

Published
2019
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8. Survey of Foodborne Pathogens, Aerobic Plate Counts, Total Coliform Counts, and Escherichia coli Counts in Leafy Greens, Sprouts, and Melons Marketed in the United States

Author

Zhang, Guodong, primary, Chen, Yi, additional, Hu, Lijun, additional, Melka, David, additional, Wang, Hua, additional, Laasri, Anna, additional, Brown, Eric W., additional, Strain, Errol, additional, Allard, Marc, additional, Bunning, Vincent K., additional, Parish, Mickey, additional, Musser, Steven M., additional, and Hammack, Thomas S., additional

Published
2018
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9. Prevalence of Salmonella in 11 Spices Offered for Sale from Retail Establishments and in Imported Shipments Offered for Entry to the United States

Author

Zhang, Guodong, primary, Hu, Lijun, additional, Pouillot, Régis, additional, Tatavarthy, Aparna, additional, Van Doren, Jane M., additional, Kleinmeier, Daria, additional, Ziobro, George C., additional, Melka, David, additional, Wang, Hua, additional, Brown, Eric W., additional, Strain, Errol, additional, Bunning, Vincent K., additional, Musser, Steven M., additional, and Hammack, Thomas S., additional

Published
2017
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11. Whole Genome and Core Genome Multilocus Sequence Typing and Single Nucleotide Polymorphism Analyses of Listeria monocytogenes Isolates Associated with an Outbreak Linked to Cheese, United States, 2013

Author

Chen, Yi, primary, Luo, Yan, additional, Carleton, Heather, additional, Timme, Ruth, additional, Melka, David, additional, Muruvanda, Tim, additional, Wang, Charles, additional, Kastanis, George, additional, Katz, Lee S., additional, Turner, Lauren, additional, Fritzinger, Angela, additional, Moore, Terence, additional, Stones, Robert, additional, Blankenship, Joseph, additional, Salter, Monique, additional, Parish, Mickey, additional, Hammack, Thomas S., additional, Evans, Peter S., additional, Tarr, Cheryl L., additional, Allard, Marc W., additional, Strain, Errol A., additional, and Brown, Eric W., additional

Published
2017
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13. Prevalence of Salmonella in Cashews, Hazelnuts, Macadamia Nuts, Pecans, Pine Nuts, and Walnuts in the United States

Author

Zhang, Guodong, primary, Hu, Lijun, additional, Melka, David, additional, Wang, Hua, additional, Laasri, Anna, additional, Brown, Eric W., additional, Strain, Errol, additional, Allard, Marc, additional, Bunning, Vincent K., additional, Musser, Steven M., additional, Johnson, Rhoma, additional, Farakos, Sofia M.Santillana, additional, Scott, Virginia N., additional, Pouillot, Régis, additional, Van Doren, Jane M., additional, and Hammack, Thomas S., additional

Published
2017
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14. Singleton Sequence Type 382, an Emerging Clonal Group of Listeria monocytogenes Associated with Three Multistate Outbreaks Linked to Contaminated Stone Fruit, Caramel Apples, and Leafy Green Salad

Author

Chen, Yi, primary, Luo, Yan, additional, Pettengill, James, additional, Timme, Ruth, additional, Melka, David, additional, Doyle, Matthew, additional, Jackson, Alikeh, additional, Parish, Mickey, additional, Hammack, Thomas S., additional, Allard, Marc W., additional, Brown, Eric W., additional, and Strain, Errol A., additional

Published
2017
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15. Assessing the genome level diversity of Listeria monocytogenes from contaminated ice cream and environmental samples linked to a listeriosis outbreak in the United States

Author

Chen, Yi, primary, Luo, Yan, additional, Curry, Phillip, additional, Timme, Ruth, additional, Melka, David, additional, Doyle, Matthew, additional, Parish, Mickey, additional, Hammack, Thomas S., additional, Allard, Marc W., additional, Brown, Eric W., additional, and Strain, Errol A., additional

Published
2017
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16. Listeria monocytogenes in Stone Fruits Linked to a Multistate Outbreak: Enumeration of Cells and Whole-Genome Sequencing

Author

Chen, Yi, primary, Burall, Laurel S., additional, Luo, Yan, additional, Timme, Ruth, additional, Melka, David, additional, Muruvanda, Tim, additional, Payne, Justin, additional, Wang, Charles, additional, Kastanis, George, additional, Maounounen-Laasri, Anna, additional, De Jesus, Antonio J., additional, Curry, Phillip E., additional, Stones, Robert, additional, K'Aluoch, Okumu, additional, Liu, Eileen, additional, Salter, Monique, additional, Hammack, Thomas S., additional, Evans, Peter S., additional, Parish, Mickey, additional, Allard, Marc W., additional, Datta, Atin, additional, Strain, Errol A., additional, and Brown, Eric W., additional

Published
2016
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17. Ecological prevalence, genetic diversity, and epidemiological aspects of Salmonella isolated from tomato agricultural regions of the Virginia Eastern Shore

Author

Bell, Rebecca L., Zheng, Jie, Burrows, Erik, Allard, Sarah, Wang, Charles Y., Keys, Christine E., Melka, David C., Strain, Errol, Luo, Yan, Allard, Marc W., Rideout, Steven L., Brown, Eric W., and Virginia Agricultural Experiment Station

Subjects
food and beverages
Abstract

Virginia is the third largest producer of fresh-market tomatoes in the United States. Tomatoes grown along the eastern shore of Virginia are implicated almost yearly in Salmonella illnesses. Traceback implicates contamination occurring in the pre-harvest environment. To get a better understanding of the ecological niches of Salmonella in the tomato agricultural environment, a 2-year study was undertaken at a regional agricultural research farm in Virginia. Environmental samples, including tomato (fruit, blossoms, and leaves), irrigation water, surface water and sediment, were collected over the growing season. These samples were analyzed for the presence of Salmonella using modified FDA-BAM methods. Molecular assays were used to screen the samples. Over 1500 samples were tested. Seventy-five samples tested positive for Salmonella yielding over 230 isolates. The most commonly isolated serovars were S. Newport and S. Javiana with pulsed-field gel electrophoresis yielding 39 different patterns. Genetic diversity was further underscored among many other serotypes, which showed multiple PFGE subtypes. Whole genome sequencing (WGS) of several S. Newport isolates collected in 2010 compared to clinical isolates associated with tomato consumption showed very few single nucleotide differences between environmental isolates and clinical isolates suggesting a source link to Salmonella contaminated tomatoes. Nearly all isolates collected during two growing seasons of surveillance were obtained from surface water and sediment sources pointing to these sites as long-term reservoirs for persistent and endemic contamination of this environment.

Published
2015

20. Complete Genome Sequence of Salmonella enterica subsp. enterica serovarMinnesota Strain.

Author

Hua Wang, Hoffmann, Maria, Laasri, Anna, Jacobson, Andrew P., Melka, David, Curry, Phillip E., Hammack, Thomas S., and Jie Zheng

Subjects
FOOD pathogens, SALMONELLA enterica, MANGO, NUCLEOTIDE sequencing, BACTERIAL genomes
Abstract

Mango has been implicated as food vehicle in several Salmonella-causing foodborne outbreaks. Here, Salmonella enterica subsp. enterica serovarMinnesotawas isolated fromfresh mango fruit imported fromMexico in 2014. The complete genome sequence of S. Minnesota CFSAN017963 was sequenced using single-molecule real-time DNA sequencing. Distinct prophage regions, Salmonella pathogenicity islands, and fimbrial gene clusters were observed in comparative genomic analysis on S. Minnesota CFSAN017963with other phylogenetically closely related Salmonella serovars. Core genomemultilocus sequencing typing analysis of all the S.Minnesota isolates in theGenbank and Enterobase also revealed a high genomic diversity among the genomes analyzed. [ABSTRACT FROM AUTHOR]

Published
2017
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21. Draft Genome Sequence of Salmonella enterica subsp. enterica Serovar Give, Isolated from an Imported Chili Powder Product

Author

Wang, Hua, primary, Chen, Yi, additional, Ayers, Sherry, additional, Melka, David, additional, Laasri, Anna, additional, Payne, Justin S., additional, Zheng, Jie, additional, Son, Insook, additional, Timme, Ruth, additional, Kastanis, George, additional, Hammack, Thomas S., additional, Strain, Errol, additional, Allard, Marc W., additional, Evans, Peter S., additional, and Brown, Eric W., additional

Published
2015
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22. Ecological prevalence, genetic diversity, and epidemiological aspects of Salmonella isolated from tomato agricultural regions of the Virginia Eastern Shore

Author

Bell, Rebecca L., primary, Zheng, Jie, additional, Burrows, Erik, additional, Allard, Sarah, additional, Wang, Charles Y., additional, Keys, Christine E., additional, Melka, David C., additional, Strain, Errol, additional, Luo, Yan, additional, Allard, Marc W., additional, Rideout, Steven, additional, and Brown, Eric W., additional

Published
2015
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23. Laboratory, Environmental, and Epidemiologic Investigation and Regulatory Enforcement Actions in Response to an Outbreak of Salmonella Bredeney Infections Linked to Peanut Butter

Author

Viazis, Stelios, primary, Beal, Jennifer K., additional, Monahan, Caitlin, additional, Lanier, William A., additional, Kreil, Katherine R., additional, Melka, David C., additional, Boden, William D., additional, Dion, Jamie L., additional, Miller, Zachary A., additional, Nguyen, Thai-An, additional, Gieraltowski, Laura B., additional, and Zink, Donald L., additional

Published
2015
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24. Survey of Foodborne Pathogens, Aerobic Plate Counts, Total Coliform Counts, and Escherichia coliCounts in Leafy Greens, Sprouts, and Melons Marketed in the United States

Author

Zhang, Guodong, Chen, Yi, Hu, Lijun, Melka, David, Wang, Hua, Laasri, Anna, Brown, Eric W., Strain, Errol, Allard, Marc, Bunning, Vincent K., Parish, Mickey, Musser, Steven M., and Hammack, Thomas S.

Abstract

The objective of this research was to assess the microbiological status of leafy greens, sprouts, and melons from U.S. markets. A total of 14,183 samples of leafy greens, 2,652 samples of sprouts, and 3,411 samples of melons were collected throughout the United States from 2009 to 2014. The samples were analyzed for aerobic plate counts, total coliform counts, Escherichia colicounts, and the presence and levels of Salmonella, Shigella, Listeria monocytogenes,and Shiga toxin–producing E. coli(STEC), depending on the year and type of produce. Among the leafy greens, no E. coliO157:H7 or non-O157 STEC were detected from iceberg lettuce samples. The overall prevalences of Salmonella, E. coliO157:H7, non-O157 STEC, and L. monocytogenesin the 14,183 samples of leafy greens were 0.05, 0.01, 0.07, and 0.11%, respectively. Among sprout samples, no Salmonellaor E. coliO157:H7 was detected, and the overall prevalences of non-O157 STEC and L. monocytogeneswere 0.04 and 0.11%, respectively. Among melon samples, no Salmonellawas detected from cucumbers, no L. monocytogeneswas detected from cantaloupes, and the overall prevalences of Salmonellaand L. monocytogeneswere 0.12 and 0.23%, respectively. L. monocytogeneslevels were 0.4 to 1,470 most probable number (MPN)/g in leafy greens, 0.36 to 1,100 MPN/g in sprouts, and <0.03 to 150 MPN/g in melons, and most positive samples had low levels of these pathogens. The isolates from these foods were very diverse genetically. Foodborne pathogens, including Salmonella,STEC, and L. monocytogenes,had relatively low prevalences in the produce surveyed. Because these foods are usually consumed raw, measures should be taken to significantly minimize the presence and levels of human pathogens.

Published
2018
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25. Prevalence of Salmonellain 11 Spices Offered for Sale from Retail Establishments and in Imported Shipments Offered for Entry to the United States

Author

Zhang, Guodong, Hu, Lijun, Pouillot, Régis, Tatavarthy, Aparna, Van Doren, Jane M., Kleinmeier, Daria, Ziobro, George C., Melka, David, Wang, Hua, Brown, Eric W., Strain, Errol, Bunning, Vincent K., Musser, Steven M., and Hammack, Thomas S.

Abstract

The U.S. Food and Drug Administration conducted a survey to evaluate Salmonellaprevalence and aerobic plate counts in packaged (dried) spices offered for sale at retail establishments in the United States. The study included 7,250 retail samples of 11 spice types that were collected during November 2013 to September 2014 and October 2014 to March 2015. No Salmonella-positive samples (based on analysis of 125 g) were found among retail samples of cumin seed (whole or ground), sesame seed (whole, not roasted or toasted, and not black), and white pepper (ground or cracked), for prevalence estimates of 0.00% with 95% Clopper and Pearson's confidence intervals of 0.00 to 0.67%, 0.00 to 0.70%, and 0.00 to 0.63%, respectively. Salmonellaprevalence estimates (confidence intervals) for the other eight spice types were 0.19% (0.0048 to 1.1%) for basil leaf (whole, ground, crushed, or flakes), 0.24% (0.049 to 0.69%) for black pepper (whole, ground, or cracked), 0.56% (0.11 to 1.6%) for coriander seed (ground), 0.19% (0.0049 to 1.1%) for curry powder (ground mixture of spices), 0.49% (0.10 to 1.4%) for dehydrated garlic (powder, granules, or flakes), 0.15% (0.0038 to 0.83%) for oregano leaf (whole, ground, crushed, or flakes), 0.25% (0.03 to 0.88%) for paprika (ground or cracked), and 0.64% (0.17 to 1.6%) for red pepper (hot red pepper, e.g., chili, cayenne; ground, cracked, crushed, or flakes). Salmonellaisolates were serotyped, and genomes were sequenced. Samples of these same 11 spice types were also examined from shipments of imported spices offered for entry to the United States from 1 October 2011 to 30 September 2015. Salmonellaprevalence estimates (based on analysis of two 375-g composite samples) for shipments of imported spices were 1.7 to 18%. The Salmonellaprevalence estimates for spices offered for sale at retail establishments for all of the spice types except dehydrated garlic and basil were significantly lower than estimates for shipments of imported spice offered for entry.

Published
2017
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29. Prevalence of Salmonellain Cashews, Hazelnuts, Macadamia Nuts, Pecans, Pine Nuts, and Walnuts in the United States

Author

Zhang, Guodong, Hu, Lijun, Melka, David, Wang, Hua, Laasri, Anna, Brown, Eric W., Strain, Errol, Allard, Marc, Bunning, Vincent K., Musser, Steven M., Johnson, Rhoma, Farakos, Sofia M.Santillana, Scott, Virginia N., Pouillot, Régis, Van Doren, Jane M., and Hammack, Thomas S.

Abstract

Nuts have been identified as a vector for salmonellosis. The objective of this project was to estimate the prevalence and contamination level of Salmonellain raw tree nuts (cashews, pecans, hazelnuts, macadamia nuts, pine nuts, and walnuts) at retail markets in the United States. A total of 3,656 samples of six types of tree nuts were collected from different types of retail stores and markets nationwide between October 2014 and October 2015. These samples were analyzed using a modified version of the Salmonellaculture method from the U.S. Food and Drug Administration's Bacteriological Analytical Manual. Of the 3,656 samples collected and tested, 32 were culturally confirmed as containing Salmonella. These isolates represented 25 serotypes. Salmonellawas not detected in pecans and in-shell hazelnuts. Salmonellaprevalence estimates (and 95% confidence intervals) in cashews, shelled hazelnuts, pine nuts, walnuts, and macadamia nuts were 0.55% [0.15, 1.40], 0.35% [0.04, 1.20], 0.48% [0.10, 1.40], 1.20% [0.53, 2.40], and 4.20% [2.40, 6.90], respectively. The rates of Salmonellaisolation from major or big chain supermarkets, small chain supermarkets, discount, variety, or drug stores, and online were 0.64% [0.38, 1.00], 1.60% [0.80, 2.90], 0.00% [0.00, 2.40], and 13.64% [2.90, 35.00], respectively (Cochran-Mantel-Haenszel test: P= 0.02). The rates of Salmonellaisolation for conventional and organic nuts were not significantly different. Of the samples containing Salmonella,60.7% had levels less than 0.003 most probable number (MPN)/g. The highest contamination level observed was 0.092 MPN/g. The prevalence and levels of Salmonellain these tree nut samples were comparable to those previously reported for similar foods.

Published
2017
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30. Singleton Sequence Type 382, an Emerging Clonal Group of Listeria monocytogenesAssociated with Three Multistate Outbreaks Linked to Contaminated Stone Fruit, Caramel Apples, and Leafy Green Salad

Author

Chen, Yi, Luo, Yan, Pettengill, James, Timme, Ruth, Melka, David, Doyle, Matthew, Jackson, Alikeh, Parish, Mickey, Hammack, Thomas S., Allard, Marc W., Brown, Eric W., and Strain, Errol A.

Abstract

ABSTRACTThree multistate outbreaks between 2014 and 2016, involving case patients in and outside the United States, were linked to stone fruit, caramel apples, and packaged leafy green salad contaminated with Listeria monocytogenessingleton sequence type 382 (ST382), a serotype IVb-v1 clone with limited genomic divergence. Isolates from these outbreaks and other ST382 isolates not associated with these outbreaks were analyzed by whole-genome sequencing (WGS) analysis. The primary differences among ST382 strains were single nucleotide polymorphisms (SNPs). WGS analysis differentiated ST382 from a clonal complex 1 outbreak strain co-contaminating the caramel apples. WGS clustered food, environmental, and clinical isolates within each outbreak, and also differentiated among the three outbreak strains and epidemiologically unrelated ST382 isolates, which were indistinguishable by pulsed-field gel electrophoresis. ST382 appeared to be an emerging clone that began to diverge from its ancestor approximately 32 years before 2016. We estimated that there was 1.29 nucleotide substitution per genome (2.94 Mbp) per year for this clone.

Published
2017
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32. Listeria monocytogenes in Stone Fruits Linked to a Multistate Outbreak: Enumeration of Cells and Whole-Genome Sequencing.

Author

Yi Chen, Burall, Laurel S., Yan Luo, Timme, Ruth, Melka, David, Tim Muruvanda, Payne, Justin, Wang, Charles, Kastanis, George, Maounounen-Laasri, Anna, De Jesus, Antonio J., Curry, Phillip E., Stones, Robert, K'Aluoch, Okumu, Liu, Eileen, Salter, Monique, Hammack, Thomas S., Evans, Peter S., Parish, Mickey, and Allard, Marc W.

Subjects
*LISTERIA monocytogenes, *STONE fruit, *NUCLEOTIDE sequencing, *SINGLE nucleotide polymorphisms, *PULSED-field gel electrophoresis
Abstract

In 2014, the identification of stone fruits contaminated with Listeria monocytogenes led to the subsequent identification of a multistate outbreak. Simultaneous detection and enumeration of L. monocytogenes were performed on 105 fruits, each weighing 127 to 145 g, collected from 7 contaminated lots. The results showed that 53.3% of the fruits yielded L. monocytogenes (lower limit of detection, 5 CFU/fruit), and the levels ranged from 5 to 2,850 CFU/fruit, with a geometric mean of 11.3 CFU/fruit (0.1 CFU/g of fruit). Two serotypes, IVb-v1 and 1/2b, were identified by a combination of PCR- and antiserum-based serotyping among isolates from fruits and their packing environment; certain fruits contained a mixture of both serotypes. Single nucleotide polymorphism (SNP)-based whole-genome sequencing (WGS) analysis clustered isolates from two case-patients with the serotype IVb-v1 isolates and distinguished outbreak-associated isolates from pulsed-field gel electrophoresis (PFGE)-matched, but epidemiologically unrelated, clinical isolates. The outbreak-associated isolates differed by up to 42 SNPs. All but one serotype 1/2b isolate formed another WGS cluster and differed by up to 17 SNPs. Fully closed genomes of isolates from the stone fruits were used as references to maximize the resolution and to increase our confidence in prophage analysis. Putative prophages were conserved among isolates of each WGS cluster. All serotype IVb-v1 isolates belonged to singleton sequence type 382 (ST382); all but one serotype 1/2b isolate belonged to clonal complex 5. [ABSTRACT FROM AUTHOR]

Published
2016
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33. Notes from the field: listeriosis associated with stone fruit--United States, 2014.

Author

Jackson BR, Salter M, Tarr C, Conrad A, Harvey E, Steinbock L, Saupe A, Sorenson A, Katz L, Stroika S, Jackson KA, Carleton H, Kucerova Z, Melka D, Strain E, Parish M, and Mody RK

Subjects
Humans, Listeria monocytogenes genetics, United States epidemiology, Food Microbiology, Fruit microbiology, Listeria monocytogenes isolation & purification, Listeriosis epidemiology
Abstract

On July 19, 2014, a packing company in California (company A) voluntarily recalled certain lots of stone fruits, including whole peaches, nectarines, plums, and pluots, because of concern about contamination with Listeria monocytogenes based on internal company testing. On July 31, the recall was expanded to cover all fruit packed at their facility during June 1-July 17. After the initial recall, clinicians, state and local health departments, CDC, and the Food and Drug Administration (FDA) received many inquiries about listeriosis from concerned consumers, many of whom had received automated telephone calls informing them that they had purchased recalled fruit. During July 19-31, the CDC Listeria website received >500,000 page views, more than seven times the views received during the previous 52 weeks. However, no molecular information from L. monocytogenes isolates was available to assess whether human illnesses might be linked to these products.

Published
2015

34. Notes from the field: multistate outbreak of listeriosis linked to soft-ripened cheese--United States, 2013.

Author

Choi MJ, Jackson KA, Medus C, Beal J, Rigdon CE, Cloyd TC, Forstner MJ, Ball J, Bosch S, Bottichio L, Cantu V, Melka DC, Ishow W, Slette S, Irvin K, Wise M, Tarr C, Mahon B, Smith KE, and Silk BJ

Subjects
Adult, Aged, Cheese poisoning, Electrophoresis, Gel, Pulsed-Field, Female, Humans, Male, Middle Aged, Pregnancy, Pregnancy Complications, Infectious epidemiology, United States epidemiology, Cheese microbiology, Disease Outbreaks, Food Microbiology, Foodborne Diseases epidemiology, Listeria monocytogenes isolation & purification, Listeriosis epidemiology
Abstract

On June 27, 2013, the Minnesota Department of Health notified CDC of two patients with invasive Listeria monocytogenes infections (listeriosis) whose clinical isolates had indistinguishable pulsed-field gel electrophoresis (PFGE) patterns. A query of PulseNet, the national molecular subtyping network for foodborne disease surveillance, identified clinical and environmental isolates from other states. On June 28, CDC learned from the Food and Drug Administration's Coordinated Outbreak Response and Evaluation Network that environmental isolates indistinguishable from those of the two patients had been collected from Crave Brothers Farmstead Cheese during 2010-2011. An outbreak-related case was defined as isolation of L. monocytogenes with the outbreak PFGE pattern from an anatomic site that is normally sterile (e.g., blood or cerebrospinal fluid), or from a product of conception, with an isolate upload date during May 20-June 28, 2013. As of June 28, five cases were identified in four states (Minnesota, two cases; Illinois, Indiana, and Ohio, one each). Median age of the five patients was 58 years (range: 31-67 years). Four patients were female, including one who was pregnant at the time of infection. All five were hospitalized. One death and one miscarriage were reported.

Published
2014

35. Photogenerated charge carriers and reactive oxygen species in ZnO/Au hybrid nanostructures with enhanced photocatalytic and antibacterial activity.

Author

He W, Kim HK, Wamer WG, Melka D, Callahan JH, and Yin JJ

Subjects
Anti-Bacterial Agents chemical synthesis, Anti-Bacterial Agents chemistry, Catalysis, Dose-Response Relationship, Drug, Escherichia coli drug effects, Gold chemistry, Microbial Sensitivity Tests, Particle Size, Photochemical Processes, Staphylococcus aureus drug effects, Structure-Activity Relationship, Surface Properties, Zinc Oxide chemical synthesis, Zinc Oxide chemistry, Anti-Bacterial Agents pharmacology, Gold pharmacology, Nanostructures chemistry, Reactive Oxygen Species metabolism, Zinc Oxide pharmacology
Abstract

Semiconductor nanostructures with photocatalytic activity have the potential for many applications including remediation of environmental pollutants and use in antibacterial products. An effective way for promoting photocatalytic activity is depositing noble metal nanoparticles (NPs) on a semiconductor. In this paper, we demonstrated the successful deposition of Au NPs, having sizes smaller than 3 nm, onto ZnO NPs. ZnO/Au hybrid nanostructures having different molar ratios of Au to ZnO were synthesized. It was found that Au nanocomponents even at a very low Au/ZnO molar ratio of 0.2% can greatly enhance the photocatalytic and antibacterial activity of ZnO. Electron spin resonance spectroscopy with spin trapping and spin labeling was used to investigate the enhancing effect of Au NPs on the generation of reactive oxygen species and photoinduced charge carriers. Deposition of Au NPs onto ZnO resulted in a dramatic increase in light-induced generation of hydroxyl radical, superoxide and singlet oxygen, and production of holes and electrons. The enhancing effect of Au was dependent on the molar ratio of Au present in the ZnO/Au nanostructures. Consistent with these results from ESR measurements, ZnO/Au nanostructures also exhibited enhanced photocatalytic and antibacterial activity. These results unveiled the enhanced mechanism of Au on ZnO and these materials have great potential for use in water purification and antibacterial products.

Published
2014
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