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Zelalem A, Koran T, Abegaz K, Abera Z, Mummed B, Olani A, Aliy A, Chimdessa M, Fentahun S, Schwan CL, Vipham JL. Hygienic status of beef butcher shop facilities and antibiotic resistance profile of Salmonella enterica in Ethiopia. Braz J Microbiol 2024:10.1007/s42770-024-01312-2. [PMID: 38592593 DOI: 10.1007/s42770-024-01312-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 03/21/2024] [Indexed: 04/10/2024] Open
Abstract
The microbiological quality of meat is influenced by the conditions of hygiene prevailing during production and handling. Thus, this study aimed to assess the prevalence of Salmonella enterica and its antimicrobial resistance, load of hygiene indicator bacteria including E. coli (ECC), coliforms (CC), total coliform (TCC), Enterobacteriaceae (EB) and aerobic plate count (APC), and meat handler's food safety knowledge and hygiene practices in butcher shops in two cities, Addis Ababa and Hawassa in Ethiopia, during 2020 and 2021. A total of 360 samples of beef carcasses (n = 120), knives (n = 60), chopping boards (n = 60), weighing balance (n = 60), and personnel's hands (n = 60) were randomly collected for microbial analysis. Besides, 120 participants were selected to participate in a food safety knowledge and hygiene practices assessment. The S. enterica isolates were identified by agglutination test followed by qPCR targeting invA gene. Phenotypic antimicrobial resistance profiles of S. enterica were determined using disk diffusion assays as described in CLSI. The ECC, CC, TCC, EB, and APC populations were quantified by plating onto petrifilm plates. A structured questionnaire was used to determine food safety knowledge and hygiene practices of participants. Overall prevalence of S. enterica was 16.7% (95% CI, 8.3-26.7) and location seems to have no effect (p = 0.806). Only 20% of the S. enterica were resistant to ampicillin and tetracycline. However, the majority (80%) of S. enterica isolates were susceptible to the panel of 11 antimicrobials tested. The overall mean ± SD (log CFU/cm2) of ECC, CC, TCC, EB, and APC were 4.31 ± 1.15; 4.61 ± 1.33; 4.77 ± 1.32; 4.59 ± 1.38 and 5.87 ± 1.52, respectively. No significant difference (p = 0.123) in E. coli contamination was observed between samples of beef carcasses and chopping boards. The EB contamination showed no significant difference (p > 0.05) among sample sources. The APC contamination levels on beef carcass were significantly higher (p > 0.05) than other sample sources. A total of 56% (95% CI: 46.7 - 65.0) of the participants had poor knowledge and 65% (95% CI: 56.7 - 73.3) had poor hygiene practices towards food safety. This study highlighted the poor hygiene status of butcher facilities with a potential risk of beef safety. Thus, appropriate food safety control strategies and inspection is needed at retail establishments.
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Affiliation(s)
- Andarge Zelalem
- School of Biological Sciences and Biotechnology, College of Natural and Computational Sciences, Haramaya University, Dire Dawa, Ethiopia.
| | | | - Kebede Abegaz
- Department of Food Science & Technology, College of Agriculture, Hawassa University, Hawassa, Ethiopia
| | - Zelalem Abera
- Univeristy Laboratory Management Directorate, Central Laboratories, Haramaya University, Dire Dawa, Ethiopia
| | - Bahar Mummed
- College of Veterinary Medicine, Haramaya University, Dire Dawa, Ethiopia
| | | | - Abde Aliy
- Animal Health Institute, Sebeta, Ethiopia
| | - Meseret Chimdessa
- School of Biological Sciences and Biotechnology, College of Natural and Computational Sciences, Haramaya University, Dire Dawa, Ethiopia
| | - Selam Fentahun
- School of Public Health, College of Medicine and Health Sciences, Hawassa University, Hawassa, Ethiopia
| | - Carla L Schwan
- Department of Nutritional Sciences, College of Family and Consumer Sciences, University of Georgia, Athens, GA, 30602, USA
| | - Jessie L Vipham
- Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS, USA
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Schwan CL, Bastos LM, Young S, Domesle K, Ge B, Hsu CH, Li C, Strain E, Vipham J, Jones C, Amachawadi R, Nagaraja TG, Trinetta V. Graphical abstractGenotypic and Phenotypic Characterization of Antimicrobial and Heavy Metal tolerance in Salmonella enterica and Escherichia coli Isolates from Swine Feed Mills. J Food Prot 2023:100113. [PMID: 37290750 DOI: 10.1016/j.jfp.2023.100113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 05/29/2023] [Accepted: 05/31/2023] [Indexed: 06/10/2023]
Abstract
Antimicrobials and heavy metals are commonly used in the animal feed industry. The role of in-feed antimicrobials on the evolution and persistence of resistance in enteric bacteria is not well described. Whole-Genome Sequencing (WGS) is widely used for genetic characterizations of bacterial isolates, including antimicrobial resistance, heavy metal tolerance, virulence factors, and relatedness to other sequenced isolates. The goals of this study were to i) use WGS to characterize Salmonella enterica (n = 33) and Escherichia coli (n = 30) isolated from swine feed and feed mill environments; and ii) investigate their genotypic and phenotypic antimicrobial and heavy metal tolerance. Salmonella isolates belonged to 10 serovars, the most common being Cubana, Senftenberg, and Tennessee. E. coli isolates were grouped into 22 O groups. Phenotypic resistance to at least one antimicrobial was observed in 19 Salmonella (57.6%) and 17 E. coli (56.7%) isolates, whereas multidrug resistance (resistant to ≥ 3 antimicrobial classes) was observed in four Salmonella (12%) and two E. coli (7%) isolates. Antimicrobial resistance genes were identified in 17 Salmonella (51%) and 29 E. coli (97%), with 11 and 29 isolates possessing genes conferring resistance to multiple antimicrobial classes. Phenotypically, 53% Salmonella and 58% E. coli presented resistance to copper and arsenic. All isolates that possessed the copper resistance operon were resistant to the highest concentration tested (40 mM). Heavy metal tolerance genes to copper and silver were present in 26 Salmonella isolates. Our study showed a strong agreement between predicted and measured resistances when comparing genotypic and phenotypic data for antimicrobial resistance, with an overall concordance of 99% and 98.3% for Salmonella and E. coli, respectively.
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Affiliation(s)
- Carla L Schwan
- Department of Nutritional Sciences, University of Georgia, Athens, GA, USA
| | - Leonardo M Bastos
- Department of Crop and Soil Sciences, University of Georgia, Athens, GA, USA
| | - Shenia Young
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Kelly Domesle
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Beilei Ge
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Chih-Hao Hsu
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Cong Li
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Errol Strain
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Jessie Vipham
- Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS, USA
| | - Cassandra Jones
- Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS, USA
| | - Raghavendra Amachawadi
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Tiruvoor G Nagaraja
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Valentina Trinetta
- Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS, USA.
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Schwan CL, Dallman TJ, Cook PW, Vipham J. A case report of Salmonella enterica serovar Corvallis from environmental isolates from Cambodia and clinical isolates in the UK. Access Microbiol 2022; 4:000315. [PMID: 35252753 PMCID: PMC8895601 DOI: 10.1099/acmi.0.000315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 12/10/2021] [Indexed: 11/18/2022] Open
Abstract
Salmonella enterica subspecies enterica serovar Corvallis (S. Corvallis) has been identified as a human pathogen and as a food contaminant. Diarrhoeal disease is a common diagnosis in tourists visiting Southeast Asia, often with unknown aetiology. However, numerous public health institutes have identified Salmonella as a common causative agent when consuming contaminated food and water. Genomic data from environmental isolates from a Cambodian informal market were uploaded to the National Center for Biotechnology Information (NCBI) platform, allowing the novel sequences to be compared to global whole-genome sequence archives. The comparison revealed that two human clinical isolates from England and four of the environmental isolates were closely related, with an average single nucleotide polymorphism (SNP) difference of 1 (0-3 SNPs). A maximum-likelihood tree based on core SNPs was generated comparing the 4 isolates recovered from a Cambodian informal market with 239 isolates of S. Corvallis received from routine surveillance of human salmonellosis in England and confirmed the close relationship. In addition, the environmental isolates clustered into a broader phylogenetic group within the S. Corvallis population containing 68 additional human isolates, of which 42 were from patients who reported recent international travel, almost exclusively to Southeast Asia. The environmental isolates of S. Corvallis isolated from an informal market in Cambodia are concerning for public health due to their genetic similarity to isolates (e.g. clinical isolates from the UK) with known human virulence and pathogenicity. This study emphasizes the benefits of global and public data sharing of pathogen genomes.
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Affiliation(s)
- Carla L. Schwan
- Department of Nutritional Sciences, University of Georgia, 300 Carlton St., Athens, GA 30602, USA
| | | | - Peter W. Cook
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Jessie Vipham
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, KS, USA
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Schwan CL, Lomonaco S, Bastos LM, Cook PW, Maher J, Trinetta V, Bhullar M, Phebus RK, Gragg S, Kastner J, Vipham JL. Genotypic and Phenotypic Characterization of Antimicrobial Resistance Profiles in Non-typhoidal Salmonella enterica Strains Isolated From Cambodian Informal Markets. Front Microbiol 2021; 12:711472. [PMID: 34603240 PMCID: PMC8481621 DOI: 10.3389/fmicb.2021.711472] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 08/26/2021] [Indexed: 12/03/2022] Open
Abstract
Non-typhoidal Salmonella enterica is a pathogen of global importance, particularly in low and middle-income countries (LMICs). The presence of antimicrobial resistant (AMR) strains in market environments poses a serious health threat to consumers. In this study we identified and characterized the genotypic and phenotypic AMR profiles of 81 environmental S. enterica strains isolated from samples from informal markets in Cambodia in 2018–2019. AMR genotypes were retrieved from the NCBI Pathogen Detection website (https://www.ncbi.nlm.nih.gov/pathogens/) and using ResFinder (https://cge.cbs.dtu.dk/services/) Salmonella pathogenicity islands (SPIs) were identified with SPIFinder (https://cge.cbs.dtu.dk/services/). Susceptibility testing was performed by broth microdilution according to the Clinical and Laboratory Standards Institute (CLSI) standard guidelines M100-S22 using the National Antimicrobial Resistance Monitoring System (NARMS) Sensititre Gram Negative plate. A total of 17 unique AMR genes were detected in 53% (43/81) of the isolates, including those encoding tetracycline, beta-lactam, sulfonamide, quinolone, aminoglycoside, phenicol, and trimethoprim resistance. A total of 10 SPIs (SPI-1, 3–5, 8, 9, 12–14, and centisome 63 [C63PI]) were detected in 59 isolates. C63PI, an iron transport system in SPI-1, was observed in 56% of the isolates (n = 46). SPI-1, SPI-4, and SPI-9 were present in 13, 2, and 5% of the isolates, respectively. The most common phenotypic resistances were observed to tetracycline (47%; n = 38), ampicillin (37%; n = 30), streptomycin (20%; n = 16), chloramphenicol (17%; n = 14), and trimethoprim-sulfamethoxazole (16%; n = 13). This study contributes to understanding the AMR genes present in S. enterica isolates from informal markets in Cambodia, as well as support domestic epidemiological investigations of multidrug resistance (MDR) profiles.
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Affiliation(s)
- Carla L Schwan
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, KS, United States
| | - Sara Lomonaco
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, United States
| | - Leonardo M Bastos
- Department of Agronomy, Kansas State University, Manhattan, KS, United States
| | - Peter W Cook
- Centers for Disease Control and Prevention, Atlanta, GA, United States
| | - Joshua Maher
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, KS, United States
| | - Valentina Trinetta
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, KS, United States
| | - Manreet Bhullar
- Department of Horticulture and Natural Resources, Kansas State University, Olathe, KS, United States
| | - Randall K Phebus
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, KS, United States
| | - Sara Gragg
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, KS, United States
| | - Justin Kastner
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS, United States
| | - Jessie L Vipham
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, KS, United States
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Desiree K, Schwan CL, Ly V, Hok L, Bello NM, Nwadike L, Phebus RK, Vipham JL. Investigating Salmonella enterica, Escherichia coli, and Coliforms on Fresh Vegetables Sold in Informal Markets in Cambodia†. J Food Prot 2021; 84:843-849. [PMID: 33320940 DOI: 10.4315/jfp-20-219] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 12/11/2020] [Indexed: 11/11/2022]
Abstract
ABSTRACT Vegetables in Cambodia are commonly sold in informal markets lacking food safety standards and controls. Current data on microbial contamination of vegetables in Cambodian informal markets are limited. The purpose of this study was to investigate Salmonella enterica and indicator organisms (Escherichia coli and coliforms) on the surface of fresh vegetables sold in informal markets in Cambodia. Samples of loose-leaf lettuce, tomatoes, and cucumbers were collected from 104 vendors at four informal markets in Battambang and Siem Reap provinces during the rainy and dry seasons. Detection methods for S. enterica were adapted from the U.S. Food and Drug Administration's Bacteriological Analytical Manual. Coliform and E. coli populations were quantified by plating onto E. coli/coliform count plates. S. enterica was most prevalent on lettuce during the dry season (56.5%, 95% confidence interval [CI] [41.0, 70.8]) than during the rainy season (15.4%, 95% CI [7.5, 29.1]), whereas no significant seasonal differences were apparent for tomatoes and cucumbers. Regardless of season, levels of S. enterica were highest on lettuce (5.7 log CFU/g, 95% CI [5.5, 5.9]), relative to cucumbers (4.2 log CFU/g, 95% CI [3.8, 4.6]) and tomatoes (4.3 log CFU/g, 95% CI [4.1, 4.6]). For E. coli, prevalence was higher during the rainy season (34.0%, 95% CI [25.4, 43.8]) than during the dry season (9.1%, 95% CI [4.9, 16.5]), with the highest prevalence estimated on lettuce. Coliform levels on lettuce and tomatoes were greater during the rainy season (6.3 and 5.3 log CFU/g, 95% CI [5.7, 6.8] and [4.7, 5.8], respectively) than during the dry season (5.2 and 3.9 log CFU/g, 95% CI [4.7, 5.7] and [3.4, 4.4], respectively). These results indicate seasonal patterns for microbial prevalence in lettuce and an overall high level of bacterial contamination on raw vegetables sold in Cambodian informal markets. HIGHLIGHTS
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Affiliation(s)
- Karina Desiree
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA.,https://orcid.org/0000-0001-5910-4195 [K.D.]
| | - Carla L Schwan
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA.,https://orcid.org/0000-0002-1853-2553 [C.L.S.]
| | - Visoth Ly
- Faculty of Agro-Industry, Royal University of Agriculture, Phnom Penh, Cambodia
| | - Lyda Hok
- Faculty of Agronomy and Center of Excellence on Sustainable Agricultural Intensification and Nutrition, Royal University of Agriculture, Phnom Penh, Cambodia (ORCID: https://orcid.org/0000-0003-2175-1412 [L.H.])
| | - Nora M Bello
- Department of Statistics, Kansas State University, Manhattan, Kansas 66506, USA
| | - Londa Nwadike
- Research and Extension, Kansas State University and University of Missouri, Olathe, Kansas 66061, USA (ORCID: https://orcid.org/0000-0002-4683-0224 [L.N.])
| | - Randall K Phebus
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA.,https://orcid.org/0000-0003-3427-9751 [R.K.P.]
| | - Jessie L Vipham
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA.,https://orcid.org/0000-0002-2918-1058 [J.L.V.]
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Schwan CL, Desiree K, Bello NM, Bastos L, Hok L, Phebus RK, Gragg S, Kastner J, Vipham JL. Prevalence of Salmonella enterica Isolated from Food Contact and Nonfood Contact Surfaces in Cambodian Informal Markets. J Food Prot 2021; 84:73-79. [PMID: 33393619 DOI: 10.4315/jfp-20-112] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 08/21/2020] [Indexed: 11/11/2022]
Abstract
ABSTRACT The lack of hygiene and sanitation practices and insufficient infrastructure in Cambodian informal markets may increase the risk of food contamination, specifically raw vegetables, which in turn may increase the chances of contracting a foodborne disease. The aims of this study in informal markets in Cambodia were (i) to quantify the prevalence of Salmonella enterica based upon differences in season of the year (rainy versus dry), surface types (food contact surfaces versus nonfood contact surfaces), and location of vendors within the market (inside versus outside) and (ii) to characterize S. enterica serotype prevalence. A total of 310 samples were screened for S. enterica prevalence following the U.S. Department of Agriculture guidelines, and results were confirmed by PCR assay. Whole genome sequencing was used to determine the serotype for each isolate in silico using SeqSero 1.0 on draft genomes. A total of 78 samples were confirmed positive for S. enterica. During the dry season, S. enterica was more prevalent on food contact surfaces than on nonfood contact surfaces (estimated probability of detection [confidence interval]: 0.41 [0.25, 0.59] and 0.17 [0.08, 0.32], respectively; P = 0.002), but no differences were apparent in the rainy season. No differences in S. enterica prevalence were found based on location within the market (P = 0.61). Sixteen S. enterica serotypes were detected across multiple surfaces. The most common S. enterica serotypes were Rissen (18 isolates), Hvittingfoss (11), Corvallis (10), Krefeld (8), Weltevreden (6), and Altona (6). Accurate data on the prevalence of S. enterica in informal markets are crucial for the development of effective surveillance and implementation of suitable intervention strategies at the domestic level, thus preventing foodborne illness. HIGHLIGHTS
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Affiliation(s)
- Carla L Schwan
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA (ORCID: https://orcid.org/0000-0002-1853-2553 [C.L.S.])
| | - Karina Desiree
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA (ORCID: https://orcid.org/0000-0002-1853-2553 [C.L.S.])
| | - Nora M Bello
- Department of Statistics, Kansas State University, Manhattan, Kansas 66506, USA
| | - Leonardo Bastos
- Department of Agronomy, Kansas State University, Manhattan, Kansas 66506, USA
| | - Lyda Hok
- Faculty of Agronomy and Center of Excellence on Sustainable Agricultural Intensification and Nutrition, Royal University of Agriculture, Phnom Penh, Cambodia
| | - Randall K Phebus
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA (ORCID: https://orcid.org/0000-0002-1853-2553 [C.L.S.])
| | - Sara Gragg
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA (ORCID: https://orcid.org/0000-0002-1853-2553 [C.L.S.])
| | - Justin Kastner
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, Kansas 66506, USA
| | - Jessie L Vipham
- Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA (ORCID: https://orcid.org/0000-0002-1853-2553 [C.L.S.])
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Channaiah LH, Holmgren ES, Michael M, Sevart NJ, Milke D, Schwan CL, Krug M, Wilder A, Phebus RK, Thippareddi H, Milliken G. Validation of Baking To Control Salmonella Serovars in Hamburger Bun Manufacturing, and Evaluation of Enterococcus faecium ATCC 8459 and Saccharomyces cerevisiae as Nonpathogenic Surrogate Indicators. J Food Prot 2016; 79:544-52. [PMID: 27052857 DOI: 10.4315/0362-028x.jfp-15-241] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study was conducted to validate a simulated commercial baking process for hamburger buns to destroy Salmonella serovars and to determine the appropriateness of using nonpathogenic surrogates (Enterococcus faecium ATCC 8459 or Saccharomyces cerevisiae) for in-plant process validation studies. Wheat flour was inoculated (∼6 log CFU/g) with three Salmonella serovars (Typhimurium, Newport, or Senftenberg 775W) or with E. faecium. Dough was formed, proofed, and baked to mimic commercial manufacturing conditions. Buns were baked for up to 13 min in a conventional oven (218.3°C), with internal crumb temperature increasing to ∼100°C during the first 8 min of baking and remaining at this temperature until removal from the oven. Salmonella and E. faecium populations were undetectable by enrichment (>6-log CFU/g reductions) after 9.0 and 11.5 min of baking, respectively, and ≥5-log-cycle reductions were achieved by 6.0 and 7.75 min, respectively. D-values of Salmonella (three-serovar cocktail) and E. faecium 8459 in dough were 28.64 and 133.33, 7.61 and 55.67, and 3.14 and 14.72 min at 55, 58, and 61°C, respectively, whereas D-values of S. cerevisiae were 18.73, 5.67, and 1.03 min at 52, 55, and 58°C, respectivly. The z-values of Salmonella, E. faecium, and S. cerevisiae were 6.58, 6.25, and 4.74°C, respectively. A high level of thermal lethality was observed for baking of typical hamburger bun dough, resulting in rapid elimination of high levels of the three-strain Salmonella cocktail; however, the lethality and microbial destruction kinetics should not be extrapolated to other bakery products without further research. E. faecium demonstrated greater thermal resistance compared with Salmonella during bun baking and could serve as a conservative surrogate to validate thermal process lethality in commercial bun baking operations. Low thermal tolerance of S. cerevisiae relative to Salmonella serovars limits its usefulness as a surrogate for process validations.
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Affiliation(s)
| | | | - Minto Michael
- Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA
| | - Nicholas J Sevart
- Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA
| | - Donka Milke
- Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA
| | - Carla L Schwan
- Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA
| | - Matthew Krug
- Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA
| | - Amanda Wilder
- Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA
| | - Randall K Phebus
- Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA.
| | | | - George Milliken
- Department of Statistics, Kansas State University, Manhattan, Kansas 66506, USA
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