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Wang X, Tian S, Wu Y, Li H, Bai LI, Liu H, Zhang X, Dong Q. Strain Variability in Growth and Thermal Inactivation Characteristics of Listeria monocytogenes Strains after Acid Adaptation. J Food Prot 2021; 84:2229-2236. [PMID: 34197590 DOI: 10.4315/jfp-20-387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [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: 09/23/2020] [Accepted: 06/24/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT Given the importance of strain variability to predictive microbiology and risk assessment, this study aimed to quantify the magnitude of strain variability in growth and thermal inactivation kinetics behaviors after acid adaptation. Thirty-three Listeria monocytogenes strains were exposed to acid-adapted tryptic soy broth supplemented with yeast extract (TSBYE; pH 5.5) and non-acid-adapted TSBYE (pH 7.0) for 20 h. Next, the growth parameters of these adapted and nonadapted strains that grew in nonbuffered TSBYE at 25°C were estimated. The tested strains were inactivated at 60°C in nonbuffered broth to obtain the heat resistance parameters. The results revealed that strain variability was present in the growth and thermal inactivation characteristics. The maximum specific growth rate ranged from 0.21 to 0.44 h-1 and from 0.20 to 0.45 h-1 after acid and nonacid adaptation, respectively. The lag times were from 0.69 to 2.56 h and from 0.24 to 3.36 h for acid-adapted and non-acid-adapted cells, respectively. The apparent D-values at 60°C of the pathogen ranged between 0.56 and 3.93 min and between 0.52 and 3.63 min for the presence and absence of acid adaptation condition, respectively. Acid adaptation significantly (P < 0.05) increased the magnitude of strain variability in the thermal inactivation characteristics of L. monocytogenes, with the coefficient of variation increasing to 0.17, whereas acid adaptation did not significantly (P ≥ 0.05) influence the variabilities in the growth parameters of the tested strains. Furthermore, the subsequent growth behaviors of all strains did not exhibit significant (P > 0.05) changes after exposure to acidic broth. However, the thermal resistance of most (25 of 33) of the tested strains increased (P < 0.05) after growing in acid-adapted broth. The relevant data generated in the present study can be used to describe the strain variability in predictive microbiology and to deeply understand the behavioral responses of different strains to acid adaptation. HIGHLIGHTS
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Affiliation(s)
- Xiang Wang
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, People's Republic of China
| | - Shihong Tian
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, People's Republic of China
| | - Yufan Wu
- Technology Center of Zhangjiagang Customs, Jiangsu 310012, People's Republic of China
| | - Hongmei Li
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, People's Republic of China
| | - L I Bai
- China National Center for Food Safety Risk Assessment, Beijing 100021, People's Republic of China
| | - Hong Liu
- Shanghai Municipal Center for Disease Control & Prevention, Shanghai 200336, People's Republic of China
| | - Xibin Zhang
- New Hope Liuhe Co., Ltd., Beijing 100102, People's Republic of China
| | - Qingli Dong
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, People's Republic of China
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Hwang D, Kim SM, Kim HJ. Transcriptome changes and polymyxin resistance of acid-adapted Escherichia coli O157:H7 ATCC 43889. Gut Pathog 2020; 12:52. [PMID: 33292490 DOI: 10.1186/s13099-020-00390-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/18/2020] [Indexed: 12/25/2022] Open
Abstract
Background Acid treatment is commonly used for controlling or killing pathogenic microorganisms on medical devices and environments; however, inadequate acid treatment may cause acid tolerance response (ATR) and offer cross-protection against environmental stresses, including antimicrobials. This study aimed to characterise an Escherichia coli strain that can survive in the acidic gastrointestinal environment. Results We developed an acid-tolerant E. coli O157:H7 ATCC 43889 (ATCC 43889) strain that can survive at pH 2.75 via cell adaptation in low pH conditions. We also performed RNA sequencing and qRT-PCR to compare differentially expressed transcripts between acid-adapted and non-adapted cells. Genes related to stress resistance, including kdpA and bshA were upregulated in the acid-adapted ATCC 43889 strain. Furthermore, the polymyxin resistance gene arnA was upregulated in the acid-adapted cells, and resistance against polymyxin B and colistin (polymyxin E) was observed. As polymyxins are important antibiotics, effective against multidrug-resistant gram-negative bacterial infections, the emergence of polymyxin resistance in acid-adapted E. coli is a serious public health concern. Conclusion The transcriptomic and phenotypic changes analysed in this study during the adaptation of E. coli to acid environments can provide useful information for developing intervention technologies and mitigating the risk associated with the emergence and spread of antimicrobial resistance.
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Gavriil A, Paramithiotis S, Skordaki A, Tsiripov E, Papaioannou A, Skandamis PN. Prior exposure to different combinations of pH and undissociated acetic acid can affect the induced resistance of Salmonella spp. strains in mayonnaise stored under refrigeration and the regulation of acid-resistance related genes. Food Microbiol 2020; 95:103680. [PMID: 33397612 DOI: 10.1016/j.fm.2020.103680] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [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: 09/05/2020] [Revised: 11/08/2020] [Accepted: 11/09/2020] [Indexed: 11/16/2022]
Abstract
The innate and inducible resistance of six Salmonella strains (4/74, FS8, FS115, P167807, ATCC 13076, WT) in mayonnaise at 5 °C following adaptation to different pH/undissociated acetic acid (UAA) combinations (15mM/pH5.0, 35mM/pH5.5, 45mM/pH6.0) was investigated. The inherent and acid-induced responses were strain-dependent. Two strains (ATCC 13076, WT), albeit not the most resistant innately, exhibited the most prominent adaptive potential. Limited/no adaptability was observed regarding the rest strains, though being more resistant inherently. The individual effect of pH and UAA adaptation in the phenotypic and transcriptomic profiles of ATCC 13076 and WT was further examined. The type (pH, UAA) and magnitude of stress intensity affected their responses. Variations in the type and magnitude of stress intensity also determined the relative gene expression of four genes (adiA, cadB, rpoS, ompR) implicated in Salmonella acid resistance mechanisms. adiA and cadB were overexpressed following adaptation to some treatments; rpoS and ompR were downregulated following adaptation to 15mM/pH5.0 and 35mM/pH5.5, respectively. Nonetheless, the transcriptomic profiles did not always correlate with the corresponding phenotypes. In conclusion, strain variations in Salmonella are extensive. The ability of the strains to adapt and induce resistant phenotypes and acid resistance-related genes is affected by the type and magnitude of the stress applied during adaptation.
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Affiliation(s)
- Alkmini Gavriil
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens, 11855, Greece
| | - Spiros Paramithiotis
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens, 11855, Greece
| | - Asimina Skordaki
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens, 11855, Greece
| | - Eleni Tsiripov
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens, 11855, Greece
| | - Adamantia Papaioannou
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens, 11855, Greece
| | - Panagiotis N Skandamis
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens, 11855, Greece.
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Kang JW, Kim WJ, Kang DH. Synergistic effect of 222-nm krypton-chlorine excilamp and mild heating combined treatment on inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium in apple juice. Int J Food Microbiol 2020; 329:108665. [PMID: 32497789 DOI: 10.1016/j.ijfoodmicro.2020.108665] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [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: 11/26/2019] [Revised: 03/20/2020] [Accepted: 05/16/2020] [Indexed: 10/24/2022]
Abstract
Simultaneous treatment with 222-nm KrCl excilamp and mild heating (EX-MH) at 45, 50 and 55 °C showed synergistic bactericidal effects on non-acid and acid adapted cells of Escherichia coli O157:H7 and Salmonella Typhimurium in apple juice. In particular, acid-adapted pathogens exhibited increased resistance to EX-MH compared to pathogenic bacteria that were not acid-adapted. Also, elucidation of the synergistic bactericidal mechanism of EX-MH was performed through several assays and this mechanism was described as follows: (i) when KrCl excilamp (EX) and mild heating (MH) are applied simultaneously, MH reversibly inactivates the antioxidant enzyme, superoxide dismutase (SOD), thereby increasing accumulation of reactive oxygen species (ROS) generated by EX and thus inducing synergistic ROS generation, (ii) ROS production induces lipid peroxidation occurrence in the cell membrane, (iii) this lipid peroxidation occurrence in the cell membrane induces synergistic destruction of cell membrane, resulting in synergistic cell death. While EX-MH of 45, 50, or 55 °C reduced E. coli O157:H7 (the pathogen most resistant to EX-MH) in apple juice by 5-log, the qualities such as color (L*, a*, and b*), total phenolic compounds (TPC), and DPPH free radical scavenging activity of apple juice did not change significantly (P > 0.05). This study not only suggests the applicability of EX-MH to the apple juice industry, but also can be used as baseline data for future relevant research.
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Affiliation(s)
- Jun-Won Kang
- Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Woo-Ju Kim
- Department of Food Science and Technology, The Ohio State University, 2015 Fyffe road, Columbus, OH 43210, USA
| | - Dong-Hyun Kang
- Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea; Institutes of Green Bio Science & Technology, Seoul National University, Pyeongchang-gun, Gangwon-do 25354, Republic of Korea.
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Abstract
It is important to assess acid tolerance in lactic acid bacteria, particularly for probiotics, although it involves multiple mechanisms. Measuring the difference between intracellular and extracellular pH (ΔpH) using the fluorescent probe CFDA-SE is particularly effective for such assessments because it gives direct information on the level of tolerance in the extracellular acidic pH range from 7 to 2.5. It also enables acid adaptation to be induced and observed by slowly introducing HCl into the medium and decreasing the extracellular pH. The difference of acid tolerance between anaerobic and aerobic conditions in lactic acid bacteria can also be evaluated by measuring ΔpH.
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Wang C, Cui Y, Qu X. Identification of proteins regulated by acid adaptation related two component system HPK1/RR1 in Lactobacillus delbrueckii subsp. bulgaricus. Arch Microbiol 2018; 200:1381-1393. [PMID: 30022229 DOI: 10.1007/s00203-018-1552-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 05/02/2018] [Accepted: 07/13/2018] [Indexed: 11/25/2022]
Abstract
Lactobacillus delbrueckii subsp. bulgaricus is currently one of the most valuable lactic acid bacteria (LAB) and widely used in global dairy industry. The acid tolerance and adaptation ability of LAB is the key point of their survival and proliferation during fermentation process and in gastrointestinal tract of human body. Two component system (TCS) is one of the most important mechanisms to allow bacteria to sense and respond to changes of environmental conditions. TCS typically consists of a histidine protein kinase (HPK) and a corresponding response regulator (RR). Our previous study indicated a TCS (JN675228/JN675229) was involved in acid adaptation in L. bulgaricus. To reveal the role of JN675228 (HPK1)/JN675229 (RR1) in acid adaptation, the target genes of JN675228 (HPK1)/JN675229 (RR1) were identified by means of a proteomic approach complemented with transcription data in the present study. The results indicated that HPK1/RR1 regulated the acid adaptation ability of bacteria by means of many pathways, including the proton pump related protein, classical stress shock proteins, carbohydrate metabolism, nucleotide biosynthesis, DNA repair, transcription and translation, peptide transport and degradation, and cell wall biosynthesis, etc. To our knowledge, this is the first report with the effect of acid adaptation-related TCS HPK1/RR1 on its target genes. This study will offer experimental basis for clarifying the acid adaptation regulation mechanism of L. bulgaricus, and provide a theoretical basis for this bacterium in industry application.
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Affiliation(s)
- Chao Wang
- Department of Food Science and Engineering, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, 150090, People's Republic of China
| | - Yanhua Cui
- Department of Food Science and Engineering, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, 150090, People's Republic of China.
| | - Xiaojun Qu
- Institute of Microbiology, Heilongjiang Academy of Sciences, Harbin, 150010, People's Republic of China
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Srisukchayakul P, Charalampopoulos D, Karatzas KA. Study on the effect of citric acid adaptation toward the subsequent survival of Lactobacillus plantarum NCIMB 8826 in low pH fruit juices during refrigerated storage. Food Res Int 2018; 111:198-204. [PMID: 30007676 DOI: 10.1016/j.foodres.2018.05.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Revised: 05/05/2018] [Accepted: 05/08/2018] [Indexed: 01/16/2023]
Abstract
Pre-treatment of stationary phase cells of Lactobacillus plantarum NCMIB 8826 with citric acid (pH 3 to 6) for a short period of time significantly improved subsequent cell survival in several highly acidic fruit juices namely cranberry (pH 2.7), pomegranate (pH 3.5), and lemon & lime juices (pH 2.8). Although the mechanism for this adaptation is still unclear, the analysis of the cellular fatty acid content of acid adapted cells and the reverse transcription polymerase chain reaction (RT-PCR) showed a significant increase (by ~1.7 fold) of the cellular cyclopropane fatty acid, cis-11,12-methylene octadecanoic acid (C19:0cyclow7c) and a significant upregulation (~12 fold) of cyclopropane synthase (cfa) were observed, respectively, during acid adaptation. It is likely that these changes led to a decrease in membrane fluidity and to lower membrane permeability, which prevents the cells from proton influx during storage in these low pH fruit juices.
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Affiliation(s)
- Pornpoj Srisukchayakul
- Department of Food and Nutritional Sciences, University of Reading, PO Box 226, Whiteknights, Reading RG6 6AP, United Kingdom
| | - Dimitris Charalampopoulos
- Department of Food and Nutritional Sciences, University of Reading, PO Box 226, Whiteknights, Reading RG6 6AP, United Kingdom
| | - Kimon Andreas Karatzas
- Department of Food and Nutritional Sciences, University of Reading, PO Box 226, Whiteknights, Reading RG6 6AP, United Kingdom; CINN (Centre for Integrative Neuroscience and Neurodynamics), University of Reading, Whiteknights, Reading RG6 6BE, United Kingdom.
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Liu YF, Hsieh CW, Chang YS, Wung BS. Effect of acetic acid on ethanol production by Zymomonas mobilis mutant strains through continuous adaptation. BMC Biotechnol 2017; 17:63. [PMID: 28764759 PMCID: PMC5540488 DOI: 10.1186/s12896-017-0385-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [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: 05/11/2017] [Accepted: 07/25/2017] [Indexed: 02/03/2023] Open
Abstract
Background Acetic acid is a predominant by-product of lignocellulosic biofuel process, which inhibits microbial biocatalysts. Development of bacterial strains that are tolerant to acetic acid is challenging due to poor understanding of the underlying molecular mechanisms. Results In this study, we generated and characterized two acetic acid-tolerant strains of Zymomonas mobilis using N-methyl-N′-nitro-N-nitrosoguanidine (NTG)-acetate adaptive breeding. Two mutants, ZMA-142 and ZMA-167, were obtained, showing a significant growth rate at a concentration of 244 mM sodium acetate, while the growth of Z. mobilis ATCC 31823 were completely inhibited in presence of 195 mM sodium acetate. Our data showed that acetate-tolerance of ZMA-167 was attributed to a co-transcription of nhaA from ZMO0117, whereas the co-transcription was absent in ATCC 31823 and ZMA-142. Moreover, ZMA-142 and ZMA-167 exhibited a converstion rate (practical ethanol yield to theorical ethanol yield) of 90.16% and 86% at 195 mM acetate-pH 5 stress condition, respectively. We showed that acid adaptation of ZMA-142 and ZMA-167 to 146 mM acetate increased ZMA-142 and ZMA-167 resulted in an increase in ethanol yield by 32.21% and 21.16% under 195 mM acetate-pH 5 stress condition, respectively. Conclusion The results indicate the acetate-adaptive seed culture of acetate-tolerant strains, ZMA-142 and ZMA-167, could enhance the ethanol production during fermentation.
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Affiliation(s)
- Yu-Fan Liu
- Division of Allergy, Department of Pediatrics, Chung-Shan Medical University Hospital, Taichung, Taiwan.,Department of Biomedical Sciences, College of Medicine Sciences and Technology, Chung Shan Medical University, Taichung, Taiwan
| | - Chia-Wen Hsieh
- Department of Microbiology, Immunology and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan.
| | - Yao-Sheng Chang
- Department of Microbiology, Immunology and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan
| | - Being-Sun Wung
- Department of Microbiology, Immunology and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan
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Metselaar KI, Saá Ibusquiza P, Ortiz Camargo AR, Krieg M, Zwietering MH, den Besten HMW, Abee T. Performance of stress resistant variants of Listeria monocytogenes in mixed species biofilms with Lactobacillus plantarum. Int J Food Microbiol 2015; 213:24-30. [PMID: 25935090 DOI: 10.1016/j.ijfoodmicro.2015.04.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [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: 01/30/2015] [Revised: 04/13/2015] [Accepted: 04/15/2015] [Indexed: 11/25/2022]
Abstract
Population diversity and the ability to adapt to changing environments allow Listeria monocytogenes to grow and survive under a wide range of environmental conditions. In this study, we aimed to evaluate the performance of a set of acid resistant L. monocytogenes variants in mixed-species biofilms with Lactobacillus plantarum as well as their benzalkonium chloride (BAC) resistance in these biofilms. L. monocytogenes LO28 wild type and acid resistant variants were capable of forming mixed biofilms with L. plantarum at 20°C and 30°C in BHI supplemented with manganese and glucose. Homolactic fermentation of glucose by L. plantarum created an acidic environment with pH values below the growth boundary of L. monocytogenes. Some of the variants were able to withstand the low pH in the mixed biofilms for a longer time than the WT and there were clear differences in survival between the variants which could not be correlated to (lactic) acid resistance alone. Adaptation to mild pH of liquid cultures during growth to stationary phase increased the acid resistance of some variants to a greater extent than of others, indicating differences in adaptive behaviour between the variants. Two variants that showed a high level of acid adaptation when grown in liquid cultures, showed also better performance in mixed species biofilms. There were no clear differences in BAC resistance between the wild type and variants in mixed biofilms. It can be concluded that acid resistant variants of L. monocytogenes show diversity in their adaptation to acidic conditions and their capacity to survive in mixed cultures and biofilms with L. plantarum.
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Affiliation(s)
- Karin I Metselaar
- Top Institute Food and Nutrition, P.O. Box 557, 6700 AN Wageningen, The Netherlands; Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands
| | - Paula Saá Ibusquiza
- Top Institute Food and Nutrition, P.O. Box 557, 6700 AN Wageningen, The Netherlands; Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands
| | - Angela R Ortiz Camargo
- Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands
| | - Myriam Krieg
- Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands
| | - Marcel H Zwietering
- Top Institute Food and Nutrition, P.O. Box 557, 6700 AN Wageningen, The Netherlands; Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands
| | - Heidy M W den Besten
- Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands
| | - Tjakko Abee
- Top Institute Food and Nutrition, P.O. Box 557, 6700 AN Wageningen, The Netherlands; Laboratory of Food Microbiology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
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Giaouris E, Chorianopoulos N, Nychas GJ. Acquired acid adaptation of Listeria monocytogenes during its planktonic growth enhances subsequent survival of its sessile population to disinfection with natural organic compounds. Food Res Int 2014; 64:896-900. [PMID: 30011730 DOI: 10.1016/j.foodres.2014.08.044] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [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: 05/30/2014] [Revised: 08/19/2014] [Accepted: 08/30/2014] [Indexed: 12/20/2022]
Abstract
The abilities of Listeria monocytogenes to adapt to stress and also to attach to surfaces are believed to contribute to its persistence in food processing environments. In this study, the possible influence of acid adaptation of L. monocytogenes cells during their planktonic growth on their subsequent resistance against 3 different natural disinfection treatments (0.05% lactic acid, 1% essential oil or 100% hydrosol of S. thymbra) upon their attachment to stainless steel (SS) was evaluated by simultaneously using the bead vortexing technique and a conductance method. Prior to disinfection, both nonadapted and acid-adapted stationary phase bacteria were left to attach to SS coupons statically incubated for 10days into Brain Heart Infusion (BHI) broth under 3 different temperatures (5, 16 or 30°C). Results revealed that both essential oil and hydrosol presented sufficient bactericidal activity against all formed sessile populations, always resulting in counts following disinfection below the plate counting detection limit. However, the conductance method, able to detect metabolically active sessile bacteria unable to be recovered by the bead vortexing, revealed the positive influence of previously acquired acid adaptation on disinfection resistance of attached cells against these plant extracts. A similar effect of acid adaptation was also evident for lactic acid disinfection.
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Affiliation(s)
- Efstathios Giaouris
- Department of Food Science and Nutrition, Faculty of the Environment, University of the Aegean, Mitropoliti Ioakeim 2, Myrina 81400, Lemnos Island, Greece.
| | - Nikos Chorianopoulos
- Veterinary Research Institute of Athens, Greek Agricultural Organization "Demeter", Neapoleos 25, Aghia Paraskevi 15310, Greece
| | - George-John Nychas
- Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, Faculty of Foods, Biotechnology and Development, Agricultural University of Athens (AUA), Iera Odos 75, Athens 11855, Greece
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Giaouris E, Chorianopoulos N, Nychas GJ. Impact of acid adaptation on attachment of Listeria monocytogenes to stainless steel during long-term incubation under low or moderate temperature conditions and on subsequent recalcitrance of attached cells to lethal acid treatments. Int J Food Microbiol 2013; 171:1-7. [PMID: 24296256 DOI: 10.1016/j.ijfoodmicro.2013.11.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [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: 09/25/2013] [Revised: 11/06/2013] [Accepted: 11/11/2013] [Indexed: 10/26/2022]
Abstract
This study aimed to evaluate the possible impact of acid adaptation of Listeria monocytogenes cells on their attachment to stainless steel (SS) during long-term incubation under either low or moderate temperature conditions and on the subsequent recalcitrance of attached cells to lethal acid treatments. Initially, nonadapted or acid-adapted stationary phase L. monocytogenes cells were used to inoculate (ca. 10⁸ CFU/ml) brain-heart infusion (BHI) broth in test tubes containing vertically placed SS coupons. Incubation was carried out at either 5 or 30 °C for up to 15 days, under static conditions. On the 5th, 10th and 15th days of incubation, attached cells were subjected to lethal acid treatments by exposing them, for either 6 or 60 min, to pH 2, adjusted with either hydrochloric or lactic acid. Following the acid treatments, remaining viable cells were detached (through strong vortexing with glass beads) and enumerated by agar plating, and also indirectly quantified by conductance measurements via their metabolic activity. Results obtained from both quantification techniques, employed here in parallel, revealed that although the numbers of attached cells for nonadapted and acid-adapted ones were similar, the latter were found to present significantly (p<0.05) increased recalcitrance to all the acid treatments for both incubation temperatures and all sampling days. In addition and regardless of acid adaptation, when long (60 min) acid treatments were applied, conductance measurements revealed that the weak organic lactic acid exhibited significantly (p<0.05) stronger antilisterial activity compared to the strong inorganic hydrochloric acid (at the same pH value of 2). To conclude, present results show that acid adaptation of L. monocytogenes cells during their planktonic growth is conserved even after 15 days of incubation under both low and moderate temperature conditions, and results in the increased recalcitrance of their sessile population to otherwise lethal acid treatments. This "stress hardening" should be severely taken into account when acidic decontamination interventions are used to kill attached to equipment surfaces cells of this important pathogenic bacterium.
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Affiliation(s)
- Efstathios Giaouris
- Department of Food Science and Nutrition, Faculty of the Environment, University of the Aegean, Mitropoliti Ioakeim 2, Myrina 81400, Lemnos Island, Greece.
| | - Nikos Chorianopoulos
- Veterinary Research Institute of Athens, Greek Agricultural Organization "Demeter", Neapoleos 25, Aghia Paraskeui 15310, Greece
| | - George-John Nychas
- Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, Faculty of Foods, Biotechnology and Development, Agricultural University of Athens (AUA) Iera Odos 75, Athens 11855, Greece
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