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The Transcriptional Regulator SpxA1 Influences the Morphology and Virulence of Listeria monocytogenes. Infect Immun 2022; 90:e0021122. [PMID: 36102657 PMCID: PMC9584327 DOI: 10.1128/iai.00211-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Listeria monocytogenes is a Gram-positive facultative anaerobe and an excellent model pathogen for investigating regulatory changes that occur during infection of a mammalian host. SpxA1 is a widely conserved transcriptional regulator that induces expression of peroxide-detoxifying genes in L. monocytogenes and is thus required for aerobic growth. SpxA1 is also required for L. monocytogenes virulence, although the SpxA1-dependent genes important in this context remain to be identified. Here, we sought to investigate the role of SpxA1 in a tissue culture model of infection and made the surprising discovery that ΔspxA1 cells are dramatically elongated during growth in the host cytosol. Quantitative microscopy revealed that ΔspxA1 cells also form elongated filaments extracellularly during early exponential phase in rich medium. Scanning and transmission electron microscopy analysis found that the likely cause of this morphological phenotype is aberrantly placed division septa localized outside cell midpoints. Quantitative mass spectrometry of whole-cell lysates identified SpxA1-dependent changes in protein abundance, including a significant number of motility and flagellar proteins that were depleted in the ΔspxA1 mutant. Accordingly, we found that both the filamentation and the lack of motility contributed to decreased phagocytosis of ΔspxA1 cells by macrophages. Overall, we identify a novel role for SpxA1 in regulating cell elongation and motility, both of which impact L. monocytogenes virulence.
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Huang SH, Hsieh MS, Hu SY, Huang SC, Tsai CA, Hsu CY, Lin TC, Lee YC, Liao SH. Performance of Scoring Systems in Predicting Clinical Outcomes in Patients with Bacteremia of Listeria monocytogenes: A 9-Year Hospital-Based Study. BIOLOGY 2021; 10:1073. [PMID: 34827066 PMCID: PMC8615254 DOI: 10.3390/biology10111073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 10/15/2021] [Accepted: 10/18/2021] [Indexed: 11/16/2022]
Abstract
BACKGROUND Listeria monocytogenes (LM) is a facultative anaerobe, Gram-positive bacillus which is widely distributed in nature, and can be separated from soil, water, and rotten vegetables. Immunocompetent people are less likely to suffer from LM infection or may only show gastrointestinal symptoms. However, immunocompromised elderly people, pregnant women, and newborns may develop life-threatening invasive infections. The mortality rate of LM infection is as high as 25-30%. The aim of this study is to investigate clinical scores of patients with bacteremia of LM confirmed by one or more blood cultures. We analyzed their demographics and laboratory findings in relation to their clinical outcomes. MATERIALS AND METHODS This was a hospital-based retrospective study on patients with bacteremia of LM. Data were collected from the electronic clinical database of Taichung Veterans General Hospital between January 2012 and December 2020. Bacteremia of LM was confirmed by at least one blood culture. Demographics, clinical characteristics, and laboratory data were collected for analysis. A variety of clinical scoring systems were used to predict the clinical outcome. RESULTS A total of 39 patients had confirmed bacteremia of LM. Among them, 1 neonatal patient was excluded. The remaining 38 patients were studied. They included 16 males (42.1%) and 22 females (57.9%), with a mean age of 59.9 ± 19.6 years. Their hospital stay averaged 23.3 ± 20.9 days. The in-hospital mortality rate was 36.8%. Mortality in Emergency Department Sepsis (MEDS) Score was 6.6 ± 4.0 for survivors and 12.4 ± 4.4 for non-survivors (P < 0.001). The National Early Warning Score (NEWS) was 3.9 ± 2.8 for survivors and 7.8 ± 3.1 for non-survivors (P = 0.001). Regarding the prediction of mortality risk, the AUC of ROC was 0.829 for MEDS and 0.815 for NEWS. CONCLUSIONS MEDS and NEWS were both good predictors of the clinical outcome in LM bacteremic patients. In those with higher scores of MEDS (≥10) and NEWS (≥8), we recommended an early goal-directed therapy and appropriate antibiotic treatment as early as possible to reduce mortality. Further large-scale studies are required to gain a deeper understanding of this disease and to ensure patient safety.
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Affiliation(s)
- Shang-Hsuan Huang
- Department of Emergency Medicine, Taichung Veterans General Hospital, Taichung 40705, Taiwan; (S.-H.H.); (T.-C.L.)
- Department of Emergency Medicine, Taichung Armed Forces General Hospital, Taichung 40466, Taiwan
| | - Ming-Shun Hsieh
- Department of Emergency Medicine, Taipei Veterans General Hospital, Taoyuan Branch, Taoyuan 330, Taiwan; (M.-S.H.); (Y.-C.L.)
- Department of Emergency Medicine, Taipei Veterans General Hospital, Taipei 11217, Taiwan
- School of Medicine, National Yang Ming Chiao Tung University, Taipei 11221, Taiwan
| | - Sung-Yuan Hu
- Department of Emergency Medicine, Taichung Veterans General Hospital, Taichung 40705, Taiwan; (S.-H.H.); (T.-C.L.)
- School of Medicine, National Yang Ming Chiao Tung University, Taipei 11221, Taiwan
- School of Medicine, National Chung Hsing University, Taichung 402, Taiwan
- School of Medicine, Chung Shan Medical University, Taichung 40201, Taiwan;
- Institute of Medicine, Chung Shan Medical University, Taichung 40201, Taiwan
- Department of Nursing, College of Health, National Taichung University of Science and Technology, Taichung 404, Taiwan
| | - Shih-Che Huang
- School of Medicine, Chung Shan Medical University, Taichung 40201, Taiwan;
- Department of Emergency Medicine, Chung Shan Medical University Hospital, Taichung 40201, Taiwan
- Lung Cancer Research Center, Chung Shan Medical University Hospital, Taichung 40201, Taiwan
| | - Che-An Tsai
- Division of Infectious Disease, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung 40705, Taiwan;
| | - Chiann-Yi Hsu
- Biostatistics Task Force, Department of Medical Research, Taichung Veterans General Hospital, Taichung 40705, Taiwan;
| | - Tzu-Chieh Lin
- Department of Emergency Medicine, Taichung Veterans General Hospital, Taichung 40705, Taiwan; (S.-H.H.); (T.-C.L.)
- School of Medicine, National Chung Hsing University, Taichung 402, Taiwan
- School of Medicine, Chung Shan Medical University, Taichung 40201, Taiwan;
| | - Yi-Chen Lee
- Department of Emergency Medicine, Taipei Veterans General Hospital, Taoyuan Branch, Taoyuan 330, Taiwan; (M.-S.H.); (Y.-C.L.)
| | - Shu-Hui Liao
- Department of Pathology and Laboratory, Taipei Veterans General Hospital, Taoyuan Branch, Taoyuan 330, Taiwan;
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Alinda SD, Margono A, Putranto AW, Maharti ID, Amalina R, Rahmi SF. The Comparison of Biofilm Formation, Mechanical and Chemical Properties between Glass Ionomer Cement and Giomer. Open Dent J 2021. [DOI: 10.2174/1874210602115010274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aims:
The aim of this study was to compare compressive strength and its correlation with the surface morphology and chemical elements of GIC and Giomer, as well as to determine the fluoride amount effect on the bacterial biofilm formation of GIC and Giomer.
Background:
The liability of Glass Ionomer Cement (GIC) mechanical properties is overcome with better antibacterial properties among restorative materials. Another fluoride-releasing restorative material, such as Giomer, has been discovered and is expected to overcome the issues with GIC’s mechanical properties; however, no research has been conducted related to antibacterial properties in Giomer.
Objective:
To compare compressive strength and its correlation with the surface morphology and chemical elements, then determine the fluoride amount effect on the bacterial biofilm formation of GIC and Giomer.
Methods:
Sixteen specimens of GIC and Giomer were prepared for a compressive strength measurement with the Universal Testing Machine. Sixteen specimens of GIC and Giomer were incubated for three days with the Streptococcus mutans culture at 37°C. The bacterial colonization was calculated using the Colony Forming Unit (CFU) and bacterial adhesion was calculated using a Scanning Electron Microscope (SEM). The mechanical properties’ compressive strength measurement, surface morphology, and chemical elements analyses were performed using SEM-EDX.
Results:
The compressive strength of Giomer was higher than GIC (P=0.001). The higher compressive strength of Giomer was reflected by a predominant regular surface, fewer voids, smaller and denser particles, and a higher content of silica and carbon. The bacterial biofilm on the surface of Giomer was higher than GIC, although there was no significant difference. GIC and Giomer have identical chemical elements: C, O, F, Na, Al, Si, P, and Ca.
Conclusion:
The compressive strength of Giomer is better than GIC; however, the biofilm formation of Giomer is higher than GIC, whereas GIC has a higher fluoride content but inferior in surfaces morphology characteristic
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Novickij V, Stanevičienė R, Gruškienė R, Badokas K, Lukša J, Sereikaitė J, Mažeika K, Višniakov N, Novickij J, Servienė E. Inactivation of Bacteria Using Bioactive Nanoparticles and Alternating Magnetic Fields. NANOMATERIALS 2021; 11:nano11020342. [PMID: 33573001 PMCID: PMC7911490 DOI: 10.3390/nano11020342] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 01/18/2021] [Accepted: 01/26/2021] [Indexed: 12/19/2022]
Abstract
Foodborne pathogens are frequently associated with risks and outbreaks of many diseases; therefore, food safety and processing remain a priority to control and minimize these risks. In this work, nisin-loaded magnetic nanoparticles were used and activated by alternating 10 and 125 mT (peak to peak) magnetic fields (AMFs) for biocontrol of bacteria Listeria innocua, a suitable model to study the inactivation of common foodborne pathogen L. monocytogenes. It was shown that L. innocua features high resistance to nisin-based bioactive nanoparticles, however, application of AMFs (15 and 30 min exposure) significantly potentiates the treatment resulting in considerable log reduction of viable cells. The morphological changes and the resulting cellular damage, which was induced by the synergistic treatment, was confirmed using scanning electron microscopy. The thermal effects were also estimated in the study. The results are useful for the development of new methods for treatment of the drug-resistant foodborne pathogens to minimize the risks of invasive infections. The proposed methodology is a contactless alternative to the currently established pulsed-electric field-based treatment in food processing.
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Affiliation(s)
- Vitalij Novickij
- Faculty of Electronics, Vilnius Gediminas Technical University, 03227 Vilnius, Lithuania;
- Correspondence: (V.N.); (E.S.)
| | - Ramunė Stanevičienė
- Laboratory of Genetics, Nature Research Centre, 08412 Vilnius, Lithuania; (R.S.); (J.L.)
| | - Rūta Gruškienė
- Faculty of Fundamental Sciences, Vilnius Gediminas Technical University, 10223 Vilnius, Lithuania; (R.G.); (J.S.)
| | - Kazimieras Badokas
- Institute of Photonics and Nanotechnology, Vilnius University, 10257 Vilnius, Lithuania;
| | - Juliana Lukša
- Laboratory of Genetics, Nature Research Centre, 08412 Vilnius, Lithuania; (R.S.); (J.L.)
| | - Jolanta Sereikaitė
- Faculty of Fundamental Sciences, Vilnius Gediminas Technical University, 10223 Vilnius, Lithuania; (R.G.); (J.S.)
| | - Kęstutis Mažeika
- Center for Physical Sciences and Technology, 02300 Vilnius, Lithuania;
| | - Nikolaj Višniakov
- Faculty of Mechanics, Vilnius Gediminas Technical University, 03224 Vilnius, Lithuania;
| | - Jurij Novickij
- Faculty of Electronics, Vilnius Gediminas Technical University, 03227 Vilnius, Lithuania;
| | - Elena Servienė
- Laboratory of Genetics, Nature Research Centre, 08412 Vilnius, Lithuania; (R.S.); (J.L.)
- Faculty of Fundamental Sciences, Vilnius Gediminas Technical University, 10223 Vilnius, Lithuania; (R.G.); (J.S.)
- Correspondence: (V.N.); (E.S.)
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Boucher C, Waite-Cusic J, Stone D, Kovacevic J. Relative performance of commercial citric acid and quaternary ammonium sanitizers against Listeria monocytogenes under conditions relevant to food industry. Food Microbiol 2021; 97:103752. [PMID: 33653525 DOI: 10.1016/j.fm.2021.103752] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 11/16/2022]
Abstract
Growth of Listeria monocytogenes in cold temperatures coupled with its tolerance of antimicrobials can promote its survival and persistence in food processing environments. The food industry relies heavily on cleaning and sanitation to control L. monocytogenes; therefore, it is important to understand the environmental context (i.e., temperature) on the efficacy of antimicrobials used in food industry. The minimum bactericidal concentrations (MBCs) of an "eco-friendly" citric acid-based (CAB) sanitizer and a conventional quaternary ammonium compound (CQAC) sanitizer were determined against 14 L. monocytogenes isolates at 4-30 °C. A subset of isolates (n = 3) was also exposed to sub-lethal concentrations of sanitizers to assess differences in growth behavior. CAB and CQAC were effective at manufacturer recommended concentrations in liquid assays. The MBC of CAB was significantly lower at 4 °C compared to 23 °C (p < 0.05), whereas the MBC of CQAC was unchanged between 4 °C and 23 °C. Manufacturers' recommendations for dose and duration of CAB and CQAC were unable to consistently achieve a >5-log reduction of L. monocytogenes attached to surfaces. Findings from this study demonstrate the importance of sanitizer evaluation under conditions representative of their use in the food industry.
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Affiliation(s)
- Cara Boucher
- Food Innovation Center, 1207 NW Naito Parkway, Oregon State University, Portland, OR, 97209, USA
| | - Joy Waite-Cusic
- Department of Food Science and Technology, 100 Wiegand Hall, Oregon State University, Corvallis, OR, 97331, USA
| | - David Stone
- Food Innovation Center, 1207 NW Naito Parkway, Oregon State University, Portland, OR, 97209, USA
| | - Jovana Kovacevic
- Food Innovation Center, 1207 NW Naito Parkway, Oregon State University, Portland, OR, 97209, USA.
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Clemente-Carazo M, Cebrián G, Garre A, Palop A. Variability in the heat resistance of Listeria monocytogenes under dynamic conditions can be more relevant than that evidenced by isothermal treatments. Food Res Int 2020; 137:109538. [PMID: 33233166 DOI: 10.1016/j.foodres.2020.109538] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 07/06/2020] [Accepted: 07/09/2020] [Indexed: 10/23/2022]
Abstract
Heterogeneity in the response of microbial cells to environmental conditions is inherent to every biological system and can be very relevant for food safety, potentially being as important as intrinsic and extrinsic factors. However, previous studies analyzing variability in the microbial response to thermal treatments were limited to data obtained under isothermal conditions, whereas in the reality, environmental conditions are dynamic. In this article we analyse both empirically and through mathematical modelling the variability in the microbial response to thermal treatments under isothermal and dynamic conditions. Heat resistance was studied for four strains of Listeria monocytogenes (Scott A, CECT 4031, CECT 4032 and 12MOB052), in three different matrices (buffered peptone water, pH 7 Mcllvaine buffer and semi-skimmed milk). Under isothermal conditions, between-strain and between-media variability had no impact in the heat resistance, whereas it was very relevant for dynamic conditions. Therefore, the differences observed under dynamic conditions can be attributed to the variability in the ability for developing stress acclimation. The highest acclimation was observed in strain CECT 4031 (10-fold increase of the D-value), while the lowest acclimation was observed in strain CECT 4032 (50% increase of the D-value). Concerning the different media, acclimation was higher in buffered peptone water and semi-skimmed milk than in Mcllvaine buffer of pH 7.0. To the knowledge of the authors, this is the first research work that specifically analyses the variability of microbial adaptation processes that take place under dynamic conditions. It highlights that microbial heat resistance under dynamic conditions are sometimes determined by mechanisms that cannot be observed when cells are treated in isothermal conditions (e.g. acclimation) and can also be affected by variability. Consequently, empirical evidence on variability gathered under isothermal conditions should be extrapolated with care for dynamic conditions.
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Affiliation(s)
- Marta Clemente-Carazo
- Dpto. Ingeniería Agronómica, Instituto de Biotecnología Vegetal, Campus de Excelencia Internacional Regional "Campus Mare Nostrum", Escuela Técnica Superior de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Spain
| | - Guillermo Cebrián
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Instituto Agroalimentario de Aragón - IA2 - (Universidad de Zaragoza-CITA), Zaragoza, Spain
| | - Alberto Garre
- Food Microbiology, Wageningen University & Research, P.O. Box 17, 6700 AA, Wageningen, the Netherlands
| | - Alfredo Palop
- Dpto. Ingeniería Agronómica, Instituto de Biotecnología Vegetal, Campus de Excelencia Internacional Regional "Campus Mare Nostrum", Escuela Técnica Superior de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Spain.
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8
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Growth delay analysis of heat-injured Salmonella Enteritidis in ground beef by real-time PCR. Lebensm Wiss Technol 2018. [DOI: 10.1016/j.lwt.2017.12.066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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9
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Belda-Galbis CM, Jiménez-Carretón A, Pina-Pérez MC, Martínez A, Rodrigo D. Antimicrobial activity of açaí against Listeria innocua. Food Control 2015. [DOI: 10.1016/j.foodcont.2015.01.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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10
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High resolution scanning electron microscopy of cells using dielectrophoresis. PLoS One 2014; 9:e104109. [PMID: 25089528 PMCID: PMC4121316 DOI: 10.1371/journal.pone.0104109] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 07/08/2014] [Indexed: 12/02/2022] Open
Abstract
Ultrastructural analysis of cells can reveal valuable information about their morphological, physiological, and biochemical characteristics. Scanning electron microscopy (SEM) has been widely used to provide high-resolution images from the surface of biological samples. However, samples need to be dehydrated and coated with conductive materials for SEM imaging. Besides, immobilizing non-adherent cells during processing and analysis is challenging and requires complex fixation protocols. In this work, we developed a novel dielectrophoresis based microfluidic platform for interfacing non-adherent cells with high-resolution SEM at low vacuum mode. The system enables rapid immobilization and dehydration of samples without deposition of chemical residues over the cell surface. Moreover, it enables the on-chip chemical stimulation and fixation of immobilized cells with minimum dislodgement. These advantages were demonstrated for comparing the morphological changes of non-budding and budding yeast cells following Lyticase treatment.
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11
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Noriega E, Velliou EG, Van Derlinden E, Mertens L, Van Impe JFM. Role of growth morphology in the formulation of NaCl-based selective media for injury detection of Escherichia coli, Salmonella Typhimurium and Listeria innocua. Food Res Int 2014; 64:402-411. [PMID: 30011667 DOI: 10.1016/j.foodres.2014.06.047] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 06/26/2014] [Accepted: 06/29/2014] [Indexed: 11/26/2022]
Abstract
Sublethal injury (SI) poses major public health concerns since injured cells are responsible for serious limitations in food diagnostics and are susceptible to recovery, often developing adaptive stress responses. Detection of SI is based on the difference in plate counts between non-selective media, which represent the total cell population, and selective media, to which injured cells become sensitive. Selective media for detection of sublethal membrane damage are often based on NaCl supplement, although there is a lack of consensus in the literature about appropriate levels. Planktonic cells are generally used to investigate SI mechanisms, although they often exhibit different stress tolerance than cell colonies in/on solid food (model) systems. In this work, the effect of growth morphology, colony size and concentration of the gelling agent in the growth media, on the maximum non-inhibitory NaCl concentration in the plating medium was assessed for Escherichia coli, Salmonella Typhimurium and Listeria innocua. Stationary phase cultures of planktonic cells and large and small colonies grown in either 1.5% (w/v) xanthan gum-based system or 2.5% (w/v) xanthan gum-based system exhibited significantly different viable counts and osmotolerance. The effect of cell arrangement and xanthan gum percentage in the growth media depended on the microorganism under investigation. Additionally, differences in the maximum non-inhibitory concentration were evident, with 5.0% (w/v) NaCl for the Gram-negative bacteria and 6.5% (w/v), for L. innocua. Different extent of colony shrinkage and morphological damage was observed as NaCl concentration in the plating medium increased. This information will contribute to define NaCl-based selective media for accurate SI detection under realistic scenarios.
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Affiliation(s)
- Estefanía Noriega
- CPMF(2) - Flemish Cluster Predictive Microbiology in Foods, http://www.cpmf2.be, Belgium; BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
| | - Eirini G Velliou
- CPMF(2) - Flemish Cluster Predictive Microbiology in Foods, http://www.cpmf2.be, Belgium; BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
| | - Eva Van Derlinden
- CPMF(2) - Flemish Cluster Predictive Microbiology in Foods, http://www.cpmf2.be, Belgium; BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
| | - Laurence Mertens
- CPMF(2) - Flemish Cluster Predictive Microbiology in Foods, http://www.cpmf2.be, Belgium; BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
| | - Jan F M Van Impe
- CPMF(2) - Flemish Cluster Predictive Microbiology in Foods, http://www.cpmf2.be, Belgium; BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
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Aguirre JS, Monis A, García de Fernando GD. Improvement in the lag phase estimation of individual cells that have survived mild heat treatment. Int J Food Sci Technol 2013. [DOI: 10.1111/ijfs.12382] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Juan S. Aguirre
- Grupo de Tecnología de los Alimentos de Origen Animal; Depto. Nutrición, Bromatología y Tecnología de los Alimentos; Facultad de Veterinaria; Universidad Complutense; Ciudad Universitaria; Madrid 28040 Spain
| | - Almira Monis
- Grupo de Tecnología de los Alimentos de Origen Animal; Depto. Nutrición, Bromatología y Tecnología de los Alimentos; Facultad de Veterinaria; Universidad Complutense; Ciudad Universitaria; Madrid 28040 Spain
| | - Gonzalo D. García de Fernando
- Grupo de Tecnología de los Alimentos de Origen Animal; Depto. Nutrición, Bromatología y Tecnología de los Alimentos; Facultad de Veterinaria; Universidad Complutense; Ciudad Universitaria; Madrid 28040 Spain
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Belda-Galbis CM, Pina-Pérez MC, Espinosa J, Marco-Celdrán A, Martínez A, Rodrigo D. Use of the modified Gompertz equation to assess the Stevia rebaudiana Bertoni antilisterial kinetics. Food Microbiol 2013; 38:56-61. [PMID: 24290626 DOI: 10.1016/j.fm.2013.08.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 06/27/2013] [Accepted: 08/15/2013] [Indexed: 11/27/2022]
Abstract
In order to assess the antibacterial activity of Stevia rebaudiana Bertoni (Stevia), Listeria innocua growth was characterized at 37 °C, in reference medium supplemented with a leaf infusion, a crude extract, and a steviol glycosides purified extract. Experimental data were fitted to the modified Gompertz model and the antibacterial activity of Stevia was determined based on the lag time (λ) and the maximum growth rate (μmax) reached, depending on the incubation conditions. As the leaf infusion showed the most marked elongation of λ and the most marked μmax reduction, its antimicrobial effect was evaluated at different concentrations, at 37, 22 and 10 °C. According to the results obtained, in general, the lower the temperature or the higher the Stevia concentration, the longer the λ and the lower the μmax, statistically significant being the effect of reducing temperature from 37 or 22 to 10 °C, the effect of increasing Stevia concentration from 0 or 0.5 to 1.5 or 2.5% (w/v), at 37 °C, and the elongation of λ observed in presence of 1.5 and 2.5% (w/v) of Stevia, at 22 °C. These results show that Stevia could be a bacterial growth control measure if a cold chain failure occurs.
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Affiliation(s)
- Clara Miracle Belda-Galbis
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC), Carrer del Catedràtic Agustín Escardino Benlloch 7, 46980, Paterna, València, Spain
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Noriega E, Velliou E, Van Derlinden E, Mertens L, Van Impe JFM. Effect of cell immobilization on heat-induced sublethal injury of Escherichia coli, Salmonella Typhimurium and Listeria innocua. Food Microbiol 2013; 36:355-64. [PMID: 24010617 DOI: 10.1016/j.fm.2013.06.015] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 05/15/2013] [Accepted: 06/14/2013] [Indexed: 10/26/2022]
Abstract
The occurrence of sublethally injured cells in foods poses major public health concerns and is an essential aspect when assessing the microbial response to food preservation strategies, yet there is limited research dealing with its specific implications for mild heating. All available studies so far have been performed in broths colonized by planktonic cells, although their susceptibility to lethal agents has often been reported to be markedly different to the stress tolerance of cell colonies developed in solid foods. In this work, the effect of planktonic and colony growth, as well as the influence of colony density on sublethal injury induced by mild heating of Escherichia coli, Salmonella Typhimurium and Listeria innocua were assessed in food model systems. Detection of injured survivors relied on their inability to form visible colonies on salt-based selective media, which do not affect the growth of healthy cells. Sublethal injury (SI) increased rapidly with shorter exposure times and afterwards, decreased progressively, suggesting a mechanism of cumulative damage triggering lethal instead of SI. Cell arrangement affected the degree of SI, higher values being generally found for gelified systems, although the effect of colony density depended on the target microorganism. This information is essential for optimizing the design of food safety assurance systems.
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Vasan A, Leong WM, Ingham SC, Ingham BH. Thermal tolerance characteristics of non-O157 Shiga toxigenic strains of Escherichia coli (STEC) in a beef broth model system are similar to those of O157:H7 STEC. J Food Prot 2013; 76:1120-8. [PMID: 23834785 DOI: 10.4315/0362-028x.jfp-12-500] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The non-O157 Shiga toxigenic Escherichia coli (STEC) serogroups most commonly associated with illness are O26, O45, O103, O111, O121, and O145. In the United States, these serogroups are considered adulterants in raw nonintact beef. To begin to understand the behavior of these pathogens in meat systems, we compared the thermal tolerance of acid-adapted cells of non-O157 STEC and O157:H7 STEC in a beef-derived broth. D58°C-values were determined for at least three strains per serogroup, and D54.6°C-values and D63.6°C-values were determined for one strain per serogroup. Each strain was grown to stationary phase in brain heart infusion broth (BHIB; pH 7.0) and inoculated into prewarmed BHIB in a shaking water bath for thermotolerance experiments at 54.6, 58.0, or 63.6°C (three trials per strain). Samples were heated for up to 160 min at 54.6°C, 3 min at 58.0°C, or 45 s at 63.6°C, with periodic sampling followed by rapid cooling and plating on modified Levine's eosin methylene blue agar. For each strain and temperature, the log CFU per milliliter was plotted versus time, and D-values were determined. Across all strains, the least and most heat tolerant STEC serogroups at 58°C were O145 and O157, respectively. D58°C-values in BHIB ranged from 0.44 min for an O145 strain to 1.42 min for an O157:H7 strain. D58°C-values for O157 STEC strains were significantly higher than those for at least one strain in each of the non-O157 STEC serogroups (P < 0.05) except for serogroup O103. At 54.6°C, the most heat-resistant STEC strain belonged to serogroup O103 and was significantly more heat tolerant than the O157:H7 strains (P < 0.05). Grouping the strains, there were no significant differences in heat tolerance between O157 and non-O157 STEC at 63.6°C (P ≥ 0.05). The z-values for non-O157 STEC strains were comparable to those for O157:H7 STEC strains (P ≥ 0.05), ranging from 4.10 to 5.21°C. These results suggest that thermal processing interventions that target destruction of E. coli O157:H7 may have adequate lethality against non-O157 STEC.
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Affiliation(s)
- Akhila Vasan
- Department of Food Science, University of Wisconsin-Madison, 1605 Linden Drive, Madison, Wisconsin 53706, USA
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van Lieverloo JHM, de Roode M, Fox MB, Zwietering MH, Wells-Bennik MH. Multiple regression model for thermal inactivation of Listeria monocytogenes in liquid food products. Food Control 2013. [DOI: 10.1016/j.foodcont.2012.05.078] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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17
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Studies on the pathogenesis and survival of different culture forms of Listeria monocytogenes to pulsed UV-light irradiation after exposure to mild-food processing stresses. Food Microbiol 2012; 30:330-9. [DOI: 10.1016/j.fm.2011.12.024] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 12/27/2011] [Accepted: 12/28/2011] [Indexed: 12/22/2022]
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18
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Felício MTS, Ramalheira R, Ferreira V, Brandão T, Silva J, Hogg T, Teixeira P. Thermal inactivation of Listeria monocytogenes from alheiras, traditional Portuguese sausage during cooking. Food Control 2011. [DOI: 10.1016/j.foodcont.2011.05.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19
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Aguirre JS, Rodríguez MR, García de Fernando GD. Effects of electron beam irradiation on the variability in survivor number and duration of lag phase of four food-borne organisms. Int J Food Microbiol 2011; 149:236-46. [DOI: 10.1016/j.ijfoodmicro.2011.07.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 04/12/2011] [Accepted: 07/03/2011] [Indexed: 11/26/2022]
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20
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Dunkel J, Talbot J, Schötz EM. Memory and obesity affect the population dynamics of asexual freshwater planarians. Phys Biol 2011; 8:026003. [PMID: 21263170 DOI: 10.1088/1478-3975/8/2/026003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Asexual reproduction in multicellular organisms is a complex biophysical process that is not yet well understood quantitatively. Here, we report a detailed population study for the asexual freshwater planarian Schmidtea mediterranea, which can reproduce via transverse fission due to a large stem cell contingent. Our long-term observations of isolated non-interacting planarian populations reveal that the characteristic fission waiting time distributions for head and tail fragments differ significantly from each other. The stochastic fission dynamics of tail fragments exhibits non-negligible memory effects, implying that an accurate mathematical description of future data should be based on non-Markovian tree models. By comparing the effective growth of non-interacting planarian populations with those of self-interacting populations, we are able to quantify the influence of interactions between flatworms and physical conditions on the population growth. A surprising result is the non-monotonic relationship between effective population growth rate and nutrient supply: planarians exhibit a tendency to become 'obese' if the feeding frequency exceeds a critical level, resulting in a decreased reproduction activity. This suggests that these flatworms, which possess many genes homologous to those of humans, could become a new model system for studying dietary effects on reproduction and regeneration in multicellular organisms.
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Affiliation(s)
- Jörn Dunkel
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, UK.
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21
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Halder A, Black DG, Davidson PM, Datta A. Development of associations and kinetic models for microbiological data to be used in comprehensive food safety prediction software. J Food Sci 2011; 75:R107-20. [PMID: 20722946 DOI: 10.1111/j.1750-3841.2010.01687.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The objective of this study was to use an existing database of food products and their associated processes, link it with a list of the foodborne pathogenic microorganisms associated with those products and finally identify growth and inactivation kinetic parameters associated with those pathogens. The database was to be used as a part of the development of comprehensive software which could predict food safety and quality for any food product. The main issues in building such a predictive system included selection of predictive models, associations of different food types with pathogens (as determined from outbreak histories), and variability in data from different experiments. More than 1000 data sets from published literature were analyzed and grouped according to microorganisms and food types. Final grouping of data consisted of the 8 most prevalent pathogens for 14 different food groups, covering all of the foods (>7000) listed in the USDA Natl. Nutrient Database. Data for each group were analyzed in terms of 1st-order inactivation, 1st-order growth, and sigmoidal growth models, and their kinetic response for growth and inactivation as a function of temperature were reported. Means and 95% confidence intervals were calculated for prediction equations. The primary advantage in obtaining group-specific kinetic data is the ability to extend microbiological growth and death simulation to a large array of product and process possibilities, while still being reasonably accurate. Such simulation capability could provide vital ''what if'' scenarios for industry, Extension, and academia in food safety.
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Affiliation(s)
- Amit Halder
- Biological and Environmental Engineering, Cornell Univ., Ithaca, NY 14853, USA
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22
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Szlachta K, Keller SE, Shazer A, Chirtel S. Thermal resistance of Listeria monocytogenes Scott A in ultrafiltered milk as related to the effect of different milk components. J Food Prot 2010; 73:2110-5. [PMID: 21219727 DOI: 10.4315/0362-028x-73.11.2110] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Pasteurization parameters for grade A milk are well established and set by regulation. However, as solids levels increase, an increased amount of heat is required to destroy any pathogens present. This effect is not well characterized. In this work, the effect of increased dairy solids levels on the thermal resistance of Listeria monocytogenes was examined through the use of ultrafiltered (UF) milk, reconstituted milk powder, and the milk components lactose and caseinate. From the results obtained, lactose and caseinate did not appear to affect thermal resistance. In addition, the level of milk fat, up to 10% of the total solids in UF whole milk, did not result in statistically significant changes to thermal resistance when compared with UF skim milk. Reconstituted skim milk powder at 27% total solids (D⁶²-value = 1.16 ± 0.2 [SD] min, z = 5.7) did result in increased thermal resistance, as compared with reconstituted skim milk powder at 17.5% (D⁶²-value = 0.86 ± 0.02 min, z = 5.57) and UF whole milk at 27% total solids (D⁶²-value = 0.66 ± 0.07 min, z = 5.16). However, that increase appeared to be due to the increase in salt levels, not to increases in caseinate, fat, or lactose. Consequently, total solids, as a single measure, could not be used to predict increased thermal resistance of L. monocytogenes in concentrated milk.
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Affiliation(s)
- Kinga Szlachta
- Illinois Institute of Technology, Summit-Argo, Illinois 60501, USA
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23
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Ágoston R, Soni K, Jesudhasan PR, Russell WK, Mohácsi-Farkas C, Pillai SD. Differential Expression of Proteins inListeria monocytogenesUnder Thermotolerance-Inducing, Heat Shock, and Prolonged Heat Shock Conditions. Foodborne Pathog Dis 2009; 6:1133-40. [DOI: 10.1089/fpd.2009.0286] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Réka Ágoston
- Corvinus University of Budapest, Budapest, Hungary
| | - Kamlesh Soni
- Departments of Poultry Science and Nutrition and Food Science, Texas A&M University, College Station, Texas
| | - Palmy R. Jesudhasan
- Departments of Poultry Science and Nutrition and Food Science, Texas A&M University, College Station, Texas
| | - William K. Russell
- Departments of Poultry Science and Nutrition and Food Science, Texas A&M University, College Station, Texas
| | | | - Suresh D. Pillai
- Departments of Poultry Science and Nutrition and Food Science, Texas A&M University, College Station, Texas
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24
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Pina-Pérez MC, Silva-Angulo AB, Muguerza-Marquínez B, Aliaga DR, López AM. Synergistic Effect of High Hydrostatic Pressure and Natural Antimicrobials on Inactivation Kinetics ofBacillus cereusin a Liquid Whole Egg and Skim Milk Mixed Beverage. Foodborne Pathog Dis 2009; 6:649-56. [DOI: 10.1089/fpd.2009.0268] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Álvarez-Ordóñez A, Fernández A, López M, Bernardo A. Relationship between membrane fatty acid composition and heat resistance of acid and cold stressed Salmonella senftenberg CECT 4384. Food Microbiol 2009; 26:347-53. [DOI: 10.1016/j.fm.2008.11.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Revised: 11/14/2008] [Accepted: 11/15/2008] [Indexed: 11/25/2022]
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26
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Sergelidis D, Abrahim A. Adaptive response of Listeria monocytogenes to heat and its impact on food safety. Food Control 2009. [DOI: 10.1016/j.foodcont.2008.01.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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27
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Álvarez-Ordóñez A, Fernández A, López M, Arenas R, Bernardo A. Modifications in membrane fatty acid composition of Salmonella typhimurium in response to growth conditions and their effect on heat resistance. Int J Food Microbiol 2008; 123:212-9. [DOI: 10.1016/j.ijfoodmicro.2008.01.015] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Revised: 01/29/2008] [Accepted: 01/30/2008] [Indexed: 10/22/2022]
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28
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Giotis ES, Blair IS, McDowell DA. Morphological changes in Listeria monocytogenes subjected to sublethal alkaline stress. Int J Food Microbiol 2007; 120:250-8. [DOI: 10.1016/j.ijfoodmicro.2007.08.036] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 08/28/2007] [Indexed: 11/30/2022]
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29
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Van Derlinden E, Bernaerts K, Van Impe JF. Dynamics of Escherichia coli at elevated temperatures: effect of temperature history and medium. J Appl Microbiol 2007; 104:438-53. [PMID: 17931374 DOI: 10.1111/j.1365-2672.2007.03592.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS The dynamics of Escherichia coli near the maximum temperature for growth in a rich medium are analysed. The effects of temperature history, medium composition and physiological state of the inoculum are evaluated. METHODS AND RESULTS Kinetics of E. coli K12 MG1655 is studied in 'brain-heart infusion' broth in a temperature controlled environment. Based on viable counts, 'smooth' growth curves are observed at 40, 41, 42 and 43 degrees C. The exponential growth phase at 44 and 45 degrees C is interrupted. At 46 degrees C, a period of exponential growth is followed by inactivation. Neither the physiological state of the inoculum nor medium enrichment alters the dynamics, whilst temperature pre-adaptation or chemical chaperones restore regular cell growth and division ('smooth' exponential growth). CONCLUSIONS Atypical, nonexponential growth at 44, 45 and 46 degrees C seems related to protein destabilization and can (partly) be restored by an appropriate medium design (i.e. addition of chemical chaperones) or temperature history (i.e. selection of a more resistant subpopulation). SIGNIFICANCE AND IMPACT OF THE STUDY This study indicates that the maximum temperature for growth is dependent on the temperature history and the chemical environment. These observations and the nonexponential kinetics have important implications for the development of predictive models for food safety and quality.
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Affiliation(s)
- E Van Derlinden
- Chemical and Biochemical Process Technology and Control Section (BioTeC), Department of Chemical Engineering, Katholieke Universiteit Leuven, Leuven, Belgium
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30
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Folsom JP, Frank JF. Proteomic analysis of a hypochlorous acid-tolerant Listeria monocytogenes cultural variant exhibiting enhanced biofilm production. J Food Prot 2007; 70:1129-36. [PMID: 17536671 DOI: 10.4315/0362-028x-70.5.1129] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Following exposure of Listeria monocytogenes Scott A (SA) to hypochlorous acid, rough colony variants were identified that were tolerant of hypochlorous acid and produced increased amounts of biofilm. A derivative of one of these variants was smooth, produced even more biofilm, and exhibited greater biofilm chlorine resistance. The objective of this research was to compare the protein expression of a cultural variant to SA and to identify proteins that might be associated with biofilm production and chlorine tolerance. Suspension chlorine tolerance for several cultural variants (SAR, SAR5, and SBS) was determined by exposure to 60 to 120 ppm of hypochlorous acid for 5 min. Hypochlorous acid tolerance of biofilms was determined after growing biofilms on stainless steel and then exposing them to 200 ppm of hypochlorous acid for 5 min. All cultural variants were able to survive 120 ppm of hypochlorous acid in suspension. There was little difference in the hypochlorous acid tolerance of the cultural variant planktonic cells. The cultural variants produced greater amounts of biofilm than the common form of L. monocytogenes and were more tolerant of hypochlorous acid. The SBS variant was selected for proteomic comparison because it was the variant that produced the most biofilm and was the most tolerant of hypochlorous acid when grown as a biofilm. Protein expression of planktonic and biofilm cells of SBS was compared to SA by two-dimensional difference gel electrophoresis. The 50s ribosomal protein, L10, was down-regulated in biofilm SBS. Other proteins down-regulated in planktonic SBS were the peroxide resistance protein (Dpr) and a sugar-binding protein (LMO0181). This sugar-binding protein was also up-regulated in biofilm SBS. One protein spot down-regulated in planktonic SBS contained both 50s ribosomal protein L7/L12 and an unknown protein (LM01888).
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Affiliation(s)
- James P Folsom
- Department of Food Science and Technology, University of Georgia, Athens, Georgia 30602-7610, USA
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31
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Miller FA, Brandão TRS, Teixeira P, Silva CLM. Recovery of heat-injured Listeria innocua. Int J Food Microbiol 2006; 112:261-5. [PMID: 16784792 DOI: 10.1016/j.ijfoodmicro.2006.04.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/26/2006] [Indexed: 11/13/2022]
Abstract
Listeria innocua was subjected to thermal inactivation and the extent of heat-injured cells was quantified. Cultures were heated in liquid medium for different times, using temperatures in the range of 52.5 to 65.0 degrees C, and plated on Tryptic Soy Agar with 0.6% yeast extract (TSAYE) used as non-selective medium and on TSAYE plus 5% NaCl (TSAYE+NaCl) and Palcam agar with selective supplement (Palcam agar) as selective media. The difference observed in counts in non-selective and in selective media gave an indication of cell injury during the heat treatment. D- and z- values were calculated for all conditions considered. For each temperature, D-values obtained using non-selective recovery procedures were higher than the ones obtained using the two selective media. When comparing the selective media, it can be concluded that Palcam agar allowed recovery and growth of thermally injured cells and so it was less inhibitor than TSAYE+NaCl. Another important result was the influence of temperature on the degree of cellular injury. As temperature increases, the degree of heat-injured cells also increases, and consequently concern has to be taken with the temperature and the counting medium used in food processing studies. The results of this work clearly demonstrated that selective media used for Listeria monocytogenes enumeration/detection might not be suitable for the recovery of heat-injured cells, which can dangerously underestimate the presence of this foodborne pathogen.
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Affiliation(s)
- Fátima A Miller
- Universidade Católica Portuguesa, Escola Superior de Biotecnologia, Rua Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal
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Thompson LJ, Gray V, Lindsay D, von Holy A. Carbon : nitrogen : phosphorus ratios influence biofilm formation byEnterobacter cloacaeandCitrobacter freundii. J Appl Microbiol 2006; 101:1105-13. [PMID: 17040234 DOI: 10.1111/j.1365-2672.2006.03003.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS To test the effects of C : N : P ratio modification of a well-known nutrient medium formulation, the Endo formulation on biofilm formation by Enterobacter cloacae Ecl and Citrobacter freundii Cf1 in both single-species and binary species biofilms. METHODS AND RESULTS The C : N : P atom : atom ratio of a well-known nutrient medium formulation, the Endo formulation, that has been applied in fermentative biohydrogen studies, was modified to include two different C concentrations, one containing 17.65 g l(-1) and the other 8.84 g l(-1) sucrose, each containing four different C : N : P ratios, two at higher C : N : P ratios (334 : 84 : 16.8 and 334 : 84 : 3) and two at lower C : N : P ratios (334 : 28 : 5.6 and 334 : 28 : 1). Attached cells were enumerated after dislodging the biofilms that had formed on granular activated carbon (GAC). The modified medium containing 17.65 g l(-1) sucrose and having a C : N : P ratio of 334 : 28 : 5.6 resulted in significantly (P < 0.05) higher counts of attached cells for both single-species biofilms at 7.73 log(10) CFU g(-1) GAC and 9.3 log(10)CFU g(-1) GAC for Ent. cloacae Ecl and Cit. freundii Cf1, respectively, and binary species biofilms at 8.2 log(10) CFU g(-1) GAC and 6.34 log(10) CFU g(-1) GAC for Ent. cloacae Ecl and Cit. freundii Cf1, respectively. Scanning electron micrographs showed qualitative evidence that the 334 : 28 : 5.6 ratio encouraged more complex and extensive biofilm growth for both single-species and binary species biofilms. CONCLUSIONS The differences in the attachment numbers between the different ratios were found not to be a result of the individual actions of the bacterial isolates involved but rather because of the effects of the various C : N : P ratios. The 334 : 28 : 5.6 ratio showed significantly (P < 0.05) higher counts of attached cells for both single-species and binary species biofilms. SIGNIFICANCE AND IMPACT OF THE STUDY This study indicates that C : N : P ratios should be a key consideration with regard to maximizing biofilm formation in shake flask and fluidized bed bioreactor studies as well as understanding fundamental factors affecting biofilm growth in natural environments.
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Affiliation(s)
- L J Thompson
- School of Molecular and Cell Biology, University of the Witwatersrand, Gauteng, South Africa
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Guillier L, Pardon P, Augustin JC. Influence of stress on individual lag time distributions of Listeria monocytogenes. Appl Environ Microbiol 2005; 71:2940-8. [PMID: 15932988 PMCID: PMC1151854 DOI: 10.1128/aem.71.6.2940-2948.2005] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Accepted: 01/04/2005] [Indexed: 11/20/2022] Open
Abstract
The effects of nine common food industry stresses on the times to the turbidity (T(d)) distribution of Listeria monocytogenes were determined. It was established that the main source of the variability of T(d) for stressed cells was the variability of individual lag times. The distributions of T(d) revealed that there was a noticeable difference in response to the stresses encountered by the L. monocytogenes cells. The applied stresses led to significant changes of the shape, the mean, and the variance of the distributions. The variance of T(d) of wells inoculated with single cells issued from a culture in the exponential growth phase was multiplied by at least 6 and up to 355 for wells inoculated with stressed cells. These results suggest stress-induced variability may be important in determining the reliability of predictive microbiological models.
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Affiliation(s)
- L Guillier
- Unité Mixte de Recherche ENVA-INRA RISQUAL, Ecole Nationale Vétérinaire d'Alfort, 7 avenue du Général de Gaulle, F-94704 Maisons-Alfort, France.
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Zhu M, Du M, Cordray J, Ahn DU. Control of Listeria monocytogenes Contamination in Ready-to-Eat Meat Products. Compr Rev Food Sci Food Saf 2005; 4:34-42. [DOI: 10.1111/j.1541-4337.2005.tb00071.x] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Yaqub S, Anderson JG, MacGregor SJ, Rowan NJ. Use of a fluorescent viability stain to assess lethal and sublethal injury in food-borne bacteria exposed to high-intensity pulsed electric fields. Lett Appl Microbiol 2004; 39:246-51. [PMID: 15287869 DOI: 10.1111/j.1472-765x.2004.01571.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS To apply scanning electron microscopy, image analysis and a fluorescent viability stain to assess lethal and sublethal in food-borne bacteria exposed to high-intensity pulsed electric fields (PEF). METHODS AND RESULTS A rapid cellular staining method using the fluorescent redox probes 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and 4',6-diamidino-2-phylindole was used for enumerating actively respiring cells of Listeria mononcytogenes, Bacillus cereus and Escherichia coli. This respiratory staining (RS) approach provided good agreement with the conventional plate count agar method for enumerating untreated and high-intensity PEF-treated bacteria suspended in 0.1% (w/v) peptone water. However, test organisms subjected to similar levels of lethality by heating at 56 degrees C resulted in ca 3-log-unit difference in surviving cell numbers ml(-1) when enumerated by these different viability indicators. PEF-treated bacteria were markedly altered at the cellular level when examined by scanning electron microscopy. CONCLUSIONS While PEF-treatment did not produce sublethally injured cells (P < 0.05), substantial subpopulations of test bacteria rendered incapable of forming colonies by heating may remain metabolically active. SIGNIFICANCE AND IMPACT OF THE STUDY The fluorescent staining method offers interesting perspectives on assessing established and novel microbial inactivation methods. Use of this approach may also provide a better understanding of the mechanisms involved in microbial inactivation induced by PEF.
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Affiliation(s)
- S Yaqub
- Department of Bioscience, University of Strathclyde, Glasgow, UK
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Chastanet A, Derre I, Nair S, Msadek T. clpB, a novel member of the Listeria monocytogenes CtsR regulon, is involved in virulence but not in general stress tolerance. J Bacteriol 2004; 186:1165-74. [PMID: 14762012 PMCID: PMC344206 DOI: 10.1128/jb.186.4.1165-1174.2004] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clp-HSP100 ATPases are a widespread family of ubiquitous proteins that occur in both prokaryotes and eukaryotes and play important roles in the folding of newly synthesized proteins and refolding of aggregated proteins. They have also been shown to participate in the virulence of several pathogens, including Listeria monocytogenes. Here, we describe a member of the Clp-HSP100 family of L. monocytogenes that harbors all the characteristics of the ClpB subclass, which is absent in the closely related gram-positive model organism, Bacillus subtilis. Transcriptional analysis of clpB revealed a heat shock-inducible sigma(A)-type promoter. Potential binding sites for the CtsR regulator of stress response were identified in the promoter region. In vivo and in vitro approaches were used to show that expression of clpB is repressed by CtsR, a finding indicating that clpB is a novel member of the L. monocytogenes CtsR regulon. We showed that ClpB is involved in the pathogenicity of L. monocytogenes since the DeltaclpB mutant is significantly affected by virulence in a murine model of infection; we also demonstrate that this effect is apparently not due to a defect in general stress resistance. Indeed, ClpB is not involved in tolerance to heat, salt, detergent, puromycin, or cold stress, even though its synthesis is inducible by heat shock. However, ClpB was shown to play a role in induced thermotolerance, allowing increased resistance of L. monocytogenes to lethal temperatures. This work gives the first example of a clpB gene directly controlled by CtsR and describes the first role for a ClpB protein in induced thermotolerance and virulence in a gram-positive organism.
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Affiliation(s)
- Arnaud Chastanet
- Unité de Biochimie Microbienne, Institut Pasteur, CNRS URA 2172, 75724 Paris Cedex 15, France
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Mattick KL, Phillips LE, Jørgensen F, Lappin-Scott HM, Humphrey TJ. Filament formation by Salmonella spp. inoculated into liquid food matrices at refrigeration temperatures, and growth patterns when warmed. J Food Prot 2003; 66:215-9. [PMID: 12597479 DOI: 10.4315/0362-028x-66.2.215] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In this study, the formation of multicellular filamentous Salmonella cells in response to low temperatures was investigated by using isolates of Salmonella enterica serovar Enteritidis PT4 and S. enterica serovar Typhimurium DT104 as the inocula. The formation of filamentous cells in two liquid food matrices at the recommended maximum temperature for refrigeration (8 degrees C) was monitored and compared with that in tryptone soya broth. Giemsa staining was performed to locate nuclear material within the filaments. Single filaments were warmed on agar at 37 degrees C, and the subsequent rate of septation was quantified. For all strains tested, > 70% of the Salmonella cells inoculated had become filamentous after 4 days in media at 8 degrees C, indicating that filamentation could occur during the shelf life of most refrigerated foods. Strains with impaired RpoS expression were able to form filaments at 8 degrees C, although these filaments tended to be shorter and less numerous. All strains also formed filamentous cells at 8 degrees C in retail milk or chicken meat extract. Filaments often exceeded 100 microm in length and appeared straight-sided under the microscope in media and in foods, and Giemsa staining demonstrated that regularly spaced nucleoids were present. This phenotype indicates that an early block in cell septation is probably responsible for filamentation. When filaments were warmed on agar at 37 degrees C, there was a rapid completion of septation, and for one filament, a >200-fold increase in cell number was observed within 4 h. There are clear public health implications associated with the filamentation of Salmonella in contaminated foods at refrigeration temperatures, especially when the possibility of rapid septation of filamentous cells upon warming is considered.
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Affiliation(s)
- Karen L Mattick
- PHLS Food Microbiology Collaborating Laboratory, Division of Food Animal Science, University of Bristol, and House, Lower Langford Bristol BS40 5DU, UK
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Mattick KL, Rowbury RJ, Humphrey TJ. Morphological changes to Escherichia coli O157:H7, commensal E. coli and Salmonella spp in response to marginal growth conditions, with special reference to mildly stressing temperatures. Sci Prog 2003; 86:103-13. [PMID: 12838606 PMCID: PMC10368319 DOI: 10.3184/003685003783238725] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Certain rod-shaped bacteria have been reported to form elongated filamentous cells when exposed to marginal growth conditions, including refrigeration temperatures. To expand upon these observations, the filamentation of commensal Escherichia coli, E. coli O157:H7 and Salmonella spp was investigated, following exposure to certain, mildly stressing, levels of temperature, pH or water activity (aw), with levels of cellular protein being monitored during cell elongation, in some experiments. Our studies indicated that cellular filamentation could be demonstrated in all 15 strains of the above organisms tested, following exposure to marginal conditions achieved by incubation at high or low temperatures, high or low pH values and low aw. The level of environmental stress causing filamentation tended to be specific to the particular organisms. For example, Salmonella spp formed filamentous cells at 44 degrees C, whereas E. coli strains, including O157, grew by binary fission at that temperature, but formed filamentous cells at 46 degrees C. In addition, plate count techniques to enumerate bacteria during filamentation, failed to reflect the increase in cell biomass that was occurring, whereas measurements of protein concentration demonstrated the increase quite strikingly. These findings have important implications for our understanding of the ability of food-borne pathogens to cause disease, since the infectious dose of a microorganism implicated in an outbreak of such disease is typically determined by a viable count method, which could underestimate the number of potential infectious units present in a food that had been stored in such a way as to provide marginal growth conditions.
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Sörqvist S. Heat resistance in liquids of Enterococcus spp., Listeria spp., Escherichia coli, Yersinia enterocolitica, Salmonella spp. and Campylobacter spp. Acta Vet Scand 2003; 44:1-19. [PMID: 14650540 PMCID: PMC1831557 DOI: 10.1186/1751-0147-44-1] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2002] [Accepted: 10/28/2002] [Indexed: 11/19/2022] Open
Abstract
The aim of the work was to collect, evaluate, summarize and compare heat resistance data reported for Campylobacter, Enterococcus, Escherichia, Listeria, Salmonella and Yersinia spp. The work was limited to resistance in liquids with pH values 6-8. Results obtained under similar experimental conditions were sought. Thermal destruction lines for the various bacterial groups studied were constructed using log10 D values and treatment temperatures. There was a good linear relationship between log10 D and temperature with Escherichia coli, listerias and salmonellas. For campylobacters, enterococci and yersinias the relationships were weaker but, nevertheless, present. Using the slopes of the lines and their 95% confidence limits, z values and their 95% confidence limits were calculated. z values were compared with z values obtained from reports. The equations for the lines were also used for calculation of predicted means of D values at various treatment temperatures. 95% confidence limits on predicted means of D values and on predicted individual D values were also calculated. Lines and values are shown in figures and tables. Differences in heat resistance noted between and within the bacterial groups studied are discussed.
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Affiliation(s)
- S Sörqvist
- Department of Food Hygiene, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala, Sweden.
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40
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To MS, Favrin S, Romanova N, Griffiths MW. Postadaptational resistance to benzalkonium chloride and subsequent physicochemical modifications of Listeria monocytogenes. Appl Environ Microbiol 2002; 68:5258-64. [PMID: 12406712 PMCID: PMC129876 DOI: 10.1128/aem.68.11.5258-5264.2002] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2002] [Accepted: 08/05/2002] [Indexed: 11/20/2022] Open
Abstract
Many studies have demonstrated that bacteria, including Listeria monocytogenes, are capable of adapting to disinfectants used in industrial settings after prolonged exposure to sublethal concentrations. However, the consequent alterations of the cell surface due to sanitizer adaptation of this pathogen are not fully understood. Two resistant and four sensitive L. monocytogenes strains from different sources were progressively subcultured with increasing sublethal concentrations of a surfactant, benzalkonium chloride (BC). To evaluate the effects of acquired tolerance to BC, parent and adapted strains were compared by using several morphological and physiological tests. Sensitive strains showed at least a fivefold increase in the MIC, while the MIC doubled for resistant strains after the adaptation period. The hydrophobicities of cells of parent and adapted strains were similar. Serological testing indicated that antigen types 1 and 4 were both present on the cell surface of adapted cells. The data suggest that efflux pumps are the major mechanism of adaptation in sensitive strains and are less important in originally resistant isolates. A different, unknown mechanism was responsible for the original tolerance of resistant isolates. In an originally resistant strain, there was a slight shift in the fatty acid profile after adaptation, whereas sensitive strains had similar profiles. Electron micrographs revealed morphological differences after adaptation. The changes in cell surface antigens, efflux pump utilization, and fatty acid profiles suggest that different mechanisms are used by resistant and sensitive strains for adaptation to BC.
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Affiliation(s)
- Monica S To
- Department of Food Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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41
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Lenz LL, Portnoy DA. Identification of a second Listeria secA gene associated with protein secretion and the rough phenotype. Mol Microbiol 2002; 45:1043-56. [PMID: 12180923 DOI: 10.1046/j.1365-2958.2002.03072.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We describe the identification and characterization of a second secA gene in Listeria monocytogenes. This gene, termed secA2, is involved in smooth-rough phenotypic variation and secA2 expression contributes to bacterial virulence. Spontaneous rough (R-) variants of L. monocytogenes grow in chains and form rough colonies on solid media. A subset of R-variants, classified here as type I, also shows reduced secretion of an autolysin, p60. We find that disruptions and in frame deletions in secA2 confer phenotypes identical to those of spontaneous type I R-variants. Additionally, the secA2 genes from two spontaneous type I R-variants encoded truncated SecA2 proteins. Mutations were not found in the secA2 genes from the remaining five independent R-variants, four of which showed a distinct (type II) rough morphology and secreted wild-type levels of p60. Expression of an epitope-tagged SecA2 in the DeltasecA2 strain and a spontaneous R-variant restored normal cell septation and smooth colony morphology. These data suggest that mutations in both secA2 and other genes contribute to smooth-rough phase variation in L. monocytogenes. Expression of the full-length SecA2 also promotes secretion of p60 and a set of additional L. monocytogenes proteins. We hypothesize that SecA2-dependent protein secretion plays a role in the colonization of environmental and host surfaces.
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Affiliation(s)
- Laurel L Lenz
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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42
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Rowan NJ, MacGregor SJ, Anderson JG, Cameron D, Farish O. Inactivation of Mycobacterium paratuberculosis by pulsed electric fields. Appl Environ Microbiol 2001; 67:2833-6. [PMID: 11375202 PMCID: PMC92946 DOI: 10.1128/aem.67.6.2833-2836.2001] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2000] [Accepted: 03/19/2001] [Indexed: 11/20/2022] Open
Abstract
The influence of treatment temperature and pulsed electric fields (PEF) on the viability of Mycobacterium paratuberculosis cells suspended in 0.1% (wt/vol) peptone water and in sterilized cow's milk was assessed by direct viable counts and by transmission electron microscopy (TEM). PEF treatment at 50 degrees C (2,500 pulses at 30 kV/cm) reduced the level of viable M. paratuberculosis cells by approximately 5.3 and 5.9 log(10) CFU/ml in 0.1% peptone water and in cow's milk, respectively, while PEF treatment of M. paratuberculosis at lower temperatures resulted in less lethality. Heating alone at 50 degrees C for 25 min or at 72 degrees C for 25 s (extended high-temperature, short-time pasteurization) resulted in reductions of M. paratuberculosis of approximately 0.01 and 2.4 log(10) CFU/ml, respectively. TEM studies revealed that exposure to PEF treatment resulted in substantial damage at the cellular level to M. paratuberculosis.
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Affiliation(s)
- N J Rowan
- Department of Bioscience and Biotechnology, University of Strathclyde, Glasgow, Scotland.
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Abstract
The heat resistance data on Listeria monocytogenes in culture media and foods are summarized. Most heat resistance data for foods have been obtained in dairy, meat, poultry, and egg products. Limited data have been published on seafood, fruits, and vegetables. The methodologies employed have evolved over time; hence data from earlier experiments are not directly comparable to more recent studies. Many factors influence the heat resistance of L. monocytogenes. Variation exists among different strains in their ability to withstand heat treatment. In addition, heat resistance is influenced by age of the culture, growth conditions, recovery media, and characteristics of foods such as salt content, a(w), acidity, and the presence of other inhibitors. Listeriae are more heat resistant than most other nonspore-forming foodborne pathogens, and thus, processing recommendations based on data from experiments with Salmonella spp. or pathogenic Escherichia coli may not be sufficient to eliminate similar numbers of L. monocytogenes. The data provided in this review may prove useful for food processors in determining appropriate times and temperatures for producing foods free of vegetative pathogens.
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Affiliation(s)
- M E Doyle
- Food Research Institute, University of Wisconsin, Madison 53706, USA
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Rowan NJ, Anderson JG, Candlish AA. Cellular morphology of rough forms of Listeria monocytogenes isolated from clinical and food samples. Lett Appl Microbiol 2000; 31:319-22. [PMID: 11068915 DOI: 10.1046/j.1472-765x.2000.00821.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Transmission electron microscopy (TEM) studies revealed that rough cell-forms of L. monocytogenes (designated FR variants), isolated from clinical and food samples (and under conditions of sublethal heat stress), consist of either single or paired long-filaments. These FR variants markedly contrast in cell morphology from other previously described avirulent rough-mutants of L. monocytogenes that form long chains consisting of multiple cells of similar size (designated MCR variants). The identity of these Listeria isolates was determined using a commercially available, anti-Listeria polyclonal KPL antibody and by the API Listeria biochemical gallery. This study shows that filamentous rough-forms of L. monocytogenes may occur in clinical and food samples that are of undetermined pathogenicity.
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Affiliation(s)
- N J Rowan
- Department of Bioscience and Biotechnology, University of Strathclyde, Glasgow, UK.
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Rowan NJ, MacGregor SJ, Anderson JG, Fouracre RA, Farish O. Pulsed electric field inactivation of diarrhoeagenic Bacillus cereus through irreversible electroporation. Lett Appl Microbiol 2000; 31:110-4. [PMID: 10972710 DOI: 10.1046/j.1365-2672.2000.00772.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The physical effects of high-intensity pulsed electric fields (PEF) on the inactivation of diarrhoeagenic Bacillus cereus cells suspended in 0.1% peptone water were examined by transmission electron microscopy (TEM). The levels of PEF-induced microbial cell death were determined by enumeration on tryptone soy yeast extract agar and Bacillus cereus-selective agar plates. Following exposure to lethal levels of PEF, TEM investigation revealed irreversible cell membrane rupture at a number of locations, with the apparent leakage of intracellular contents. This study provides a clearer understanding of the mechanism of PEF-induced cellular damage, information that is essential for the further optimization of this emerging food-processing technology.
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Affiliation(s)
- N J Rowan
- Departments of Bioscience and Biotechnology, University of Strathclyde, Glasgow, Scotland, UK.
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Rowan NJ, Candlish AA, Bubert A, Anderson JG, Kramer K, McLauchlin J. Virulent rough filaments of Listeria monocytogenes from clinical and food samples secreting wild-type levels of cell-free p60 protein. J Clin Microbiol 2000; 38:2643-8. [PMID: 10878057 PMCID: PMC86987 DOI: 10.1128/jcm.38.7.2643-2648.2000] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Atypical rough cell filaments of Listeria monocytogenes (designated FR variants), isolated from clinical and food samples, form long filaments up to 96 microm in length and demonstrated wild-type levels of adherence, invasion, and cytotoxicity to human epithelial HEp-2, Caco-2, and HeLa cells. Unlike previously described avirulent rough mutants of L. monocytogenes that secrete diminished levels of the major extracellular protein p60 and that form long chains that consist of multiple cells of similar size (designated MCR variants), FR variants secreted wild-type or greater levels of p60. This study shows that virulent filamentous forms of L. monocytogenes occur in clinical and food environments and have atypical morphological characteristics compared to those of the wild-type form.
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Affiliation(s)
- N J Rowan
- Department of Bioscience and Biotechnology, University of Strathclyde, Glasgow, United Kingdom.
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47
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Rowan NJ. Evidence that inimical food-preservation barriers alter microbial resistance, cell morphology and virulence. Trends Food Sci Technol 1999. [DOI: 10.1016/s0924-2244(99)00060-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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48
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Annous BA, Kozempel MF, Kurantz MJ. Changes in membrane fatty acid composition of Pediococcus sp. strain NRRL B-2354 in response to growth conditions and its effect on thermal resistance. Appl Environ Microbiol 1999; 65:2857-62. [PMID: 10388676 PMCID: PMC91429 DOI: 10.1128/aem.65.7.2857-2862.1999] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Membrane fatty acid composition and thermal resistance (D value) of Pediococcus sp. were determined for mid-exponential-phase (ME) and stationary-phase (ST) cells grown in tryptic soy broth (TSB) and tryptone-glucose-yeast extract (TGY) at 28 and 37 degrees C. As the cells entered the stationary phase of growth, the unsaturated fatty acid, C18:1 n11c, produced during the exponential phase of growth was converted to its cyclic form, C19:0 Delta9c. This shift in membrane fatty acid composition was accompanied by an increase in the D values of this bacterium. Data from this study suggest that the membrane fatty acid composition of Pediococcus sp. is dependent on the growth conditions and that membrane fatty acid composition plays a critical role in thermal resistance. Thermal inactivation curves of Pediococcus sp. cells grown in TGY at 28 degrees C indicated the presence of a cell population that is heterogeneous in thermal resistance. The growth of this bacterium in TGY at 37 degrees C and in TSB at 28 and 37 degrees C resulted in cell populations that were uniform in thermal resistance with a lag time for thermal inactivation. Thermal inactivation curves of ME and ST cultures were similar. The data presented here suggest that the cell population's uniformity of thermal inactivation is independent of the growth phase of the culture.
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Affiliation(s)
- B A Annous
- Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania 19038, USA.
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