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Fracassetti D, Vigentini I, Faro A, Foschino R, Tirelli A, Orioli M, Iriti M. Il contributo dei batteri lattici per la presenza di melatonina nel vino rosso. BIO Web Conf 2019. [DOI: 10.1051/bioconf/20191204006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
La melatonina (MEL) è un'indolammina implicata nella regolazione dei cicli circadiani e che possiede attività antiossidante. La presenza di MEL è stata dimostrata nelle piante e negli alimenti con particolare attenzione agli alimenti e bevande fermentati, tra cui il vino. L'uva è una fonte di MEL e nel vino l'attività metabolica del lievito svolge un ruolo cruciale per la produzione di MEL. È stato recentemente suggerito che anche i batteri lattici (LAB) posseggano tale abilità. In questo studio è stata indagata la sintesi di MEL da parte dei LAB in condizioni enologiche e di laboratorio. Sono stati analizzati 8 vini rossi prodotti su scala industriale in 4 cantine. Inoltre, 11 ceppi di LAB sono stati inoculati in terreno sintetico simil-vino. Dai risultati ottenuti è emerso che nei vini prodotti in due delle quattro cantine è stato osservato un aumento di MEL al termine della fermentazione malolattica. Tutti i ceppi oggetto dello studio hanno prodotto MEL in condizioni di laboratorio in quantità variabile a seconda del ceppo. I risultati mettono in evidenza per la prima volta che i LAB sono capaci di rilasciare MEL sia in condizioni di laboratorio che nel vino prodotto industrialmente. The contribution of lactic bacteria on melatonin in red wine
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Boiocchi F, Porcellato D, Limonta L, Picozzi C, Vigentini I, Locatelli D, Foschino R. Insect frass in stored cereal products as a potential source ofLactobacillus sanfranciscensisfor sourdough ecosystem. J Appl Microbiol 2017; 123:944-955. [DOI: 10.1111/jam.13546] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/18/2017] [Accepted: 07/18/2017] [Indexed: 12/16/2022]
Affiliation(s)
- F. Boiocchi
- Department of Food, Environmental and Nutritional Sciences (DeFENS); Università degli Studi di Milano; Milano Italy
| | - D. Porcellato
- Faculty of Chemistry; Biotechnology and Food Science; Norwegian University of Life Sciences (NMBU); Ås Norway
| | - L. Limonta
- Department of Food, Environmental and Nutritional Sciences (DeFENS); Università degli Studi di Milano; Milano Italy
| | - C. Picozzi
- Department of Food, Environmental and Nutritional Sciences (DeFENS); Università degli Studi di Milano; Milano Italy
| | - I. Vigentini
- Department of Food, Environmental and Nutritional Sciences (DeFENS); Università degli Studi di Milano; Milano Italy
| | - D.P. Locatelli
- Department of Food, Environmental and Nutritional Sciences (DeFENS); Università degli Studi di Milano; Milano Italy
| | - R. Foschino
- Department of Food, Environmental and Nutritional Sciences (DeFENS); Università degli Studi di Milano; Milano Italy
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Picozzi C, Antoniani D, Vigentini I, Foschino R. Genotypic Characterization and Biofilm Formation of Shiga-toxin producing
Escherichia coli. FEMS Microbiol Lett 2016; 364:fnw291. [DOI: 10.1093/femsle/fnw291] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 12/21/2016] [Indexed: 11/13/2022] Open
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Picozzi C, Mariotti M, Cappa C, Tedesco B, Vigentini I, Foschino R, Lucisano M. Development of a Type I gluten-free sourdough. Lett Appl Microbiol 2016; 62:119-25. [PMID: 26581944 DOI: 10.1111/lam.12525] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [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: 09/04/2015] [Revised: 10/30/2015] [Accepted: 11/04/2015] [Indexed: 12/26/2022]
Abstract
UNLABELLED The aim of this study was the setting up of a gluten-free sourdough from selected lactobacilli and yeasts isolated from a traditional wheat-based Type I sourdough. A gluten-free matrix was inoculated with Lactobacillus sanfranciscensis and Candida humilis, fermented to pH 4·0, and constantly propagated for ten times. A stable association between micro-organisms was observed from the second refreshment with mean values of 9·08 ± 0·25 log CFU g(-1) for lactobacilli and 7·81 ± 0·07 log CFU g(-1) for yeasts. In order to have a good workability of the dough, a 230 BU consistency was considered. Rheofermentographic indices remained constant over the ten refreshments, showing an average value of 23·2 mm dough height in about 7·5 h. The CO2 production and retention volumes reached average values of 1430 and 1238 ml respectively. The microbiological and technological data obtained highlighted that a GF sourdough was effectively developed. SIGNIFICANCE AND IMPACT OF THE STUDY Type I sourdough has a long tradition as a leavening agent of baked goods as its use results in an improved texture, flavour, taste and extended shelf-life of the final products. In this study a Type I gluten-free sourdough was obtained. After few refreshments in controlled conditions, the sourdough presented a stable association between Lactobacillus sanfranciscensis and Candida humilis, constant fermentation times and technological properties (in terms of dough consistency, dough maximum height, CO2 production and retention). The results showed that the gluten-free sourdough developed in this study can improve the overall quality of gluten-free baked products.
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Affiliation(s)
- C Picozzi
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
| | - M Mariotti
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
| | - C Cappa
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
| | - B Tedesco
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
| | - I Vigentini
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
| | - R Foschino
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
| | - M Lucisano
- Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
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Vigentini I, Praz A, Domeneghetti D, Zenato S, Picozzi C, Barmaz A, Foschino R. Characterization of malolactic bacteria isolated from Aosta Valley wines and evidence of psychrotrophy in some strains. J Appl Microbiol 2016; 120:934-45. [PMID: 26820246 DOI: 10.1111/jam.13080] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 11/23/2015] [Accepted: 01/04/2016] [Indexed: 11/27/2022]
Affiliation(s)
- I. Vigentini
- Department of Food, Environmental and Nutrition Sciences; Università degli studi di Milano; Milan Italy
| | - A. Praz
- Department of Food, Environmental and Nutrition Sciences; Università degli studi di Milano; Milan Italy
| | | | - S. Zenato
- Institut Agricole Régional of Aosta; Aosta Italy
| | - C. Picozzi
- Department of Food, Environmental and Nutrition Sciences; Università degli studi di Milano; Milan Italy
| | - A. Barmaz
- Institut Agricole Régional of Aosta; Aosta Italy
| | - R. Foschino
- Department of Food, Environmental and Nutrition Sciences; Università degli studi di Milano; Milan Italy
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Fabrizio V, Vigentini I, Parisi N, Picozzi C, Compagno C, Foschino R. Heat inactivation of wine spoilage yeast Dekkera bruxellensis by hot water treatment. Lett Appl Microbiol 2015; 61:186-91. [PMID: 25989358 DOI: 10.1111/lam.12444] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 05/06/2015] [Accepted: 05/07/2015] [Indexed: 11/28/2022]
Abstract
UNLABELLED Cell suspensions of four Dekkera bruxellensis strains (CBS 2499, CBS 2797, CBS 4459 and CBS 4601) were subjected to heat treatment in deionized water at four different temperatures (55·0, 57·5, 60·0 and 62·5°C) to investigate their thermal resistance. The decimal reduction times at a specific temperature were calculated from the resulting inactivation curves: the D-values at 55·0°C ranged from 63 to 79·4 s, at 57·5°C from 39·6 to 46·1 s, at 60·0°C from 19·5 to 20·7 s, at 62·5°C from 10·2 to 13·7 s. The z-values were between 9·2 and 10·2°C, confirming that heat resistance is a strain-dependent character. A protocol for the sanitization of 225 l casks by immersion in hot water was set up and applied to contaminated 3-year-old barrels. The heat penetration through the staves was evaluated for each investigated temperature by positioning a thermal probe at 8 mm deep. A treatment at 60°C for an exposure time of 19 min allowed to eliminate the yeast populations up to a log count reduction of 8. SIGNIFICANCE AND IMPACT OF THE STUDY Brettanomyces/Dekkera bruxellensis is the main yeast involved in red wine spoilage that occurs during ageing in barrel, generating considerable economic losses. Current sanitization protocols, performed using different chemicals, are ineffective due to the porous nature of the wood. The thermal inactivation of D. bruxellensis cells by hot water treatment proves to be efficacious and easy to perform, provided that the holding time at the killing temperature takes into account the filling time of the vessel and the time for the heat penetration into the wood structure.
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Affiliation(s)
- V Fabrizio
- Centro di Ricerca, Formazione e Servizi della Vite e del Vino, Riccagioia S.C.p.A., Torrazza Coste (PV), Italy
| | - I Vigentini
- Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Milan, Italy
| | - N Parisi
- Co.Pro.Vi. Societa' Cooperativa, Casteggio (PV), Italy
| | - C Picozzi
- Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Milan, Italy
| | - C Compagno
- Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Milan, Italy
| | - R Foschino
- Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Milan, Italy
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Volponi G, Rooks DJ, Smith DL, Picozzi C, Allison HE, Vigentini I, Foschino R, McCarthy AJ. Short communication: Characterization of Shiga toxin 2-carrying bacteriophages induced from Shiga-toxigenic Escherichia coli isolated from Italian dairy products. J Dairy Sci 2012; 95:6949-56. [PMID: 22999287 DOI: 10.3168/jds.2012-5831] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 08/09/2012] [Indexed: 11/19/2022]
Abstract
Forty samples of raw milk cheese and 25 samples of raw milk itself were subjected to enrichment culture for Shiga-toxigenic Escherichia coli (STEC), and a single Shiga toxin 2- (Stx(2)) positive strain was obtained from one of the cheese samples. Thus, aged cheeses in which the curd is subsequently heat treated (48°C) cannot be presumed to be STEC free. Infective Stx(2) bacteriophages were induced from 3 STEC strains isolated elsewhere from raw milk and 1 STEC strain from aged cheese sourced in Italy. Data on E. coli host range, morphology, genome size, and genetic variation determined by restriction fragment length polymorphism and multi-locus genotyping are presented. Although all 4 bacteriophages were found to be short-tailed Podoviridae, they exhibited considerable variation in both genome size and content. This extended to the Stx(2) genes themselves, whose sequences contained several point mutations, but these did not translate to amino acid substitutions.
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Affiliation(s)
- G Volponi
- Dipartmento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, Milano, Italy
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Lustrato G, Vigentini I, De Leonardis A, Alfano G, Tirelli A, Foschino R, Ranalli G. Inactivation of wine spoilage yeasts Dekkera bruxellensis using low electric current treatment (LEC). J Appl Microbiol 2010; 109:594-604. [PMID: 20148995 DOI: 10.1111/j.1365-2672.2010.04686.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS The objective of this study was to investigate the inactivation of a selected yeast Dekkera bruxellensis strain 4481 in red wine by application of low electric current treatment (LEC). METHODS AND RESULTS LEC (200 mA) was applied for 60 days to a red wine, Montepulciano d'Abruzzo, in an alternative strategy to the SO(2) addition during wine storage. The LEC effect on both cell activity and microflora viability was assessed. LEC decreased significantly the survival viable cells and increased the death rate of D. bruxellensis strain 4481 yeast. A final comparison was made of the main physico-chemical parameters of the wine after the different treatments. The study suggests the importance of an appropriate LEC treatment which limits wine deterioration in terms of off-flavours synthesis. CONCLUSIONS The results demonstrate that the growth of undesirable Dekkera can be inhibited by low voltage treatment; LEC was shown to be useful to prevent wine spoilage and has the potential of being a concrete alternative method for controlling wine spoilage. SIGNIFICANCE AND IMPACT OF THE STUDY Wine spoilage can be avoided by preventing the growth of undesirable Dekkera yeasts, through the effective use of LEC in the winemaking process.
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Affiliation(s)
- G Lustrato
- DISTAT, Università del Molise, Pesche, Italy
| | | | | | - G Alfano
- DISTAT, Università del Molise, Pesche, Italy
| | - A Tirelli
- DISTAM Università di Milano, Milano, Italy
| | - R Foschino
- DISTAM Università di Milano, Milano, Italy
| | - G Ranalli
- DISTAT, Università del Molise, Pesche, Italy
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Agnolucci M, Vigentini I, Capurso G, Merico A, Tirelli A, Compagno C, Foschino R, Nuti M. Genetic diversity and physiological traits of Brettanomyces bruxellensis strains isolated from Tuscan Sangiovese wines. Int J Food Microbiol 2009; 130:238-44. [DOI: 10.1016/j.ijfoodmicro.2009.01.025] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 01/08/2009] [Accepted: 01/25/2009] [Indexed: 11/17/2022]
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Foschino R, Nucera D, Volponi G, Picozzi C, Ortoffi M, Bottero MT. Comparison of Lactococcus garvieae strains isolated in northern Italy from dairy products and fishes through molecular typing. J Appl Microbiol 2008; 105:652-62. [PMID: 18341557 DOI: 10.1111/j.1365-2672.2008.03780.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS To investigate the genetic relatedness between Lactococcus garvieae strains isolated from fish and dairy samples collected in northern Italy, using random-amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR), Sau-PCR and amplified fragment length polymorphism (AFLP). METHODS AND RESULTS Eighty-one isolates from bovine and caprine dairy products (n = 53) and from diseased rainbow trouts and other fishes (n = 28) were examined. All methods showed a typeability of 100%, repeatability ranging from 84.4% to 97.5% and discriminatory powers from 0.798 to 0.986. Dairy and fish strains revealed a low genetic relatedness as they are often grouped into distinct clusters. RAPD analysis discriminated 52 genotypes when primer M13 was used, whereas with primer P5 only 27 genotypes were identified. When Sau-PCR was performed, 13 genotypes were detected while AFLP analysis allowed the differentiation of 32 genotypes. CONCLUSION L. garvieae strains isolated from dairy samples are generally not related to those collected from fish lactococcosis outbreaks. SIGNIFICANCE AND IMPACT OF THE STUDY L. garvieae strains exhibit a genetic diversity related to the specific animal host they colonize. RAPD M13 fingerprinting proved to be a molecular tool for comparing isolates, whereas Sau-PCR and AFLP analyses were useful techniques to investigate the distribution of L. garvieae populations in the environment.
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Affiliation(s)
- R Foschino
- Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, Milano, Italy.
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Fortina MG, Ricci G, Foschino R, Picozzi C, Dolci P, Zeppa G, Cocolin L, Manachini PL. Phenotypic typing, technological properties and safety aspects of Lactococcus garvieae strains from dairy environments. J Appl Microbiol 2008; 103:445-53. [PMID: 17650205 DOI: 10.1111/j.1365-2672.2006.03265.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIMS To characterize Lactococcus garvieae strains of dairy origin and to determine their technological properties and safety for their possible use in starter culture preparation. METHODS AND RESULTS Forty-seven L. garvieae isolates, recovered from two artisanal Italian cheeses were studied, in comparison with 12 fish isolates and the type strain of the species. Phenotypic typing revealed that the strains could be differentiated on the basis of their ecological niche of origin in lactose positive strains (all isolated from dairy sources) and lactose negative strains (all isolated from fish). Furthermore, the strains exhibited a high degree of physiological variability, showing the presence of 26 different biotypes. The strains possessed moderate acidifying and proteolytic activities and did not produce bacteriocins. A safety investigation revealed that all strains were sensitive to vancomycin and moderately resistant to kanamycin; some biotypes were tetracycline resistant. Production of biogenic amines or presence of genes encoding virulence determinants occurred in some isolates. CONCLUSIONS The prevalence of L. garvieae in some artisanal Italian cheeses can be linked to the typicity of the products. Although in a few cases an antimicrobial resistance or a presence of virulence determinants may imply a potential hygienic risk, most of the strains showed positive properties for their possible adjunction in a starter culture preparation, to preserve the natural bacterial population responsible for the typical sensorial characteristics of the traditional raw milk cheeses. SIGNIFICANCE AND IMPACT OF THE STUDY L. garvieae strains can be considered an important part of the microbial population associated with the natural fermentation of artisanal Italian cheeses. A deepened characterization of the strains may aid in understanding the functional and ecological significance of their presence in dairy products and in selecting new strains for the dairy industry.
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Affiliation(s)
- M G Fortina
- Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università di Milano, Milan, Italy.
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Foschino R, Venturelli E, Picozzi C. Isolation and characterization of a virulent Lactobacillus sanfranciscensis bacteriophage and its impact on microbial population in sourdough. Curr Microbiol 2005; 51:413-8. [PMID: 16235023 DOI: 10.1007/s00284-005-0122-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Accepted: 07/02/2005] [Indexed: 11/27/2022]
Abstract
Thirty-five sourdough samples used for sweet and salted Italian baked products were checked for the presence of a virus active on Lactobacillus sanfranciscensis species. One phage, named EV3, was isolated and its phenotypic and genotypic features were investigated. It belonged to the Siphoviridae family (morphotype B1); its life cycle at 25 degrees C lasted 3 h with a burst size of about 30 viral particles per infected cell. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed one major structural protein of 35 kDa and four minor proteins. The genome, approximately 32 kb long, was a double-stranded linear DNA molecule with a pac-type system. Phage spreading into sourdough did not adversely affect acidification and volume increase of the dough neither lactobacilli counts; the propagation of viral particles was shown to be hindered. This is the first report of the isolation of a L. sanfranciscensis phage.
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Affiliation(s)
- R Foschino
- Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, via Celoria, Milano 2 - 20133, Italy.
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Picozzi C, D’Anchise F, Foschino R. PCR detection of Lactobacillus sanfranciscensis in sourdough and Panettone baked product. Eur Food Res Technol 2005. [DOI: 10.1007/s00217-005-0121-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Picozzi C, Foschino R, Heuvelink A, Beumer R. Phenotypic and genotypic characterization of sorbitol-negative or slow-fermenting (suspected O157) Escherichia coli isolated from milk samples in Lombardy region. Lett Appl Microbiol 2005; 40:491-6. [PMID: 15892748 DOI: 10.1111/j.1472-765x.2005.01718.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS To investigate phenotypic and genotypic aspects of sorbitol-negative or slow-fermenting Escherichia coli, suspected to belong to O157 serogroup, isolated in Italy. METHODS AND RESULTS Milk samples originating from goats and cows were screened for the presence of E. coli O157 with cultural methods. Sorbitol-negative or slow-fermenting strains were subjected to phenotypic characterization, antibiotic resistance profiles, PCR reactions for detection of toxins (stx(1) and stx(2)) and intimin (eae(GEN) and eae(O157)) genes and clustering by pulsed field gel electrophoresis (PFGE). Only one strain revealed to be O157. Susceptibility to 11 antibiotics highlighted the high resistance to tetracycline (50%), sulfonamide and streptomycin (33%). The stx(2) gene was detected in two strains; only the strain identified as O157 exhibited an amplicon for both eae genes. PFGE identified seven distinct XbaI macrorestriction patterns at a similarity level of 41%. CONCLUSIONS The use of sorbitol fermentation as cultural method is not sufficient for STEC discrimination while PCR assay proved to be a valuable method. SIGNIFICANCE AND IMPACT OF THE STUDY The study reports presence of Shiga toxin-producing E. coli in raw milk, signalling a potential risk for humans.
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Affiliation(s)
- C Picozzi
- Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, Milan, Italy.
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Abstract
AIMS To investigate the basic properties of six temperate and three virulent phages, active on Lactobacillus fermentum, on the basis of morphology, host ranges, protein composition and genome characterization. METHODS AND RESULTS All phages belonged to the Siphoviridae family; two of them showed prolate heads. The host ranges of seven phages contained a common group of strains. SDS-PAGE protein profiles, restriction analysis of DNA and Southern blot hybridization revealed a high degree of homology between four temperate phages; partial homologies were also detected among virulent and temperate phages. Clustering derived from host range analysis was not related to the results of the DNA hybridizations. CONCLUSION The phages investigated have common characteristics with other known phages active on the genus Lactobacillus. Sensitivity to viral infection is apparently enhanced by the presence of a resident prophage. SIGNIFICANCE AND IMPACT OF THE STUDY These relationships contribute to the explanation for the origin of phage infection in food processes where Lact. fermentum is involved, such as sourdough fermentation.
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Affiliation(s)
- R Foschino
- Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Milano, Italy.
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Abstract
The efficacy of chlorine dioxide as a disinfectant was evaluated against cells of Escherichia coli ATCC 11229 in aqueous suspension and adhering to the surfaces of stainless steel AISI 304 and PVC. The concentrations tested ranged from 0.7 to 14 mg/liter; the exposure times investigated were 30 s and 1, 2, 4, and 8 min. When the bacteria were suspended in water with 1.4 mg/liter of chlorine dioxide, a 10(5)-fold reduction of the initial viable count occurred within 30 s; when cells were attached to the steel surface, the same rate of inactivation took place only after 6 min with 7 mg/liter or 4 min with 14 mg/liter of chlorine dioxide. A 5-log reduction was not obtained when organisms were adhered to polyvinyl chloride (PVC). Scanning electron microscope micrographs of contaminated surfaces revealed that the PVC was very rough with pores much larger in diameter than the cells. Time values determining a 90% reduction of the E. coli population (90% killing time) were calculated for each concentration of disinfectant tested in suspension and on the steel surface. If the same experimental conditions were strictly adopted, linear functions of the log of bacterial inactivation could be plotted (log 90% killing time versus log concentration of disinfectant). This work showed that results obtained with suspension tests could not be used to estimate disinfection of hard surfaces.
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Affiliation(s)
- R Foschino
- Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, Italy
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