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Sihto HM, Tasara T, Stephan R, Johler S. Validation of reference genes for normalization of qPCR mRNA expression levels in Staphylococcus aureus exposed to osmotic and lactic acid stress conditions encountered during food production and preservation. FEMS Microbiol Lett 2014; 356:134-40. [PMID: 24893820 DOI: 10.1111/1574-6968.12491] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 05/30/2014] [Indexed: 12/01/2022] Open
Abstract
Staphylococcus aureus represents the most prevalent cause of food-borne intoxications worldwide. While being repressed by competing bacteria in most matrices, this pathogen exhibits crucial competitive advantages during growth at high salt concentrations or low pH, conditions frequently encountered in food production and preservation. We aimed to identify reference genes that could be used to normalize qPCR mRNA expression levels during growth of S. aureus in food-related osmotic (NaCl) and acidic (lactic acid) stress adaptation models. Expression stability of nine housekeeping genes was evaluated in full (LB) and nutrient-deficient (CYGP w/o glucose) medium under conditions of osmotic (4.5% NaCl) and acidic stress (lactic acid, pH 6.0) after 2-h exposure. Among the set of candidate reference genes investigated, rplD, rpoB,gyrB, and rho were most stably expressed in LB and thus represent the most suitable reference genes for normalization of qPCR data in osmotic or lactic acid stress models in a rich medium. Under nutrient-deficient conditions, expression of rho and rpoB was highly stable across all tested conditions. The presented comprehensive data on changes in expression of various S. aureus housekeeping genes under conditions of osmotic and lactic acid stress facilitate selection of reference genes for qPCR-based stress response models.
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Affiliation(s)
- Henna-Maria Sihto
- Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Zurich, Switzerland
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Jay JM. Microorganisms in fresh ground meats: the relative safety of products with low versus high numbers. Meat Sci 2013; 43S1:59-66. [PMID: 22060641 DOI: 10.1016/0309-1740(96)00055-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The two outbreaks of haemorrhagic colitis (HC) that were traced to ground beef in 1982 were the first foodborne cases known to be caused by Escherichia coli 0157:H7. The 1993 outbreak in the U.S. Pacific Northwest is the largest foodborne disease outbreak ever traced to ground beef. Why these events occurred continues to be a matter of speculation and debate. It is the thesis of this review that HC-causing strains of E. coli, which could have been in the meat supply as early as the mid-1950s, can persist in meats that contain too few of the background bacterial biota. The antagonistic effect of background organisms against pathogenic bacteria (microbial interference) is well established. Fresh ground meats that contain 10(5)-10(6)/g of background organisms are inherently safer than those that contain, say, 10(3)/g. Although the production of fresh ground meats with as few microorganisms as possible would seem to be the ideal, there is little or no evidence to support the superior safety of such products. It is suggested that when pathogen-reduction strategies are applied to animal carcasses, the carcasses should be 'protected' against subsequent colonization by pathogens by actually adding appropriate mixtures of harmless bacteria.
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Affiliation(s)
- J M Jay
- Department of Biological Sciences, University of Nevada Las Vegas, Las Vegas NV 89154-4004, USA
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El Bassi L, Hassouna M, Shinzato N, Matsui T. Biopreservation of refrigerated and vacuum-packed Dicentrarchus labrax by lactic acid bacteria. J Food Sci 2010; 74:M335-9. [PMID: 19723220 DOI: 10.1111/j.1750-3841.2009.01246.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two lactic acid bacteria (LAB) were selected from 100 LAB isolated from various sea products to examine their use in Dicentrarchus labrax preservation. The isolates, tentatively named strain nr 3 and 7, were identified as Lactobacillus plantarum and L. pentosus, respectively. They showed antagonistic activity against psychrotroph, pathogenic, and coliform bacteria. The antagonistic activity of strain 3 was suggested to be by bacteriocins since activity was abolished by protease treatment, while that of strain 7 was due to the effect of pH decrease caused by the produced organic acids. Their use prevented total volatile basic nitrogen contents (TVB-N) and trimethylamine (TMA) to some extent, suggesting that inoculation could extend the period of storage.
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Affiliation(s)
- Leila El Bassi
- Center of Molecular Biosciences, Univ. of the Ryukyus, Nishihara-cho, Okinawa, 903-0213, Japan
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Mossel D, Pflug IJ. Occurrence, prevention, and monitoring of microbial quality loss of foods and dairy products. ACTA ACUST UNITED AC 2009. [DOI: 10.1080/10643387509381624] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Brashears MM, Amezquita A, Jaroni D. Lactic acid bacteria and their uses in animal feeding to improve food safety. ADVANCES IN FOOD AND NUTRITION RESEARCH 2005; 50:1-31. [PMID: 16263426 DOI: 10.1016/s1043-4526(05)50001-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Mindy M Brashears
- International Center for Food Industry Excellence, Department of Animal and Food Sciences, Texas Tech University, Lubbock, Texas 79409, USA
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Amézquita A, Brashears MM. Competitive inhibition of Listeria monocytogenes in ready-to-eat meat products by lactic acid bacteria. J Food Prot 2002; 65:316-25. [PMID: 11848562 DOI: 10.4315/0362-028x-65.2.316] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Forty-nine strains of lactic acid bacteria (LAB), isolated from commercially available ready-to-eat (RTE) meat products, were screened for their ability to inhibit the growth of Listeria monocytogenes at refrigeration (5 degrees C) temperatures on agar spot tests. The three most inhibitory strains were identified as Pediococcus acidilactici, Lactobacillus casei, and Lactobacillus paracasei by 16S rDNA sequence analysis. Their antilisterial activity was quantified in associative cultures in deMan Rogosa Sharpe (MRS) broth at 5 degrees C for 28 days, resulting in a pathogen reduction of 3.5 log10 cycles compared to its initial level. A combined culture of these strains was added to frankfurters and cooked ham coinoculated with L. monocytogenes, vacuum packaged, and stored at 5 degrees C for 28 days. Bacteriostatic activity was observed in cooked ham, whereas bactericidal activity was observed in frankfurters. Numbers of L. monocytogenes were 4.2 to 4.7 log10 and 2.6 log10 cycles lower than controls in frankfurters and cooked ham, respectively, after the 28-day refrigerated storage. In all cases, numbers of LAB increased by only 1 log10 cycle. The strain identified as P. acidilactici was possibly a bacteriocin producer, whereas the antilisterial activity of the other two strains was due to the production of organic acids. There was no significant difference (P > 0.05) in the antilisterial activity detected in frankfurters whether the LAB strains were used individually or as combined cultures. Further studies over a 56-day period indicated no impact on the quality of the product. This method represents a potential antilisterial intervention in RTE meats, because it inhibited the growth of the pathogen at refrigeration temperatures without causing sensory changes.
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Affiliation(s)
- A Amézquita
- Department of Food Science and Technology, University of Nebraska, Lincoln 68583-0919, USA
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Vold L, Holck A, Wasteson Y, Nissen H. High levels of background flora inhibits growth of Escherichia coli O157:H7 in ground beef. Int J Food Microbiol 2000; 56:219-25. [PMID: 10857548 DOI: 10.1016/s0168-1605(00)00215-4] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The influence of natural background flora under aerobic and anaerobic incubation on the growth of Escherichia coli O157:H7 in ground beef was investigated. The background flora from eight different commercial ground beef were added to ground beef spiked with E. coli O157:H7 and stored either aerobically or anaerobically at 12 degrees C. The results showed that the presence of a large number of background bacteria in the ground meat inhibited the growth of E. coli O157:H7 both aerobically and anaerobically. Inhibition was more pronounced under anaerobic conditions. The background floras consisted mainly of lactic acid bacteria of which approximately 80% were Lactobacillus sakei. These results show the importance of the natural background flora in meat for inhibition of growth of E. coli O157:H7.
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Affiliation(s)
- L Vold
- Department of Pharmacology, Microbiology and Food Hygiene, The Norwegian School of Veterinary Science, Oslo
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Mossel DA, Weenk GH, Morris GP, Struijk CB. Identification, assessment and management of food-related microbiological hazards: historical, fundamental and psycho-social essentials. Int J Food Microbiol 1998; 39:19-51. [PMID: 9562875 DOI: 10.1016/s0168-1605(97)00115-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Microbiological risk assessment aimed at devising measures of hazard management, should take into account all perceived hazards, including those not empirically identified. It should also recognise that safety cannot be "inspected into" a food. Rather hazard management should be the product of intervention strategies in accordance with the approach made mandatory in the EU Directive 93/43 and the USDA FSIS Pathogen Reduction HACCP system; Final Rule. It is essential too that the inherent variability of the biological attributes affecting food safety is recognised in any risk assessment. The above strategic principles may be conceptualised as a four-step sequence, involving (i) identification and quantification of hazards; (ii) design and codification of longitudinally integrated ("holistic") technological processes and procedures to eliminate, or control growth and metabolism of, pathogenic and toxinogenic organisms; (iii) elaboration of microbiological analytical standard operating procedures, permitting validation of "due diligence" or responsible care, i.e. adherence to adopted intervention strategies. This should be supported by empirically assessed reference ranges, particularly for marker organisms, while the term "zero tolerance" is refined throughout to tolerable safety limit; (iv) when called for, the need to address concerns arising from lay perceptions of risk which may lack scientific foundation. In relation to infectious and toxic hazards in the practical context the following general models for quantitative holistic risk assessment are presented: (i) the first order, basic lethality model; (ii) a second approximation taking into account the amount of food ingested in a given period of time; (iii) a further adjustment accounting for changes in colonization levels during storage and distribution of food commodities and the effects of these on proliferation of pathogens and toxin production by bacteria and moulds. Guidelines are provided to address: (i) unsubstantiated consumer concern over the wholesomeness of foods processed by an innovative procedure; and (ii) reluctance of small food businesses to adopt novel strategies in food safety. Progress here calls for close cooperation with behavioural scientists to ensure that investment in developing measures to contain risk deliver real benefit.
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Affiliation(s)
- D A Mossel
- Eijkman Foundation, Utrecht University, Netherlands
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Abstract
Biopreservation refers to extended storage life and enhanced safety of foods using the natural microflora and (or) their antibacterial products. Lactic acid bacteria have a major potential for use in biopreservation because they are safe to consume and during storage they naturally dominate the microflora of many foods. In milk, brined vegetables, many cereal products and meats with added carbohydrate, the growth of lactic acid bacteria produces a new food product. In raw meats and fish that are chill stored under vacuum or in an environment with elevated carbon dioxide concentration, the lactic acid bacteria become the dominant population and preserve the meat with a "hidden' fermentation. The same applies to processed meats provided that the lactic acid bacteria survive the heat treatment or they are inoculated onto the product after heat treatment. This paper reviews the current status and potential for controlled biopreservation of foods.
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Affiliation(s)
- M E Stiles
- Department of Agricultural, Food and Nutritional Science University of Alberta, Edmonton, Canada
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PAYNE C, MOODY W, LANGLOIS B, MEANS W, AARON D. Microbial Characteristics of Three Formulations of Precooked, Vacuum-packaged Restructured Beef Steaks. J Food Sci 1991. [DOI: 10.1111/j.1365-2621.1991.tb04719.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Nychas GJ, Arkoudelos JS. Staphylococci: their role in fermented sausages. SOCIETY FOR APPLIED BACTERIOLOGY SYMPOSIUM SERIES 1990; 19:167S-188S. [PMID: 2119063 DOI: 10.1111/j.1365-2672.1990.tb01806.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- G J Nychas
- Ministry of Agriculture, Institute of Technology of Agricultural Products, Athens, Greece
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NEWSOME R, SEMAN D, LANGLOIS B, MOODY W, FOX J, GAY N. Microbiological Quality of Restructured and Conventional Steaks Manufactured from Electrically Stimulated Hot- and Cold-Boned Carcasses. J Food Sci 1987. [DOI: 10.1111/j.1365-2621.1987.tb14228.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Loveland J, Kesler E, Doores S. Fermentation of a Mixture of Waste Milk and Colostrum for Feeding Young Calves. J Dairy Sci 1983. [DOI: 10.3168/jds.s0022-0302(83)81940-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Barefoot SF, Klaenhammer TR. Detection and activity of lactacin B, a bacteriocin produced by Lactobacillus acidophilus. Appl Environ Microbiol 1983; 45:1808-15. [PMID: 6410990 PMCID: PMC242543 DOI: 10.1128/aem.45.6.1808-1815.1983] [Citation(s) in RCA: 379] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
A total of 52 strains of Lactobacillus acidophilus were examined for production of bacteriocins. A majority (63%) demonstrated inhibitory activity against all members of a four-species grouping of Lactobacillus leichmannii, Lactobacillus bulgaricus, Lactobacillus helveticus, and Lactobacillus lactis. Four L. acidophilus strains with this activity also inhibited Streptococcus faecalis and Lactobacillus fermentum, suggesting a second system of antagonism. Under conditions eliminating the effects of organic acids and hydrogen peroxide, no inhibition of other gram-positive or -negative genera was demonstrated by L. acidophilus. The agent produced by L. acidophilus N2 and responsible for inhibition of L. leichmannii, L. bulgaricus, L. helveticus, and L. lactis was investigated. Ultrafiltration studies indicated a molecular weight of approximately 100,000 for the crude inhibitor. The agent was sensitive to proteolytic enzymes and retained full activity after 60 min at 100 degrees C (pH 5). Activity against sensitive cells was bactericidal but not bacteriolytic. These characteristics identified the inhibitory agent as a bacteriocin, designated lactacin B. Examination of strains of L. acidophilus within the six homology groupings of Johnson et al. (Int. J. Syst. Bacteriol. 30:53-68, 1980) demonstrated that production of the bacteriocin lactacin B could not be used in classification of neotype L. acidophilus strains. However, the usefulness of employing sensitivity to lactacin B in classification of dairy lactobacilli is suggested.
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Klaenhammer T. Microbiological Considerations in Selection and Preparation of Lactobacillus Strains for Use as Dietary Adjuncts. J Dairy Sci 1982. [DOI: 10.3168/jds.s0022-0302(82)82351-5] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Lindell JO, Edqvist LE, Gustafsson B. Oophorectomy during different stages of pregnancy in the cow. Acta Vet Scand 1981. [PMID: 7344538 DOI: 10.1186/bf03548679] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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BARTHOLOMEW DT, BLUMER TN. INHIBITION OF Staphylococcus BY ILACTIC ACID BACTERIA IN COUNTRY-STYLE HAMS. J Food Sci 1980. [DOI: 10.1111/j.1365-2621.1980.tb04065.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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OUBOIS GEORGES, BEAUMIER HELENE, CHARBONNEAU RAYMOND. INHIBITION OF BACTERIA ISOLATED FROM GROUND MEAT BY STREPTOCOCCACEAE AND LACTOBACILLACEAE. J Food Sci 1979. [DOI: 10.1111/j.1365-2621.1979.tb09108.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Gill C, Newton K. The ecology of bacterial spoilage of fresh meat at chill temperatures. Meat Sci 1978; 2:207-17. [DOI: 10.1016/0309-1740(78)90006-2] [Citation(s) in RCA: 128] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/1977] [Indexed: 11/30/2022]
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Newton KG, Gill CO. The development of the anaerobic spoilage flora of meat stored at chill temperatures. THE JOURNAL OF APPLIED BACTERIOLOGY 1978; 44:91-5. [PMID: 416012 DOI: 10.1111/j.1365-2672.1978.tb00779.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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GILLILAND SE, SPECK ML. INHIBITION OF PSYCHROTROPHIC BACTERIA BY LACTOBACILLI AND PEDIOCOCCI IN NONFERMENTED REFRIGERATED FOODS. J Food Sci 1975. [DOI: 10.1111/j.1365-2621.1975.tb02229.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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