Czech Journal of Food Sciences, 2009 (vol. 27), Special Issue 2

Influence of Enterococci and Lactobacilli on Listeria

Kateřina Kučerová, Ivana Korbová, Šárka HORÁČKOVÁ, Eva Šviráková, Milada Plocková

Czech J. Food Sci., 2009, 27(11):SII12-SII17 | DOI: 10.17221/676-CJFS  

A collection of lactic acid bacteria (38 Enterococcus and 41 Lactobacillus strains) was tested for the antilisterial activity against 15 Listeria spp. strains (two L. monocytogenes, one L. ivanovii and 12 L. innocua strains) using agar spot method. Out of all 79 bacteria only six Enterococcus strains (1/3A, 3/3A, 6/4D, 6/1A, 1282 and EN3) exhibited antilisterial activity against almost all used indicator strains, when their live cells were tested. When their cell free neutralised supernatants (CFNS) were tested against four selected indicator strains (L. innocua Ln-03, Ln-06, Ln-10 and L. monocytogenes CCM5576) only two Enterococcus spp. strains were...

Problems with detection of proteolytic microorganisms and their undesirable activities in milk

Irena Němečková, Marta Pechačová, Petr Roubal

Czech J. Food Sci., 2009, 27(11):SII82-SII89 | DOI: 10.17221/666-CJFS  

Occurrence of proteolytic enzymes in milk is often associated with technological problems and sensory, rheological and functional defects of final dairy products. Thus, the simple, cost-effective and available laboratory method for evaluation of undesirable proteolysis risk is needed. In our work we have tested cultivation plate methods and chemical methods (formol titration, ammonium reflectometric determination, the Kjeldahl method, the agar-well diffusion assay and spectrofotometry after cleavage of azo-casein) to choose the proper ones which can provide information on undesirable proteolytic changes especially in raw milk. Although the microbiological...

Effect of Lactococcus sp. on the growth of Listeria sp. in the model UHT milk system

Eva ŠVIRÁKOVÁ, Ivana SLOŽILOVÁ, Petr TICHOVSKÝ, Milada Plocková

Czech J. Food Sci., 2009, 27(11):SII8-SII11 | DOI: 10.17221/672-CJFS  

The work was aimed at the growth suppression of cultured listerias strains by cultured lactococci strains or commercial mesophilic cheese cultures during common cultivations in the model UHT milk system (0.5% w/w of milk fat content) at 30°C during 18 h aerobically. Milk was primarily fermented by lactococci at the level of 10⁸ CFU/ml and secondarily contaminated by listerias at the level of 10³ CFU/ml. The most intensive growth suppressions of both Listeria innocua (CCM 5884 or Ln-03) strains were caused by Lactococcus lactis subsp. lactis (LCC 416 or CHCC 2281) strains or DELVO-ADD® 100-X DSF cheese...

Characterisation of antibodies for the immunochemical detection of Enterobacter sakazakii

Igor Hochel, Jiří Škvor

Czech J. Food Sci., 2009, 27(11):SII66-SII74 | DOI: 10.17221/206/2009-CJFS  

An indirect competitive enzyme immunoassay of Enterobacter sakazakii has been developed. The rabbit polyclonal antibodies to heat-labile or heat-stable antigen of the type strain E. sakazakii CNCTC 5739^T were prepared for these purposes. The detection limits of enzyme immunoassays were within the range 0.6-14.4 × 10⁵ cells/ml. Antibodies raised to heat-labile antigen were serotype-specific. Although they contain non-specific IgG fractions binding periplasmatic and cytosol proteins, the interactions of these immunoglobulins are not manifested under conditions of ELISA developed.

The expression of selected genes encoding enterotoxins in Staphylococcus aureus strains

Lukáš Valihrach, Kateřina Demnerová, Renata Karpíšková, Ivana Melenová

Czech J. Food Sci., 2009, 27(11):SII56-SII65 | DOI: 10.17221/208/2009-CJFS  

Staphylococcus aureus is an important food-borne pathogen, which produces many toxic substances that cause a variety of illnesses. Some strains of S. aureus produce thermostable enterotoxins that can be responsible for alimentary intoxication. The aim of this work was to establish a protocol for the study of 9 enterotoxin genes expression (sea-sej). First, a method for the detection of genes encoding enterotoxins was established and then a method for the determination of the expression of these genes was optimised, using a range of the PCR techniques (multiplex, touchdown and real-time). The expression of staphylococcal...

Production of biogenic amines by Enterococci

Kateřina Kučerová, Hana Svobodová, Štěpán Tůma, Iva Ondráčková, Milada Plocková

Czech J. Food Sci., 2009, 27(11):SII50-SII55 | DOI: 10.17221/673-CJFS  

Enterococci were presented in all tested samples of raw cow milk (six samples) at the level 10³-10⁵ CFU/ml, fresh cheeses (five samples) at the level 10²-10⁶ CFU/g and semi-hard cheeses (five samples) at the level 10³-10⁵ CFU/g. All 33 isolated Enterococcus strains were screened for decarboxylase activity by usage differential growth medium and 20 of them possessed tyrosine decarboxylase activity. A collection of eight strains with the strongest decarboxylase activity were identified by species specific PCR as E. faecium (Z3, Z4, Br4 and 6/4D strains) and E. faecalis...

Interferences of PCR effectivity: importance for quantitative analyse

Jan Hodek, Jaroslava Ovesná, Ladislav Kučera

Czech J. Food Sci., 2009, 27(11):SII42-SII49 | DOI: 10.17221/677-CJFS  

Importance of the Polymerase chain reaction (PCR) have already crossed the border of mere target DNA sequence present or absence analysis. For number analyses e.g. Genetically Modified Organisms (GMOs) or gene expression assesment the DNA quantification is demanded. Real-time (or quantitative) PCR is the most used tool for nucleic acids quantification. PCR efficiency has relevant importance on DNA quantification - it should be almost same for each PCR and its value should varied between 90-100%. There are a lot of PCR enhancers and inhibitors well known. We described impact of used DNA solvent and used laboratory plastic on real-time PCR efficiency.

Findings of methicillin-resistant strains of Staphylococcus aureus in livestock

Zora Šťástková, Sylva Karpíšková, Renáta Karpíšková

Czech J. Food Sci., 2009, 27(11):SII36-SII41 | DOI: 10.17221/209/2009-CJFS  

The aim of our study was to determine the occurrence of methicillin resistant Staphylococcus aureus (MRSA) at dairy farms in the Czech Republic. Altogether 1061 samples from 95 farms were examined. The samples analysed were milk (individual and bulk tank milk samples), animal swabs and swabs from the farm environment. In total, 299 S. aureus isolates were obtained, of which 23 were MRSA. These MRSA isolates originated from three farms (13 isolates from farm A and 5 isolates from each of farms B and C). All MRSA isolates carried the mecA gene while none of them carried the genes for PVL, TSST-1 and exfoliatins. Only the isolates...

Occurrence and characteristics of Listeria monocytogenes in ready-to-eat food from retail market in the Czech Republic

Tereza Gelbíčová, Renata Karpíšková

Czech J. Food Sci., 2009, 27(11):SII3-SII7 | DOI: 10.17221/210/2009-CJFS  

The study objectives were to test ready-to-eat food from the retail market in the Czech Republic for the presence of L. monocytogenes and, based on typing methods, to investigate probable causes of contamination. A total 2180 samples of ready-to-eat food (meat, dairy, fish, delicatessen and confectionery products and fresh fruit and vegetables) were analysed qualitatively and quantitatively. L. monocytogenes isolates were characterised by serotyping and macrorestriction analysis after digestion with the restriction enzyme AscI. In 2004-2008 L. monocytogenes was most often detected in delicatessen (5.2%), meat (3.4%) and dairy...

The effect of temperature and water activity on the growth of Staphylococcus aureus

Alžbeta Medveďová, Ľubomír Valík, Adriana Studeničová

Czech J. Food Sci., 2009, 27(11):SII28-SII35 | DOI: 10.17221/204/2009-CJFS  

The growth responses of Staphylococcus aureus 2064 as affected by water activity and incubation temperature were studied in two different laboratory media. Growth parameters at temperatures from 7 to 51°C and a_w in the range from 1.0 to 0.86 were fitted using Ratkowsky models. The effect of temperature within its whole range on the specific growth rate was modelled by the extended model under the following equation: √µ = 0.0456 (T - T_min) [1 - e^{0.447(T - T_max)}]. The water activity values of tested media were adjusted by sodium chloride...

Quantification of Geotrichum candidum growth in co-culture with lactic acid bacteria

Anna Hudecová, Ľubomír Valík, Denisa Liptáková

Czech J. Food Sci., 2009, 27(11):SII18-SII27 | DOI: 10.17221/205/2009-CJFS  

The growth dynamics of filamentous fungus G. candidum was studied during the co-cultivation with the commercial lactic acid bacteria (LAB) culture Fresco. The experiments were carried out in milk and on the surface of a milk agar at the temperature ranging from 5 to 37°C. Ratkowsky model was used to describe the relationships of the fungal growth rate to the temperature during both, single and co-cultivation with LAB in milk. Simultaneous growth of LAB affected significantly the growth rate of the filamentous fungus. The growth of G. candidum was in average 39% slower in the co-culture than in the single cultivation. LAB pre-inoculated...

PCR-based identification of toxinogenic Fusarium species

Iva Lacmanová, Jarmila Pazlarová, Marta Kostelanská, Jana Hajšlová

Czech J. Food Sci., 2009, 27(11):SII90-SII94 | DOI: 10.17221/634-CJFS  

Aim of this study was to develop sensitive PCR assay for mycotoxin producing Fusarium species. Strains Fusarium oxysporum 4199 and Fusarium culmorum 4044 were used as representatives of this group. Primers JB chosen to demonstrate the affiliation to genus Fusarium were derived from ITS region of rDNA. Gene from trichothecene pathway Tri4 was employed to design primers for toxin biosynthesis. Specificity of PCR based on JB primers was tested on DNA isolated from F. culmorum 4044, F. oxysporum 4199, Aspergillus oryzae 4002 and Mucor circinelloides 4018, Trichoderma sp. Both...