Hypochlorite inactivation kinetics of lactococcal bacteriophages

Ten heat-resistant lactococcal phages in M17 broth were inactivated by exposure to a range of different hypochlorite concentrations (2000-5000 mgl(-1)). Deviations from first-order kinetics as sigmoidal shapes were observed in the survival curves of all bacteriophages. Therefore, an empirical model with four parameters was used to describe hypochlorite inactivation. The model provided good fit for all phages; however, it was observed that there was a high correlation between the parameters of this model. That is why, the number of parameters was reduced from four to two with a slight loss of goodness-of-fit and this reduced model produced fits comparable to the original model. Alternative D and z values were also proposed for the model. By comparing the times necessary to reduce the number of phages six- or seven-logs, the most hypochlorite-resistant phages were found as: phi pld67 37, phi pll47 21 and phi pld66 36. Demonstration of this model may also be used for other bacteriophages inactivated by other biocides. (C) 2006 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved

Isolation and partial characterization of a novel bacteriocin produced by Lactococcus lactis ssp lactis MC38

This work presents the isolation and partial characterization of a new lactococcal bacteriocin produced by Lactococcus lactis ssp. lactis MC38. The bacteriocin demonstrated broad spectrum of inhibition activity against both pathogenic and food spoilage organisms, and various lactic acid bacteria. This antimicrobial substance appeared to be proteinaceous because its activity was completely inactivated by proteinase K and alpha-chymotrypsin. It was heat and pH stable. The apparent molecular mass of the purified bacteriocin, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was 8.0 kDa. The amino acid composition of the studied bacteriocin was found to be quite different from known lactococcal bacteriocins. The calculation of the number of amino acid residues in the bacteriocin molecule revealed that it contained 62 amino acids

EFFECT OF HIGH PRESSURE ON LACTOCOCCAL BACTERIOPHAGES

Four different host-specific lactococcal bacteriophages were subjected to high hydrostatic pressure and heat treatments. Pressure treatments were done at room temperature at 300 and 350 MPa for 5-40 min. Complete inactivation of bacteriophages was observed starting at 350 MPa for 20-min treatment at room temperature. The effect of heat on the bacteriophages was analyzed by heat treatment at 71.7C for predetermined lengths of time (1-5 min). Decrease in bacteriophage number was observed after 3 min of heat treatment at 71.7C. Pressure treatment at 350 MPa/5 min and heat treatment at 71.7C/3 min were both found to be effective for the inactivation of lactococcal bacteriophages. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis indicated that protein profiles of pressure-treated (350 MPa, 25 min) bacteriophages were altered

Molecular evaluation and antimicrobial susceptibility testing of Escherichia coli isolates from food products in Turkey

WOS: 000354886300028Some strains of Escherichia coli can be important food borne pathogens. Characterization and antimicrobial resistance testing of 28 E. coli isolates from random food samples obtained in Van, Turkey were performed. Primers for 6 indicator genes (fliC, stx1, stx2, eae, hlyA, and rfbE) for shiga toxin-producing E. coli and 5 indicator genes for each pathogroup (bfpA, aggR, ipaH, daaD, st, and lt) were used. E. coli isolates were also typed using pulsed field gel electrophoresis with the XbaI restriction enzyme. Antimicrobial susceptibility of E. coli isolates was determined using the disk diffusion method for 17 antimicrobials. E. coli isolates were non-pathogenic strains represented by 25 distinguishable PFGE patterns. Antimicrobial susceptibility testing revealed that more than 40% of the E. coli isolates showed resistance to ampicillin, sulphafurazole, and tetracycline. Antimicrobial susceptibility of commensal E. coli should be monitored because these bacteria are becoming reservoirs of antimicrobial resistance genes.Middle East Technical University (METU), Department of Food Engineering, Ankara, TurkeyMiddle East Technical University; METU Scientific Research Project (BAP)Middle East Technical UniversityThis study was supported by a grant from Middle East Technical University (METU), Department of Food Engineering, Ankara, Turkey. The METU Scientific Research Project (BAP) provided financial support. Dr. Kadir Halkman and Dr. Belkis Levent provided reference strains for STEC and pathogenic E. coli respectively. Dr. Martin Weidmann allowed use of bionumerics in the laboratory

A kinetic study on the plasmid stability of three Lactococcus lactis strains

The plasmid stability of three wild type Lactococcus lactis strains and their mutants was investigated at different incubation time and temperatures in two different media [M17 broth and reconstituted skim milk (RSM)]. The results showed that both incubation times and temperature are effective on plasmid loss. The plasmid profiles of wild type strains exhibited 8 to 9 distinct plasmid species with molecular weights from 2.1 to 24.0 kb. Lactose fermentation ability was found to be encoded by 22.2 (strain U70), 23.6 (strain U29) and 24.0 (strain U52) kb plasmids in the wild type strains, respectively. The stabilities of the plasmids were explained by applying a second-order polynomial modeling system. Reasonable fittings were obtained for the model and the adjusted regression coefficients (R-adj(2)) were between 0.76 and 0.99 for the overall data. Overall, it was found that incubation time had the most profound effect on plasmid stability, with plasmid loss occurring after 72 h, while temperatures in the range of 15-40 degrees C also induced plasmid instability

Effects of an antibiotic and two phytogenic substances (cinnamaldehyde and 1,8-cineole) on yolk fatty acid profile and storage period-associated egg lipid peroxidation level

This study was aimed at determining the effects of two phytogenic antioxidants, namely, cinnamaldehyde and 1,8-cineole, and an antibiotic added to laying hen feed on the fatty acid profile of egg yolk and the weight loss and lipid peroxidation levels of eggs stored for different periods. Ninety-six 48-week-old Bovans White hens were randomly assigned to four groups, each with four replicates of six hens per replicate. The four groups were provided with the following feeds: maize and soybean-based laying hen feed, basal ration (control group); basal ration added 500 mg/kg of an antibiotic; basal ration added 100 mg/kg of cinnamaldehyde; and basal ration added 100 mg/kg of 1,8-cineole. At the end of an eight-week feeding schedule, 48 eggs, including 12 from each group, were used for yolk fatty acid analysis. In total, 240 eggs, including 48 eggs for each of the five different storage periods tested (1, 14, 28, 42, and 56 days), were collected for the detection of egg weight loss and yolk malondialdehyde (MDA) levels. The feed supplements cinnamaldehyde and 1,8-cineole were determined to have significantly reduced lipid peroxidation in the yolk of eggs stored for 14, 28, 42, and 56 days, when compared with the results of the control group and antibiotic-treated group. Furthermore, dietary cinnamaldehyde supplementation was determined to have decreased the yolk level of myristic acid, a saturated fatty acid, and to have increased the yolk level of oleic acid, the major unsaturated fatty acid found in egg yolk (46.28%) in comparison with the levels measured in the other three groups. Cinnamaldehyde and 1,8-cineole were determined to extend the shelf life of eggs by providing protection against free oxygen radicals. Cinnamaldehyde could be used as an alternative feed supplement to enrich the yolk fatty acid profile in unsaturated fatty acid

Recombinant plasmid-based quantitative Real-Time PCR analysis of Salmonella enterica serotypes and its application to milk samples

WOS: 000371368200011PubMed ID: 26820062The aim of the current study was to develop, a new, rapid, sensitive and quantitative Salmonella detection method using a Real-Time PCR technique based on an inexpensive, easy to produce, convenient and standardized recombinant plasmid positive control. To achieve this, two recombinant plasmids were constructed as reference molecules by cloning the two most commonly used Salmonella-specific target gene regions, invA and ttrRSBC The more rapid detection enabled by the developed method (21 h) compared to the traditional culture method (90 h) allows the quantitative evaluation of Salmonella (quantification limits of 10(1) CFU/ml and 10(0) CFU/ml for the invA target and the ttrRSBC target, respectively), as illustrated using milk samples. Three advantages illustrated by the current study demonstrate the potential of the newly developed method to be used in routine analyses in the medical, veterinary, food and water/environmental sectors: I - The method provides fast analyses including the simultaneous detection and determination of correct pathogen counts; II - The method is applicable to challenging samples, such as milk; III - The method's positive controls (recombinant plasmids) are reproducible in large quantities without the need to construct new calibration curves. (C) 2016 Elsevier B.V. All rights reserved.Middle East Technical University (METU) [BAP-03-14-2010-05]This study was supported by Middle East Technical University (METU) research fund: BAP-03-14-2010-05

Recombinant plasmid-based quantitative Real-Time PCR analysis of Salmonella enterica serotypes and its application to milk samples

The aim of the current study was to develop, a new, rapid, sensitive and quantitative Salmonella detection method using a Real-Time PCR technique based on an inexpensive, easy to produce, convenient and standardized recombinant plasmid positive control. To achieve this, two recombinant plasmids were constructed as reference molecules by cloning the two most commonly used Salmonella-specific target gene regions, invA and ttrRSBC The more rapid detection enabled by the developed method (21 h) compared to the traditional culture method (90 h) allows the quantitative evaluation of Salmonella (quantification limits of 10(1) CFU/ml and 10(0) CFU/ml for the invA target and the ttrRSBC target, respectively), as illustrated using milk samples. Three advantages illustrated by the current study demonstrate the potential of the newly developed method to be used in routine analyses in the medical, veterinary, food and water/environmental sectors: I - The method provides fast analyses including the simultaneous detection and determination of correct pathogen counts; II - The method is applicable to challenging samples, such as milk; III - The method's positive controls (recombinant plasmids) are reproducible in large quantities without the need to construct new calibration curves. (C) 2016 Elsevier B.V. All rights reserved

Phenotyping and genetic characterization of Salmonella enterica isolates from Turkey revealing arise of different features specific to geography

WOS: 000390071600012PubMed ID: 27768932192 Food samples (commonly consumed 8 food types), 355 animal samples (animal feces of bovine, ovine, goat and chicken) and 50 samples from clinical human cases in Sanliurfa city, Turkey in a year were collected to determine the Salmonella enterica subsp. enterica mosaic in Turkey. 161 Salmonella isolates represented 17 serotypes, 20 sequence types (STs) and 44 PFGE patterns (PTs). 3 serotypes, S. Enteritidis, S. Typhimurium and S. Kentucky, were recovered from three different hosts. The highest discriminatory power was obtained by PFGE (SID = 0.945), followed by MLST (SID = 0.902) and serotyping (SID = 0.885) for all isolates. The prevalence of antimicrobial resistance genes (aadA1, aadA2, strA, strB, aphA(1-lab) bla(TEM-1), bla(PSE-1), tetA) was highly correlated with phenotypic profiles of aminoglycoside, beta-lactam and tetracycline groups (kappa >0.85). From our knowledge, this is the first study reporting spatial and temporal distribution of Salmonella species through phenotypic and genetic approaches over farm to fork chain in Turkey. Thus, our data provided further information for evolution, ecology and transmission of Salmonella in Turkey. (C) 2016 Published by Elsevier B.V.Scientific and Technical Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TUBITAK 3501(1120192)]We acknowledge Dr. Martin Wiedmann from Cornell University for using BioNumerics, Dr. Nihat Dilsiz from Harran University Medicine Faculty, Harran University Veterinary Faculty for the valuable discussion, and Dr. Tolga Can from Middle East Technical University, Computer Engineering for building a web-based database. This work is partially supported by The Scientific and Technical Council of Turkey Grant TUBITAK 3501(1120192)