The spoilage flora of vacuum-packaged, sodium nitrite or potassium nitrate treated, cold-smoked rainbow trout stored at 4°C or 8°C

http://www.elsevier.nl/locate/01681605The spoilage flora of vacuum-packaged, salted, cold-smoked rainbow trout fillets, with or without the addition of nitrate or nitrite, stored at 4°C and 8°C, was studied. Of 620 isolates, lactic acid bacteria were the major fraction (76%), predominating in all samples of spoiled product. However, the phenotypical tests used were insufficient to identify the lactic acid bacteria to the species level. Gram-positive, catalase-positive cocci, Gram-negative, oxidase-negative rods and Gram-negative, oxidase-positive rods were found in 6%, 16% and 2% of the samples, respectively. Of 39 Gram-positive, catalase-positive cocci, 29 were identified as staphylococci and 10 as micrococci. Eighty-five isolates were found to belong to the family Enterobacteriaceae, with 45 of those being Serratia plymuthica. Eleven isolates from the nitrate treated samples stored at 8°C were identified as Pseudomonas aeruginosa. The occurrence of P. aeruginosa and staphylococci in the nitrate-containing samples, stored at 8°C, may cause problems with respect to the safety of the product. The types of lactic acid and other bacteria in the spoilage flora were generally reduced by the addition of nitrate or nitrite to fillets

Antibacterial activity of different organic honeys against food pathogenic bacterium Clostridium perfringens

Clostridium perfringens is one of the most common causes of food poisonings and is known to cause human and animal diseases. It has been reported that C. perfringens has developed resistance to antibiotics. Antimicrobial properties of honey have been studied in order to confirm its action as a potential antimicrobial agent and also as a potential food preservative through inactivation, growth delay or growth prevention of food pathogenic microorganisms. This study had two different parts related on virulence of C. perfringens. In the first part of the study antimicrobial activity of five multifloral organic honeys from different parts of Finland and one multifloral honey originated from Argentina and Hungary were investigated against C. perfringens. Honeys were tested at the concentrations of 50% (w/v), 25% (w/v), 20% (w/v), 15% (w/v) and 10% (w/v). For the antimicrobial assessment a disc diffusion method was used and zone of inhibition was expressed as diameter. The minimum concentrations (minimum inhibitory concentration, MIC) needed for inhibition of bacterial growth were determined for honeys showing activity in dilutions of 50%. Four of the studied honeys showed good inhibitory activity (diameter >8 mm) compared to control sugar solution (diameter of 6.1 ± 1.5) against C. perfringens at the concentration of 50 % (w/v). All the active honeys were of Finnish origin. The broadest zone of inhibition was induced by North Carelien multifloral organic honey with willow herb as the main floral source (referred here as F) (diameter of 14,3 mm ± 0.6), followed by other North Carelien multifloral organic honey (diameter of 11 mm ± 2) with clover as the main floral source (referred here as E). In terms of MIC values North Carelien organic honey F was also the most efficient honey against C. perfringens and showed moderate antibacterial activity (diameter of 7-8 mm) even at 10% (w/v). The other active honeys showed moderate inhibitory activity in the dilution of 15%. To our knowledge this is the first report on the antimicrobial activity of organic honeys and antimicrobial activity of honey against C. perfringens. (Oinaala et al 2015) In the second part of the work C. perfringens isolates from healthy broilers and from broilers suffering from necrotic enteritis (NE) were analyzed by polymerase chain reaction (PCR) method in order to determine the presence of gene coding the NE toxin B (NetB), a novel toxin that has been strongly associated with the pathogenesis of NE. The netB toxin gene was detected in 30% isolates from broilers with necrotic enteritis and in 32.5% isolates from healthy broilers. In this study the presence of netB gene gives not enough information for predicting the virulence of C. perfringens isolates, thus, further investigations are needed

Characterisation of lactic acid bacteria from spoiled, vacuum-packaged, cold-smoked rainbow trout using ribotyping

http://www.elsevier.nl/locate/01681605A total of 405 lactic acid bacteria (LAB) isolated from spoiled, vacuum-packaged, salted, sodium nitrite- or potassium nitrate-treated, cold-smoked rainbow trout stored at 48C or 88C were characterised and identified using a molecular method. The isolates were initially classified according to their restriction endonuclease profiles using HindIII and EcoRI restriction endonucleases and further characterised by rRNA gene restriction patterns (ribotypes). Numerical analysis of these ribopatterns was performed together with 19 reference LAB strain patterns in order to identify the isolates to species level. The strains were divided with HindIII and EcoRI ribopatterns into ten and nine clusters at the similarity level of 65% and 50%, respectively. The Leuconostoc-clusters and the Lb. sakei /Lb. curvatus-clusters formed the two main groups. Only one isolate was identified as Lactobacillus plantarum and no Carnobacterium strains were discovered. For both enzymes, the 35 isolates possessing six individual ribotypes and forming five clusters could not be identified further with the reference strains used. The relative proportion of Leuconostoc mesenteroides subsp. mesenteroides was higher in all samples stored at 48C. Most of the Leuconostoc citreum were found in the samples stored at 88C, and particularly in the nitrite-treated samples

Identification of lactic acid bacteria from spoiled, vacuum-packaged ’gravad’ rainbow trout using ribotyping

http://www.elsevier.com/locate/01681605A total of 296 lactic acid bacteria (LAB) isolated from spoiled, vacuum-packaged ‘gravad’ rainbow trout stored at 3ºC and 8ºC were characterised and identified using a molecular approach. The isolates were initially grouped according to their HindIII restriction endonuclease profiles and further identified to species level using a rRNA gene restriction pattern (ribotype) identification database. Lactobacillus sakei, Lactobacillus curvatus and Carnobacterium piscicola were the three main species detected. Only one isolate was identified as Carnobacterium divergens. Most of the carnobacteria were found in the samples stored at 3ºC. The relative proportion of L. sakei was higher in the samples stored at 8ºC

A longitudinal study of Campylobacter distribution in a turkey

Background: Campylobacter is the most common cause of bacterial enteritis worldwide. Handling and eating of contaminated poultry meat has considered as one of the risk factors for human campylobacteriosis.Campylobacter contamination can occur at all stages of a poultry production cycle. The objective of this study was to determine the occurrence of Campylobacter during a complete turkey production cycle which lasts for 1,5 years of time. For detection of Campylobacter, a conventional culture method was compared with a PCR method. Campylobacter isolates from different types of samples have been identified to the species level by a multiplex PCR assay. Methods: Samples (N = 456) were regularly collected from one turkey parent flock, the hatchery, six different commercial turkey farms and from 11 different stages at the slaughterhouse. For the detection of Campylobacter, a conventional culture and a PCR method were used. Campylobacter isolates (n = 143) were identified to species level by a multiplex PCR assay. Results: No Campylobacter were detected in either the samples from the turkey parent flock or from hatchery samples using the culture method. PCR detected Campylobacter DNA in five faecal samples and one fluff and eggshell sample. Six flocks out of 12 commercial turkey flocks where found negative at the farm level but only two were negative at the slaughterhouse. Conclusion: During the brooding period Campylobacter might have contact with the birds without spreading of the contamination within the flock. Contamination of working surfaces and equipment during slaughter of a Campylobacter positive turkey flock can persist and lead to possible contamination of negative flocks even after the end of the day's cleaning and desinfection. Reduction of contamination at farm by a high level of biosecurity control and hygiene may be one of the most efficient ways to reduce the amount of contaminated poultry meat in Finland. Due to the low numbers of Campylobacter in the Finnish turkey production chain, enrichment PCR seems to be the optimal detection method here

A longitudinal study of Campylobacter distribution in a turkey production chain

Background: Campylobacter is the most common cause of bacterial enteritis worldwide. Handling and eating of contaminated poultry meat has considered as one of the risk factors for human campylobacteriosis.Campylobacter contamination can occur at all stages of a poultry production cycle. The objective of this study was to determine the occurrence of Campylobacter during a complete turkey production cycle which lasts for 1,5 years of time. For detection of Campylobacter, a conventional culture method was compared with a PCR method. Campylobacter isolates from different types of samples have been identified to the species level by a multiplex PCR assay. Methods: Samples (N = 456) were regularly collected from one turkey parent flock, the hatchery, six different commercial turkey farms and from 11 different stages at the slaughterhouse. For the detection of Campylobacter, a conventional culture and a PCR method were used. Campylobacter isolates (n = 143) were identified to species level by a multiplex PCR assay. Results: No Campylobacter were detected in either the samples from the turkey parent flock or from hatchery samples using the culture method. PCR detected Campylobacter DNA in five faecal samples and one fluff and eggshell sample. Six flocks out of 12 commercial turkey flocks where found negative at the farm level but only two were negative at the slaughterhouse. Conclusion: During the brooding period Campylobacter might have contact with the birds without spreading of the contamination within the flock. Contamination of working surfaces and equipment during slaughter of a Campylobacter positive turkey flock can persist and lead to possible contamination of negative flocks even after the end of the day's cleaning and desinfection. Reduction of contamination at farm by a high level of biosecurity control and hygiene may be one of the most efficient ways to reduce the amount of contaminated poultry meat in Finland. Due to the low numbers of Campylobacter in the Finnish turkey production chain, enrichment PCR seems to be the optimal detection method here

Lactobacillus alimentarius : a specific spoilage organism in marinated herring

http://www.elsevier.nl/locate/01681605Spoilage characterised by bulging of lids and gas formation affected various product lots of different marinated herring types. Microbiological analyses resulted in growth on MRS and Rogosa SL agar. Altogether, 206 randomly selected colonies from two unspoiled and ten spoiled samples were characterised using phenotypical key tests and a 16123S rRNA gene-based RFLP identification database. L. alimentarius was found to be the specific spoilage organism in all samples. All isolates obtained from the different product types were of the same clonal type. The slight rise in pH value together with marked gas production suggested a rare lactic acid bacteria spoilage type called ‘protein swell’. L. alimentarius has not been previously associated with herring spoilage

Bovine mastitis bacteria resolved by MALDI-TOF mass spectrometry

Matrix-assisted laser desorption/ionization timeof-flight mass spectrometry (MALDI-TOF MS) is a fast and reliable method to identify the most common pathogenic bacteria in humans and animals. The goals of this study were to amend a commercial database with additional species, evaluate the amended database for identification of bacterial genera and species causing bovine mastitis, and describe the plethora of species involved. In total, 500 udder pathogenic isolates were subjected to MALDI-TOF MS using bacterial or fungal colony material; 93.5% could be identified to the species level, and 6.5% were identified only to the genus level. Isolates identified to the genus level required further identification to the species level by conventional methods or 16S rDNA sequencing. Mass spectra from verified species were used to expand the MALDI-TOF MS database to improve future identification ability. A total of 24 genera and 61 species were identified in this study. Identified isolates were mainly staphylococci, streptococci, Enterobacteriaceae, and coryneforme bacteria. In conclusion, MALDI-TOF MS is a powerful, rapid, and reliable technique to identify the most common microorganisms causing bovine mastitis, and the database can be continuously expanded and improved with additional species.Peer reviewe